• Home
• About ATSDR
• Press Room
• A-Z Index
• Glossary
• Employment
• Contact Us
• CDC

ATSDR en Español

Search:

Skip directly to: content | left navigation | search

---

Find a Publication

1. ATSDR > Public Health Assessments & Consultations

PUBLIC HEALTH ASSESSMENT

SHERWOOD MEDICAL COMPANY
NORFOLK, MADISON COUNTY, NEBRASKA

ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS

This section of the public health assessment describes environmental sampling previously conducted at the site and identifies contaminants of concern found in specific environmental media. The contaminants of concern are evaluated later in the health assessment to determine if exposure to them will affect the public's health.

ATSDR selects and discusses contaminants of concern using the following information:

1. concentrations of contaminants on and off the site;

2. quality of field and laboratory data, and sample design;

3. comparison of on- and off-site contaminant concentrations with comparison values for noncancer and cancer endpoints; and

4. community health concerns.

As discussed previously, the listing of a contaminant in the following tables does not mean that it will cause adverse health effects if people are exposed at the reported concentrations. Rather, the listing of a contaminant indicates that the contaminant will be evaluated further in this public health assessment. When a contaminant is selected as a contaminant of concern in one medium, its presence or absence in all media sampled will be discussed. In addition, when a contaminant is identified as a contaminant of concern on site, its potential to migrate off site will also be discussed.

The data tables include the following acronyms and abbreviations:

Comparison Values (CVs)

Comparison values are contaminant concentrations in specific media used to select contaminants for further evaluation. These values include Environmental Media Evaluation Guides (EMEGs), Reference Dose Media Evaluation Guides (RMEGs), Cancer Risk Evaluation Guides (CREGs), and other relevant guidelines.

EMEGs are media-specific values developed by ATSDR for use in selecting environmental contaminants of potential health concern. EMEGs are calculated using noncancer health endpoints and do not consider potential carcinogenic effects. RMEGs are media-specific values developed by ATSDR from EPA Reference Doses (RfDs). RfDs are EPA's estimate of the daily exposure to a contaminant that is unlikely to cause adverse health effects. CREGs are estimated contaminant concentrations expected to cause no more than one excess cancer in a million persons exposed over a lifetime (70 years). Maximum Contaminant Level Goals (MCLGs) are EPA-developed drinking water health goals. EPA believes that MCLGs represent levels at which no known or anticipated adverse effect on the health of persons should occur that allow an adequate margin of safety. Proposed Maximum Contaminant Level Goals (PMCLGs) are MCLGs that are being proposed. Maximum Contaminant Levels (MCLs) represent contaminant concentrations that EPA deems to be protective of public health (considering the availability and economics of water treatment technology) over a lifetime (70 years) at an exposure rate of 2 liters water per day. EPA's Lifetime Health Advisories (LTHAs) represent the level of a contaminant in drinking water (with a margin of safety) at which adverse noncancer health effects would not be anticipated during a lifetime (70 years) of exposure. MCLs are regulatory concentrations; PMCLGs, MCLGs, and LTHAs are not.

A considerable amount of sampling data has been collected from environmental media on and off the Sherwood Medical site since October 1987. The data were obtained mainly by the Nebraska Department of Environmental Control, the Nebraska Department of Health, and the U.S. EPA (through contractors.) Relevant contaminant data from the past sampling efforts, which were described in the Site Description and History section, are discussed and evaluated in the On-Site Contamination and Off-Site Contamination subsections following. For the purpose of this health assessment, "on-site" refers to sampling locations on the Sherwood Medical plant property, while "off-site" indicates sampling locations outside the plant property line (e.g., at the Park Mobile Home Court.)

A. On-Site Contamination

Waste Material

As previously discussed, in September 1989 an EPA contractor inactivated a 2,000-gallon UST and concrete settling basin at the Sherwood Medical plant. During the inactivation, the contractor removed waste liquids and sludge solids from the UST and settling basin and sampled the liquids for VOCs and the solids for VOCs and EP toxic metals. At that time, liquids and solids in an on-site facility septic tank also were sampled for VOCs and EP toxic metals (solids only). In December 1990, sludge solids from the facility septic tank, which had been taken out of service during the previous month, were sampled for VOCs and metals. The location of the UST and settling basin is shown in Figure 3.

As indicated in Table 1a, several VOCs were detected in liquid wastes from the UST/settling basin and septic tank.

The waste sludge solids contained several VOCs and metals (Table 1b). Sludge metals generally were found at levels similar to background soil levels for the western United States (12), except antimony and mercury, which were found at slightly elevated levels.

Table 1a. Contaminant Concentrations in On-site Waste Materials (Liquid Wastes from UST & Septic Tank)

Contaminant	Concentration Range (µg/L)	Date	Reference
Chloroform	500M - 1,000M	9/89	13, 14
1,1-dichloroethane	1,900 - 2,600	9/89	13, 14
1,1-dichloroethene	500M	9/89	13, 14
1,2-dichloroethene	4,700	9/89	13, 14
Methylene chloride	78,000*	9/89	13, 14
1,1,2,2-tetrachloroethane	1,000M	9/89	13, 14
Tetrachloroethylene	8,300	9/89	13, 14
1,1,1-trichloroethane	21,000 - 22,400	9/89	13, 14
1,1,2-trichloroethane	500M	9/89	13, 14

*concentration in washwater from pressure cleaning of UST

Table 1b. Contaminant Concentrations in On-site Waste Materials (Sludge Solids from UST & Septic Tank)

During the July 1988 expanded site investigation, samples from four of the plant's wastewater discharges to Sherwood Lake were collected and analyzed for VOCs. The April and May 1991 RI/FS activities also included collection of wastewater samples, which were analyzed for VOCs and metals. Figure 4 shows the locations of the wastewater effluent samples. As shown in Table 1c., the 1988 wastewater samples contained low levels of several VOCs. These samples were collected while the plant was using untreated VOC-contaminated well water (from Sherwood well #5) for cooling water purposes and, after use, discharging the cooling water to Sherwood Lake. In September 1989, the plant discontinued the use of Sherwood well #5 as a cooling water source, as evidenced by the 1991 wastewater samples, which showed only trace levels of one VOC--1,1,1-TCA (Table 1c). The 1991 samples also contained low levels of several metals; only arsenic was found at levels exceeding ATSDR's comparison values.

Table 1c. Contaminant Concentrations in On-site Waste Materials (Wastewater Discharges to Sherwood Lake)

Soil

On-site soil samples were collected from monitoring well borings during Stage I and Stage IB RI/FS drilling activities in April and May 1991 and August 1991, respectively. Each sample represented a 2-foot soil segment taken between 0 and 14 feet below ground surface; therefore, data for surface soil (less than or equal to 3 inches deep) could not be separated out. The samples were analyzed for EPA Contract Laboratory Program (CLP) VOCs and Target Analyte List (TAL) inorganic analytes. Figure 4 shows the soil sampling locations.

As indicated in Table 2a, several VOCs and metals were detected in the soil samples. The levels of metals found, however, were similar to background soil concentrations for the western United States (12). It should be noted that the concentrations of VOCs detected in on-site soil samples generally increased with depth from 0 to 14 feet below ground surface. Soil samples collected at depths above the normal influence of groundwater did not contain detectable levels of VOCs. However, soil samples from below the normal water table surface did contain low concentrations of VOCs. Those findings indicate that VOC contamination of site soils is generally due to contact with VOCs in site groundwater.

In June 1992, approximately 15 soil samples were collected from Stage II soil borings at four areas identified from previous sampling results as potential groundwater contamination sources. The four areas identified were the CS/CN Area, the UST Area, the Cullet Silo Area, and the Grassy Knoll Area (see Figure 3). Each sample represented a 2-foot soil segment collected at a depth ranging from 0 feet to a maximum of 12 feet below ground surface.

The results of the VOC analyses of the Stage II soil samples (Table 2b) are discussed in the following paragraphs.

At the UST and Grassy Knoll areas, the only contaminants detected were PCE and toluene, respectively.

At the Cullet Silo Area, PCE was detected in one sample at a depth of 0 to 2 feet, while benzene, toluene, ethylbenzene, and xylene (BTEX compounds) were found in samples at depths of 8 to 12 feet. The presence of these BTEX contaminants is likely due to gasoline leakage from a 550-gallon UST in use from 1977 to 1991. The gasoline storage tank, which was removed in November 1991, was directly upgradient of the area where BTEX soil contaminants were found.

At the CS/CN Area, PCE, TCA, and toluene were detected in samples from two soil borings. The highest levels of these compounds were found at a depth of 6-8 feet below ground surface. In addition, the level of PCE increased with depth from 2 to 8 feet. Because the normal depth to the groundwater surface in this area ranges from about 7 to 11 feet, significant soil contamination in the vadose (unsaturated) zone is indicated in the CS/CN area.

In summary, the soil sampling results indicate significant VOC soil contaminant above the water table in the CS/CN areas but not in any of the other three suspected source areas. However, VOC soil contamination below the groundwater surface is possible at the CS/CN area and the UST area.

It is noted that no on-site surface soil (0 inches - 3 inches deep) samples were collected during the RI. However, analytical data from soil samples taken at a depth of 0 to 2 feet below ground surface show that significant VOC soil contamination is not present above a depth of 2 feet. Instead, soil contamination at the site is generally limited to a depth of 7 to 11 feet except at the CS/CN area where contamination is present at a depth of 6-8 feet. These findings are reasonable because VOC soil contamination at the site resulted from subsurface sources, such as solvents from the UST/septic system, and from contact with contaminants in the groundwater table. Because contamination of surface soils is not believed to be a problem at the site, the lack of surface soil sampling data is not important.

Table 2a. Contaminant Concentrations in On-site Soil Samples (at depths between 0' and 14') - Stages I & IB

Contaminant	Concentration Range (mg/kg)	Date	Reference	Comparison Value
				mg/kg	Source
1,1-dichloroethane	ND - 0.026	(1)	2	None
Tetrachloroethylene	ND - 2.4	(1)	2	10	CREG
1,1,1-trichloroethane	ND - 0.10	(1)	2	None
Arsenic	ND - 3.5	(1)	2	0.4	CREG
Barium	21.2B - 383	(1)	2	100	RMEG
Beryllium	ND - 0.61B	(1)	2	0.2	CREG
Lead	1.5 - 11.9	(1)	2	None
Mercury	ND - 0.19	(1)	2	None
Vanadium	2.6B - 20.6	(1)	2	6	EMEG

¹Sampling Dates: 4/91, 5/91, & 8/91

Table 2b. Contaminant Concentrations in On-site Soil Samples (at depths between 0' and 12') - Stage II

Contaminant	Concentration Range (mg/kg)	Date	Reference	Comparison Value
				mg/kg	Source
Tetrachloroethylene	ND - 3,400	6/92	7	10	CREG
1,1,1-trichloroethane	ND - 580	6/92	7	None
Benzene	ND - 0.22	6/92	7	20	CREG
Ethylbenzene	ND - 0.26	6/92	7	200	RMEG
Toluene	ND - 14	400	7	400	RMEG
m & p-Xylene	ND - 0.78J	6/92	7	4,000	RMEG
o-Xylene	ND - 0.54J	6/92	7	4,000	RMEG

Groundwater - Monitoring Wells

As previously discussed, groundwater monitoring wells were installed at the Sherwood Medical site during Stage I RI/FS field activities in April and May 1991 and during Stage IB in August and September 1991. A total of 45 monitoring wells--30 on site and 13 off site--were drilled. Forty-two of the wells were screened in the alluvial aquifer; the remainder were screened in bedrock. The location of the monitoring wells is shown in Figures 3 and 4. Round 1 groundwater samples were collected in June 1991 from the 35 Stage I monitoring wells and analyzed for VOCs, metals, semi-volatile organic compounds, and pesticides. Round 2 and Round 3 groundwater samples were collected in September 1991 and December 1991, respectively, from Stage 1 and 1B monitoring wells. The Round 2 samples were analyzed for VOCs; the Round 3 samples were tested for VOCs and metals. Note: Filtered and unfiltered samples were collected for metals analysis in Rounds 1 and 3. However, only data from the unfiltered samples will be presented and evaluated in this public health assessment because using data from filtered samples could underestimate actual groundwater contaminant loads and potential human exposure levels. The use of data from unfiltered samples for risk assessment purposes is also consistent with EPA Superfund guidance (17).

Groundwater monitoring results indicated the presence of VOCs at several locations. The primary contaminants of concern detected were 1,1-dichloroethene (1,1-DCE), 1,1-DCA, 1,1,1-TCA, PCE, and TCE. However, as shown in Table 3, other VOCs also were present at levels of concern. In addition, various metals were found in unfiltered groundwater samples from the on-site monitoring wells; the concentrations, however, were generally similar to levels found in the off-site background monitoring well (MW 1).

Metals found in the unfiltered groundwater samples were believed to be associated with sample turbidity, and not the result of site contamination, because 1) the levels of metals in unfiltered groundwater samples were higher than metal levels in filtered samples, and 2) the levels of metals in upgradient well samples were equal to or greater than the levels in downgradient well samples. In addition, metals found in on-site soils were at levels similar to natural background soil levels.

To demonstrate that levels of metals found in the groundwater samples were not representative of groundwater conditions at the site, a Metals Verification Test (MVT) was conducted in April and May 1992. As part of the MVT, non-turbid, non-filtered groundwater samples (referred to as Round 4 samples) were collected from selected background and on-site monitoring wells to determine the level of mobile metals (i.e., metals that move with the groundwater) in site groundwater. For comparison purposes, filtered and unfiltered samples were also collected using the same sampling procedures that were used for Rounds 1, 2, and 3.

Table 3a. Contaminant Concentrations in On-site Groundwater Monitoring Well Samples (Rounds 1, 2, and 3)

Contaminant	Concentration Range (µg/L)	Date	Reference	Comparison Value
				µg/L	Source
Benzene	ND - 230E	(1)	2, 6	1	CREG
Carbon tetrachloride	ND - 1,000E	(1)	2, 6	0.3	CREG
Chloroethane	ND - 7	(1)	2, 6	None
1,2-dibromoethane	ND - 19	(1)	2, 6	0.0004	CREG
1,1-dichloroethane	ND - 1,700D	(1)	2, 6	None
1,2-dichloroethane	ND - 51E	(1)	2, 6	0.4	CREG
1,1-dichloroethene	ND - 26,000E	(1)	2, 6	0.06	CREG
Methylene chloride	ND - 1,300DJ	(1)	2, 6	5	CREG
Tetrachloroethylene	ND - 14,000D	(1)	2, 6	0.7	CREG
1,1,1-trichloroethane	ND - 43,000E	(1)	2, 6	200	LTHA
1,1,2-trichloroethane	ND - 130E	(1)	2, 6	0.6	CREG
Trichloroethylene	ND - 100	(1)	2, 6	3	CREG
Vinyl chloride	ND - 4	(1)	2, 6	0.7	EMEG
Antimony	ND - 25.5B	(2)	2, 6	3	LTHA
Arsenic	ND - 218J	(2)	2, 6	0.02	CREG
Barium	195B - 1,470J	(2)	2, 6	2000	LTHA
Beryllium	ND - 7.4J	(2)	2, 6	0.008	CREG
Cadmium	ND - 8.7	(2)	2, 6	20	EMEG
Chromium	ND - 56.3J	(2)	2, 6	100	LTHA
Lead	ND - 80	(2)	2, 6	15	AL
Manganese	32.5 - 4,650J	(2)	2, 6	200	RMEG
Vanadium	ND - 194J	(2)	2, 6	100	EMEG

¹Sampling dates: 6/91, 9/91, & 12/91; ²Sampling dates: 6/91 & 12/91

Analytical results from the Round 4 MVT samples (non-turbid, unfiltered) are presented in Table 3b. These data showed that the concentrations of metals in the non-turbid Round 4 samples were much lower than the levels in the turbid samples from Rounds 1, 2, and 3. Moreover, only two metals--arsenic and manganese--were detected at levels exceeding ATSDR's comparison values. The results of the MVT confirmed that 1) the presence of metals in the Round 1, 2, and 3 groundwater samples was due to fine-grained, filterable particles (i.e., turbidity) from the aquifer formation, and 2) site groundwater has not been contaminated by metals from site activities (7,18).

Table 3b. Contaminant Concentrations in On-site Groundwater Monitoring Well Samples (Round 4)

Contaminant	Concentration Range (µg/L)	Date	Reference	Comparison Value
				µg/L	Source
Antimony	ND	4/92, 5/92	7, 18	3	LTHA
Arsenic	ND - 16.3	4/92, 5/92	7, 18	0.02	CREG
Barium	160 - 431	4/92, 5/92	7, 18	2000	LTHA
Beryllium	ND	4/92, 5/92	7, 18	0.008	CREG
Cadmium	ND	4/92, 5/92	7, 18	20	EMEG
Chromium	ND	4/92, 5/92	7, 18	100	LTHA
Lead	ND	4/92, 5/92	7, 18	15	AL
Manganese	ND - 826J	4/92, 5/92	7, 18	200	RMEG
Vanadium	ND	4/92, 5/92	7, 18	100	EMEG

The RI monitoring well data indicate that two groundwater VOC plumes are present at the site. Figure 5 shows the approximate location and extent of the two plumes.

The larger VOC plume originated from the UST/settling basin area (where solvents such as 1,1,1-TCA were disposed of) on the southwestern side of the plant. That plume descends from the source area in a northeasterly direction to the mid and deep portions of the alluvial aquifer, as indicated by data from monitoring wells 5, 6, and 7. The western edge of the plume is east of the MW 12 location (2).

The second, smaller VOC plume originated from contaminated soil at the MW 8--CS/CN area on the northern part of the plant property. The groundwater contamination from that area has been limited primarily to the shallow well at MW 8. The clayey soil layer found at the MW 8 location, between the depths of 8 and 16 feet, has likely inhibited vertical downward migration of the contaminants from the MW 8--CS/CN point source area. The MW 8--CS/CN source area has likely contributed to the Park Mobile Home Court main well contamination and may be responsible for contamination detected in the shallow well at MW 10. The MW 10 location, however, is not directly downgradient of the MW 8--CS/CN area (2).

The eastern edge of the UST/settling basin plume and the western edge of the MW 8-- CS/CN plume are believed to merge downgradient of the MW 8--CS/CN source area. The combined plume extends northeasterly to approximately the MW 11 and MW 14 areas. The eastern edge of the contamination likely runs along a line between MW 2, MW 9, and MW 11, primarily within the upper and intermediate portions of the alluvial aquifer (2).

Groundwater - On-Site Supply Wells

Sherwood Medical industrial supply wells 3, 4, 5, and 6 have been sampled for VOCS at various times since December 1987. The four wells were tested for VOCs during the expanded site investigation (ESI) follow-up activities in January 1989, and during the RI/FS field activities (Round 3) in December 1991. In addition, Sherwood supply well 3 has been tested regularly (approximately once a month) for VOCs since installation of the mobile home park water treatment system in September 1989. Also, as part of the first two RI/FS sampling rounds, Sherwood well 5 was tested in July 1991 for VOCs and metals, and Sherwood well 4 was sampled for VOCs in September 1991. Figure 3 shows the locations of the plant supply wells.

The results of the groundwater analyses showed high levels of VOCs, including 1,1-DCA, 1,1-DCE, PCE, and 1,1,1-TCA, in the plant's industrial supply wells. Several metals also were detected in concentrations similar to those found in the background monitoring well (Table 4). However, none of the metals, except arsenic, were at levels exceeding the applicable comparison value.

Table 4. Contaminant Concentrations in On-site Groundwater Supply Wells

Contaminant	Concentration Range (µg/L)	Date	Reference	Comparison Value
				µg/L	Source
Benzene	ND	(1)	(3)	1	CREG
Carbon tetrachloride	ND - 10.8	(1)	(3)	0.3	CREG
Chloroethane	ND - 2.6	(1)	(3)	None
Chloromethane	ND - 2.5	(1)	(3)	3	LTHA
1,2-dibromoethane	ND	(1)	(3)	0.0004	CREG
1,1-dichloroethane	ND - 280	(1)	(3)	None
1,2-dichloroethane	ND - 2	(1)	(3)	0.4	CREG
1,1-dichloroethene	ND - 5,400	(1)	(3)	0.06	CREG
Methylene chloride	ND - 88J	(1)	(3)	5	CREG
Tetrachloroethylene	ND - 18,100	(1)	(3)	0.7	CREG
1,1,2,2-tetrachloroethane	ND - 6	(1)	(3)	0.2	CREG
1,1,1-trichloroethane	ND - 10,000	(1)	(3)	200	LTHA
1,1,2-trichloroethane	ND - 8	(1)	(3)	0.6	CREG
Trichloroethylene	ND - 34	(1)	(3)	3	CREG
Vinyl chloride	ND	(1)	(3)	0.7	EMEG
Antimony	ND	(2)	(4)	3	LTHA
Arsenic	ND - 6.8B	(2)	(4)	0.02	CREG
Barium	280 - 301	(2)	(4)	2,000	LTHA
Beryllium	ND	(2)	(4)	0.008	CREG
Cadmium	ND	(2)	(4)	20	EMEG
Chromium	ND	(2)	(4)	100	LTHA
Lead	ND - 5.4	(2)	(4)	15	AL
Manganese	ND - 8.4B	(2)	(4)	200	RMEG
Vanadium	ND - 5B	(2)	(4)	100	EMEG

¹Sampling dates: 12/87, 4/88, 1/89, 9/89-2/91, 7/91, 9/91 & 12/91; ²Sampling dates: 7/91 & 12/91; ³References: 1,2,5,6,18,19,20,21; ⁴References: 2,5

Surface Water

Surface water samples from Sherwood Lake were taken in July 1988 (VOCs only) during the ESI and in May 1991 (VOCs and metals) during the RI/FS field activities. The RI/FS surface water sampling locations are shown in Figure 4. Low levels of two VOCs--1,1-DCA and 1,1,1-TCA--were found in the 1988 surface water samples (Table 5). These samples were collected while the plant was discharging VOC-contaminated cooling water to Sherwood Lake. In September 1989, the plant discontinued the use of VOC-contaminated well water for cooling water. Therefore, the 1991 Sherwood Lake water samples contained no VOCs (Table 5). Several metals were detected in the 1991 samples, but only arsenic was at levels in excess of the ATSDR comparison value.

Table 5. Contaminant Concentrations in On-site Surface Water Samples (Sherwood Lake)

Contaminant	Concentration Range (µg/L)		Reference	Comparison Value
	July 1988 Samples	May 1991 Samples		µg/L	Source
1,1-dichloroethane	ND - 8.0	ND	2, 16	None
1,1,1-trichloroethane	ND - 31.0	ND	2, 16	200	LTHA
Arsenic	NA	ND - 5B	2	3	EMEG
Barium	NA	145B -160B	2	700	RMEG
Chromium	NA	ND - 5.3B	2	50	RMEG
Lead	NA	ND - 6.2J	2	15	AL
Manganese	NA	7.3B - 8.1B	2	50	RMEG

Sediment

Sediment samples from Sherwood Lake were taken in July 1988 (VOCs only) during the ESI and in May 1991 (VOCs and metals) during the RI/FS field activities (see Figure 4). No VOCs were detected in sediments at levels of concern. As shown in Table 6, several metals were found at levels exceeding ATSDR's comparison values. However, the levels were generally similar to background soil levels for the western U.S. (12).

Table 6. Contaminant Concentrations in On-site Sediment Samples (Sherwood Lake)

Contaminant	Concentration Range (mg/kg)	Date	Reference	Comparison Value
				mg/kg	Source
Antimony	ND - 11.2J	5/91	2	0.8	RMEG
Arsenic	0.87J - 5.6J	5/91	2	0.4	CREG
Barium	54.3 - 194	5/91	2	100	RMEG
Chromium	3.5 - 21.4	5/91	2	10	RMEG
Lead	3.9J - 29.7J	5/91	2	None
Vanadium	5.5B - 17.6	5/91	2	6	EMEG

Ambient Air

No on-site ambient air data were available to ATSDR during the development of this public health assessment. However, based on the levels of VOCs in site groundwater, soil, and soil gas, it is unlikely that ambient air is contaminated at the site.

Soil Gas

Soil gas samples on the Sherwood Medical property were collected and analyzed for PCE and 1,1,1-TCA during the ESI in July 1988 and during the ESI follow-up in January 1989. Also, during the April and August 1991 RI/FS field activities, diffusional organic vapor monitors were installed on the Sherwood property to monitor VOCs in ambient soil gas. The monitors remained in place for 31 days and then were submitted to a laboratory and analyzed for 1,1-DCE, 1,1-DCA, 1,1,1-TCA, and PCE.

Results of the soil gas sampling events are shown in Table 7 and Figure 6. The data indicated four areas on the Sherwood Medical site where organic vapors were found at measurable levels. The four areas identified, as shown in Figures 3 and 6, were 1) the former UST/settling basin area on the western side of the plant building (near the entrance); 2) the monitoring well 8 (MW-08)--CS/CN area; 3) the cullet silos area on the eastern side of the plant; and 4) the Grassy Knoll on the northeastern portion of the site (2).

Table 7. Contaminant Concentrations in On-site Soil Gas Samples

Contaminant	Concentration Range (ppb)	Date	Reference	Comparison Value
				ppb	Source
1,1-dichloroethane	ND - 247	(1)	2, 16, 22	None
1,1-dichloroethene	ND - 5	(1)	2, 16, 22	0.005	CREG
1,1,1-trichloroethane	ND - 9,010	(1)	2, 16, 22	700	EMEG
Tetrachloroethylene	ND - 9,428	(1)	2, 16, 22	0.3	CREG

¹Sampling dates: 7/88, 1/89, 4/91, 5/91, 8/91, & 9/91

The results of the soil gas survey at the former UST/settling basin area and the MW-08--CS/CN area indicated two discrete areas of high soil gas concentrations, surrounded by an area with rapidly decreasing levels. Groundwater contamination in these two areas was confirmed by shallow monitoring well samples that contained VOCs at the parts per million (ppm) level. In addition, analysis of Stage II soil boring samples revealed significant VOC soil contamination in the CS/CN area.

VOCs found in soil gas near the cullet silos on the eastern side of the plant likely volatilized from shallow contaminated groundwater (2). However, the VOCs may also have volatilized from gasoline-contaminated soils near a former gasoline UST in that area.

Finally, soil gas sampling in the Grassy Knoll area (northeast of MW-09) indicated the presence of 1,1,1-TCA during both the ESI and RI/FS. The source of VOC contamination in the Grassy Knoll area, however, has not been clearly identified (2).

Soil gas survey results for the north leachfield area (north of the UST) indicated low concentrations of VOCs. However, the absence of detectable VOCs in MW-12, which is 250 feet northeast (downgradient) of the north leachfield, indicates that the north leachfield is not a source of groundwater contamination. The presence of VOCs in soil gas samples from the north leachfield area could be attributed to the plant's concrete parking lot, which would tend to prevent residual VOCs in underlying soils from escaping into the ambient air.

B. Off-Site Contamination

Soil

Off-site soil samples were collected in May 1991 during the installation of MW 10. The samples, which were obtained from borings 6 to 8 feet below ground surface, were analyzed for EPA Contract Laboratory Program (CLP) VOCs and Target Analyte List (TAL) inorganic analytes. Figure 4 shows the soil sampling locations. As shown in Table 8, no VOCs were detected in the soil samples; however, several metals were detected at levels similar to those found in background soil concentrations for the western United States (12).

No surface soil (less than or equal to 3 inches deep) data were available for off-site areas. However, contaminants from the site are unlikely to have affected off-site surface soils.

Table 8. Contaminant Concentrations in Off-site Soil Samples (Depths between 6' and 8')

Contaminant	Concentration Range (mg/kg)	Date	Reference	Comparison Value
				mg/kg	Source
1,1-dichloroethane	ND	5/91	2	None
Tetrachloroethylene	ND	5/91	2	10	CREG
1,1,1-trichloroethane	ND	5/91	2	None
Arsenic	ND	5/91	2	0.4	CREG
Barium	25.2B - 36B	5/91	2	100	RMEG
Beryllium	ND	5/91	2	0.2	CREG
Lead	2.7J - 3J	5/91	2	None
Mercury	ND	5/91	2	None
Vanadium	3B - 3.4B	5/91	2	6	EMEG

Groundwater - Monitoring Wells

Off-site groundwater monitoring wells (MW 10, 11, and 14) were sampled during the 1991 RI/FS field activities. The locations of the wells are shown in Figures 3 and 4. Round 1 groundwater samples were collected in June 1991 from monitoring wells 10 and 11 and analyzed for VOCs, metals, semi-volatile organic compounds, and pesticides. Round 2 and 3 groundwater samples were collected in September 1991 and December 1991, respectively, from monitoring wells 10, 11, and 14. Round 2 samples were analyzed for VOCs; Round 3 samples were tested for VOCs and metals.

The groundwater sampling results (Table 9) indicated the presence of various VOCs in the off-site monitoring wells. The primary contaminants of concern were the same as those found in the on-site monitoring wells. However, the off-site concentrations were generally about two orders of magnitude lower than the on-site levels. Several metals were detected in groundwater samples at levels similar to those measured in the background monitoring well (MW-1). Metals found at levels exceeding their respective comparison values are shown in Table 9.

Table 9. Contaminant Concentrations in Off-site Groundwater Monitoring Wells

Contaminant	Concentration Range (µg/L)	Date	Reference	Comparison Value
				µg/L	Source
Benzene	ND	(1)	2, 6	1	CREG
Carbon tetrachloride	ND	(1)	2, 6	0.3	CREG
Chloroethane	ND - 1	(1)	2, 6	None
1,2-dibromoethane	ND	(1)	2, 6	0.0004	CREG
1,1-dichloroethane	ND - 48E	(1)	2, 6	None
1,2-dichloroethane	ND - 1	(1)	2, 6	0.4	CREG
1,1-dichloroethene	ND - 160D	(1)	2, 6	0.06	CREG
Methylene chloride	ND - 4J	(1)	2, 6	5	CREG
Tetrachloroethylene	ND - 26	(1)	2, 6	0.7	CREG
1,1,1-trichloroethane	ND - 860D	(1)	2, 6	200	LTHA
1,1,2-trichloroethane	ND	(1)	2, 6	0.6	CREG
Trichloroethylene	ND - 10	(1)	2, 6	3	CREG
Vinyl chloride	ND - 2	(2)	2, 6	0.2	EMEG
Arsenic	6.2J - 25.6	(2)	2, 6	0.02	CREG
Barium	280 - 1,270	(2)	2, 6	700	RMEG
Beryllium	ND - 4.5B	(2)	2, 6	0.008	CREG
Cadmium	ND - 31.7	(2)	2, 6	7	EMEG
Chromium	ND - 103	(2)	2, 6	50	RMEG
Lead	3.4 - 51	(2)	2, 6	15	AL
Manganese	91.1 - 1,870J	(2)	2, 6	50	RMEG
Vanadium	ND - 129	(2)	2, 6	30	EMEG

¹Sampling dates: 6/91, 9/91, & 12/91; ²Sampling dates: 6/91 & 12/91

Groundwater - Private Wells

The principal off-site private wells near the Sherwood Medical plant include the two Park Mobile Home Court wells (main and back-up) and several residential and commercial wells. For convenience, the two private well categories are discussed in separate subsections of this public health assessment. Private wells in the site area are identified in Figures 2 and 3.

Park Mobile Home Court Wells

VOCs were initially found in the two Park Mobile Home Court wells in 1987. Since that time, the wells have been resampled several times, most recently during the 1991 RI/FS field activities.

Sampling data for the mobile home park wells are presented in Table 10a. This table contains only data from samples collected while the mobile home park wells were being used as a water supply source for the mobile home park residents. Therefore, data from well samples collected after September 1989, when the mobile home park was hooked up to the Sherwood Medical plant's new central water treatment system and use of the mobile home park wells was discontinued, are excluded. Table 10a also includes data from samples collected between February 1988 and September 1989 when water from the mobile home park wells was being treated by a temporary carbon treatment system. Because the water samples were obtained after the water had passed through the treatment system, they should be representative of the quality of the mobile home park's drinking water during that time.

As shown in Table 10a, low-to-moderate levels of various VOCs were found in the mobile home park wells. The principal contaminants of concern were generally the same as those found in other on- and off-site groundwater samples. Chloroform and chlorodibromomethane, which were not found in other well samples, were identified as contaminants of concern in the mobile home park wells. These two contaminants may have been associated with the mobile home park's chlorination system rather than the site's groundwater VOC contamination. No sampling data for metals in the mobile home park wells were found during the development of this public health assessment.

Table 10a. Contaminant Concentrations in Park Mobile Home Court Wells (Main & Backup)

Contaminant	Concentration Range (µg/L)	Date	Reference	Comparison Value
				µg/L	Source
Benzene	ND	(1)	(2)	1	CREG
Carbon tetrachloride	ND - 25	(1)	(2)	0.3	CREG
Chloroethane	ND - 9	(1)	(2)	None
Chloroform	ND - 260	(1)	(2)	6	CREG
Chloromethane	ND - 13	(1)	(2)	3	LTHA
Chlorodibromomethane	ND - 2	(1)	(2)	0.4	CREG
1,2-dibromoethane	ND	(1)	(2)	0.0004	CREG
1,1-dichloroethane	ND - 89	(1)	(2)	None
1,2-dichloroethane	ND - 6.6	(1)	(2)	0.4	CREG
1,1-dichloroethene	ND - 24	(1)	(2)	0.06	CREG
Methylene chloride	ND	(1)	(2)	5	CREG
Tetrachloroethylene	ND - 100	(1)	(2)	0.7	CREG
1,1,2,2-tetrachloroethane	ND	(1)	(2)	0.2	CREG
1,1,1-trichloroethane	ND - 180	(1)	(2)	200	LTHA
1,1,2-trichloroethane	ND - 1	(1)	(2)	0.6	CREG
Trichloroethylene	ND - 12	(1)	(2)	3	CREG
Vinyl chloride	ND - 2	(1)	(2)	0.2	EMEG

¹Sampling dates: 10/87, 11/87, 2/88, 1/89*, 6/89*, & 8/89*; ²References: 1,2,5,6,18
*sample collected after passing through PMHC carbon filter

Other Private Wells

Private residential and commercial wells in the vicinity of the Sherwood Medical plant have been tested for VOCs several times since December 1987. (The wells have not been sampled for metals.) Sampling was most comprehensive during the ESI follow-up activities in January 1989 and during the RI/FS field activities in June, September, and December 1991; additional limited sampling was conducted in December 1994. No VOCs were detected in any of the upgradient residential wells along Sherwood Road. However, as seen in Table 10b, low levels of several VOCs, primarily 1,1-DCA, 1,1,1-TCA, TCE, and PCE, were found in five commercial or industrial wells downgradient of the Sherwood Medical property. Two of the wells are at private businesses northeast of the Sherwood Medical property; the other three are at the Madison County Maintenance Building, the Madison County Weed Control Shop, and the Civil Defense/Emergency Management Building north of the plant property. Note: Sherwood Medical Co. has provided potable drinking water to the two private businesses since 1992 or 1993 and to the three county operations since early 1995; therefore, these five affected wells are no longer used for drinking water purposes.

Table 10b. Contaminant Concentrations in Off-site Private Wells (excluding PMHC wells)

Contaminant	Concentration Range (µg/L)	Date	Reference	Comparison Value
				µg/L	Source
Benzene	ND - 1J	(1)	(2)	1	CREG
Carbon tetrachloride	ND	(1)	(2)	0.3	CREG
Chloroethane	ND	(1)	(2)	None
Chloromethane	ND - 0.56J	(1)	(2)	3	LTHA
1,2-dibromoethane	ND	(1)	(2)	0.0004	CREG
1,1-dichloroethane	ND - 10	(1)	(2)	None
1,2-dichloroethane	ND	(1)	(2)	0.4	CREG
1,1-dichloroethene	ND - 2	(1)	(2)	0.06	CREG
Methylene chloride	ND - 7J	(1)	(2)	5	CREG
Tetrachloroethylene	ND - 8.5J	(1)	(2)	0.7	CREG
1,1,2,2-tetrachloroethane	ND	(1)	(2)	0.2	CREG
1,1,1-trichloroethane	ND - 21	(1)	(2)	200	LTHA
1,1,2-trichloroethane	ND	(1)	(2)	0.6	CREG
Trichloroethylene	ND - 2.9J	(1)	(2)	3	CREG
Vinyl chloride	ND	(1)	(2)	0.2	EMEG

¹Sampling dates: 12/87, 3/88, 4/88, 1/89, 6/91, 9/91, 12/91, & 12/94* (*data from the wells at the three county operations only)
²References: 1,2,4,5,6,18

Groundwater - Public Supplies

No sampling data for public water supply wells were found during the development of this public health assessment. The nearest public wells (city of Norfolk) are more than 2.5 miles from the Park Mobile Home Court and the furthest edge of the site groundwater plume. Therefore, no public wells are likely to be affected by site-related groundwater contamination.

Surface Water

Surface water samples for VOCs were collected from Medelmans Lake, which is just north of the PMHC, in July 1988 during the ESI. No VOCs were detected in the surface water samples.

Sediment

Sediment samples from Medelmans Lake were taken in July 1988 during the ESI. No VOCs were found at detectable levels in the sediment samples.

Ambient Air

No ambient air data for the site area were found during the development of this health assessment. However, as previously discussed, ambient air is not likely to be significantly affected by contaminants from the site.

Soil Gas

Off-site soil gas samples were collected for 1,1,1-TCA and PCE as part of the ESI in July 1988 and as part of the ESI follow-up in January 1989. The off-site soil gas data are shown in Table 11.

Low concentrations of 1,1,1-TCA and PCE were detected in the soil gas samples at the Park Mobile Home Court. Higher levels of PCE and 1,1,1-TCA were found at two locations east of the Sherwood Medical property--near the western edge of the former Ron Kinning facility and near the northern end of the Theisen Brothers property. Soil gas contamination in those two areas is probably from unrelated, isolated sources, especially since buried drums and debris were discovered there and nearby dumping was reported.

Table 11. Contaminant Concentrations in Off-site Soil Gas Samples

Contaminant	Concentration Range (ppb)	Date	Reference	Comparison Value
				ppb	Source
1,1-dichloroethane	N/A	(1)	16, 22	None
1,1-dichloroethene	N/A	(1)	16, 22	0.005	CREG
1,1,1-trichloroethane	ND - 50	(1)	16, 22	700	EMEG
Tetrachloroethylene	ND - 23	(1)	16, 22	0.3	CREG

¹Sampling dates: 7/88 & 1/89

C. Toxics Release Inventory (TRI) Review

ATSDR conducted a search of the EPA Toxics Release Inventory (TRI) records for facilities in the Norfolk, Nebraska, area. The search showed that some area facilities, including Sherwood Medical Company, have released VOCs, such as 1,1,1-TCA, into the air. The TRI contained no record of VOC disposal via land, surface water, or groundwater during the 1987 through 1989 reporting period. The database does not provide sufficient information to estimate any airborne contaminant concentrations. Also, airborne VOC releases are not likely to contribute to groundwater contamination at the site. Therefore, the reported airborne releases are not considered further in this public health assessment.

D. Quality Assurance and Quality Control

The laboratory reports and data sheets reviewed for this public health assessment indicate that, in general, appropriate quality assurance/quality control (QA/QC) procedures were followed during data collection and analysis. RI/FS documents, for example, report that RI/FS field activities adhered to the QA/QC procedures and methods specified in the Field Sampling Plan and Quality Assurance Project Plan (QAPP). In addition, each analytical report was validated by an EPA contractor. Data qualifiers resulting from the validation have been included, where appropriate, in the preceding contaminant tables.

E. Physical and Other Hazards

No significant chemical or physical hazards were observed during the January 1992 site visit. However, at the time of the site visit, access to the plant property was not restricted. Therefore, it was thought that children living near the plant were at some risk of drowning in Sherwood Lake or at risk of injury from broken glass noted near the solid waste disposal bin near the east side of the plant. Since the site visit, the plant property has been posted with "no trespassing" signs. Furthermore, according to the company, no children have ever been observed trespassing on the plant property. For these reasons, it now seems unlikely that children will come into contact with any potential physical hazards at the site.

PATHWAYS ANALYSES

To determine whether nearby populations are exposed to contaminants from the Sherwood Medical Company site, ATSDR has evaluated the environmental and human components leading to human exposure. This pathway analysis considers five elements: 1) a source of contamination; 2) an environmental medium (e.g., air, water, soil) in which contaminants may be present or through which contaminants may be transported; 3) a point of exposure, 4) a route of human exposure, and 5) an exposed population.

ATSDR classifies exposure pathways as completed or potential. For a completed pathway to exist, all five elements must exist and indicate that exposure to a contaminant has occurred in the past, is currently occurring, or will occur in the future. A potential pathway exists when at least one of the five elements is missing, but could exist (e.g., exposure to a contaminant could have occurred in the past, could be currently occurring, or could occur in the future.) A pathway is eliminated when at least one of the five elements is missing and will never exist.

Pathway analyses conducted for the Sherwood Medical Company site indicate that there are two completed pathways associated with groundwater. The completed pathway elements are summarized in Table 12 of this section. The analyses also show several potential pathways involving groundwater, surface water, and soil. The potential pathway elements are summarized in Table 13 of this section.

Estimates of the number of exposed persons for completed exposure pathways and the number of potentially exposed persons for potential exposure pathways are shown in Tables 14 and 15, respectively, of this section.

The discussion that follows the four tables pertains only to pathways considered important or relevant to the site. Exposure pathways that have been eliminated are also discussed.

Table 12. Completed Exposure Pathways

PATHWAY NAME	EXPOSURE PATHWAY ELEMENTS					TIME
	SOURCE	MEDIUM	POINT OF EXPOSURE	ROUTE OF EXPOSURE	EXPOSED POPULATION
Park Mobile Home Court (PMHC) Wells	On-site wastes	Groundwater	Residences (taps)	Ingestion Inhalation Skin contact	PMHC Residents	Past
Industrial/ Commercial Wells	On-site wastes	Groundwater	Nearby (downgradient) industrial and commercial operations with contaminated wells	Ingestion Inhalation Skin contact	Business Owners/ Employees	Past

Table 13. Potential Exposure Pathways

PATHWAY NAME	EXPOSURE PATHWAY ELEMENTS					TIME
	SOURCE	MEDIUM	POINT OF EXPOSURE	ROUTE OF EXPOSURE	EXPOSED POPULATION
Worker- Waste Material	On-site chemicals and wastes	Source chemicals; waste materials and soil	In-plant areas where solvents were used and handled; UST/septic tank area	Skin contact Inhalation Ingestion	Plant employees; site workers	Past
Worker-Drinking Water	On-site wastes	Groundwater	In-plant drinking water	Ingestion	Plant employees	Past
Other Private Wells	On-site wastes	Groundwater	Nearby businesses and/or residences with private wells not currently impacted by site contamination	Ingestion Inhalation Skin contact	Business owners/ employees and residents who use such wells	Future

Table 14. Estimated Population for Completed Exposure Pathways

ESTIMATED EXPOSED POPULATIONS THAT ARE AFFECTED BY A COMPLETED EXPOSURE PATHWAY*
EXPOSED POPULATIONS		COMPLETED EXPOSURE PATHWAY FOR:
Location (on/off site)	Est. Number	1,1-DCA	1,1,1-TCA	TCE	PCE	Other VOCs (e.g., 1,1-DCE)
PMHC residents previously supplied by the two contaminated PMHC wells (off site)	300	PMHC Wells	PMHC Wells	PMHC Wells	PMHC Wells	PMHC Wells
Owners and employees of downgradient commercial & industrial operations with contaminated wells (off site)	Not Known	Industrial/ Commercial Wells	Industrial/ Commercial Wells	Industrial/ Commercial Wells	Industrial/ Commercial Wells	Industrial/ Commercial Wells
* Refer to Table 12 for summary of completed exposure pathways.

Table 15. Estimated Population for Potential Exposure Pathways

ESTIMATED POTENTIALLY EXPOSED POPULATIONS THAT ARE AFFECTED BY A POTENTIAL EXPOSURE PATHWAY*
POTENTIALLY EXPOSED POPULATIONS		POTENTIAL EXPOSURE PATHWAY FOR:
Location (on/off site)	Est. Number	1,1-DCA	1,1,1-TCA	TCE	PCE	Other VOCs (e.g., 1,1-DCE)
Plant employees (on site)	450	Worker- Drinking Water; Worker- Waste Material	Worker- Drinking Water; Worker- Waste Material	Worker- Drinking Water; Worker- Waste Material	Worker-Drinking Water; Worker- Waste Material	Worker-Drinking Water; Worker- Waste Material
Site workers (on site)	Not Known	Worker- Waste Material	Worker- Waste Material	Worker- Waste Material	Worker- Waste Material	Worker- Waste Material
Nearby business owners and employees and residents with private wells not currently affected by site contamination (off site)	Not Known	Other Private Wells	Other Private Wells	Other Private Wells	Other Private Wells	Other Private Wells
* Refer to Table 13 for summary of potential exposure pathways.

A. Completed Exposure Pathways

Park Mobile Home Court (PMHC) Wells Pathway

Previous studies and environmental sampling indicate that waste sources at the Sherwood Medical site, such as the facility UST and septic tank and an undetermined source in the CS/CN area, have contaminated the underlying soils and groundwater with various VOCs. In general, VOCs such as those found at the site are fairly mobile in soil and groundwater, especially in soils of low organic carbon that have low adsorption capacities. Those compounds, therefore, are likely to migrate from on-site source areas into groundwater. Migration of the site contaminants has, in fact, been confirmed by several sampling events that have detected VOCs in both on- and off-site wells, including the two Park Mobile Home Court wells.

Residents of the Park Mobile Home Court were exposed to VOCs in water drawn from the two water supply wells (before being shut down in September 1989) for drinking and other domestic purposes (e.g., bathing, showering). Exposure to VOCs would have occurred primarily via ingestion of contaminated drinking water and via inhalation of contaminants that have volatilized into the air during showering and bathing. Limited exposure to VOCs via dermal contact with contaminated water during showering and bathing was also possible because these compounds can be absorbed through the skin.

Sampling data for metals in the Park Mobile Home Court wells are not available. Unfiltered groundwater samples from site monitoring wells and supply wells contained low levels of metals. However, further groundwater sampling revealed that metals present in the earlier samples were the result of turbidity from the aquifer formation that was introduced into samples when they were collected. More importantly, the later sampling results indicate that site groundwater is not contaminated by metals. Therefore, it is unlikely that the Park Mobile Home Court residents were exposed to significant levels of metals in their drinking water.

It is estimated that up to 300 persons in the Park Mobile Home Court were exposed to groundwater VOCs before use of the mobile home park wells was discontinued. This figure was calculated using the highest reported mobile home park occupancy (117 units, in 1987), and the average residential occupancy rate for Madison County (2.6 persons per residence). As previously indicated, the Sherwood Medical plant has been operating since 1961 and has used chlorinated solvents (primarily 1,1,1-TCA) since 1963. Because the mobile home park was first occupied in late 1966 (5), and water from the mobile home park's wells was not carbon treated until February 1988 (when the EPA temporary treatment system was installed), the maximum period of exposure to site-related contaminants would have been about 21 years. This estimated exposure period is reasonable even when contaminant transport time is considered. For example, using the estimated flow velocity of 800 feet per year for groundwater in the site area (7) and the estimated site-specific retardation factor for PCE of 1.5 (7) results in a contaminant transport velocity of 533 feet per year. At that rate, contaminants released from the Sherwood UST/septic tank area would reach the main mobile home park well--about 1450 feet away--in approximately 3 years. Therefore, contaminants released on site as early as 1963 could have migrated to the mobile home park wells by 1966. This means that residents of the mobile home park could have been exposed to site-related VOCs from late 1966 to early 1989, or for a maximum period of about 21 years. It should be noted, however, that only those residents who lived in the mobile home park continuously from 1966 through 1989 would have been exposed to site-related contaminants for the estimated maximum 21-year period.

Industrial/Commercial Wells Pathway

Two private wells at commercial operations northeast (approximately 2300 to 2600 feet) of the Sherwood Medical plant and east of the Park Mobile Home Court are used primarily to wash down industrial equipment. These wells were also believed to have been used in the past as a source of drinking water. The two wells are downgradient of the plant and, based on previous soil gas investigations, are believed to be within the plume of groundwater contamination. Moreover, past groundwater sampling indicates that the two wells are contaminated with low levels of VOCs. The compounds detected include 1,1-DCA, 1,1-DCE, 1,1,1-TCA, PCE, and TCE. Owners and workers at the commercial operations who drank water from these wells were subject to exposure in the past to those contaminants. It is likely that exposure to contaminants via dermal contact and inhalation was minimal when compared with exposure via ingestion.

Sampling data for metals are not available for these two wells. However, as previously discussed, sampling data from groundwater monitoring wells indicate that site groundwater is not contaminated with metals. Therefore, persons who drank water from these two wells were not likely to be significantly exposed to metals.

The number of persons exposed to VOCs in groundwater used at the two commercial operations is not known. However, because the operations are believed to be family owned and operated, the number is likely to be relatively small.

It is not known when the two businesses began operating at their current locations; therefore, the period of exposure cannot be calculated. By assuming that the operations have been in existence since the mobile home park was established, and by using the contaminant transport rate and distance discussed previously, it can be estimated that exposure to contaminants could have begun as early as 1968. Exposures to VOCs from the commercial wells likely ceased in 1992 or 1993 when Sherwood Medical began supplying these businesses with potable drinking water. Therefore, the maximum exposure period would not have exceeded 24 or 25 years. The results of past groundwater sampling suggest that the actual exposure period may have been much shorter.

As previously discussed, although exposure to low levels of VOCs in the two industrial wells has probably occurred in the past, exposure is no longer believed to be occurring because Sherwood Medical Company supplies the two businesses with bottled drinking water (4,9,11).

Three additional wells, at the Madison County Maintenance Building, the Madison County Weed Control Shop, and the Civil Defense/Emergency Management Building, have also been shown to contain low levels of VOCs. Contaminants detected in those wells included 1,1-DCA, PCE, and TCE. The wells are adjacent to the Park Mobile Home Court, approximately 1,500 to 1,700 feet north-northeast of the Sherwood Medical UST/septic tank area. The wells are believed to be used primarily for equipment washing and maintenance. These wells were also believed to have been used in the past for drinking water supply. Therefore, exposure to well contaminants would be mainly via ingestion (i.e., through drinking water.) Exposure via inhalation and dermal contact is assumed to be minimal. Although sampling data for metals are not available, significant exposure to metals in groundwater from these two wells is unlikely.

The number of persons exposed to contaminants in the three wells is not known, but would include any county workers or other personnel who used the wells for drinking water. The length of the exposure period is also unknown but would not have exceeded 27 or 28 years because groundwater contaminants could not have reached the wells before 1966 and the wells have not been used for drinking water since early 1995. Past groundwater sampling data suggest that the actual exposure period may have been much shorter. Human exposure to contaminants from the wells is no longer occurring because occupants of the three buildings are supplied with bottled drinking water.

B. Potential Exposure Pathways

Worker-Waste Material Pathway

Sherwood Medical Company employees who used or handled chlorinated solvents, primarily 1,1,1-TCA, on the job may have been exposed in the past to VOCs through skin contact, inhalation, and possibly incidental ingestion. However, the extent of potential exposure and contaminant uptake cannot be estimated using available information. The potential for Sherwood Medical employees to be exposed to VOCs on the job was eliminated in 1992 when the use of all chlorinated solvents by the plant was discontinued.

Contractor workers who participated in the September 1989 and November 1990 activities involving removal of waste materials from the plant's septic tank and UST could have been exposed to VOCs via skin contact, inhalation, and possibly incidental ingestion of waste materials and contaminated soils. Available information indicates that appropriate personal protective equipment was used during the removal activities. Therefore, any exposure to contaminants in the waste material was probably insignificant.

Worker-Drinking Water Pathway

Significant levels of several VOCs, including 1,1-DCA, 1,1-DCE, PCE, 1,1,1-TCA, have been found in the Sherwood Medical plant's water supply wells #4 and #5. Before September 1989, these wells were used to supply the plant's water needs including potable drinking water. Therefore, employees who worked at the Sherwood Medical plant in the past could have been exposed to VOCs in the plant's drinking water. Exposure to VOCs from the drinking water supply via inhalation and skin contact is assumed to be insignificant compared with exposure via ingestion.

Although the levels of VOCs actually ingested by plant employees are unknown, the levels were probably much lower than the contaminant levels found in the water supply wells. According to company officials, the plant's drinking water supply was carbon treated, either at the wellhead (before 1979), or at the point of use (i.e., drinking fountains) (from 1979 to September 1989) even before the plant's current carbon treatment units were installed in September 1989. Therefore, the company believes that VOCs were never present at significant levels in the plant's drinking water. To support its position, the company submitted the analytical results of a sample collected from the plant's water distribution system in December 1987 showing virtually no detectable levels of VOCs. ATSDR believes that one sample over a period of more than 25 years is insufficient to adequately characterize the plant's drinking water quality; therefore, it is possible that plant employees were exposed to VOCs to some extent from the plant's drinking water before September 1989.

The number of persons potentially exposed in the past to contaminants via ingestion of plant drinking water cannot be accurately determined; however, a maximum estimate based on past employment levels at the plant would be 450 (5). The exact period of potential exposure is also not known, but probably would not have exceeded 25 years. That figure was estimated using the following assumptions:

• contamination of groundwater in the septic tank area began no earlier than 1963;

• contaminants reached the nearest of the supply wells approximately one year later (using a maximum migration rate of 533 feet per year and a distance of 675 feet to the nearest supply well);

• exposures stopped in September 1989 when the plant's new water treatment system was installed.

Since September 1989, all water pumped from the plant's supply wells has been treated by a large, centralized carbon treatment system to remove VOCs before distribution within the plant; therefore, plant employees are not likely to be exposed to VOCs from the plant's drinking water supply now or in the future.

Other Private Wells Pathway

A number of private wells (residential and commercial) are near the Sherwood Medical plant. These wells include the private residential wells along Sherwood Road just south of the plant, the two Park Mobile Home Court wells north/northeast of the plant, and several commercial wells north, northeast, and east of the plant. Among these, only the PMHC wells and 5 commercial wells north and northeast of the site have been shown to be contaminated with VOCs (see previous discussion under Completed Exposure Pathways--Industrial/Commercial Wells heading). However, it is possible that some of the remaining private wells close to the site, especially those downgradient (i.e., northeast) of the Sherwood Medical plant, could become contaminated by groundwater VOCs migrating from the site. Users of such wells could be exposed, via ingestion, inhalation, skin contact or all three, in the future to VOCs in their well water. Future levels of groundwater contaminants and the number of persons who might be exposed are unknown. It should be noted that future groundwater remediation actions could minimize or eliminate such potential exposures.

C. Eliminated Exposure Pathways

Surface Water Pathway

Trespassers, especially children from the Park Mobile Home Court and from homes along Sherwood Road, who wade or swim in Sherwood Lake could theoretically be exposed to contaminants in the lake. Exposures could occur through skin contact and, to a lesser extent, through incidental ingestion. However, the most recent sampling data (from the 1991 RI/FS) showed no VOCs in the lake surface water or sediment and only one low-level VOC in the plant's wastewater discharges to the lake. Furthermore, company officials report that the plant property has been posted and no trespassers have ever been found in or around Sherwood Lake. Because 1) VOCs are not likely to be present in the lake at levels of concern, 2) any VOCs discharged to the lake will rapidly volatilize to the atmosphere, and 3) children are not likely to come in contact with the lake, exposures to VOCs in Sherwood Lake are not expected. Therefore, this potential exposure pathway is being eliminated from further discussion in this public health assessment.

Soil Gas Pathway

Groundwater at the Sherwood Medical plant and Park Mobile Home Court has been shown to be contaminated with various volatile compounds. In the areas where groundwater is contaminated, volatile compounds are likely to be released from the water table into the overlying soil. In fact, previous site investigations have confirmed the presence of volatile compounds in soil gas samples collected above contaminated groundwater areas, such as the UST area and the CS/CN area. The volatile soil gas contaminants can migrate upward to ground level and enter buildings overlying the soil through crawl spaces, plumbing holes, other floor holes, and foundation cracks. Volatile contaminants entering the buildings can accumulate in confined spaces, such as basements, thereby subjecting the building occupants to inhalation exposures.

At the Sherwood Medical site, human exposure to VOCs in indoor air is not expected for the following reasons. First, previous investigations did not indicate that significant levels of VOCs were migrating in soil gas other than in the suspected source areas. Second, only one home with a basement is close to or downgradient of the site. This residence, which is north of the site, is not underlain by contaminated groundwater and is several hundred feet from the nearest location where soil gas contaminants were detected. Third, mobile homes in the Park Mobile Home Court located over areas of contaminated groundwater do not have foundations and do not sit directly on the ground surface. Therefore, soil gas VOCs migrating to the ground surface are not likely to accumulate in any of the mobile homes. For these reasons, significant exposures to VOCs from site soil gas are unlikely and will not be discussed further in this public health assessment.

Food Chain Pathways

Agricultural land uses have not been identified in the immediate vicinity of the Sherwood Medical site. Therefore, exposures involving site-related contaminants in commercially grown food crops are unlikely.

Exposure to site-related contaminants from eating home-grown vegetables is not a concern because the types of contaminants found in site soils and groundwater (volatile organic compounds) are not significantly taken up by plants. Furthermore, residents most likely to have vegetable gardens are upgradient of the Sherwood Medical plant (along Sherwood Road) and are not affected by groundwater contamination.

Exposure to site-related contaminants from eating domestic livestock or wild game that may have consumed VOC-contaminated water or plants in contact with VOC-contaminated water is unlikely because animals do not accumulate VOCs to significant levels.

Finally, the potential for exposure to VOCs via consumption of fish is remote because 1) VOCs were found only at low levels in Sherwood Lake, VOCs do not accumulate significantly in fish, and consumption of significant quantities of fish from the lake is unlikely.

For these reasons, potential exposures via food chain pathways will not be considered further in this public health assessment.

PUBLIC HEALTH IMPLICATIONS

In this section, we will evaluate the potential health effects in persons exposed to the contaminants of concern for which completed and potential pathways exist, discuss health outcome data, and address the specific community health concerns.

A. Toxicological Evaluation

To evaluate health effects, we have estimated human exposure doses of the groundwater contaminants and compared these with health effects information in the ATSDR toxicological profiles. This discussion is limited to potential health effects that can occur at exposure levels similar to those found at this site or a discussion of effects at the lowest doses that can produce an effect. ATSDR has developed Minimal Risk Levels (MRLs) to evaluate non-cancer health effects. An MRL is an estimate of daily human exposure, in milligrams per kilogram of body weight per day (mg/kg/day), to a contaminant below which non-cancer, adverse health effects are unlikely to occur. MRLs are developed for the oral and inhalation routes of exposure, and for the length of exposure, such as acute (14 days or less), intermediate (15 to 365 days), and chronic (greater than 365 days). An EPA Reference Dose (RfD) is an estimate of a daily exposure (mg/kg/day) of the general public to a contaminant that is likely to be without an appreciable risk of deleterious effects during a lifetime. Cancer effects are evaluated by estimating the risk of developing cancer over a lifetime. The EPA has estimated cancer slope factors (CSF) for certain chemicals. These CSFs are estimates of the potency of a chemical to cause cancer and are used in conjunction with the exposure dose to estimate the cancer risk.

The toxicological evaluation of exposure to the contaminants discussed in this section assumes that residents used the groundwater for drinking and cooking (ingestion) and other household uses (bathing and showering, which would involve inhalation and dermal contact) daily for 21 years. The exposure dose assessment assumes that adults drink 2 liters of tap water per day and children drink 1 liter of tap water per day. For noncarcinogens, ingestion assumptions for children were evaluated because children receive a larger dose as a result of their larger ingestion-to-body weight ratio than adults. When evaluating the carcinogenic potential, it is assumed that an adult drank the maximum contaminant level detected for 21 years. Inhalation of volatilized VOCs during showering and other activities is assumed to be equivalent to ingestion exposure.

PMHC Wells

Carbon Tetrachloride

Only the residents of PMHC were known to be exposed to carbon tetrachloride in groundwater. Levels as high as 25 ppb have been detected. Levels such as this exceed EPA's chronic oral RfD (0.0007 mg/kg/day) when children's exposure is estimated. Estimated exposures of adults would not exceed the RfD. Animal studies and reports of human poisoning have shown that the liver is the primary target organ; the kidneys also show sensitivity to carbon tetrachloride. No adverse noncancer health effects have been reported at levels as low as those seen in the groundwater at this site. The lowest-observed-adverse-effect-levels (LOAEL) in animal studies (10 mg/kg/day) resulted in liver serum enzyme and tissue changes (23).

Both the International Agency for Research on Cancer (IARC) and EPA have concluded there is sufficient evidence that carbon tetrachloride is carcinogenic in experimental animals. Animal studies have shown it to cause liver tumors. Drinking water contaminated with 25 ppb carbon tetrachloride for 21 years would result in no apparent increased risk of cancer.

Assuming an equivalent exposure via inhalation of volatilized carbon tetrachloride, the combined ingestion and inhalation dose would exceed the RfD for an adult. However, this dose would not be expected to result in any adverse noncancer health effects. Insufficient toxicokinetic information precludes a dose estimation from dermal exposure.

Chloroform

Chloroform was detected in the PMHC wells at levels up to 260 ppb but not in other off-site wells or the plant supply wells. Chloroform is a byproduct of water chlorination. The maximum level of 260 ppb exceeds ATSDR's chronic oral MRL (0.01 mg/kg/day) when children's exposure is estimated . Estimated adult exposure doses would not exceed the MRL. The liver is the primary target of chloroform. The lowest oral dose administered to animals in chronic studies was 15 mg/kg/day, which increased liver enzymes. Biochemical tests indicate that liver function in humans was affected by use of mouthwash for 5 years providing 2.46 mg/kg/day chloroform. The kidney is also a target of chloroform, although less sensitive (24). The levels of chloroform found in the PMHC wells are well below the levels that would result in adverse noncancer health effects.

Chloroform is classified by EPA as a probable human carcinogen and by IARC as a possible human carcinogen. Chloroform has not been identified as the sole or primary cause of increased cancer risks associated with chlorinated water, but it is one of several volatile organic contaminants found in drinking water that are considered to have carcinogenic potential. Chloroform has been shown to cause kidney and liver tumors in animal studies. Drinking water contaminated with 260 ppb of chloroform for 21 years would result in no apparent increased risk of cancer.

Assuming an equivalent exposure via inhalation of volatilized chloroform, the combined ingestion and inhalation dose would be approximately equal to the chronic MRL for an adult. Insufficient toxicokinetic information precludes a dose estimation from dermal exposure.

1,1-Dichloroethene (DCE)

DCE was detected in the PMHC wells at levels up to 24 ppb. This maximum level does not exceed ATSDR's chronic oral MRL (0.009 mg/kg/day) for either children or adults. The liver is the primary target organ of this chemical. The MRL is based on the lowest observed adverse effect level of 9 mg/kg/day, corresponding to a concentration of 50,000 ppb in water. The effect was a minimal amount of liver cellular swelling and an increase in cellular fat. At higher doses, an increase in serum enzymes, indicating liver dysfunction, may be seen. There is some evidence in animals that poor nutritional status increases DCE liver toxicity (25). Exposure to DCE at levels found in the PMHC wells would not be expected to result in adverse noncancer health effects.

DCE is classified by EPA as a possible human carcinogen. This classification applies to chemicals for which there is limited evidence of carcinogenicity in animals. Drinking water contaminated with 24 ppb of DCE for 21 years could result in a low increased risk of cancer.

DCE volatilizes into the air during normal household use of the well water. An MRL of 0.02 ppm has been developed for intermediate-duration inhalation exposure (15-365 days) to DCE. This MRL is based on a no-observed-adverse-effect-level of 5 ppm for hepatic effects in guinea pigs continuously exposed to DCE. The limited information on human exposure to DCE indicates that inhalation of volatilized DCE is probably toxic to the human liver and kidney, although effective exposure doses are unknown.

EPA has derived a cancer potency factor for inhalation of DCE based on an animal study reporting an increase in total mammary tumors. The lowest dose producing tumors (cancer effect level) was 10 ppm. The study had a number of limitations; therefore, the evidence for carcinogenicity from inhalation exposure is considered to be inconclusive (25). Because air sampling was not conducted, health effects from inhalation of DCE cannot be evaluated.

Assuming an equivalent exposure via inhalation of volatilized DCE, the combined ingestion and inhalation dose would not change the results. Insufficient toxicokinetic information precludes a dose estimation from dermal exposure.

Tetrachloroethylene (PCE)

PCE was detected in the PMHC wells at levels up to 100 ppb. Levels such as this are approximately equal to the chronic oral RfD (0.01 mg/kg/day) when children's exposure is estimated. Adult exposure would not exceed the RfD. In experimental animals, the liver is the primary target organ of PCE via ingestion. The lowest observed adverse effect level of 100 mg/kg/day has resulted in increased liver weight in mice. Higher levels will begin to cause liver necrosis and an increase in certain serum enzymes. The kidney is a target organ for PCE but is less sensitive than the liver (26). No adverse noncancer health effects would be expected from drinking water containing 100 ppb of PCE.

IARC has classified PCE as reasonably anticipated to be a carcinogen. The EPA is considering classifying PCE as either a probable human carcinogen or possible human carcinogen. Drinking water contaminated with 100 ppb of PCE for 21 years would result in no apparent increased cancer risk. The National Cancer Institute conducted a carcinogenicity bioassay of rats and mice (26). No increases in tumor incidence were observed for the treated rats. Statistically significant increases in liver tumors occurred in the mice; however, the study had a number of limitations. These limitations included a small control group, numerous dose adjustments during the study, early mortality, and pneumonia.

Assuming an equivalent exposure via inhalation of volatilized PCE, the combined ingestion and inhalation dose would exceed the oral RfD for a child's exposure but not for an adult's exposure. Neither the adult's nor the child's combined exposure dose would expected to result in adverse noncancer health effects. Dermal uptake cannot be estimated from the available information.

Trichloroethylene (TCE)

TCE was detected in the PMHC wells at levels up to 12 ppb. This maximum level does not exceed ATSDR's intermediate (15-365 days) oral MRL of 0.002 mg/kg/day for estimated exposures of children or adults. For this site, an intermediate MRL is not as appropriate as a chronic MRL; however, ATSDR has not developed one. In addition, no other long-term health guidelines are available. As a regulatory standard, EPA has established a MCL of 5 ppb and a MCLG of 0; however, these values are not applicable for the evaluation of health effects from TCE exposure at this site.

The intermediate oral MRL is based on a study in which heart abnormalities were noted in the developing fetuses of pregnant rats exposed to TCE in drinking water before and during pregnancy. These findings were supported by a similar study with chicken embryos that found an association between TCE exposure and heart abnormalities, and by a human epidemiological study that found increased incidence of congenital heart defects in children born to mothers who were exposed to TCE in drinking water.

TCE exposure may also affect the nervous system, liver, and kidney based on effects reported in humans or animals or both (27). No adverse noncancer health effects would be expected from drinking water contaminated with TCE at the levels found in the PMHC wells.

The link between oral exposure to TCE and the incidence of cancer in humans is controversial. Support for an association comes from a report of increased childhood leukemia among a population in Woburn, Massachusetts. That population drank TCE-contaminated well water. This association was supported by a second study of New Jersey communities where an increase in the standardized mortality ratio for leukemia was found in women exposed to TCE-contaminated drinking water. However, these studies had serous shortcomings. A number of researchers have questioned the associations drawn from these studies between the incidence of leukemia and other cancers and oral exposure to TCE.

IARC lists TCE as not classifiable for cancer. EPA assigned a classification of B2 (probable human carcinogen) to TCE in 1987 and derived a cancer potency estimate for TCE based on incidence data for lung tumors in female Swiss mice and tumor incidence data from other studies. In 1988, the Scientific Advisory Board for EPA indicated that TCE would be more accurately classified between C and B2 (possible-probable human carcinogen). At present, the weight-of-evidence classification for TCE is "under review" by EPA. For the Sherwood Medical site, ATSDR evaluated the cancer risk associated with ingestion of TCE-contaminated water by using the 1987 EPA cancer potency factor. This evaluation indicates that drinking water containing 12 ppb TCE for 21 years from the PMHC wells would pose no increased cancer risk.

Assuming an equivalent exposure via inhalation of volatilized TCE, the combined ingestion and inhalation dose would not change the results. Dermal uptake cannot be estimated from the available information.

Vinyl Chloride

Vinyl chloride was detected in the PMHC wells at levels up to 2 ppb. This maximum level exceeds ATSDR's chronic oral MRL (0.00002 mg/kg/day) for children and adults. The liver is the primary target organ of this chemical. The MRL is based on the lowest-observed-adverse-effect-level of 0.018 mg/kg/day, which caused an increase in certain types of cellular nuclei in the liver. At slightly higher doses, animals have been shown to experience increased blood coagulation and an increase in skin collagen (28).

Vinyl chloride is classified as a human carcinogen by EPA and IARC. Long-term cancer studies have shown vinyl chloride to cause liver tumors in experimental rats and mice. Drinking water containing vinyl chloride at 2 ppb would cause no apparent increased cancer risk.

Given an equivalent exposure dose via inhalation of volatilized vinyl chloride, the combined ingestion and inhalation dose would be doubled. Similar to ingestion, the liver is the primary target organ for inhalation of volatilized vinyl chloride. The adverse effect first noted from inhalation exposure is increased liver weight. A combined ingestion and inhalation dose for a child would be almost 50 times less than the lowest dose which produced an observed adverse effect in rats, and, for adults, more than 150 times less than the lowest observed adverse effects level. Therefore, a combined ingestion and inhalation exposure to water contaminated with 2 ppb of vinyl chloride would not be expected to result in adverse noncancer health effects. Dermal uptake cannot be estimated from the available information.

1,1,1-Trichloroethane

Toxicological information on 1,1,1-trichloroethane is limited but it is clear from the existing studies that high levels are required to produce adverse health effects. Slight to moderate reversible skin irritation has been seen in animal studies (29). The levels in groundwater at the PMHC (180 ppb) appear to be far below the levels producing any adverse health effects.

Chloroethane

Chloroethane was detected in the PMHC wells at levels up to 9 ppb. Toxicological information on chloroethane is very limited and the existing information is concerned principally with inhalation and, secondarily, dermal exposure. Existing information indicates that high levels are required to produce adverse health effects. Formerly, chloroethane was used as a medical anesthetic (30). The levels detected in the groundwater at the PMHC are far below those that could cause adverse health effects.

Chloromethane

Chloromethane was detected in the PMHC wells at levels up to 13 ppb. No information is available on the health effects from oral exposure to chloromethane. Animal studies of long-term inhalation exposure to chloromethane have shown effects to the liver, kidney, nervous system, and reproductive system (31). Residential exposure to volatilized chloromethane would not be at levels of health concern.

1,1-Dichloroethane

Toxicological information on 1,1-dichloroethane is very limited. Knowledge of health effects via ingestion is limited to animal studies at high exposures. The available cancer studies with experimental animals have been inconclusive because of study limitations and errors. A 1977 NCI study suggested that 1,1-dichloroethane can cause tumors in blood vessels, mammary glands, and the uterus of rats and mice. Information on health effects via inhalation is available only for very high levels of exposure (32). The maximum level of 1,1-dichloroethane detected in the PMHC wells was 89 ppb. Exposure at this level would not be expected to result in adverse health effects.

1,2-Dichloroethane

1,2-dichloroethane was detected in the PMHC wells at levels up to 6.6 ppb. Most of the available toxicological information on this chemical describes effects of acute, high-dose exposures. Chronic, low-dose animal studies have involved principally liver and kidney effects. Liver tumors have developed in rats after ingestion of low levels of 1,2-dichloroethane (33). Combining inhalation and ingestion doses would result in an exposure far less than the ATSDR intermediate oral MRL of 0.2 mg/kg/day; therefore, no adverse noncancer health effects would be expected.

EPA has classified 1,2-dichloroethane as a probable human carcinogen for both oral and inhalation routes of exposure. A combined inhalation and ingestion exposure to water contaminated with 6.6 ppb of 1,2-dichloroethane for 21 years would pose no apparent increased cancer risk.

Chemical Mixtures

Insufficient toxicological information is available to evaluate the health effects from exposure to this site's mixture of groundwater contaminants. The effect of two or more chemicals given simultaneously could produce a response that may be simply additive of the individual responses or a response that may be greater or less than that expected by addition of the individual responses. Residents of PMHC were exposed to a mixture of the chemicals previously discussed; however, that exposure was not likely to have been at maximum levels at any one time. The contaminants were chlorinated solvents with similar target organs for chronic, low-level exposure. The liver and kidneys are the susceptible to most of these chemicals. Although the health effects of exposure to a mixture of these chemicals are unknown, the contaminants are similar and do affect the same organs. Therefore, it is possible that the adverse effects from the combined exposure would be greater than effects from the individual constituents.

In summary, long-term (i.e., 21-year) exposure to VOCs in the PMHC wells may have represented a public health hazard for noncancer health effects and may have posed a low increased risk of cancer for PMHC residents.

As stated earlier, metals were not analyzed in the PMHC wells. Metals were detected in the off-site monitoring wells and in the on-site supply wells at levels generally similar to the off-site background monitoring well. The levels of these metals in groundwater would not be expected to be of public health concern.

Other Private Wells

The data evaluated from the five downgradient commercial wells contained several chlorinated solvents that were not at levels of public health concern. Sampling for metals was not conducted, but if the metal levels are similar to the levels in on-site and off-site monitoring wells, health effects are unlikely.

Occupational Exposure

On-Site Supply Wells

Although VOCs, including DCE and PCE, were detected in the plant's water supply wells were at levels of public health concern, the contaminant levels actually ingested by plant employees from the plant's drinking water system are not known. Because the plant's drinking water was historically carbon treated to some extent, the VOC levels in the drinking water were probably much lower than the levels in the supply wells themselves. Therefore, it is unlikely that plant employees would suffered any health effects from ingesting VOCs in the plant's drinking water.

Process Exposure

Some plant employees were exposed to chlorinated solvents, primarily 1,1,1-trichloroethane (TCA), as part of their on-the-job activities. The exposures were principally via inhalation and dermal contact. Although actual exposure data are not available, an employee's report of drunken-like reactions after inhalation of solvent vapors is consistent with the known neurological effects of TCA. These effects include dizziness, lightheadedness, and loss of coordination from inhalation exposure at moderate to high TCA levels (>500 ppm). At somewhat lower levels of exposure (>175 ppm), impaired performance of psychophysiological function tests has been observed. The effects tend to subside rapidly after exposure has ceased. In addition to neurological effects, acute exposure to TCA has also been associated with hypotension, cardiac arrhythmia, diarrhea and vomiting, mild hepatic effects, and dermal and ocular irritation.

Studies involving chronic (long-term) human exposure to TCA are limited and do not provide definitive conclusions about the health effects of chronic TCA exposure. A recent report suggests that impaired memory and deficits in balance were persistent effects in a group of workers after chronic exposure to moderate to high levels of TCA. However, the validity of these new findings has not yet been determined.

B. Health Outcome Data Evaluation

Health outcome data refer to information on the health status of a population. This information may include pre-existing health conditions and morbidity (disease) and mortality (death) rates. Health outcome data were not evaluated in this assessment for the following reasons. The health outcome databases are not appropriate for the study of a population the size of the PMHC. The smallest population unit for which health outcome data have been summarized is Madison County, which is too large an area in comparison to the PMHC. For example, cancer rates are not elevated in Madison County but this may not be reflective of PMHC (34). The rates in PMHC may be diluted when combined with the rest of the county. In addition, only a small number of residents have resided at the PMHC for 21 years. This number of residents would not be statistically large enough to show effects from exposures at these contamination levels. Finally, many of the exposed residents have likely moved away and may not be included in the Madison County health data.

C. Community Health Concerns Evaluation

The community health concerns gathered as part of this public health assessment involve worker exposure to chemicals used on the job. As is often the case, workers are exposed to higher levels of chemicals in the normal course of their work than are surrounding residents. Known health effects associated with worker exposure to site chemicals are discussed in the Occupational Exposure, Toxicologic Evaluation subsection of the Public Health Implications section of this public health assessment.

The Occupational Safety and Health Administration (OSHA) and its state counterparts are the government agencies responsible for safeguarding workers' health and safety. ATSDR recognizes the valid concerns of workers at the Sherwood Medical plant and has referred them to the appropriate agencies.

Next Section          Table of Contents

Agency for Toxic Substances and Disease Registry, 1825 Century Blvd, Atlanta, GA 30345
Contact CDC: 800-232-4636 / TTY: 888-232-6348 

Department of Health and Human Services