Soil Bioavailability at Superfund Sites

Bioavailability is the amount of a contaminant absorbed into the body following skin contact, ingestion or inhalation. Relative bioavailability of a contaminant in soil is how much of a contaminant is absorbed from soil as compared to how much of that contaminant is absorbed from a reference exposure medium (e.g., food, water) that relates back to the toxicity value of the contaminant. This website describes how EPA is incorporating relative bioavailability information for human exposures at Superfund sites exposed to soil contaminants via oral pathway. The website does not address non-human exposures.

For the general public

Relative bioavailability is how much of a contaminant is absorbed from soil as compared to how much of that contaminant is absorbed from food or water.

For site assessors

Oral relative bioavailability is the fraction of an ingested dose that crosses the lining of the intestines and becomes available for distribution to human tissues and organs relative to an experimentally reported absorption value. As defined above, relative bioavailability and oral absorption fraction are equivalent terms.

EPA is providing this information so that site assessors can use bioavailability data to make more informed cleanup decisions. This definition does not consider the case of metals that may act directly upon the lining of the intestines (e.g., irritants and corrosives).