PFAS
PFOA
PFOA, or perfluorooctanoic acid, is one of the best-studied PFAS and carries an EPA drinking water limit of 4.0 parts per trillion under the national PFAS drinking water rule.
PFOA stands for perfluorooctanoic acid. It is one of the two PFAS that EPA studied longest, along with PFOS. It was used in industry and consumer products.
EPA's PFAS drinking water page lists PFOA among the PFAS with their own enforceable limit, called a maximum contaminant level. The table shows the PFOA limit as 4.0 parts per trillion.
The rule is still moving. On May 18, 2026, EPA announced proposed rules that keep the PFOA and PFOS limits but would let water systems request two more years, to 2031, to comply. Check EPA's page for the current status before you plan around a date.
Private wells are not covered by these public water system limits. If you own property in Missouri with a well, or a site with a PFAS history, a lab test is the only way to know your number. Learn the units in parts per trillion first.
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