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Both chlorinated and brominated trihalomethanes (THMs) and haloacetic acids (HAAs) are regulated under the US Environmental Protection Agency's Stage 2 Disinfectants and Disinfection Byproducts Rule (DBPR). All four chlorinated and brominated THMs are regulated as total THMs (TTHM) and of the nine HAAs, the sum of five HAAs (HAA5) are regulated; the four unregulated HAAs are all brominated species. The objective of this study was to assess national occurrence of all nine HAAs (HAA9) and disinfection byproduct (DBP) speciation. Modeling techniques are applied and validated to estimate HAA9 concentrations using TTHM and HAA5 species, as HAA9 data are limited. DBP speciation is assessed using bromine incorporation factors (BIFs). While national HAA9 occurrence, assessed using modeled HAA9 concentrations, decreased from 2005 through 2014, it increased in the two years after the Stage 2 DBPR implementation (when different sampling locations were used) compared with the two years prior. BIF values increased from 2005 through 2014, and spatial analysis showed higher BIF values in Southern California and Texas.
Samson et al. (Mon,) studied this question.