Oil companies use dozens of extremely hazardous chemicals to acidize wells in California, raising water contamination and public-safety concerns, according to a new study in the Journal of Toxicological and Environmental Chemistry.

The University of California-Los Angeles study, which has national significance because it seems to be the first ever to examine the toxicity of acidization chemicals, finds that almost 200 different chemicals have been used in the process, which is frequently employed in urban areas of Los Angeles County.

Researchers at UCLA’s Institute of the Environment and Sustainability found that at least 28 of these substances are F-graded hazardous chemicals — carcinogens, mutagens, reproductive toxins, developmental toxins, endocrine disruptors or high acute toxicity chemicals. Hydrofluoric acid, for example, is acutely toxic, and exposure to fumes or very short-term contact with its liquid form can cause severe burns.

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