title: Polychlorinated biphenyls and neurodegenerative disease mortality in an occupational cohort.
abstract: BACKGROUND
  Production of polychlorinated biphenyls (PCBs) ended in the United States in the 1970s, but PCBs persist in the environment and are detectable in the blood of approximately 80% of Americans over age 50. PCBs decrease dopamine levels in rats and monkeys. Loss of dopamine is the hallmark of Parkinson disease, a neurodegenerative disease. There are no epidemiologic studies of PCBs and neurodegenerative disease.
  
  
  METHODS
  We conducted a retrospective mortality study of 17,321 PCB-exposed workers to determine whether mortality from Parkinson disease, dementia, and amyotrophic lateral sclerosis was elevated compared with the U.S. population. All workers had a least 90 days employment in 1 of 3 electrical capacitor plants using PCBs from the 1940s to the 1970s. PCB serum levels from a sample of these workers in the 1970s were approximately 10 times the level of community controls.
  
  
  RESULTS
  We found no overall excess of Parkinson disease, amyotrophic lateral sclerosis, or dementia in the PCB-exposed cohort (standardized mortality ratios [SMRs]-1.40, 1.11, and 1.26, respectively, and number of deaths-14, 10, and 28 respectively). However, sex-specific analyses revealed that women had an excess of amyotrophic lateral sclerosis (SMR-2.26; 95% confidence interval [CI] = 1.08-4.15; 10 deaths). Furthermore, among highly exposed women (defined by a job-exposure matrix), we found an excess of Parkinson disease (SMR-2.95; 95% CI = 1.08-6.42; 6 deaths) and dementia (SMR-2.04; 95% CI = 1.12-3.43; 14 deaths).
  
  
  CONCLUSIONS
  Our data are limited due to small numbers and reliance on mortality rather than incidence data, but are suggestive of an effect of PCBs on neurodegenerative disease for women. The literature does not offer an explanation for why women would be more affected than men by PCB exposure for these outcomes.
authors.affiliation: Rollins School of Public Health, Emory University, 1518 Clifton Rd., Atlanta, Georgia 30322, USA. nsteenl@sph.emory.edu
authors.forename: Kyle
authors.initials: K
authors.lastname: Steenland
authors.forename: Misty J
authors.initials: MJ
authors.lastname: Hein
authors.forename: Rick T
authors.initials: RT
authors.lastname: Cassinelli
authors.forename: Mary M
authors.initials: MM
authors.lastname: Prince
authors.forename: Nancy B
authors.initials: NB
authors.lastname: Nilsen
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Whelan
authors.forename: Martha A
authors.initials: MA
authors.lastname: Waters
authors.forename: Avima M
authors.initials: AM
authors.lastname: Ruder
authors.forename: Teresa M
authors.initials: TM
authors.lastname: Schnorr
mesh_terms: D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D008297:Male; D019636:Neurodegenerative Diseases / Q000139:chemically induced* / Q000401:mortality; D016273:Occupational Exposure; D011078:Polychlorinated Biphenyls / Q000633:toxicity*; D012189:Retrospective Studies; D014481:United States / Q000453:epidemiology
chemical_list: D011078:Polychlorinated Biphenyls