You are here:
THE TOXICOLOGY OF COMPLEX MIXTURES OF DISINFECTION BY-PRODUCTS
Citation:
SIMMONS, J. E. THE TOXICOLOGY OF COMPLEX MIXTURES OF DISINFECTION BY-PRODUCTS. Presented at Society of Toxicology, National Capital Area, Toxicology of Chemical Mixtures Symposium, Bethesda, MD, May 24, 2005.
Description:
Chemical disinfection of water is a major public health advance that has decreased dramatically water-borne disease. Chemical disinfectants react with naturally occurring organic and inorganic matter in water to produce a wide variety of disinfection byproducts (DBPs). DBP number, chemical type and concentration are dependent on source-water and treatment-scenario characteristics. Although more than 500 DBPs have been identified, ~50% of the total organic halide (TOX) mass formed during chlorination remains unidentified. Some epidemiological investigations have suggested associations, albeit weak, between human consumption of chlorinated drinking water and adverse health outcomes such as developmental and reproductive effects, and bladder, colon and rectal cancer. The health effects observed in some epidemiological studies are unexpected based on the available data from experimental-animal single-chemical DBP studies. Understanding the human health risk(s) associated with consumption and use of chemically disinfected water will require relevant toxicological information on individual DBPs, defined DBP mixtures of known composition and complex, environmentally realistic mixtures of DBPs. Individual DBP assessments are essential but do not account for potential interactions that influence toxicity. Component-based assessment of simple, defined mixtures are needed as four trihalomethanes (THMs, chloroform, bromoform, bromodichloromethane and chlorodibromomethane) and five haloacetic acids (HAAs, monochloro-, dichloro-, trichloro-, monobromo-, and dibromoacetic acid) are regulated together, respectively, under a total THM and a total HAA standard, Defined mixture data provide important information, but are not by themselves sufficient because a significant portion of the DBP mixture mass remains unidentified. Methods are needed to determine the portion of any observed toxicity attributable to the unidentified fraction of the mixture. This talk will summarize recent data on individual DBPs and both defined and complex mixture of DBPs. (This abstract does not represent EPA policy.)