On April 8, 2021, the US EPA released an updated toxicity assessment for perfluorobutane sulfonic acid (PFBS), which is a PFAS. The toxicity assessment was one of the key goals of the EPA’s PFAS Action Plan. It is expected that the EPA, states, local governments and tribal communities will use this toxicity assessment to determine whether to take action on PFBS to address human health risks in their communities. PFBS was used as a replacement chemical for PFOS, which was phased out of US manufacturing by 2002. PFBS has been identified in many products as well as in the environment across the US.

The toxicity assessment is part of the EPA’s human health risk assessment process, and is a summary of the potential health effects of PFBS. The assessment also identified the exposure levels at which those health effects may occur. EPA developed a chronic and subchronic oral reference dose for PFBS. These reference doses refer to the amount of a chemical a human can ingest daily over a lifetime (chronic) or less time (subchronic) that is unlikely to cause adverse health effects. The reference doses EPA developed are as follows:

Chemical	Subchronic Reference Dose	Chronic Reference Dose
PFBS	0.001 mg/kg-day	0.0003 mg/kg-day

 

This toxicity assessment suggests that PFBS is less toxic for humans than the more widely studied compounds PFOA and PFOS, which have chronic reference doses of 0.00002 mg/kg-day each.

At this time, EPA has reported that they are not issuing a regulation for PFBS, but are providing this toxicity assessment to the public to give state, local, and tribal agencies information to determine whether local action may be necessary.