PETITIONED PUBLIC HEALTH ASSESSMENT
SOUTHERN MARYLAND WOOD TREATING
NATIONAL PRIORITIES LIST (NPL) SITE
HOLLYWOOD, ST. MARY'S COUNTY, MARYLAND
ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS
The tables in Appendix 2 list contaminants in each medium. Those contaminants are evaluated in subsequent sections of the public health assessment update to determine if exposure to them has public health significance. ATSDR selects and discusses contaminants based upon several factors. They include concentrations on and off site, the quality of the field and laboratory data, sample design, comparison of on- and off-site concentrations to background concentrations (if available), comparison of on- and off-site concentrations to public health assessment comparison values for noncarcinogenic and carcinogenic endpoints, and community health concerns.
The listing of a contaminant in the tables does not mean that it will cause adverse health effects if exposure occurs at the specified concentrations. Contaminants included in the tables are further evaluated in this public health assessment update. The potential for adverse health effects resulting from exposure to contaminants of health concern is discussed in the Public Health Implications section.
Comparison values for ATSDR public health assessments are contaminant concentrations in specific media that are used to select contaminants for further evaluation. ATSDR and other agencies developed those values to provide guidelines for estimating the media concentrations of a contaminant that are unlikely to cause adverse health effects, given a standard daily ingestion rate and standard body weight. See Appendix 3 for a description of the comparison values used in this public health assessment update.
EPA completed a more extensive investigation of the contamination in all media at the SMWT site since the original ATSDR public health assessment was prepared. Figure 7 shows the location of the monitoring wells and soil samples. The public health assessment presents the maximum concentrations of the contaminants of health concern found at the site. No distinction is made between RI/FS data previously reviewed and the more recently collected remediation predesign data. The quality of both data sets is comparable (see the Quality Assurance and Quality Control section for further discussion); therefore, combining the values does not present a quality assurance problem.
Analytical data obtained from EPA show the presence of polynuclear aromatic hydrocarbons (PAHs), the main constituents of creosote; phenolic compounds, a class of chemicals associated with pentachlorophenol (PCP) wood-treatment processes; and volatile organic compounds (VOCs), most likely from fuel oil or carrier oils used to dilute the creosote and PCP for use in wood treatment. PAHs found at the SMWT site were grouped as carcinogenic and noncarcinogenic; the health effects of the chemicals within the respective groups are similar. The concentrations of specific PAHs in each group are totalled for each medium, on and off site, and appear in the tables (see Appendix 2)(1,10).
SOIL
The highest concentrations of contaminants at the SMWT site are in the soils within the piling containment wall (the process area, also called the containment area) and in the land treatment area. In only a few samples were metals detected at concentrations greater than those normally found in Maryland soils (1).
In one small area on the northeastern side of the SMWT property, EPA's sampling indicated slight soil contamination outside the fence. That area is near a former railroad which may be a source of the low-level contamination. The contamination is limited to surface soils, which are covered by grasses, locust trees, and briars. The area is not very accessible, and EPA plans to remove the soil during the remediation. Table 4 lists the contaminants found in the area, and Figure 8 shows the areas where EPA plans to remediate the surface soils throughout the SMWT site.
Many contaminants are more concentrated in subsurface soils (greater than 2 feet deep) than in surface soils (0-2 feet deep). It is not unusual to find higher contaminant concentrations in subsurface soils at inactive sites, where sources of continued contamination have been eliminated because the more volatile organic compounds evaporate and because many contaminants migrate downward over time. Table 1 (all tables are in Appendix 2) shows the maximum concentrations of specific contaminants found in soils on site.
SEDIMENT/SURFACE WATER
The only surface water on site is a freshwater pond in the southwestern corner of the site. The surface water contains low concentrations of a few contaminants. See Table 1 for the maximum concentrations of contaminants found in on-site sediments. Table 2 shows the maximum concentrations of contaminants in on-site surface water.
GROUNDWATER
PAHs, VOCs, and PCP-related phenolic compounds are found only in the shallow water table aquifer under the SMWT site. There are two organic layers in the shallow aquifer, one floating on top of the water table and one settled at the bottom. EPA installed a piling wall around the process area that contains most of the contaminated shallow groundwater. There is some shallow groundwater contamination outside the piling wall (on the south side) in the vicinity of monitoring well 12 (MW12)(see Figure 7). Table 2 lists the maximum concentrations of the contaminants found in the groundwater on site (1).
According to data reviewed, no on-site analyses of water from the Nanjemoy or Aquia aquifers had been conducted. EPA tried to sample the on-site production well, but the well was obstructed and samples could not be obtained. Water samples from four monitoring wells in the Upper Chesapeake aquifer do not have detectable contamination.
AIR
Air samples were taken near workers and at site boundaries during an 11-day period when an EPA contractor was installing monitoring wells and collecting samples on site. All but three of the 79 samples were taken at four air monitoring stations at the fence line near the pond, near the processing area, at the main entrance, and near the tanks on the east side of the site. Those monitoring stations were designed to measure the concentrations of particulates and coal tar pitch volatiles (CTPVs), which include PAHs, in the ambient air at the perimeter of the site. The other samples were obtained from monitors in the drilling zone while employees were drilling the wells. Only three samples had detectable CTPVs (0.17, 0.13, and 0.068 milligrams per cubic meter (mg/m3); all are within the permissible exposure limit (PEL) of 0.2 mg/m3 set by the Occupational Safety and Health Administration (OSHA) (11). That PEL applies to workers only. ATSDR is unable to evaluate nearby resident's past exposures to air contaminants due to limitations of the data. However, ATSDR will review air emissions information associated with site remediation design and implementation. For more detail, see ATSDR's Plan of Action to Evaluate the Proposed Remedial Alternative for the Southern Maryland Wood Treating Site. Particulate concentrations were extremely low, ranging from a detection limit of 0.0099 mg/m3 to 0.577 mg/m3. The American Conference of Governmental Industrial Hygienists (ACGIH) standard for particulates is 10 mg/m3 (12). The EPA particulate standards for ambient air are 0.150 mg/m3 (24-hour average), and 0.050 mg/m3 (annual median) for particulates smaller than 10 microns in diameter. Because EPA samples were collected to determine compliance with the OSHA standards during remedial activities, the particulate analyses were for total nuisance particulates. Therefore, the particulate analytical results cannot be compared to the ambient air standard, which is set at levels to protect the general population.
WASTES
There are 13 above-ground tanks, one underground fuel tank, a propane tank, a boiler treatment-water makeup tank, and two retorts on site. Three tanks are empty; one contains water from RI/FS activities, and two contain 26 gallons or less of liquid. None of the tanks sampled contained 2,3,7,8-tetrachloro-di-benzo-p-dioxin (2,3,7,8-TCDD). However, approximately 11,960 gallons of wastes contain other dioxin isomers. There are approximately 2,140 gallons of wastes from the original process plant in tanks that do not contain any dioxin isomers. Table 3 lists the maximum concentrations of the contaminants found in the liquids and sediments in the tanks on site (1).
The tanks seen during the site visit were constructed of single-wall steel with a coating of asphalt. The materials used at the facility could have damaged that type of coating during spills and overfills while the facility was in operation. The tanks were not equipped with spill and overfill protection. The asphalt coating, even if in good condition, offers poor protection from corrosion, and does not meet current standards for corrosion protection. Also, the high soil-moisture content and high groundwater level at the site could speed up the corrosion process.
In addition to the possibility of a release as a result of corrosion, there is a potential for tank puncture as a result of hunting in the area. During the site visit, ATSDR staff observed three deer on site, and local sources said that hunting is common in the area. A stray bullet from a rifle could pierce the wall of the tank and cause a sudden release into the environment. Because there are no alarms or secondary containment systems, the liquid contents could be completely released before such an accident was discovered.
Although the tanks did not appear to be leaking during the site visit, they are old and unmaintained. EPA has not conducted integrity testing on any tanks. Several tanks are outside of the containment wall area.
Several waste drums off site have been used during the remedial and sampling activities. Access to the drums is unrestricted at various locations in the woods and fields around the site. The off-site drums are not labeled and could be vandalized. EPA has advised ATSDR that the drums contain groundwater from bailing the monitoring wells when samples are collected. Empty shotgun shells were found near some of the off-site drums (13,14).
BUILDINGS
Several buildings and sheds remain on the property. The buildings are constructed of cinder blocks; the sheds are made of treated lumber poles and tin roofing and siding. The locations of those structures are shown in Figure 3. ATSDR's previous public health assessment identified the structures as pathways for potential exposure to site-related contaminants. The wood-scrape tests on which that determination was based are not representative of contamination that occurred during the facility's operation because the samples were collected from treated lumber. However, no information was available regarding surface contamination of the cinder blocks and concrete in the buildings. During plant operations, it is likely that wood-treating chemicals were spilled in the process building.
SEDIMENT/SURFACE WATER
Two streams are on the SMWT property - Old Tom's Run, which begins at the discharge of the pond on site, and a tributary on the eastern side of the site that begins outside of the fenced area (see Figures 2 and 9). The two streams join approximately 1950 feet south of the site. Questionable surface-water results were reported for chromium at one sampling location. The duplicate samples showed markedly different concentrations of chromium; one showed 323 ppb, the other was a nondetect. Because other samples from the eastern tributary did not have elevated chromium levels, and the duplicate sample showed nondetectable levels of the metal, that single high-chromium analytical result is considered inaccurate and is not included in Table 5.
The upper section of Old Tom's Run has contamination from discharges associated with the SMWT site. The surface water contains phenolic compounds (14). Samples in Old Tom's Run also had elevated lead concentrations, both in the surface water and sediments. See Table 5 for the maximum concentrations of contaminants in the surface water of Old Tom's Run. Because most of the contaminants at the SMWT site are not very water soluble, the highest concentrations of contaminants are found in the Old Tom's Run sediments (see Table 4). EPA took 17 samples from Old Tom's Run, above the confluence with the eastern tributary, and 20 samples below that point (see Figure 9). However, EPA has not sampled the banks along the creek to adequately determine the horizontal extent of contamination that may have occurred during flooding along the creek bed.
GROUNDWATER
Off-site groundwater sampling has been conducted in monitoring wells and private drinking-water wells in the area. Sampling has been done by both EPA and the state of Maryland (through the St. Mary's County Health Department [SMCHD]). Thus far, no contaminants from sources on the SMWT site have been measured in either the shallow or the deep groundwater residential wells off site (see Figure 10). However, some elevated metal concentrations and low PAH concentrations have been detected in shallow monitoring well 15 (MW 15)(see Figure 7) outside the fenced area near the SMWT site.
Since 1978, the SMCHD has sampled seven residential wells near the SMWT plant. The depth of five of the wells is 300-350 feet; the other two wells are less than 50 feet deep. Initially, all the wells were sampled monthly; sampling frequency was decreased to quarterly beginning in 1986. The sampling is ongoing, and no contaminants have been detected in those wells (15). However, all but one of those wells are upgradient of the SMWT site; therefore, no contamination is expected in those areas.
EPA has several monitoring wells in the shallow water-table aquifer and four wells in the Upper Chesapeake aquifer outside the plume of contamination. The shallow wells can be used to monitor for plume movement in all directions in the shallow aquifer. Samples taken from the four Upper Chesapeake aquifer monitoring wells do not show any contamination; however, none of them are downgradient from the plume of contamination in the shallow aquifer. See Table 5 for the maximum concentrations of contaminants of concern in the off-site groundwater aquifers.
AIR
Based on data presented in the on-site air contamination section, no PAHs or particulate contaminants at levels of concern are currently migrating off site. However, in the past, SMCHD officials received complaints from area residents about odors and black residue coating their houses when the plant was in operation (15). No air sampling was conducted during that time to determine what chemicals, if any, were migrating off site.
C. Quality Assurance and Quality Control (QA/QC)
The conclusions in this public health assessment update are based largely upon data developed by EPA contractors and SMCHD. When descriptions were provided, the QA/QC measures appeared consistent with measures normally taken with environmental sampling and analysis. The data are assumed to be accurate unless specifically qualified.
A brief discussion of data quality is in Appendix F of the RI/FS. The RI/FS was prepared by CDM Federal Programs Corporation. The only major data problem identified resulted from incorrect tuning of the Gas Chromatograph/Mass Spectrophotometer (GC/MS), which affected the Phase II volatile organic analyses. Those results are designated by EPA to be used for engineering purposes only because effects of the improper instrument calibration on the data quality could not be determined (10).
The analytical data developed by Dames and Moore and presented in the "Hazardous Waste Remedial Action Predesign Report" appear to be of high quality for the contaminants listed in the ATSDR tables (See Appendix 2). There were some analytical difficulties with laboratory control samples for certain organic compounds, which resulted in a few PAH data points for environmental media being listed as estimated (J). The laboratory reports stated that the PAHs were present in the samples, but, due to the laboratory difficulties associated with the determination of PAHs, the quantities were estimated. However, because of the laboratory difficulties, those values are estimated higher than the true values are believed to be (1). To be conservative, the J values from the PAHs have been included in all ATSDR tables in Appendix 2.
In tank samples, there were matrix effects on some contaminants resulting from high concentrations of organic compounds. When samples were diluted to overcome the matrix effects, Dames and Moore qualified the diluted data points as estimated (J). When summing the carcinogenic and noncarcinogenic PAHs, if any value had a J qualifier, the total is qualified with a J in the ATSDR tables (1).
Two QA/QC issues were associated with the Dames and Moore analytical data for the metals of concern. Analysis of duplicate water samples from monitoring well 22 showed conflicting results. One sample showed 87.5 ppb lead; but, in the other sample, lead was not detected at 2 ppb. Because the 87.5 ppb was not confirmed in the duplicate sample, ATSDR has not included that data point in the tables. Analysis of duplicate surface-water samples from one sampling location in the eastern tributary also showed conflicting results. One sample showed 323 ppb chromium; chromium was not detected in the other sample. Because the duplicate sample showed nondetectable levels of the metal, that single high-chromium analytical result is considered inaccurate and is not included in Table 5 (1).
Some of the water samples analyzed for metals were filtered, a procedure which removes any metals adhering to particulates and also removes colloidal chemicals. The filtered samples reflect only dissolved metals concentrations instead of total metals; therefore, the metals concentrations reported may be low. Metals data from filtered samples do not represent the true dose to humans if the unfiltered water is ingested. ATSDR does not consider filtered samples adequate for comparison to EPA Drinking Water Standards, which are based on unfiltered samples. The samples taken of residential wells by St. Mary's County Health Department were unfiltered (16). All water samples taken by Dames and Moore were filtered before metals analysis (1,17). The RI/FS does not state whether the contractor filtered the water samples before analysis for metals, but it does say that the organic compound samples were unfiltered before analysis, which could imply that the metals samples were filtered (10). ATSDR has assumed that all water samples taken by EPA contractors for metals analysis were filtered. The metals data in Tables 2 and 5 are all from EPA contractors and are assumed to represent dissolved metals concentrations.
There are no apparent physical hazards to the general public associated with the site because it is secured by a high fence.
TOXIC CHEMICAL RELEASE INVENTORY
ATSDR conducted a search of the EPA Toxic Chemical Release
Inventory for St. Mary's County for 1987, 1988, and 1989. For
any of 300-plus toxic chemicals, EPA requires that the
manufacturing industry report annual estimated releases into the
environment. No facility chemical releases were listed for the
county during those three years.
To determine if people are exposed to contaminants released from the SMWT site, ATSDR evaluated the environmental and human components that lead to human exposure. This pathways analysis consists of five elements: 1) source of contamination, 2) environmental medium in which the contaminants may be present or may migrate, 3) points of human exposure, 4) routes of human exposure such as ingestion, inhalation, or dermal absorption, and 5) receptor population. ATSDR classifies exposure pathways as completed, potential, or eliminated. A completed exposure pathway existed in the past, and may exist in the present or future if all five elements of an exposure pathway link the contaminant source to a receptor population. Potential pathways, however, are defined as situations in which at least one of the five elements is missing, but could exist. Potential pathways indicate that exposure to a contaminant could have occurred in the past, could be occurring now, or could occur in the future. Pathways are eliminated when at least one of the five elements is missing and will never be present. Completed and potential pathways may also be eliminated when they are unlikely to exist. A list of all completed, potential, and eliminated exposure pathways at SMWT appear in Table 6 of Appendix 2.
A. Completed Exposure Pathways
Several exposure pathways are likely to have been completed in the past at the SMWT site. Plant workers and nearby residents could have been exposed to wood-treating chemicals predominantly through air releases during plant operation. However, concentrations of hazardous materials reaching receptor populations are unknown because no environmental sampling was done during active facility operations. Those pathways are described here.
ON-SITE WORKERS
Plant employees were probably exposed to wood-treating chemicals during plant operations via inhalation, skin contact, and inadvertent ingestion of compounds. SMCHD staff said that the skin of plant workers appeared yellow. The Chief Medical Officer for SMCHD said that a study of occupational exposure of plant workers, in collaboration with Johns Hopkins University, was proposed, but never undertaken (15).
OFF-SITE AIR
Staff from SMCHD also reported that nearby residents were concerned about plant operations emitting odors and depositing black residue on their houses. However, specific information about those releases is unavailable (15).
Although plant workers and nearby residents were probably exposed to wood-treating chemicals in the past, ATSDR is unable to evaluate such exposures because the concentrations of chemicals that reached the people working, living, or playing near the site are unknown.
B. Potential Exposure Pathways
ON-SITE MEDIA
Trespassers may also have been exposed to environmental contaminants on site before the fence was put up around the property. The fence appears to have virtually eliminated unauthorized entry. The potential for short-term exposures to contaminated soils, surface water, sediments, and ambient air exists for any persons on site. Details regarding possible contact of trespassers with on-site contaminants cannot be determined because specific activities that would lead to exposure are unknown.
OFF-SITE SEDIMENTS
A potential off-site exposure pathway exists because PAHs, phenolic compounds, and metals were detected in sediment and surface water in Old Tom's Run. The creek flows through a forested area with sparse undergrowth. A path along the western side of the SMWT site property leads to the creek. Access to the area is unrestricted, and it is possible that children play in the stream. Residences are less than half a mile northwest of the area. Skin contact with and ingestion of sediments and surface water by children during play could occur, however, the frequency and duration of exposure to contaminants is difficult to evaluate. Possible exposure scenarios will be presented in the Public Health Implications section of this public health assessment update.
OFF-SITE GROUNDWATER
Groundwater contaminated with VOCs, phenolic compounds, PAHs, and metals is confined at present to the shallow aquifer at the SMWT site. There are no on-site drinking water wells, and off-site residential wells in the vicinity showed no site-related contaminants when analyzed by EPA in 1986. SMCHD has been monitoring residential wells quarterly since 1978, and continues to do so. However, the analytes measured do not include all site-related contaminants. Although the plume appears to be largely confined to the site, samples from monitoring well 15 west of the SMWT boundary (see Figure 7) showed contamination. The shallow groundwater follows local topography, which should prevent contaminants from affecting the shallow wells of two homes less than half a mile west of the boundary. In addition, periodic sampling of EPA's shallow monitoring wells should detect plume movement before local, shallow residential wells are affected.
In addition to the concern about lateral movement of contaminants in the shallow aquifer, vertical migration of chemicals to deeper groundwater is possible. An abandoned supply well believed to have been built in 1965 transects the shallow groundwater contamination plume. Deterioration of the well casing could allow contaminants to reach the underlying Aquia and Piney Point-Nanjemoy aquifers. Groundwater flow in those aquifers is largely toward the southeast. Drinking water for area residents is drawn from both aquifers. Until the abandoned supply well on site is properly sealed, the potential exists for contamination of the deeper aquifers.
Lead was detected in on- and off-site monitoring wells. However, no residential wells had elevated levels of lead, based on results reported by SMCHD.
C. Eliminated Exposure Pathways
REMEDIAL WORKERS
Past, present, and future exposure to contaminants in a variety of environmental media is possible for on-site remedial workers. It is unlikely that such exposures would be at levels of concern however, provided appropriate work practices, as defined by the state or federal regulatory or permitting authorities, such as the Occupational Safety and Health Administration (OSHA), are followed. Those include worker education, certification, supervision and training, and use of personal protective equipment.
ON-SITE BUILDINGS
ATSDR's previous public health assessment identified the buildings on the SMWT site as a potential exposure pathway for site-related contaminants. However, the data show that building samples were actually collected from treated timbers. The presence of PAHs and PCPs would be expected because the structural timbers are treated with those chemicals to prevent decay. Timbers impregnated with wood-treating chemicals are widely used as construction materials.
It is possible that surface contamination of the cinder blocks and concrete in the process building may have occurred during plant operations. However, no additional sampling of the buildings has been done other than that previously described. The buildings, shown in Figure 8, will be demolished if remediation of contaminated soils takes place at the SMWT site (14). Therefore, based on available information, the on-site buildings represent an eliminated pathway rather than a potential pathway.
OFF-SITE SOILS
Surface soils are also contaminated in a small area off site, immediately northeast of the property boundary (see Figure 8). Residential areas to the north and west are within one half mile, and it is possible that children may occasionally be in the vicinity. Exposure to contaminants is unlikely, however, because the contaminated soils are covered by grasses, and the area is overgrown with briars and thorny locust saplings.
FOOD CHAIN
Food-chain exposure pathways include the consumption of plants, animals, or other food products raised in contaminated soils, in contaminated water, or irrigated with contaminated groundwater or surface water. Some chemicals may accumulate in biota. Chemicals such as mercury and other metals can concentrate in tissues of certain organisms at levels higher than the chemicals' concentration in water or in vegetation. No biota sampling has been conducted at the SMWT site.
Mercury was found in sediments and surface water of stream discharges from the SMWT site. The most contaminated surface-water sample was 0.3 ppb, which exceeds the EPA Ambient Water Quality Criterion of 0.146 ppb. The water criteria are intended to protect humans who eat fish and other aquatic species. Inorganic mercury can be converted into methylmercury in the environment. That organic form of mercury can have higher concentrations in certain fish than in environmental media. The EPA water criteria consider the uptake of contaminants and bioconcentration by aquatic species. The criteria use average fish consumption values of 6.5 grams per day for an individual. The streams and surface-water runoff immediately downstream from the SMWT site are too small to support an edible fish population. The first point at which a small edible fish population might exist is at the Morgan Road Pond, which is approximately 2 miles downstream from the SMWT site. Sediment samples and surface water samples for mercury at that point were below detection limits. Fish consumption is an unlikely source of exposure to contaminants at the SMWT site (19).
Because the site is fenced, it is unlikely that humans would
contact plants or aquatic organisms on site. Terrestrial animals
such as deer, rabbits, and squirrels could be exposed to on-site
contaminants in the soil, surface water, or food chain. There
are insufficient data and protocols to determine if game
consumption would be a point of potential human contact with
site-related contaminants. It is unlikely that game would obtain
a most of their food on site because of the limited vegetation,
and the fence limits access. Therefore, it is not likely that
game consumption or other food chain pathways would result in
human exposures to SMWT contaminants.
Health effects resulting from the exposure of an individual to a hazardous substance in the environment depend on several factors. One is the route of exposure: that is, whether the chemical is breathed, consumed with food or water, or contacts the skin. Other factors include the dose to which a person is exposed and the amount actually absorbed. Mechanisms by which chemicals are altered in the environment, or inside the body once absorbed, are also important. There is much variation in those mechanisms among individuals.
ATSDR has prepared toxicological profiles for many substances found at hazardous waste sites. Those documents present data and interpret information on the substances. Preparers of this public health assessment update have reviewed the profiles for the contaminants of concern at SMWT. Background information on incineration has also been reviewed.
There do not currently appear to be completed exposure pathways of public health concern. Remedial workers are required to follow OSHA health and safety guidelines. Brief discussions of the toxicity of contaminants at the SMWT site are in Appendix 4. Under present conditions, the contaminants associated with the SMWT site would not be expected to cause illness or disease either in the local population or in properly protected remedial workers. The health effects described in Appendix 4 would be caused by higher doses than those associated with possible exposure at the SMWT site. Because access to the site is restricted, even exposure at those lower doses is unlikely.
Worker exposure to site contaminants during previous facility operations is likely. Data are insufficient to determine the doses to which on-site workers may have been exposed in the past. Workers and nearby residents may have been exposed to contaminants by way of completed air pathways that existed in the past. However, because no air monitoring data are available for past exposures, the amount or duration of exposure is not known, and a dose cannot be reconstructed. Therefore, it is not possible to determine likely health outcomes from past exposures to contaminated air.
A number of site-related chemicals were detected in off-site sediments and surface water in Old Tom's Run. Access to the stream is unrestricted, and the nearest residence is within one- half mile. It is possible that children play in Old Tom's Run and contact contaminated surface water and sediments. The most likely route of exposure would be ingestion of or dermal contact with contaminated media. However, the stream is not used as a drinking-water source, and only inadvertent consumption of small amounts of water or sediments might occur if children were playing in the area. Limited dermal contact with contaminated media may also occur during play. Such exposures would likely be intermittent if they occurred at all.
Although measurable quantities of both carcinogenic and noncarcinogenic compounds were found in sediments and surface water, only pentachlorophenol (PCP) and cPAHs exceeded health-based comparison values. The health guideline used for cPAHs is derived from an interim cancer slope factor. The comparison value used for cPAHs assumes a daily exposure to soils containing 100 percent benzo(a)pyrene.
The health guidelines currently available for 2,3,7,8-TCDD toxic equivalents only consider effects other than cancer (see Tables 4 and 5 in Appendix 2, and Appendix 3). The PCP health guideline considers the carcinogenic potential of that compound over a lifetime of exposure. PCP, carcinogenic PAHs (the group represented by benzo[a]pyrene), and 2,3,7,8-TCDD and similar compounds are considered probable carcinogens (category B2) by EPA. That is, they are believed to have the potential to cause cancer in humans. Animal data strongly support that likelihood, even though human data are not sufficient to conclude that those compounds cause cancer in humans (20,21,22,23).
Consequently, the small amount of contaminated surface water or sediments to which children might occasionally be exposed while playing in the stream is unlikely to adversely affect their health.
B. Health Outcome Data Evaluation
Evaluation of health outcome data can give a general picture of the health of a community. Those data can confirm the presence of excess disease or illness. However, elevated rates of a particular disease are not always associated with hazardous substances in the environment. And, even if elevated rates are not found, a contaminant may still have caused illness or disease.
ATSDR must depend on previously gathered data to perform a public health assessment. Pre-existing health outcome data are usually reported for population units, such as counties. Groups of people likely to have been affected by the contaminants associated with a particular site are usually much smaller. Any evidence of excess illness or disease in the smaller group may be hidden within the larger groups' rates. Also, when populations are small, the number of people who have a particular illness or disease is also small. Small changes in the number of affected people from year to year can cause a large change in the rate; that is, the rate is considered "unstable." For those reasons, health outcome data must be evaluated with caution.
ATSDR staff determined that it is unlikely that exposures to contaminants associated with SMWT could occur at a level which could cause illness or disease, including cancer. However, because local residents expressed concern about the rates of cancer in Maryland and their county, ATSDR staff examined available health outcome data.
ATSDR staff met with the Chief Medical Officer of St. Mary's County and discussed what health outcome data could be obtained. As a result of that discussion, and other discussions with state health department officials, ATSDR determined that the available health outcome data were limited. The only registry data available were from the Maryland Cancer Registry. Hospital discharge data were not consistently available. Vital statistics were difficult to obtain and were not available at less than a county level (15,16).
Because residents expressed concern about the cancer rate, ATSDR staff evaluated the available cancer data for Maryland and St. Mary's County. The Maryland Cancer Registry was established in 1982; however, reporting was incomplete. ATSDR staff examined data from that registry; those data were provided by the Governor's Council on Cancer. Cancer registries are designed to record diagnosed cases. Not everyone who is diagnosed with cancer dies because of its effects. If the number of diagnosed cases is accurately reported, it will exceed the number of cancer deaths over time. For the period between 1982 and 1990, the total number of cancer cases reported to the Maryland Cancer Registry was less than the number of deaths from cancer in just one year of that period. Therefore, reporting could not have been complete.
Because reporting diagnosed cases of cancer was not required in Maryland before July, 1991, many cases have not yet been included in the registry. All clinics, hospitals, and laboratories were required July 1, 1991, to begin reporting all cancer diagnoses (24). Currently, registry personnel are searching death and medical records in an effort to find and verify past cases that were not been reported. Updating the registry is a major effort and has only been completed for the area of the state known as the Eastern Shore. Data for St. Mary's County, part of the Western Shore area, are expected to be verified and usable within a year (8). ATSDR staff believe the currently available data cannot be used to generate incidence rates (rates of newly diagnosed cases of cancer per year). However, should more complete data become available, ATSDR will evaluate it.
Because the filing of death certificates was required by Maryland law, reporting of causes of death tended to be more complete than reporting of cancer diagnoses. ATSDR staff reviewed the data in the Maryland Vital Statistics Annual Report: 1986 and the Maryland Vital Statistics Annual Report: 1987. Cancer death (mortality) rates for Maryland and St. Mary's County were compared with cancer death rates for the United States (U.S.). The U.S. rates were obtained from the Centers for Disease Control's Compressed Mortality database on WONDER (Wideranging ONline Data for Epidemiologic Research). The rates were based on the same ICD-9 codes (standard codes for medical diagnoses) and were all age-adjusted to the 1940 U.S. standard population, which is used for reporting vital statistics by Maryland's Center for Health Statistics (6,7,9). Age-adjustment is a process that compensates for the effects on rates of death and disease of differences in the age distribution of populations. When one population has many more older people than another, the death rate for the older group will be higher because more older people die. Comparing rates of the two populations is misleading, because the rates of the older population appear higher than the rates in the younger population. The older population would appear to have an excess of disease; the younger population, however, actually may be more affected. By age-adjusting the data, it is possible to determine the rate at which deaths would occur if the populations had the same number of people in each age group. Age-adjustment allows an accurate comparison of the rates for one population with the rates for another.
When compared on a county-by-county basis, St. Mary's County ranked in the lowest third of the counties in Maryland for cancer deaths during the 1984-1986 period (6). When the average cancer death rates for the 1985-1987 period were compared (7), there was a marked change in the average rate. St. Mary's County ranked seventh out of Maryland's 23 counties. The population of the county is relatively small; therefore, its cancer death rates are more "unstable" than the rates of larger counties. For example, Prince George's County has approximately 10 times the population of St. Mary's County; therefore, its death rates do not vary as much year to year.
Because of the variation in death rates for St. Mary's County, ATSDR staff believed that reviewing data for a longer period would provide a more valid comparison. The Compressed Mortality data in WONDER for the 10-year period between 1979 and 1988 were reviewed. Table 7 shows the cancer death rates reported for St. Mary's County, Maryland, and the U.S. during that period (9).
If any association existed between the operation of SMWT facility and the cancer rates in St. Mary's County, that association would have been expected to begin to be apparent during the 10-year period for which data were examined. The facility operated from 1965 to 1978. Most cancers develop after a latency period of 15 to 30 years. That is, exposure to the carcinogen occurs 15 to 30 years before a specific cancer type can be detected. If exposure to site contaminants had caused excess cancer, increased cancer death rates would be seen beginning in about 1980, provided all three of the following conditions were met:
Table 7. Age-Adjusted Mortality Rates* for Cancer in Maryland, St. Mary's County, and the United States, 1979-1988**
| Year | St. Mary's County | Maryland | United States |
| 1979 | 140.8 | 148.2 | 130.8 |
| 1980 | 142.4 | 148.8 | 132.4 |
| 1981 | 174.8 | 149.3 | 131.6 |
| 1982 | 144.5 | 151.7 | 132.4 |
| 1983 | 157.4 | 151.8 | 132.7 |
| 1984 | 114.1 | 149.8 | 133.4 |
| 1985 | 128.7 | 149.9 | 133.6 |
| 1986 | 137.7 | 151.4 | 133.3 |
| 1987 | 169.9 | 149.6 | 133.0 |
| 1988 | 123.1 | 149.3 | 132.5 |
As can be seen from Table 7, the cancer death rates for St. Mary's County varied more from year to year than rates for Maryland or the U.S. However, some variation was seen for all the populations. For seven out of 10 years, the cancer death rate was lower in St. Mary's County than in the state of Maryland. Three out of 10 years, the cancer death rate for the county was lower than the rate for the U.S. It does not appear that the rate of cancer death in St. Mary's County is either increasing or decreasing in any consistent pattern. However, 10 years may be too short a period for detecting a trend in such a small population (6).
Because of the variation, ATSDR staff believed that looking at cancer death rates on a yearly basis was less reliable than looking at the average rates over several years. Because small numbers of cancer deaths were recorded for individual body organs, any rates generated for those cancer types would not allow determination of reliable trends over time. Therefore, the combined death rates for all organs were examined. Over the 10-year period, Maryland had the highest average cancer death rate in the nation: 150.0 deaths per 100,000 person-years. The 10-year average cancer death rate in St. Mary's County was 142.9 deaths per 100,000 person-years. St. Mary's County ranked eleventh out of 23 among Maryland's counties for that period, well behind the county with the highest rate. That county, Somerset, had an average 10-year cancer death rate of 172.5 deaths per 100,000 person-years (6).
A person's risk of developing cancer has been associated with many factors, including both gender and ethnic group. Therefore, ATSDR staff compared cancer death rates by gender and ethnic group for Maryland, the U.S., and St. Mary's County. Women in St. Mary's County died from cancer at a rate similar to women in the U.S. The rate was below the death rate for women in Maryland. On the other hand, men in St. Mary's County had a cancer mortality rate close to, but still below, the average for Maryland. The rate was well above the rate for men in the U.S. When the data were examined by ethnic group (white and black (including African-American)), the difference between cancer death rates in men and women remained similar. As was true of both Maryland and the U.S., blacks (including African-Americans) of both genders had higher cancer death rates than did whites of both genders. Table 8 shows cancer death rates by gender and ethnic group.
Table 8. Ten-year Average Age-Adjusted Cancer Mortality Rates* By Gender and Ethnic Group** for St. Mary's County, Maryland, and the United States, 1979-1988***
| Area | White Males |
Black Males |
White Females |
Black Females |
| St. Mary's County | 171.1 | 252.8 | 107.2 | 125.4 |
| Maryland | 174.6 | 262.2 | 119.7 | 145.2 |
| United States | 158.8 | 230.1 | 108.8 | 129.9 |
In summary, when cancer death rates were compared for the period between 1979 and 1988, women in St. Mary's County died from cancer at about the average rate for the U.S. The death rates for all women in Maryland were much higher. Men in St. Mary's County died at a rate which was close to, but still below, the average cancer death rate for Maryland. Maryland's cancer death rates for both sexes were higher than the national averages. Rates of incidence (based on newly diagnosed cases of cancer each year) could not be determined with available data. Based on the evaluation of contaminants and pathways, and of health outcome data, ATSDR does not believe that exposure to contaminants associated with the SMWT site is likely to result, or have resulted, in the development of illnesses and diseases, including cancer.
ATSDR staff would have been able to evaluate the general health of local residents more thoroughly if more health outcome data had been available. Specifically, data were not available for groups of people smaller than the total population of the county (such as census tract). Also, hospital discharge data and registry data were either not available or not usable. ATSDR staff evaluate available health outcome data to determine which data are of value in describing the health of the local community.
C. Community Health Concerns Evaluation
1. The major community health concern expressed to ATSDR involves the potential health implications of the incineration process EPA is planning to use to remediate the site. Specifically, how will the stack emissions, such as products of incomplete combustion (PICs) and metals, affect community health? How will equipment failures, process upsets, and other emergency situations affect air releases associated with remediation?
Emissions from the incinerator into the air represent a major exposure pathway to be considered by ATSDR during the second phase of this Agency's involvement in the SMWT site remediation (see ATSDR's Plan of Action to Evaluate the Proposed Remedial Alternative for the Southern Maryland Wood Treating Site for expanded discussion of those issues).
Design and operating plans; trial burn plans and test results; air pollution control systems; and other facility provisions help to define the air emission characteristics of an incineration facility. Consequently, those provisions will be carefully reviewed by ATSDR as the design moves toward implementation. Similarly, ATSDR will review contingency plans, monitoring plans, and system safeguards to determine the potential for excessive emissions and the effectiveness of corrective measures planned to minimize the impact of such conditions. Through careful planning, good design, operator training, and appropriate monitoring, excessive stack emissions should not be released.
The community expressed concern to ATSDR that all PICs produced by incineration have not been identified. Although that is true for incineration, it is also true for virtually all forms of combustion. It is likely to remain true as long as analytic chemistry methods cannot define all chemicals down to the level of individual molecules. Regarding identification of PICs caused by various combustion processes, hazardous waste incineration has been reviewed in considerable detail during research and as part of the incineration permitting process. The most prevalent PICs (by mass and occurrence) have been identified and examined for health implications using conservative (worst case) exposure situations. When an incinerator performs as required for efficient hazardous waste destruction and removal, identified PICs have been found at very low levels, below health concern.
The community's concern about the environmental fate of metals in the incineration process is valid and must be examined with respect to site-specific metals contamination, and system performance characteristics, to see if health effects would be apparent or significant. The levels of metals in the soils and sediments to be treated at the SMWT site; the specific air pollution control systems; and actual trial burn results need to be reviewed. Both metals and PIC data should be modelled using local meteorologic data to identify pollutant air dispersion patterns and locations of maximum expected ground-level concentrations in relation to area populations. That level of site-specific understanding is essential in order to evaluate potential community health implications.
As part of this Agency's commitment to evaluate the public health impacts of the SMWT site, ATSDR plans to review all relevant information developed for site remediation. Although it is anticipated that most of the appropriate information will be developed as a routine part of EPA's management of this project, ATSDR will identify data gaps, if any, and work with EPA to fill any information needed to determine public health implications.
2. Is the current groundwater monitoring program adequate to detect contamination of drinking water wells in the area? The public is concerned that the production well may cause contamination of the deep aquifers.
Groundwater monitoring at SMWT is being performed both on and off site and appears adequate to detect the migration of contaminants within the shallow water table aquifer. Quarterly monitoring of nearby residential wells, including two wells drawing from the shallow aquifer, by the St. Mary's County Health Department has not detected any contamination. EPA's analysis of 10 private residential wells also did not show contamination by site contaminants. ATSDR recommends continued monitoring of downgradient residential wells with a focus on site contaminants. None of the on-site monitoring wells in the Upper Chesapeake aquifer have shown any contamination.
The characterization of the Upper Chesapeake Aquifer downgradient of the site does not adequately identify potential migration of contaminants. The potential for contaminant migration into the deep drinking water aquifers, Aquia and Piney Point-Nanjemoy, has not been evaluated beneath the site. Most of the domestic wells used by residents who live near the site draw from those deeper aquifers.
ATSDR concurs with the public concern about potential contamination of the deeper drinking-water aquifers beneath the site from possible vertical movement of contaminants along the casing of the on-site production well. ATSDR recommended in the 1989 public health assessment of this site, and again in this public health assessment update, that the on-site production well be properly closed.
Previous attempts by EPA to collect a sample from the on-site production well were unsuccessful because the well is obstructed. Prior to proper closure of the well, EPA should attempt to remove the blockage and obtain samples to determine if the Aquia aquifer is contaminated.
3. What is the effect of the site's contaminants on the food chain? Because some chemicals bioaccumulate in plants and animals, are the fish, shellfish, game, and crops in the area currently affected? Will the incinerator emissions affect the food chain?
The food chain should not be affected by contaminants at the SMWT site. Because the site is fenced, human exposure resulting from consumption of plants and animals harvested on site is unlikely.
Mercury was found at elevated levels in the sediments and surface water of streams that originate on the SMWT site. Because the surface-water tributaries leaving the site are too small to support edible fish populations, that potential food chain pathway is not a likely health concern. Morgan Road Pond is the first downstream body of water that could support a small edible fish population; sediments and surface water in that area did not show elevated levels of mercury. Therefore, fish consumption does not represent a likely source of exposure. See the Pathways Analysis section for a more detailed discussion of food chain exposures.
There is insufficient information to evaluate effects of incinerator emissions on the food chain. Once trial burn and air dispersion modelling data are available, ATSDR will evaluate that pathway.
4. Does the county have a high cancer rate?
Data were not available on cancer incidence, that is, the rate of newly diagnosed cancer cases per year. ATSDR evaluated available data on cancer death rates for all Maryland counties. When cancer death rates were compared for the period between 1979 and 1988, women in St. Mary's County died from cancer at about the average rate for the United States. That rate was less than the rate for all women in Maryland. Men died at a rate that was close to, but still below, the average cancer death rate for Maryland. Maryland's cancer death rates were higher for both sexes than the national averages. Mortality rates are affected by many factors, including access to medical care and whether early diagnosis and treatment is available. An evaluation of available data, limitations of the data, and an interpretation of the data are contained in the Health Outcome Data Evaluation section.
5. How will sensitive populations be affected by this site and by remediation activities?
Currently, there are no known completed pathways of exposure. Therefore, no people are likely to be affected. Once remediation plans are final, ATSDR will review them and assess any potential health effects that the remedial activities at the site might cause for sensitive populations living nearby.
6. Are the chemicals at SMWT and the potential incinerator-stack emissions cancer promoters or initiators?
For the specific hazardous substances associated with the SMWT site, it is not known for certain if they are initiators, promoters, or both. ATSDR evaluates all cancer-causing substances as "complete" carcinogens. That is, ATSDR assumes that no interactions with other substances are needed for a particular substance to be able to cause cancer. Exposure to either an initiator or promoter might result in development of cancer. Whether a person will develop cancer depends on several factors. Among those factors are the level of exposure and length of time the person was exposed. Because it is uncertain how cancers are caused, cancer risk is estimated using levels and time of exposure, not whether the substance is an initiator or promoter.
It is best not to think of cancer as a single disease, but as a set of diseases that develop by similar processes. Cancers may be inherited, or may result from exposures to viruses, chemicals, or physical forces such as radiation. One of several theories of how cancers develop following exposure to chemicals is that substances may be either initiators or promoters. Research suggests that the first step, initiation, changes the cell into a pre-cancerous cell. This is believed to involve a change in the genes (damaged DNA). The second step, promotion, causes a cell to express the change (25).
Substances which result in changes to a cell's genes are initiators, and substances which alter the expression of a changed gene are promoters. Promoters are believed to increase the rate of expression of cancers that occur spontaneously, or as a result of previous initiation (25). In general, initiators are believed to be more strongly associated with development of cancers than are promoters. A substance might be both an initiator and a promoter (25).
7. Will ATSDR do any follow-up health studies of the community to see if the remediation activities affected the health of residents?
Because there are no currently completed pathways, and past exposures cannot be defined, no health studies are indicated at this time. However, once EPA's plans for remediation become final, ATSDR will evaluate them to determine if health studies are needed in association with those activities. If health studies are needed, ATSDR would undertake them in conjunction with the community and state and local health authorities.
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