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DISCUSSION

The groundwater, soil, and sediment samples collected in 1991 and 1995 are the subject of the present review. The purpose of the sampling was to compare on-site samples with downgradient and background samples. The locations of 1991 samples (3 groundwater and 9 soil and sediment samples) are presented in Attachment 5. No sampling location map was available for the samples (3 groundwater and 10 soil and sediment samples) taken in 1995, but the small site area makes the exact sample locations less important. All 3 groundwater samples taken in 1991 were collected upgradient to the tar pit: GW1 from the on-site industrial/washroom well, GW2 from a residential private well approximately 400 feet south of the site, and GW3 from a subdivision public well about 0.25 miles north of the site, which was also used as a background sample. In 1995, groundwater samples were collected from on-site wells (G101, G102) and a residential private well (G103).

Soil and sediment samples collected in 1991 were from 0 to 6 inches in depth. Because each core sample represented a mixed sample, it was impossible to separate data on surface soil (less than or equal to 3" deep) from data on subsurface soil (more than 3" deep). Sample S1 served as the background reference. The appearance and locations of these samples are presented in Table 2. The description and exact locations of the 1995 soil and sediment samples were not available for review. The background samples are S101 and S201. Sample S102 is sediment from the quarry pond, S103-105 are from the surface soil, and S202-205 are from the former creek beds.

The Quality Assurance/Quality Control (QA/QC) summary for 1991 sampling was obtained from IEPA. It states that field data and sampling quality during the site assessment were satisfactory. No analytical problems were noted in the QA/QC summary. No QA/QC summary for 1995 sampling was available for review, but in preparing this health assessment, IDPH assumes that adequate QA/QC measures were followed during the sampling, laboratory procedures, and data reporting. IDPH also assumes the soil and sediment samples are representative of surface soil.

During the site visit, IDPH noted that access to the site from the western and southern sides of the property is limited only by a wooded area and Sugar Run Creek. Children have occasionally played in these wooded areas, and, though improbable, they could enter the site. The quarry pond is not fenced and is a physical hazard because trespassers, especially children, could fall in it. The tar pit is double fenced, but both fences are inclined toward the pit and would be easy to climb.

The contaminant concentrations detected in samples taken in 1991 and 1995 were compared with appropriate comparison values (see Attachment 6 for explanation of comparison values) to select contaminants that may pose a public health threat upon exposure. The levels of metals were compared with IEPA mean concentrations from urbanized areas expected to represent naturally occurring soil background in Illinois (5). Chemicals exceeding comparison values and those for which no comparison values were available, were selected for further evaluation for both exposure and for non-carcinogenic and carcinogenic effects if exposure occurs. These contaminants, their concentrations from both 1991 and 1995 sampling events, and the appropriate comparison values are presented in Table 3 (for soil) and Table 4 (for groundwater). Table 5 lists the contaminants found in samples collected in 1991 and 1995 that were at levels greater than comparison values .

Exceeding a comparison value does not mean that adverse health effects will occur upon exposure. The amount of the contaminant, as well as the duration and route of exposure, and the health status and receptivity of exposed individuals, are important factors in determining the potential for adverse health effects. The cancer potency of polycyclic aromatic hydrocarbons (PAHs) was estimated based on their relative potency to benzo(a)pyrene (BaP) by using USEPA Toxicity Equivalency Factors (TEFs).

An exposure pathway consists of a source of contamination, environmental media and transport mechanisms, a point of exposure, a route of exposure, and a receptor population. Exposure to a contaminant may have occurred in the past, may be occurring now, or may occur in the future. When all the five elements that link the contaminant source to an exposed population are known, a completed exposure pathway exists. When information on one or more of the five elements is missing, only a potential exposure pathway exists. Completed and potential exposure pathways at Matheson Gas are presented in Table 6.

Of the contaminants selected, BaP, chrysene, arsenic, and lead may pose a health risk to people if they are exposed to concentrations present in the contaminated soil and sediment on the site. Cadmium was found in the tar pit at elevated levels, but it is known to cause cancer only by inhalation and intramuscular injection. Ingestion of cadmium may cause adverse, non-cancer effects, but no one would likely ingest enough cadmium present in the tar pit to cause any adverse effects. Exposure to contaminated soil and sediment by ingestion or skin contact is unlikely to cause cancer. The low concentrations of the other contaminants are unlikely to cause adverse health effects. The highest concentrations of contaminants capable of causing adverse health effects were inside and at the edges of the tar pit, the quarry pond, and the dry former creek beds. High levels of iron and manganese were found in all groundwater samples taken in 1991, including the off-site background well. They can produce an unpleasant taste or water appearance and contribute to the deposition of scale on pipe walls, but these chemicals are unlikely to affect health at the levels found. None of the 1995 on-site and off-site groundwater samples contained contaminants at levels that exceeded comparison values.

Currently, no hazardous waste is generated at Matheson Gas, but contaminants from the past refinery activities exist at the site. Past, current, and future completed exposure pathways are present for contaminated surface soil and sediment at several on-site points of exposure: the tar pit, quarry pond, and dry creek beds. The 1991 and 1995 comparative levels of contaminants of concern (BaP, chrysene, arsenic, and lead) at these locations are presented in Table 7. The tar pit holds refinery waste that is still contained in the unit, but there are no controls to prevent a release. In the 1991 tar pit samples, chrysene measured 44 milligrams per kilogram (mg/kg) and lead measured 318 mg/kg. No analytical results were available for samples taken in 1995.

The quarry pond, which poses a drowning hazard, is an active unit that manages wastewater discharge and where scrap cylinders have been disposed in the past. It has no release controls. In the Quarry Pond 1991 sampling, arsenic was present at 27.7 mg/kg, and lead was present at 378 mg/kg. BaP and chrysene were not detected. The quarry pond is used for fishing. Although some fish bioaccumulate arsenic in their tissues, most of this is in a non-toxic form (6). Moreover, facility personnel reported that no one eats the fish. In the 1995 sampling, BaP was present at 3 mg/kg, chrysene at 5.3 mg/kg, and arsenic and lead were not detected. While the tar pit and quarry pond are waste management units, the dry former creek beds contamination suggests that on-site chemicals migrated downgradient from the site. In the 1991 dry creek bed samples, chrysene was present at 5.5 mg/kg, lead at 318 mg/kg, and BaP and arsenic were not detected. In 1995 samples, BaP was present at 5.4 mg/kg, chrysene at 5.9 mg/kg, and lead at 1,410 mg/kg.

IDPH compared the 1991 and 1995 contaminant levels and found an increase in the levels of BaP and lead over time. BaP was not detected in the Quarry Pond and former creek beds samples in 1991, but BaP exceeded comparison values in the 1995 samples. Lead levels in the former creek beds rose from about 4 times the Illinois soil background level in 1991 to about 20 times the background level in 1995. If no hazardous waste is currently generated at Matheson Gas, then the source of these increased pollutants levels might be a recent migration from past refinery activity sites, the corroded scrap cylinders buried 20 to 30 years ago, or an unknown activity at the site or in the vicinity.

The 26 on-site workers and occasional trespassers are exposed by ingesting contaminated soil and sediment found in the dry creek beds, the tar pit, and the quarry pond as they work in those areas. There are fences to restrict the access to the tar pit, but they were partially down during the site visit and were easy to climb. No fences exist around the quarry pond and along the western and southern borders of the property. The posted warning signs may not be enough to deter trespassers, especially children. High lead levels in soil and former creek beds are especially harmful to children if they play at the site.

Present and future potential exposures may result if contaminants from the surface soil are blown into the air or migrate to the groundwater where the private wells draw water. Of the 26, 010 residents within a 4-mile radius of the site, about 7,169 residents are served by private well water and could be exposed by drinking, inhaling, or direct skin contact with contaminated water in their homes if private wells become contaminated. Data available for review do not adequately characterize the migration of contaminants into the groundwater because all groundwater samples taken in 1991 were collected upgradient of the tar pit and former creek beds, and only one sample was collected on the site. The tar pit manages past refinery waste, and former creek beds contain contaminants that likely migrated from the site. Also, no surface water sampling was done. Surface water runoff and groundwater flow into Sugar Run Creek, and the creek itself might carry site contaminants further downstream. The tar pit and the quarry pond are open water surfaces, and contaminants may volatilize into the air and reach nearby yards and houses. Contaminated surface soil particulates may also be windblown nearby.

The results of human and animal studies suggest that arsenic is a known human carcinogen, while BaP(7), chrysene, and lead are probable human carcinogens. Adults employed at the site for at least 15 years, might have a low increased risk of developing cancer, assuming they ingest 100 milligrams (mg) of the contaminated soil and sediment daily. If cancer occurs, it would most likely be cancer of the skin, lung, or liver. To increase their risk of getting cancer, children must play on the site daily for 6 months every year for at least 5 years and ingest 200 mg of contaminated soil and sediment each day. This scenario is very unlikely to occur.

Lead may also cause noncancerous adverse health effects if people, especially children, are exposed to concentrations found in the on-site soil and sediment samples (8). Lead can affect almost every organ and system in the body. Most sensitive is the central nervous system, particularly in children. Lead also damages the kidney and the immune system. The effects are the same whether lead is inhaled or swallowed. Exposure to lead poses the greatest danger to young and unborn children exposed through their mothers. Harmful effects include premature births, decreased birth weight, decreased mental ability in the infant, learning difficulties, and reduced growth. In adults, lead may cause headache, fatigue, slow reaction time, and weakness in fingers, wrists, or ankles. Lead may damage the blood-forming system and cause anemia. Some lead compounds have been shown to cause cancer in animals; however, no sufficient data exist to attest to the potential cancer risk in humans.



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