ECONOMY PRODUCTS COMPANY SITE
SHENANDOAH, PAGE COUNTY, IOWA
EPA is preparing for removal actions at the site. As previously mentioned, the proposal that 10 mg/kg total OC pesticide be used as a removal action level was based largely on precedence at similar EPA Region VII OC pesticide sites. However, further consideration and investigation by Region VII EPA resulted in the decision that chemical specific clean-up levels would be used at the EPC site.2 During the removal action, EPA plans to excavate soil with concentrations above the chemical specific clean-up levels.
The IDPH, Bureau of Radiological Health, Superfund Risk Assessor calculated compound specific risk-based clean-up levels using a Reasonable Maximum Exposure (RME) approach for current and future land uses.2 RME is defined by EPA as the highest exposure that is reasonably expected to occur at the site.6 RME is a high-end estimate (above the 90th percentile of the actual distribution) of exposure to a population. The RME approach is a conservative exposure estimate within the range of possible exposures and attempts to avoid estimates that are beyond the true distribution. The compound specific risk-based cleanup levels are considered protective of human health for industrial and residential scenarios.2
Media for consideration regarding potential human exposure at this site include: soil, air and groundwater. The relevant routes of human exposure for each media are:
- Soil -- Ingestion and dermal contact.
- Air -- Inhalation of vapors and dust resuspended from areas containing contamination.
- Groundwater -- Ingestion and dermal contact.
Based on the information and data reviewed, soil (surface and subsurface) and groundwater are contaminated with pesticides, VOCs, and herbicides. It appears that surficial soils surrounding the site were contaminated with pesticides as a result of the fire. However, routine use of pesticides by EMSNC, surface transport via runoff and historic residential use of pesticides may have contributed to the contamination. The highest surface and subsurface soil concentrations are located on-site. Vertical extent of contamination ranges from surficial residues at the site perimeter to the upper water bearing unit in the area where the fire occurred. The highest concentrations appear to be centered around this area. On-site contamination poses little public health threat due to its subsurface location, clay cap, and limited site access. However, if the subsurface soil is unearthed or excavated, long-term exposure could pose a health hazard to unprotected workers or site occupants. This is unlikely because EPA is planning a removal action.
Inhalation of vapors and resuspended dust from areas containing contamination is unlikely. OC pesticides have chemical properties that preclude volatilization (e.g., low volatility, tightly bind with soil and organic matter, etc.). Inhalation of vapors may have occurred during the fire, but this would have been a short-term exposure. VOCs detected in surface and subsurface soil samples and groundwater do not pose a health risk.
The upper water bearing zone beneath the former EPC site is contaminated with pesticides, VOCs, and to a limited extent herbicides. The lower water bearing zone needs to be more fully characterized. Only one downgradient groundwater sample was collected in the lower water bearing unit. The sample collected at Location No. 1 had a detectable concentration of dieldrin (0.02 µg/L). This location is downgradient and west of the area where the fire occurred. Exposure to contamination in either water bearing zone is unlikely. The City of Shenandoah obtains water from municipal wells located approximately 1.5 miles downgradient from the site. Analysis of samples from the community water supply system did not reveal any site-related contaminants. The city wells range in depth from 40-75 feet. Private residential wells do not exist near the site.
Organochlorine pesticides are neurotoxic and act by poisoning the nervous system. Based on the concentration of pesticides detected in surface soils, short-term exposure is not expected to result in neurological effects. However, some of the compounds are classified by EPA as probable human carcinogens, long-term exposure to levels above the chemical specific clean-up levels could pose a health risk. Consequently, long-term exposure is unlikely due to the location of the contamination and planned removal activities.