Average global levels are around 20–30 ng PFOS/mL in blood samples. Cohort occupational study shows increase in bladder cancer risk in exposed group. Rodent test shows that PFOS is a peroxisome proliferator, do not occur in humans. Inadequate evidence of carcinogenicity in humans and experimental animals. PFOS is a Group 3 agent (not classifiable as to its carcinogenicity to humans).