Using Good Science to Communicate Toxicity, Exposure, and Risk

摘要

Recycling of coal ash (coal combustion products, CCPs), is one of the great environmental success stories of our time. Over 42% of the coal ash produced in the U.S. is put into beneficial use, and is material that is not placed in disposal facilities. Almost 1/4 of this recycling is reuse in concrete and cement products. However, these uses are threatened by USEPA's potential regulation of coal ash as a hazardous waste, and by constant references to "toxic coal ash" by the press in response to environmental groups' writings. Therefore, a detailed health-risk based evaluation was conducted of coal ash data released in a report by the U.S. Geological Survey. This evaluation was conducted by comparing constituent concentrations in coal ash to risk-based screening levels developed by the USEPA that are protective of a child's direct exposure to residential soils (including ingestion, dermal contact and inhalation routes of exposure). These screening levels are considered by USEPA to be protective for daily exposure by humans (including sensitive groups) over a lifetime. Constituent concentrations in coal ash were also compared to background concentrations in soils in the U.S. The results indicate that with few exceptions constituent concentrations in coal ash are below screening levels for residential soils, and are similar in concentration to background U.S. soils. Thus, coal ash does not qualify as a hazardous substance based on its composition, and it also should not be classified as hazardous on a human health risk basis. Because exposure to constituents in coal ash used in beneficial applications, such as concrete, road base, or structural fill would be much lower than assumed for a residential soil scenario, these uses should also not pose a direct contact risk to human health.