A new study by the energy science and policy research institute, Physicians, Scientists, and Engineers (PSE) for Healthy Energy shows that the disposal of over 16 billion barrels of oil and gas wastewater into unlined pits over a 50-year period has introduced salts, carcinogens, and other toxins into regional aquifers.
source https://phys.org/news/2021-10-unlined-disposal-pits-endanger-groundwater.html