Bioavailability factor for improved drinking water contaminant exposure risk assessment accuracy

Despite being low in concentration, the presence of broad-spectrum chemical constituents in drinking water is a fact of modern life. The current drinking water chemical risk assessment practice predominantly relies on drinking exposure and chemical toxicity data, providing a valuable tool for regulation. However, only a fraction of chemicals is retained for a considerable duration within the human body, as the remainder are excreted or metabolized. This limits the efficacy of risk assessment when exclusively relying on water contaminants ingestion dose and toxicity potencies. We propose large scale incorporation of a bioavailability factor, F, into the calculation of chemical-mediated human health risk assessment for drinking water. Specifically, F values account for the ratio of one compound in human circulation and excretion and are multivariable specific, such as exposure route specific, and gender specific. Utilizing disinfection by-products (DBPs), an important group of chemicals commonly found in drinking water as an example, we provided detailed explanations of F values. Through incorporation of the F values, the accuracy of drinking water human health risk assessment may be improved as the biological retention ratio is accommodated, providing leniency on chemicals that less interact with the human body during internal retention. This approach has clear implications for the subsequent control measures and national drinking water standards updates for emerging pollutants.