Keywords: BCF, bioconcentration factor, dioxin levels, risk assessment, water pollution, environmental pollution, water quality, human health risks, hydrophobicity, fish contamination, contaminated sediment
Sediment dioxin levels as the basis for risk assessment and human health criteria
Methods for assessing human health risks and establishing water quality criteria under the Clean Water Act are based on the assumption that fish accumulation of dioxin is correlated with the dissolved phase of the dioxin in the water column by a water-to-fish predictive factor called a bioconcentration factor. However, dioxin does not remain dissolved in the water column to any significant degree, but sorbs to organic matter in the water column and sediment. Under Toxic Substances Control Act regulations, dioxin's hydrophobicity is recognised, and fish dioxin levels are predicted with a solids-to-fish factor. These two different predictive methods can result in extremely variable predictions of fish contaminant levels. A methodology for establishing criteria under the Clean Water Act, which considers fish uptake of sorbed hydrophobic compounds by way of ingestion of contaminated sediment, is offered as an alternative to the methods used today.