The derivation of a Reference Dose (RfD) for perfluorooctane sulfonate (PFOS) based on immune suppression

Area of Science:

• Environmental Toxicology
• Immunotoxicology
• Public Health

Background:

• Perfluorooctane sulfonate (PFOS) is a persistent environmental contaminant with widespread human exposure.
• PFOS exposure is linked to various adverse health effects, including immunosuppression.
• Assessing PFOS human health risks is a priority due to its persistence and ubiquity.

Purpose of the Study:

• To derive a health-protective Reference Dose (RfD) for chronic human exposure to PFOS, specifically focusing on immunosuppression.
• To integrate evidence from animal toxicology and human epidemiology to support the derived RfD.
• To compare the derived RfD with existing regulatory values and assess their adequacy.

Main Methods:

• Conducted an in-depth literature review to identify immunosuppression as a sensitive endpoint for PFOS toxicity.
• Derived a chronic RfD based on decreased plaque-forming cell (PFC) response in animal studies.
• Performed a weight-of-evidence analysis integrating animal and epidemiological data (decreased vaccine response, childhood infections).

Main Results:

• Established a PFOS RfD of 1.8 × 10^-6 mg/kg/day based on decreased PFC response in mice.
• Epidemiological data on reduced vaccine response and increased childhood infections support the animal study findings.
• The derived RfD suggests the U.S. Environmental Protection Agency's (USEPA) existing RfD may not sufficiently protect against PFOS-induced immunosuppression.

Conclusions:

• Immunosuppression is a sensitive endpoint for PFOS toxicity, supporting the derivation of a specific RfD.
• The newly derived RfD provides a more protective guideline for chronic PFOS exposure.
• Public health can be better protected by minimizing PFOS exposure based on this evidence-based RfD.