Page 17 - Lake Roosevelt Forum 2020 Public Guide

CALCULATING LEAD, CANCER, AND NON-CANCER RISK
Calculating Cancer Risk
EPA assesses cancer risk by calculating the probability of excess exposure to one or more chemicals of concern.
For this investigation, cancer risks were considered acceptable if there was less than a 1 in 10,000 chance of someone being sufficiently exposed to
a cancer causing chemical. Numerically, this is expressed as 10-4. For each population group, cancer risks were also summed across all cancer-causing chemicals and exposure pathways.
No results exceeded the 1 in 10,000 chance that would trigger a human health concern.
Calculating Non-Cancer Risk
EPA uses a Hazard Quotient and Hazard Index as benchmarks to assess non-cancer risks from exposure to one or more chemicals.
• Individual chemical. When calculations show a Hazard Quotient (HQ) of < 1, then no adverse health effects are expected. Conversely, if the HQ > 1, then adverse health effects are possible.
• More than one chemical. When calculations show a Hazard Index (HI) of < 1, then no adverse health effects are expected. Conversely, if the HI > 1, then adverse health effects are possible.
Sections on the Upper Columbia Valley and Fish Consumption summarizes when non-cancer risks were exceeded.
Northport Soil Cleanup
In August 2020, EPA began soil cleanup of
10 residential properties and 5 common use areas in the town of Northport. Common use areas include Lyn Kaste Gould Memorial Park, the play area at the Northport Community Garden, and lawns at the Northport Community Library, Northport American Legion vacant lot and the Northport Welcome Center.
Soil at these properties will be replaced because the lead levels are a potential threat to people’s health, especially young children. All cleanup actions are
done with the consent of property owners, and the work is expected to be completed in the fall of 2020.
EPA’s 2004 soil cleanup in Northport addressed properties with lead levels near or above 1,000 parts per million (ppm). Based on advances in scientific understanding of lead exposure risks to young children and babies, EPA lowered the removal action level for lead in soil to 700 ppm. This is the same level EPA used when overseeing work conducted by Teck American to cleanup 18 residential properties outside of Northport town limits from 2015-2018.
EPA and its contractor excavate and remove lead-contaminated soil at the Lyn Kaste Gould Memorial Park in the town of Northport.
Images Courtesy of U.S. EPA
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