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People are most likely to be exposed to contaminants in soil at 0 to 3 inches deep. When excavation occurs, such as with soil removal or grading, contaminants found in deeper soil layers are then brought to the surface and present a risk for people to be exposed to the contaminants deeper in the soils. The Mason and Dixon Tank Lines soil samples were collected from a depth of 0.5 feet to 6.5 feet and do not represent the surface layers. However, because the site is scheduled for cleanup activities that will likely involve soil removal or grading, we consider both the shallow and deep soil contamination as representative of surface soil. Any workers present on the site during the cleanup activities may be exposed to both chlordane and aluminum-contaminated dust as they perform their cleanup activities. Anyone present at the site before cleanup activities begin may have been exposed to the chlordane present in shallow soil.

Aluminum concentrations were found above the Illinois background soil concentration of 10,148 milligrams per kilogram of soil (mg/kg) (2). Elevated levels of aluminum were present mainly in the "deep" samples collected from 3.5-6.5 feet in depth, and levels ranged between 11,100 and 21,500 mg/kg. We do not have a comparison values for the metal aluminum, but we do know that high levels of airborne aluminum dust in a workplace setting may cause respiratory difficulty as a result of diffuse destruction of the small airways around dust deposits and a decrease in lung volume (3). If workers are not protected and dust control measures are not used when cleanup activities or grading is done, workers could be exposed to the aluminum attached to dust particles. Unlike in an occupational setting where the aluminum dust is fine and a good bit can be inhaled, most of the dust that would be generated would likely be ingested as it attaches to the mucus membranes and is eventually swallowed. However, some dust may enter the lungs. Aluminum concentrations were also higher than background levels in groundwater samples, but ingested aluminum is less likely to constitute a hazard to human health because it is poorly absorbed in the gastrointestinal tract (4).

Chlordane, a pesticide used mainly to control termites in homes before 1988, was found in concentrations above the soil comparison level of 400 mg/kg. Soil sample X127 collected from a depth of 0.5-2 feet contained 1,000 mg/kg of alpha-chlordane, and 1,800 mg/kg of gamma-chlordane. A worker exposed to a 1,800 mg/kg soil concentration of chlordane for 5 days a week, 50 weeks per year, for 30 years, could ingest daily a dose of 0.002 mg of chlordane for each kilogram of body weight, which surpasses the 0.0006 mg/kg/day chronic oral minimal risk level developed by the Agency for Toxic Substances and Disease Registry. The minimal risk level is an estimate of the daily human exposure to a dose of a chemical that is likely to be without an appreciable risk of adverse noncancerous health effects over a specified duration of exposure. Chlordane may affect the nervous system, the digestive system, and the liver (5).

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