A recent article by researchers at Duke University, RTI International, California State University-Bakersfield, and the Pacific Institute evaluates how trace metals from inorganic compounds in produced water used to irrigate California crops may affect human health. “Is Food Irrigated with Oilﬁeld-Produced Water in the California Central Valley Safe to Eat? A Probabilistic Human Health Risk Assessment Evaluating Trace Metals Exposure,” published in the Wiley Online Journal, is the first peer‐reviewed study to evaluate how trace metals in OPW used to irrigate California crops may affect human health.
In California, drought and a reduction in natural water availability in recent decades have led to a search for alternative water sources for agriculture. One controversial potential source is OPW, a byproduct of oil extraction. For this study, the authors modeled and quantified risks associated with consuming foods irrigated with produced water using available concentration data. The probabilistic risk assessment simulated produced water metal concentrations, crop uptake, human exposures, and potential noncancer and carcinogenic health effects. Overall, the findings indicate there is a low risk of ingesting toxic amounts of metals from the consumption of tree nuts, citrus, grapes, and root vegetables irrigated with produced water. However, the results show increased arsenic cancer risk for adult vegetarians, assuming higher consumption of multiple foods irrigated with OPW that contain high arsenic concentrations. The study finds that other cancer risks are below levels of concern and noncancer hazards are far below levels of concern.
The study scope was limited to inorganic constituents such as sodium, boron, and naturally occurring radioactive materials. It suggests that produced water may provide a safe and sustainable alternative irrigation water source if water is blended as needed prior to irrigation and water quality is adequately monitored. Future risk assessment research should model the risks of organic compounds in OPW, since this study focused on inorganic compounds.
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