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PUBLIC HEALTH ASSESSMENT

ROCKWOOL INDUSTRIES
BELTON, BELL COUNTY, TEXAS


SUMMARY

The Rockwool Industries, Inc. (RWI) National Priorities List site is a 100 acre site one-mile east of downtown Belton in Bell County, Texas. The site is bordered to the north by the Leon River and to the south and west by Nolan Creek. The facility manufactured mineral wool insulation from the mid-1950s until February 1987.

The facility manufactured two types of mineral wool insulation: blow wool and batt wool. Blow wool, which is generally spray blown into attics and other enclosed spaces for thermal insulation, is composed of bulk mineral wool fibers lightly coated with lubricating oil. Batt wool is typically used for wall insulation and consists of mineral wool that is bound with an organic resin (such as tar) and sandwiched into paper. The mineral wool was manufactured in blast furnaces using raw material such as slags from copper and antimony smelting, waste from limestone mining, as well as coke and basalts. The raw materials were melted in a coke-fired furnace and then extruded by blowing air over spinning drums to form fibers. The residue left in the furnace from the heating of the slags was a metal "shot" type material. This "spent iron shot" was the main waste type generated as part of the rockwool production process. This material was stockpiled in the North Shot Pile, the South Shot Pile, and the Cemetery Shot Pile.

Three main contaminant source areas have been identified at the site. Source 1, in the middle portion of the site, includes contaminated soil associated with the South Shot Pile. Source 2, in the northern portion of the site, includes contaminated soils associated with the North Shot Pile. Source 3, in the northwest portion of the site includes contaminated soils associated with the Cemetery Shot Pile. The primary waste types at the site include spent iron shot and baghouse dust. Secondary waste types include boiler blowdown water, stormwater runoff, recovered groundwater, and bricks.

The Texas Department of Health (TDH) and the Agency for Toxic Substances and Disease Registry (ATSDR) evaluated the environmental information available for the site and identified several exposure situations for evaluation. These exposure situations include possible contact with site contaminants in the soil, surface water, sediment, and groundwater. The potential for exposure to site contaminants through the food chain was also examined. A brief review of the evaluation, organized by hazard category, is presented below. Based on available data, we have concluded that the RWI NPL site poses an indeterminate public health hazard. In the future, additional data could change the overall conclusion category for the site.

INDETERMINATE PUBLIC HEALTH HAZARD

TDH and ATSDR concluded that the following exposure situation poses an indeterminate public health hazard. In this situation, more information is required to adequately define the potential health hazard.

  1. Potential exposure to contaminants through the foodchain is considered to be an indeterminate public health hazard. Although available data do not indicate that people are being or have been exposed to levels of contamination that would be expected to cause adverse health effects, data are not available for all environmental media to which people may be exposed. Selenium, which is known to bioaccumulate in fish, was detected at high concentrations in groundwater from the North Shot Area and at low concentrations in sediment both from the Leon River and Nolan Creek. Surface water data and fish data from the Leon River were not available for review. We have recommended that fish from the Leon River and Nolan Creek be collected and analyzed for site-related contaminants.

NO APPARENT PUBLIC HEALTH HAZARD

ATSDR concluded that the following identified exposure situations do not represent a public health hazard under current conditions either because there is no evidence that people are coming into contact with contaminated media or it is unlikely that they are coming into contact with contaminated media often enough to present a threat to public health.

  1. Exposure to contaminants in soil is considered to pose no apparent public health hazard. Although in the past, on-site workers and trespassers could have come into contact with contaminants in the soil, we were not able to evaluate the public health significance of these potential exposures. Contaminated areas on the site continue to be accessible; however, the surrounding area is sparsely populated and exposures due to trespassing are likely to be short-term and infrequent. Although it is possible that people working at the cemetery could come into contact with soil containing arsenic at levels above its carcinogenic risk screening value, we estimate that chronic exposure to this soil would result in no apparent increased lifetime risk for the development of cancer. If in the future, land use patterns change to those approximating a residential setting, the public health significance of the contaminated soil should be reevaluated.

  2. Exposure to surface water near the Rockwool Industries site is considered to present no apparent public health hazard. Although benzene was detected in surface water from Nolan Creek at a concentration exceeding its health-based screening value, we estimate that any potential exposure to this contaminant in the surface water would be short-term, infrequent, and would not pose a public health threat.

  3. Exposure to sediment from areas near the Rockwool Industries site is considered to present no apparent public health hazard. Although some of the chemicals detected in off-site sediment exceed health-based screening values, we estimate that any potential exposure to the sediment would be short-term, infrequent, and would not pose a public health threat.

NO PUBLIC HEALTH HAZARD

TDH and ATSDR have concluded that the following exposure situations do not pose a public health hazard because there is no evidence of current or past human exposure to the contaminated media and future exposure to the contaminated media is not likely to occur.

  1. Exposure to site contaminants through groundwater is considered to pose no public health hazard. Although contamination of groundwater has been documented, there is no evidence of current or past human exposure to contaminated groundwater.

  2. Exposure to site contaminants in other on-site waste sources is considered to pose no public health hazard. Although some of these sources contain contaminants at concentrations exceeding their respective screening values, exposure to contaminants in these sources is not likely.

BACKGROUND

Site Description

The inactive Rockwool Industries, Inc. (RWI) National Priorities List (NPL) site, at 1741 Taylors Valley Road, includes approximately 100 acres (zoned heavy industrial) one mile east of downtown Belton in Bell County, Texas (Figure 1). The primary waste types at the site include spent iron shot and baghouse dust. Secondary waste types include boiler blowdown water, stormwater runoff, recovered groundwater, and bricks.

Forty-seven (47) acres were used as an industrial facility, 13 acres included an evaporation lagoon, and 40 acres were used for pasture and for disposal of municipal sludge [1] (Figure 2). The site is bordered to the north by the Leon River and is bisected from east to west by Taylors Valley Road and FM 93 (Figure 2). These roads divide the site into three distinct areas. The 13 acres north of Taylors Valley Road include the North Shot Pile, the Make-up Water Pond, a materials stockpile, the water treatment building, and the Evaporation Lagoon. The middle portion of the site, which consists of 47 acres between Taylors Valley Road and FM 93, is where most of the facility operations took place. This area includes the Baghouse Dust Surface Impoundment, the South Shot Pile, the Dangerfield Slag Pile, the Boiler Blowdown Pond, the garage, and the former Kiln and Brick Plant. The former main production buildings and warehouses also are in this area and face north along the south side of Taylors Valley Road. The southernmost part of the site, south of the recently constructed FM 93, consists of approximately 40 acres of pasture land. Nolan Creek forms part of the southwestern property boundary of the site [1].

Texas Natural Resource Conservation Commission (TNRCC) identified three main contaminant source areas. Source 1, in the middle portion of the site, includes contaminated soil associated with the South Shot Pile. Source 2, in the northern portion of the site, includes contaminated soils associated with the North Shot Pile. Source 3, in the northwest portion of the site includes contaminated soils associated with the Cemetery Shot Pile.

Site History

The Rockwool Industries Inc. facility manufactured mineral wool insulation from the mid-1950s until February 1987 [2]. Previous land use is not known [1].

RWI manufactured two types of mineral wool insulation: blow wool and batt wool. Blow wool, which is generally spray blown into attics and other enclosed spaces for thermal insulation is composed of bulk mineral wool fibers lightly coated with lubricating oil. Batt wool is typically used for wall insulation and consists of mineral wool that is bound with an organic resin (such as tar) and sandwiched into paper. The mineral wool was manufactured in blast furnaces using raw material such as slags from copper and antimony smelting, waste from limestone mining, as well as coke and basalts [3]. The raw materials were melted in a coke-fired furnace and then extruded by blowing air over spinning drums to form fibers [3]. The residue left in the furnace from the heating of the slags was a metal "shot" type material. This "spent iron shot" was the main waste type generated as part of the rockwool production process. This material was stockpiled in the North Shot Pile, the South Shot Pile, and the Cemetery Shot Pile.

The North Shot Pile area began receiving spent shot material waste in the mid-1950s. By 1982 the North Shot Pile covered over three acres and there was no room for further expansion. The northern edge of the North Shot pile was on the southern bank of the Leon River and waste runoff had been detected going into the River [3]. The North Shot Pile was reduced to about two acres after waste was hauled to an off-site disposal area. In 1983, a dirt cover was placed over the North Shot Pile to reduce fugitive dust and the infiltration of rain. A french drain system was installed along the northern edge of the shot pile to intercept and collect leachate as it flowed horizontally toward the Leon River. This french drain carried the liquid to a concrete sump and the water that collected in the sump was pumped to the lined Evaporation Lagoon.

It is not clear when the South Shot Pile began receiving waste; however, beginning in 1984, some of the spent shot material was removed from the South Shot Pile and was recycled as an ingredient in brick making. The shot was mixed with cement and baghouse dust; it was shaped into bricks and then used as raw material feed for the furnace. An unknown amount of the shot was recycled in this way [4]. It is not known when the Cemetery Shot Pile began receiving waste.

During site operations, there were numerous solid waste management units that were used to dispose of process wastes. These included a Boiler Blowdown Pond, Stormwater Runoff Pond, Waste Oil Storage Tanks, On-site Landfill, Container Storage Area, Wastewater Blending Tank, West Warehouse Container Storage Area, and the previously mentioned North Shot Pile and South Shot Pile (Figure 2). A Raw Water Make-up Pond and an Old Brine Pond also were used to dispose of wastes [3]. During the preliminary assessment of the site, incomplete remediation was evident: 1) the groundwater recovery system was abandoned and 2) the main facility building was abandoned but still contained office equipment and supplies [3].

Until 1985, arsenic-contaminated baghouse dust was generated during the manufacturing process. This dust was disposed of on-site in a surface impoundment and a landfill. The Baghouse Dust Surface Impoundment (also known as Baghouse Dust Landfill or "The Dust Pocket" - Solid Waste Management Unit 1) was closed as a landfill in 1988. This was discovered at the site in 1990. Rockwool Industries proposed a closure plan for this on-site surface impoundment in April of 1990; in 1991, the hazardous wastes were removed.

In October 1991, the TNRCC issued a compliance plan and a Hazardous Waste Post-Closure Permit to Rockwool Industries to allow RWI to remove and dispose of contaminated soil, remove and stabilize sludge, and install clay covers where necessary. As part of the remediation effort they installed a groundwater recovery system to monitor groundwater in the first saturated interval.

Although numerous on-site solid waste management units (SWMUs) were closed by Rockwool Industries, remediation of the Baghouse Dust Surface Impoundment and the on-site general plant refuse landfill was not completed (Figure 2). The groundwater recovery system was abandoned and iron shot piles remained on site. RWI shut down the groundwater recovery and treatment system in September of 1994 due to financial problems.

The Preliminary Assessment was completed in December of 1995 and the Site Investigation was completed in October of 1996. The RWI site was proposed to the National Priorities List on March 6, 1998, and was finalized to the list September 29, 1998. The combined Remedial Investigation/Feasibility Study (RI/FS) began on September 30, 1998.

Site Visit

Representatives of the Texas Department of Health visited the Rockwool Industries site on October 21, 1998. TDH personnel were accompanied by the EPA project manager for the site, and a contractor for EPA. Two and one-half hours were spent examining the site and site vicinity. During the site visit we saw an office building, a production building, warehouses, and other structures on the site.

The RWI site appeared to be accessible since it was not completely surrounded by a fence. We did see fencing (three strand barbed wire) on the south and east; however, we did not see any fencing between the northern boundary of the site and the Leon River or the southwestern boundary and Nolan creek. There was a six-foot chain-link fence around the evaporation pond.

There is a cemetery directly adjacent to the west side of the North Shot Pile and within a two block distance to the west we saw the McGuire trucking company. The nearest residence was one-half mile west of the site. We saw farmland west of the RWI property line.

During the site visit we saw gravel, slag, and "shot" material on the site. We could not access Nolan Creek because of recent heavy rains. Tall grass and other vegetation in the vicinity of the North Shot Pile and the Evaporation Lagoon were still bent from rainwater flowing north, towards the Leon River.

There was dense vegetation around the Raw Makeup Water Pond and the concrete pads in buildings appeared to be intact and not cracked. We did not see any evidence that younger children frequent the site; however, we did see graffiti on walls in the production building. One old rifle casing was noted at the site.

Demographics

There are approximately 14 people living within one-half-mile of the site. According to the 1990 U.S. Census, the total residential population within a one-mile radius of the Rockwool Industries, Inc. site is estimated to be 2,855 people [5]. The population of nearby Belton is 20,330 and the population of Temple (approximately 2.5 miles northeast of the site) is 52,346 [5].

There are no residents, schools, or day care centers within 200 feet of the site [3]. It is not known how many people worked at Rockwool in the past; currently, however, the site is no longer operating and there are no on-site workers [4, 6].

Land Use and Natural Resource Use

The area around the site is industrial, commercial, and agricultural [4]. The Leon river, which runs along the northern boundary of RWI, empties into the Little River approximately nine miles downstream from the site. The Little River eventually joins with the Brazos River which flows to the Gulf of Mexico. Nolan Creek, which runs along the southwestern boundary of the site, joins with the Leon River downstream approximately 1.5 miles southeast of the site.

There are six private drinking water wells (which supply approximately 18 individuals) within one mile of the facility. The nearest domestic water well, is within one-half mile west/northwest of the site and is upgradient. The estimated depth of this well, which is not used as a drinking water source, is 42 feet and it is screened between 20 to 41 feet below ground surface (in the first interval). Also within one-mile of the facility are three industrial water wells and one well designated as "other." None of the wells used for drinking water are in the first saturated interval [1].

There are no public water supply wells within one mile of the site [4]. Drinking water for the City of Belton comes from an intake on Lake Belton which is fed by the Leon River. Lake Belton is approximately 4.5 miles northwest of the site. The City of Temple has a water intake on the Leon River approximately 1.5 miles northwest of the site. Both intakes are upstream of RWI and there are no drinking water intakes within 15 miles downstream of the RWI site.

Downstream from the site, surface water is used for recreational fishing and stock watering. Both Nolan Creek and the Leon River are fished; however, Nolan Creek is not suitable for swimming or wading due to elevated fecal coliform (bacterial) concentrations.

The topography of RWI is gently sloping. To the north of Taylors Valley Road, surface water drains north towards the Leon River. To the south of Taylors Valley Road, surface water drains south toward FM 93 and Nolan Creek [4].

General Hydrogeology

The major hydrologic unit which contains potable water in the vicinity of the Rockwool Industries, Inc. site is the Hosstom Member of the Travis Peak Formation. The water quality of the Hosstom Member is highly variable [1]. Regionally, water in the Travis Peak Formation flows to the east-southeast, however, in the Belton area heavy pumping of area wells has affected the direction of flow toward the area of withdrawal. Generally, the depth to the water table is about 50 to 100 feet below the ground surface. The Travis Peak Formation lies approximately 1,050 feet below the RWI site.

The RWI site is on top of Quaternary alluvium and terrace deposits associated with the Leon River. The terrace deposits lie generally to the north of Taylors Valley Road. They consist of limestone gravels, quartz, quartzite, chert, and jasper with varying amounts of clay and sand. The alluvial deposits consist of sand, gravel, and calcareous silts and clays with high organic content [1].

Below the Quaternary deposit is the Georgetown Formation which consists of a nodular limestone interbedded with thin marl beds. It is moderately fractured but not known to contain solution cavities to a great extent. Below the Georgetown Formation lies the Edwards Formation comprised of massive, hard, fossiliferous limestone which is often honeycombed with solution cavities. Between the Edwards and the Georgetown, approximately 100 feet below RWI from ground surface, is the Kiamichi shale. The Kiamichi shale is estimated to be 30 to 35 feet thick below the site. Below the Edwards lies the Comanche Peak and Walnut Formations. Both units are composed of alternating layers of limestone, shale, and calcareous clay. Below these lie the Glen Rose Formation, a thick sequence of alternating limestone, shale, and some anhydrate. Below the Glen Rose lies the Travis Peak Formation. The five members of the Travis Peak Formation consist of conglomerates, limestones, and shales. All of the above-mentioned formations dip to the east-southeast at a rate of 40 to 60 feet per mile [1].


ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS

Introduction

Exposure to, or contact with, chemical contaminants drive the ATSDR public health assessment process. The release or disposal of chemical contaminants into the environment does not always result in exposure or contact. Chemicals only have the potential to cause adverse health effects if people actually come into contact with them. People may be exposed to chemicals by breathing, eating, drinking, or by skin (dermal) contact with a substance containing the contaminant.

When people are exposed to chemicals, the exposure does not always result in adverse health effects. The type and severity of health effects that may occur in an individual from contact with contaminants depend on the toxicologic properties of the contaminants; how much of the contaminant to which the individual is exposed; how often and/or how long exposure is allowed to occur; the manner in which the contaminant enters or contacts the body (breathing, eating, drinking, or skin/eye contact); and the number of contaminants to which an individual is exposed (combinations of contaminants). Once exposure occurs, characteristics such as age, sex, nutritional status, genetics, life style, and health status of the exposed individual influence how the individual absorbs, distributes, metabolizes, and excretes the contaminant. These factors and characteristics influence whether exposure to a contaminant could or would result in adverse health effects.

To assess the potential health risks associated with contaminants at this site we compared contaminant concentrations to health assessment comparison (HAC) values. HAC values are media-specific contaminant concentrations that are used to screen contaminants for further evaluation. Non-cancer HAC values are called environmental media evaluation guides (EMEGs) or reference dose media evaluation guides (RMEGs) and are based respectively on ATSDR's minimal risk levels (MRLs) or EPA's reference doses (RfDs). MRLs and RfDs are estimates of a daily human exposure to a contaminant that is unlikely to cause adverse non-cancer health effects. Cancer risk evaluation guides (CREGs) are based on EPA's chemical specific cancer slope factors and an estimated excess lifetime cancer risk of one-in-one-million persons exposed for a lifetime. We used standard assumptions to calculate appropriate HAC values [7].

In some instances, we compare contaminant concentrations in water to EPA's maximum contaminant levels (MCLs). MCLs are chemical-specific maximum concentrations allowed in water delivered to the users of a public water system; they are considered protective of public health over a lifetime (70 years) of exposure at an ingestion rate of two liters per day. MCLs may be based on available technology and economic feasibility. Although MCLs only apply to public water supply systems, we often use them to help assess the public health implications of contaminants found in water from other sources.

While exceeding a HAC value does not necessarily mean that a contaminant represents a public health threat, it does suggest that the contaminant warrants further consideration. The public health significance of contaminants that exceed HAC values may be assessed by reviewing and integrating relevant toxicological information with plausible exposure scenarios. Estimated exposures may be compared to reported "No Observable" and "Lowest Observable" Adverse Effects Levels (NOAELs and LOAELs) and to known effect levels in humans, when available.

Environmental Contamination

Soil, sediment, surface water, and groundwater data included in our evaluation of the RWI site were collected during the TNRCC's March 12-14,1996, Screening Site Investigation. Fifteen soil samples, nineteen sediment samples, three surface water samples, and six groundwater samples were collected. The maximum reported concentrations for each of the contaminants detected are presented in Appendix C Tables 1 through 4. ATSDR comparison values for each of the contaminants also are listed in the tables. In preparing this Health Assessment, TDH staff members relied on the information provided in the referenced documents and assumed that adequate Quality Assurance/Quality Control (QA/QC) measures were followed with regard to chain-of-custody, laboratory procedures, and data reporting. The 1996 data packages were reviewed and validated by EPA Region 6 according to the USEPA Contract Laboratory Protocol Statement of Work. The TNRCC reviewed the inorganic and organic analyses to ensure accuracy, precision, representativeness, comparability, field custody, and completeness. The analyses and conclusions in this Health Assessment are valid only if the referenced information is valid and complete.


PATHWAYS ANALYSIS

In this section we evaluated the possible pathways for exposure to contamination at Rockwool Industries. We examined these possible exposure pathways to determine whether people near the site can be exposed to (or come into contact with) contaminants from the site. Exposure pathways consist of five elements: 1) a source of contamination, 2) transport through an environmental medium, 3) a point of exposure, 4) a plausible manner (route) for the contaminant to get into the body, and 5) an identifiable exposed population. Exposure pathways can be completed, potential, or eliminated. For a person to be exposed to a contaminant, the exposure pathway must be completed. An exposure pathway is considered completed when all five elements in the pathway are present and exposure has occurred, is occurring, or will plausibly occur in the future. A potential pathway is missing at least one of the five elements but possibly may be completed in the future as more data become available or site conditions change. Eliminated pathways are missing one or more of the five elements and will never be completed. Table 5 summarizes the exposure pathways considered in our evaluation of this site. Contaminants whose concentrations did not exceed ATSDR comparison values were excluded from the pathways analysis.

Indeterminate Public Health Hazard

TDH and ATSDR concluded that the following exposure situation poses an indeterminate public health hazard. In this situation, more information is required to adequately define the potential health hazard.

Evaluation of Possible Foodchain Exposure Pathways

Summary: Potential exposure to contaminants through the foodchain is considered to be an indeterminate public health hazard. Although available data do not indicate that people are being or have been exposed to levels of contamination that would be expected to cause adverse health effects, data are not available for all environmental media to which people may be exposed. Selenium, which is known to bioaccumulate in fish, was detected at high concentrations in groundwater from the North Shot Area and at low concentrations in sediment both from the Leon River and Nolan Creek. Surface water data and fish data from the Leon River were not available for review.

Selenium was measured above its detection limit in three (2.9 mg/kg at SE-4, 5.2 mg/kg at SE-5, and 2.7 mg/kg at SE-6 ) of the nine Leon River sediment samples and in one (SE-15, 3.4 mg/kg) of the five samples collected from Nolan Creek. It is not unusual for people to be exposed to selenium through the ingestion of fish that may have taken up selenium from high concentrations in water [8]. The estimated bioaccumulation factor for selenium in fish ranges from 485 to 1,746, depending on the species [9]. In general the more soluble and mobile forms of selenium (selenite and selenate) dominate under aerobic (high oxygen concentrations) and alkaline (high pH) conditions [8].

Humans and animals are both capable of absorbing and utilizing both organic or inorganic forms of selenium from food or water sources. Most of the selenium that enters the body is excreted in the urine within 24 hours. Selenium can build up in the body if exposure is high and occurs over a long period of time. Body burdens of selenium primarily occur in the liver, kidneys, hair, and nails. Selenium is an essential dietary element for both humans and animals in either the inorganic or organic form. Selenium has antioxidant effects which help prevent damage to tissues caused by oxygen. A selenium deficient diet can result in Keshan disease, the signs and symptoms of which may include muscle pain, cardiomyopathy, enlargement of the heart, increased red blood cell fragility, and pancreatic degeneration.

The recommended daily allowance (RDA) of selenium for maintenance of good health is 55 micrograms per day (µg/day) for women and 70 micrograms per day for men. Estimates of the average intake of selenium from food for the U.S. population range from 71 to 152 micrograms of selenium per person per day [8]. Welsh et al. reported that about three percent of Maryland residents consumed diets which contained over 200 µg of selenium per day [10]. The Food and Nutrition Board of the National Research Council has estimated the safe and adequate daily dietary intake of selenium in adults to be 50 to 200 µg [11]. However, when eaten in amounts that are not much higher than required for good nutrition, selenium becomes harmful to humans and animals [8]. Signs and symptoms of sub-acute and chronic toxicity in humans include brittleness and loss of hair and nails; blisters, eruptions and skin mottling; pitting and excessive decay of the teeth; a garlic or sour-milk breath odor; periodic episodes of nausea and vomiting; and increasing fatigue.

No human populations in the U.S. have been reported to have chronic selenium toxicity, including populations in the western part of the country where there are naturally high levels of selenium in the soil and water. In a study of 142 subjects living in a seleniferous area of South Dakota and Wyoming, there was no evidence of toxicity from selenium in subjects whose intake was as high as 724 µg/day [12]. There have been a limited number of case reports of individuals who developed minimal signs of selenium toxicity following chronic dietary intakes of 850-900 µg/day. In areas of China with selenium intakes of 3,200 to 6,690 µg/day, clinically apparent selenium toxicity was observed, while persons with daily intakes in the range of 42-750 µg/day did not produce any signs of toxicity or other adverse health effects [13].

The Agency for Toxic Substances and Disease Registry recently has established a chronic oral Minimal Risk Level (MRL) for selenium of 5 µg/kg/day [8]. For a 70 kg adult this is equivalent to an intake of 350 µg/day. The MRL is an estimate of the daily human exposure to a hazardous substance that is likely to be without appreciable risk of non-cancer health effects over a specified duration of exposure. The MRL was derived from a study involving a Chinese population with high selenium intake. Blood selenium concentrations and degree of selenosis were determined for 349 adults. The endpoint used to derive the MRL was nail disease, specifically brittleness of nails. By regression analysis the corresponding selenium dietary intakes were determined. A "no observable adverse effects level" (NOAEL) of 15 µg/kg/day, was determined. The NOAEL is the highest dose at which no statistically or biologically significant adverse effects were observed. For a 70 kg adult this dose is equivalent to a selenium intake of 1,050 µg/day. To establish the MRL, ATSDR divided the NOAEL by a factor of three to account for human variability. It is important to note that the MRL based on the Chinese study may be conservative because only dietary exposure was considered and it has been suggested that inhalation exposure to selenium in smoke was significant. The population studied cooked their meals on open fires of coal containing high concentrations of selenium.

Carcinogenicity

The EPA and the National Toxicology Program have determined that selenium is not classifiable as a carcinogen and it is rated as a Group D chemical. In fact, studies of cancer in humans suggest that lower than normal selenium levels in the diet may increase the risk of cancer. This may be because selenium is used by enzymes in the body that protect against oxidative damage to tissues and it is this damage that may be responsible for cancer promotion. One specific form of selenium, called selenium sulfide, is a probable human carcinogen. Selenium sulfide is not found in foods, and is a very different chemical from the organic and inorganic selenium commonly found in the environment. Because it is not absorbed through the skin, its primary use in the anti-dandruff shampoo Selsun Blue, is considered safe [8].

To evaluate the public health significance associated with eating fish contaminated with selenium, using ATSDR's MRL and assuming a background daily intake of selenium from other sources of 200 µg, we would estimate that approximately 150 µg/day (2.14 µg/kg/day assuming a 70 kg adult) would be an acceptable daily intake of selenium from fish.

No Apparent Public Health Hazard

ATSDR concluded that the following identified exposure situations do not represent a public health hazard under current conditions either because there is no evidence that people are coming into contact with contaminated media or it is unlikely that they are coming into contact with contaminated media often enough to present a threat to public health.

Evaluation of Possible Soil Exposure Pathways

Summary: Exposure to contaminants in soil is considered to pose no apparent public health hazard. Although in the past, on-site workers and trespassers could have come into contact with contaminants in the soil, based on available information we were not able to evaluate the public health significance of these potential exposures. Contaminated areas on the site continue to be accessible; however, the surrounding area is sparsely populated and exposures due to trespassing are likely to be short-term and infrequent. Although it is possible that people working at the cemetery could contact soil containing arsenic at levels above its carcinogenic risk screening value, using a conservative exposure scenario, we estimate that chronic exposure to this soil would result in no apparent increased lifetime risk for the development of cancer. If, in the future, land use patterns change to those approximating a residential setting, the public health significance of the contaminated soil should be reevaluated.

The TNRCC collected nine on-site and six off-site surface soil samples during the March 1996 Site Screening Inspection. Four of the on-site samples were collected in the vicinity of the Evaporation Pond (SO-9, SO-10, SO-11, and SO-12), two of the on-site samples (SO-13, SO-14) were collected in the vicinity of the Stormwater Runoff Pond and the South Shot Pile, and three of the on-site samples were collected in the pasture area south of the site and near Nolan Creek (SO-1, SO-2, and SO-3). Three off-site surface soil samples (SO-6, SO-7, SO-8) were collected at the cemetery west of the North Shot Pile, two off-site samples (SO-4 and SO-5) were collected in the Cemetery Shot Pile area, and one off-site surface soil sample (SO-15) was collected from the property southwest of the site near Nolan Creek.

None of the on-site or off-site surface soil samples contained volatile organic compounds, semi-volatile organic compounds, pesticides or PCBs at concentrations above their respective health assessment comparison values (Table 1). On the site, in the vicinity of the Evaporation Lagoon, antimony (82.3 mg/kg), arsenic (243 mg/kg), beryllium (1.2 mg/kg), lead (505 mg/kg), and manganese (1,950 mg/kg) all exceeded their respective screening values. Antimony (977 mg/kg), arsenic (54.7 mg/kg), beryllium (0.97 B), and manganese (423 mg/kg) also exceeded their respective screening values in the samples collected near the Stormwater Runoff Pond and the South Shot Pile. Off the site, in the samples taken at the cemetery west of the North Shot Pile, antimony (141 mg/kg), arsenic (62.6 mg/kg), beryllium (2.4 mg/kg), and manganese (2,640 mg/kg) exceeded their respective screening values. Antimony (79.1 mg/kg), arsenic (168 mg/kg), beryllium (1.2 mg/kg), lead (930 mg/kg), and manganese (2,600 mg/kg) also exceeded their respective screening values in the samples from the Cemetery Shot Pile and from the sample collected from the property to the southwest [antimony (55.6 mg/kg), arsenic (337 mg/kg), beryllium (2.8 mg/kg), lead (754 mg/kg), and manganese (2,780 mg/kg)].

Arsenic exceeded its carcinogenic risk evaluation screening value in several of the samples. The maximum reported concentration of arsenic (337 mg/kg) was detected in a sample from the Cemetery Shot Pile area. Assuming a worker or trespasser scenario, we estimate that a 70 kg adult ingesting 100 mg of soil containing 337 mg of arsenic per kg of soil per day, 250 days per year for nine years would experience no apparent increased lifetime risk for the development of cancer.

Evaluation of Possible Surface Water Exposure Pathways

Summary: Exposure to surface water near the Rockwool Industries site is considered to present no apparent public health hazard. Although benzene was detected in surface water from Nolan Creek at a concentration exceeding its health-based screening value, we estimate that any potential exposure to this contaminant in the surface water would be short-term, infrequent, and would not pose a public health threat.

Three surface water samples were collected. One sample (SW1) was a background sample collected upstream of the RWI site and the adjacent Cosper property [1]. Two samples (GW/SW8 and SW2) were collected at the east bank of Nolan Creek from the area where the groundwater seeps and surface water interface. The samples were analyzed for volatile organic compounds, semi-volatile organic compounds, pesticides, PCBs, and metals. The only constituent to exceed a health-based screening value was benzene which was detected in both GW/SW8 (10 µg/L UJ) and SW2 (19 µg/L J). Chronic exposure to this contaminant in the surface water at the maximum reported concentration would result in no increased lifetime risk for the development of cancer.

Evaluation of Possible Sediment Exposure Pathways

Summary: Exposure to sediment from areas near the Rockwool Industries site is considered to present no apparent public health hazard. Although some of the chemicals detected in off-site sediment exceed health-based screening values, we estimate that any potential exposure to the sediment would be short-term, infrequent, and would not pose a public health threat.

During the Screening Site Inspection, TNRCC collected 19 sediment samples in Nolan Creek and the Leon River. Two of the samples from Nolan Creek and three of the samples from Leon River were background samples. Five sediment samples from Nolan Creek and nine sediment samples from the Leon River were analyzed for volatile organic compounds, semi-volatile organic compounds, pesticides, PCBs, and metals.

Nolan Creek Sediment

Benzo(a)pyrene was detected in one Nolan Creek sediment sample at a maximum concentration (0.15 mg/kg) slightly above its carcinogenic risk screening level (0.1 mg/kg). Volatile organic compounds, semi-volatile organic compounds, pesticides and PCBs were detected at concentrations below background and/or below health-based screening values (Table 2). Arsenic (29.6 mg/kg), beryllium (0.52 mg/kg), and manganese (424 mg/kg) were detected at concentrations above both background and their respective health-based screening values. Using EPA's chemical-specific cancer potency values for benzo(a)pyrene, arsenic, and beryllium, we estimate that periodic ingestion (100 mg/day, 250 days per year for nine years) of the contaminated sediment would result in no apparent increased lifetime risk for the development of cancer.

Leon River Sediments

Volatile organic compounds, semi-volatile organic compounds, pesticides, and PCBS were below health-based screening values in Leon River Sediments. The metals antimony (59.9 mg/kg), arsenic (143 mg/kg), beryllium (0.98 mg/kg), lead (706 mg/kg), and manganese (2,660 mg/kg) were above background concentrations and above health-based comparison values (Table 3). Using EPA's chemical-specific cancer potency values for arsenic and beryllium, we estimate that periodic ingestion (100 mg/day, 250 days per year for nine years) of the contaminated sediment would result in no apparent increased lifetime risk for the development of cancer.

No Public Health Hazard

TDH and ATSDR have concluded that the following exposure situation does not pose a public health hazard because there is no evidence of current or past human exposure to the contaminated media and future exposure to the contaminated media is not likely to occur.

Evaluation of Possible Groundwater Exposure Pathways

Summary: Exposure to site contaminants through groundwater is considered to pose no public health hazard. Although contamination of groundwater has been documented, there is no evidence of current or past human exposure to contaminated groundwater.
There are a total of 38 monitoring wells on the RWI site. Thirteen of the wells (1 through 13) were drilled between 1981 and 1985, ten of the wells (14 through 23) were drilled in September of 1987, and the remainder of the monitoring wells were installed in 1990. In general, the wells were drilled to a depth of 35 feet into the first saturated interval [1].

In March 1996, the TNRCC collected five (5) on-site groundwater samples to investigate the potential for releases of on-site contaminants to the first saturated interval. Samples, collected from the North Shot Pile, the Evaporation Lagoon, and the Baghouse Dust Surface Impoundment, were analyzed for volatile organic compounds, semi-volatile organic compounds, pesticides, PCBs, and metals (Table 4).

One background sample (MW-8) was collected from an on-site monitoring well near the property boundary (Figure 2) and one background sample was collected from a private well approximately one-half mile west of the site. In the background samples, manganese was detected at a concentration above its respective screening value in water from MW-8. All other constituents either were below detection or below their respective health-based screening values.

At the North Shot Pile, antimony (227 µg/L), arsenic (12.7 µg/L), and selenium (186 µg/L) exceeded health-based screening values. At the Evaporation Lagoon, antimony (184 µg/L), arsenic (2,290 µg/L), lead (26.8 µg/L), manganese (1,050 µg/L), and zinc (4,590 µg/L) exceeded health-based screening values, and at the Baghouse Dust Surface Impoundment, antimony (559 µg/L), arsenic (811 µg/L), manganese (644J µg/L), selenium (35.7 µg/L), and vanadium (42.5 µg/L) exceeded health-based screening values. Pentachlorophenol was the only other contaminant detected at concentrations above its health-based screening value. At the Baghouse Dust Surface Impoundment, pentachlorophenol was estimated to be 41J µg/L in sample GW-6 and 25 µg/L (the detection limit) in sample GW-7.

Evaluation of Exposure To Site Contaminants Through Other On-site Waste Sources

Summary: Exposure to site contaminants in other on-site waste sources is considered to pose no public health hazard. Although some of these sources contain contaminants at concentrations exceeding their respective screening values, exposure to contaminants in these sources is not likely.

Bricks

An undated brick sample was analyzed for total metals. Metals which exceeded health-based screening values included: antimony (277 mg/kg), arsenic (57 mg/kg), lead (589 mg/kg), and manganese (2,260 mg/kg). A leachate test which also was run on a sample of the brick indicated that there is some leaching of lead from the brick material.

Boiler Pond Waste Sediment and Pond Sludge

In 1987 Boiler Pond Waste sediment and pond sludge were sampled and analyzed for metals and volatile organic compounds. In the pond sediment, 1,1,1-trichloroethane (3.42 mg/kg), propyl cyclohexane (2.27 mg/kg), and butyl cyclohexane (2.03 mg/kg) were detected at low concentrations; antimony (1,900 mg/kg), lead (620 mg/kg) and manganese (311 mg/kg) exceeded their respective health-based comparison values. In the pond sludge, arsenic (110 mg/kg) and manganese (450 mg/kg) exceeded health-based comparison values.

Follow-up samples of the Boiler Pond area were collected in 1990. Thirteen samples were collected in August and fifteen samples were collected in October. None of these exceed health-based comparison values for metals or volatile organic compounds.


COMMUNITY HEALTH CONCERNS / HEALTH OUTCOME DATA

Community Health Concerns Evaluation

As part of the public health assessment process, ATSDR and TDH try to learn what concerns people in the area may have about the impact of the site on their health. Consequently, attempts are made to actively gather information and comments from people who live or work near the site. To obtain community health concerns related to the Rockwool Industries site, we contacted different agencies and individuals by telephone. The regional offices of both the Texas Department of Health in Temple (TDH Region 7) and the Texas Natural Resource Conservation Commission (Region 9, Waco) were contacted in Winter 1999. In addition to state agencies we contacted Bell County Public Health District staff and citizens working and living in the vicinity of Rockwool Industries. No health concerns were received regarding Rockwool Industries.

Health Outcome Data Evaluation

Health outcome data (HOD) record certain health conditions that occur in populations. These data can provide information on the general health of communities living near a hazardous waste site. It also can provide information on patterns of specified health conditions. Some examples of health outcome databases are tumor registries, birth defects registries, and vital statistics. Information from local hospitals and other health care providers also may be used to investigate patterns of disease in a specific population. TDH and ATSDR look at appropriate and available health outcome data when there is a completed exposure pathway or community concern. Due to a lack of completed exposure pathways and no identified community health concerns, we did not review health outcome data.


CHILD HEALTH INITIATIVE

ATSDR's Child Health Initiative recognizes that the unique vulnerabilities of infants and children demand special emphasis in communities faced with contamination of their water, soil, air, or food. Children are at greater risk than adults from certain kinds of exposures to hazardous substances emitted from waste sites and emergency events. They are more likely to be exposed because they play outdoors and they often bring food into contaminated areas. They are shorter than adults, which means they breathe dust, soil, and heavy vapors close to the ground. Children are also smaller, resulting in higher doses of chemical exposure per body weight. The developing body systems of children can sustain permanent damage if toxic exposures occur during critical growth stages. Most importantly, children depend completely on adults for risk identification and management decisions, housing decision, and access to medical care.

ATSDR evaluated the likelihood for children living in the vicinity of the Rockwool Industries site to be exposed to site contaminants at levels of health concern. ATSDR did not identify situations in which children were likely to have been exposed to site contaminants. Children are not likely to be exposed to contaminants in sediments or soils from Rockwool Industries. There is no evidence that children are trespassing on the site. However, if children were to frequently trespass on this site they could be at risk from chemical contaminants and from physical hazards on the site.



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