Robin C. Leonard

Cross-sectional Study of Lipids and Liver Enzymes Related to a Serum Biomarker of Exposure (ammonium perfluorooctanoate or Apfo) as Part of a General Health Survey in a Cohort of Occupationally Exposed Workers

Objective: To examine the relationship between serum perfluorooctanoate (PFOA), a biomarker of ammonium perfluorooctanoate (APFO) exposure, and lipids and liver enzymes in a cross-sectional study among workers with potential occupational exposure to APFO. Methods: We conducted a cross-sectional study of 1025 active workers with potential exposure to APFO using linear regression to examine the relationship between PFOA and selected outcomes from a standard metabolic health screening survey, emphasizing lipids and liver enzymes. Results: Most outcome parameters were within normal limits. After adjusting for potential confounders, we observed a modest but statistically significant, positive relationship between serum PFOA and total cholesterol, low-density lipoprotein (LDL), very low-density lipoprotein (VLDL), and gamma glutamyl aminotransferase (GGT). No associations were seen for high-density lipoprotein (HDL) or bilirubin; associations with AST (aspartate aminotransferase) and ALT (alanine transpeptidase) did not reach statistical significance. Conclusions: Our findings indicate a modest positive association of PFOA on some lipid parameters and a need for follow-up studies.

Longitudinal study of serum lipids and liver enzymes in workers with occupational exposure to ammonium perfluorooctanoate.

Objective: To examine the relationship between serum perfluorooctanoate (PFOA), a biomarker of ammonium perfluorooctanoate exposure, and lipids and liver enzymes. Methods: We conducted a longitudinal study on 454 workers and used mixed models to examine the relationship between serum PFOA and lipids and liver enzymes. Results: One part per million (ppm) increase in serum PFOA was associated with a 1.06 mg/dL increase in total cholesterol, but was not associated with changes in triglycerides or other lipoproteins, after adjusting for potential confounders. Serum PFOA was also associated with total bilirubin (0.008 mg/dL decline/ppm) and serum aspartate aminotransferase (0.35 units increase/ppm) but not with the other liver enzymes. Conclusions: These medical surveillance data collected on workers for up to 25 years contributes useful information on the effects of ammonium perfluorooctanoate exposure on human liver and lipid chemistry.

Ischaemic heart disease mortality study among workers with occupational exposure to ammonium perfluorooctanoate

Objectives: Ammonium perfluorooctanoate (APFO) is a biopersistent surfactant used in the manufacture of several types of fluoropolymers. Based on previous findings of increased serum lipid levels associated with exposure to APFO, we evaluated ischaemic heart disease (IHD) mortality in a cohort of occupationally exposed workers. Methods: Relative risks (RR) were estimated from exposure–response analyses of cumulative exposure measures using proportional hazards regression models. Results: 239 IHD deaths have occurred in the cohort of 4747 workers with work histories from 1948 through 2002. RR estimates indicate no statistically significant increased mortality risk for IHD associated with estimated cumulative exposure. We observed a positive trend only at an exposure lag of 10 years. This finding was not reproduced in other 5-year exposure lags and was attenuated when different cutpoints for exposure categorisation were used. Conclusion: This exposure–response study shows no convincing evidence of increased IHD mortality risk for APFO-exposed workers at this plant. Further studies evaluating the incidence of IHD are being conducted.

A review of the epidemiology of 1,3-butadiene and chloroprene.

Butadiene epidemiologic research has focused primarily on one cohort of workers in the North American styrene-butadiene rubber (SBR) industry and on the largest cohort of workers in the United States butadiene monomer industry. The most recent studies of these populations are characterized by carefully enumerated study populations, extremely long and high quality mortality follow-up, accurate job categorizations, detailed exposure assessments, and comprehensive statistical analyses. Leukemia was clearly associated with increasing estimated butadiene exposure in the SBR study, but not in the monomer industry study. This has lead to hypotheses about exposure differences between these two industries and the presence of co-factors or confounders in the SBR industry. Research presented at this symposium should shed some light on these hypotheses. The chloroprene epidemiologic literature, on the other hand, is in an early stage of development. The existing studies are limited by poor exposure characterization, lack of control of potential confounding factors, incompleteness in cohort enumeration, short follow-up periods, and small numbers of cancer cases. The state of the science for chloroprene would be advanced by arranging more comprehensive studies than those that have been conducted to date.

Mortality among workers exposed to acrylonitrile in fiber production: an update.

Objective: The investigation updates the mortality experience through 2002 for a cohort of workers exposed to acrylonitrile (AN). Methods: Standardized mortality ratios (SMR) were estimated based on two reference populations: the US population and a regional employee population. Exposure–response analyses were conducted using Cox regression models for cumulative and mean intensity exposure measures. Results: In the cohort of 2548 workers, 839 deaths have occurred with 91 deaths due to respiratory system cancer. Most standardized mortality ratio estimates are at or near no-effects levels. Hazard ratio (HR) estimates indicate no increased mortality risk for respiratory system cancer (adjusted HR = 0.96, 95% confidence interval: 0.74, 1.25). Conclusions: In summary, no mortality outcome of a priori interest, principally respiratory system cancer, is associated with increased AN exposure among fiber production workers over five decades of follow-up.