The Environmental Protection Agency is warning that two nonstick and stain-resistant compounds found in drinking water are more dangerous than previously thought and pose health risks even at levels so low they cannot currently be detected. The two compounds, known as PFOA and PFOS, have been voluntarily phased out by U.S. manufacturers, but there are a limited number of ongoing uses and the chemicals remain in the environment because they do not degrade over time. The compounds are part of a larger cluster of forever chemicals" known as PFAS that have been used in consumer products and industry since the 1940s. The EPA on Wednesday issued nonbinding health advisories that set health risk thresholds for PFOA and PFOS to near zero, replacing 2016 guidelines that had set them at 70 parts per trillion. The chemicals are found in products including cardboard packaging, carpets and firefighting foam. The toxic industrial compounds are associated with serious health conditions, including cancer and reduced birth weight. The revised health guidelines are based on new science and consider lifetime exposure to the chemicals, the EPA said. Officials are no longer confident that PFAS levels allowed under the 2016 guidelines "do not have adverse health impacts," an EPA spokesman said. PFAS chemicals have been confirmed at nearly 400 military installations and at least 200 million people in the United States are drinking water contaminated with PFAS.