ALORTON, ST. CLAIR COUNTY, ILLINOIS
On-site soil is the focus of potential exposure and possible health effects from site-related contaminants. The on-site surface soil sample results were compared to Agency for Toxic Substances and Disease Registry soil comparison values and health guidelines based on ingestion (Attachment 1). Seven polycyclic aromatic hydrocarbons (PAHs) and zinc (Table 1) exceeded comparison values. The PAHs were selected for further evaluation because of their known or suspected carcinogenic potential. Zinc was selected for further evaluation because the concentration of 51,800 ppm detected in sample X104 exceeded the comparison value.
IDPH staff estimated an exposure dose for trespassing children exposed to zinc at the concentration found in sample X104. The calculated value for zinc exposure in children was 0.01 milligrams per kilogram per day (mg/kg/day). This calculation assumes that the child weighs 10 kg; consumes 100 mg/kg per exposure; is exposed twice a week for one half the year; and is exposed for ten years. The minimal risk level for chronic ingestion of zinc is 0.3 mg/kg/day. Exposure to zinc in soil would not be expected to cause adverse health effects in children.
The seven known or suspected carcinogenic PAHs were included in the exposure assessment. An ingestion dose was calculated for children and adults for each of the PAHs. The highest concentration of each PAH was used in the calculations (Table 2). The excess cancer risk was calculated for each PAH by using its relative carcinogenic potency to that of benzo(a)pyrene (BaP). The relative potencies of each compound to BaP were then multiplied by the USEPA cancer potency factor for BaP to determine the increased cancer risk. Table 2 contains the cancer risk for each PAH separately and for all the PAHs calculated together. No apparent increased risk exists for children or adults that may be exposed to PAHs in on-site soil.
An additional cancer risk calculation was made for people who may work on the site in the future. The cancer risk was calculated for an adult who would come into contact with the soil 5 days per week for 50 weeks per year for 30 years. No apparent increased cancer risk exists for this scenario, either.