…. Wastewater from oil and gas activities (or “produced water”) contains compounds that are known to be hazardous to human health. The volume of produced water has been increasing in California for decades. Much of this water is disposed via dangerous unlined ponds that impact groundwater that is currently or could be used for drinking or agricultural irrigation in California. While the report notes that drinking water wells close to oil and gas activities generally pose greater health risks, the state lacks publicly available data on which chemicals are found in produced water and comprehensive reporting on where produced water has been stored, disposed of, or spilled. The report recommends not only stronger regulations prohibiting the disposal of this toxic sludge in unlined produced-water ponds that are prone to contaminating fresh water, but also better access to information about where the oil and gas industry has been disposing of this mess.