An approach to identifying high priority areas for research on disinfection byproducts has been
explored. Chemicals that have been identified as byproducts of chlorination for which there are
no primary data available to describe their toxicological properties were subject to quantitative
structure toxicity relationship (QSTR) analysis utilizing TOPKAT®, a program that includes
modules for predicting the probability that a chemical is a carcinogen or developmental toxicant.
The program also estimates a chronic lowest observed adverse effect level (LOAEL). The latter
parameter has been used to estimate the likely potency of a chemical, whether it acts as a
general toxicant, carcinogen or developmental toxicant. This has allowed comparisons of
different classes of disinfection byproducts (DBPs) and to identify those chemicals within a class that
may be of most concern. In general, the potency of halogenated DBPs fit within the same
ranges as observed with carcinogens in general. Median levels of chronic LOAELs of the
halogenated DBPs fall into the range of 10-100 mg/kg day<sup>-1</sup>. This potency range captures most
of the regulated DBPs, although some are seen to fall above 100 mg/kg day<sup>-1</sup>. However, there
is considerable variation in median potencies of different halogenated DBP classes. Several
classes of common halogenated DBPs appear to be significantly more potent (e.g. the
halonitriles, haloamides and furanones related to MX). The greater potency predicted for MX
and its analogs are not too surprising, but these DBPs typically occur at much lower
concentrations. It is of interest that limited exploration of non-halogenated byproducts identified
classes of DBPs that have median potencies approximately 2 orders of magnitude greater than
halogenated compounds (e.g. nitrosamines). This analysis suggests that byproducts that
involve nitrogenous precursors need to be investigated much more fully than they have to been
to date. Includes 19 references, tables, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 14 |
| Published : | 11/15/2004 |
