Citation:

Pennino, M., S. Leibowitz, J. Compton, M. Beyene, AND S. LeDuc. Wildfires can increase regulated nitrate, arsenic, and disinfection byproduct violations and concentrations in public drinking water supplies manuscript. SCIENCE OF THE TOTAL ENVIRONMENT. Elsevier BV, AMSTERDAM, Netherlands, 804:1-15, (2021). https://doi.org/10.1016/j.scitotenv.2021.149890

Impact/Purpose:

The results of this manuscript report the impacts of wildfires on public drinking water supply contaminant concentrations and violations of their maximum contaminant level across the United States.  We analyzed nitrate, arsenic, volatile organic compounds (VOCs), and two disinfection byproducts (DBPs): total trihalomethanes and haloacetic acids.  All these contaminants are regulated by the US Safe Drinking Water Act and have data compiled in EPA’s Safe Drinking Water Information System (SDWIS).  Excess nitrate is known to cause blue baby syndrome or methemoglobinemia, and arsenic, disinfection byproducts, and VOCs are known to be carcinogens.  When comparing post vs. pre-wildfire periods, wildfires were found, on average, to significantly increase violations and concentrations of nitrate in drinking water sourced from groundwater and surface water, DBPs from surface water sources, and arsenic from groundwater sources.  This analysis may inform decisions on how source water protection and other management options could best protect drinking water from contamination, when wildfires occur further upstream. 

Description:

Wildfires are a concern for water quality in the United States, particularly in the wildland-urban interface of populous areas. Wildfires combust vegetation and surface soil organic matter, reduce plant nutrient uptake, and can alter the composition of runoff and receiving waters. At the wildland-urban interface, fires can also introduce contaminants from the combustion of man-made structures. We examine post-wildfire effects on drinking water quality by evaluating concentrations and maximum contaminant level (MCL) violations of selected contaminants regulated in the U.S. at public drinking water systems (PWSs) located downstream from wildfire events. Among contaminants regulated under the U.S. Safe Drinking Water Act, nitrate, arsenic, disinfection byproducts, and volatile organic compounds (VOCs) were analyzed in watersheds that experienced major wildfires. Surface water sourced drinking water (SWDW) nitrate violations increased by an average of 0.56 violations per PWS and concentrations increased by 0.044¿mg-N/L post-wildfire. Groundwater sourced drinking water (GWDW) nitrate violations increased by 0.069 violations per PWS and concentrations increased by 0.12¿mg-N/L post-wildfire. SWDW total trihalomethane (TTHM) violations increased by 0.58 violations per PWS and concentrations increased by 10.4¿μg/L. SWDW total haloacetic acid (HAA5) violations increased by 0.82 violations per PWS and concentrations increased by 8.5¿μg/L. Arsenic violations increased by 1.08 violations per PWS and concentrations increased by 0.92¿μg/L. There was no significant effect of wildfires on average VOC violations. Nitrate violations increased in 75% of SWDW sites and 34% of GWSW sites post-wildfire, while about 71% and 50% of SWDW sites showed an increase in TTHM and HAA5 violations. Violations also increased for 35% of arsenic and 44% of VOC sites post-wildfire. These findings support the need for increased awareness about the impact of wildfires on drinking water treatment to help PWS operators adapt to the consequences of wildfires on source water quality, particularly in wildfire-prone regions.

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