Objectives Determine if perfluorooctanoic acid (PFOA) is associated with an incident disease in an occupational cohort.

Methods We interviewed 3713 workers or their next of kin in 2008–2011, and sought medical records for self-reported disease. These workers were a subset of a previously studied cohort of 32 254 community residents and workers. We estimated historical PFOA serum levels via a job-exposure matrix based on over 2000 serum measurements. Non-occupational exposure from drinking water was also estimated. Lifetime serum cumulative dose (combining occupational and non-occupational exposure) was our exposure metric. We studied 17 disease outcomes with more than 20 validated cases.

Results The median measured serum level was 113 ng/mL in 2005 (n=1881), compared with 4 ng/mL in the US. Ulcerative colitis (10-year lag) showed a significant trend (p≤0.05) with increasing dose (quartile rate ratios (RRs)=1.00, 3.00, 3.26, 6.57, n=28, p for trend=0.05), similar to earlier findings in the community study. Rheumatoid arthritis (no lag) showed a positive trend in a categorical trend test (RRs=1.00, 2.11, 4.08, 4.45, n=23, p for trend=0.04). Positive non-significant trends were also observed for prostate cancer, non-hepatitis liver disease and male hypothyroidism, which have been implicated in other studies. A significant negative trend was found for bladder cancer and asthma with medication. No marked trends were seen for high cholesterol, which had been seen in the community study.

Conclusions Ulcerative colitis and rheumatoid arthritis were positively linked to PFOA exposure among workers. Data were limited by small numbers, under-representation of hard-to-trace decedents and few low-exposed referents.