Contamination of water with perflourinated chemicals (PFC’s) persists in many communities amid increasing concerns about the potential risk to public health, even at very low levels.

This map shows the counties in Kentucky, Ohio, Pennsylvania, and West Virginia with water systems that detected some level of PFC compounds in drinking water, and how that detected level compares to the various recommendations for allowable limits of these chemicals.

Detecting the chemicals in water does not necessarily mean that there is evidence of any harm or risk. The allowable threshold for these chemicals is the subject of debate in scientific and regulatory bodies. This map allows you to see the detected level in a water system relative to what various scientists and regulators have proposed as the acceptable level for these chemicals.

What is a “safe” level?

For example, the U.S. Environmental Protection Agency has set a health advisory level of .07 ppb, or parts per billion, for the PFC chemicals PFOA and PFOS. That’s 70 parts per trillion.

Many scientific studies, however, have indicated that there is the potential for harmful effects at lower levels, and have recommended that a far lower threshold (of .001 ppb, or 1 part per trillion) is required to protect public health.

Some government bodies are following that advice to set more restrictive limits. The European Union’s guidance on PFOA recommends .001 ppb for surface water and a panel of officials in New Jersey is considering a protective level of .014 ppb.

Many water systems that detected PFAS chemicals found levels that fall somewhere in this range above (or riskier than) what many scientific studies have recommended, but below (or more protective than) what EPA’s advisory requires. You can view this range and where the test sample results fall by clicking on the affected water system data. The detected level appears along with the following, for comparison:

EPA Advisory: EPA’s 2016 advisory for PFOA and PFOS is .07 ppb (or 70 ppt).

New Jersey (proposed): State officials are considering a more restrictive limit of .014 ppb.

European Union: The European Union’s guidance on PFOA recommends .001 ppb for surface water

Latest Science: Recent scientific studies have recommended a level of .001 ppb is most appropriate to safeguard public health.

A few things to know:

These test samples offer a snapshot of information. These numbers do not necessarily reflect what is coming from your tap at any given time, but rather what was found in a set of tests required by the U.S. EPA. Some water systems were tested multiple times. If a system was tested and came up positive for a given chemical more than once, the highest value detected is presented.

The EPA’s reporting system does not fully reflect some low levels of PFCs detected. Many researchers think the sampling should have been done in a way to detect and report much lower levels of these chemicals present, as most published scientific studies do so. A recent Harvard study noted that the threshold for reporting, or minimum reporting levels, EPA used were “up to 2 orders of magnitude higher than the limit” for detection in most published studies, and far higher than the safe drinking water limit many studies have recommended.

Not all water systems conducted the testing. The EPA program did not require the same testing for small water systems serving fewer than 10,000 people, and no testing of private wells. This means that we still have no data regarding these chemicals in the drinking water for about a third of the U.S. population.