title: A panel study of occupational exposure to fine particulate matter and changes in DNA methylation over a single workday and years worked in boilermaker welders.
abstract: BACKGROUND
  Exposure to pollutants including metals and particulate air pollution can alter DNA methylation. Yet little is known about intra-individual changes in DNA methylation over time in relationship to environmental exposures. Therefore, we evaluated the effects of acute- and chronic metal-rich PM2.5 exposures on DNA methylation.
  
  
  METHODS
  Thirty-eight male boilermaker welders participated in a panel study for a total of 54 person days. Whole blood was collected prior to any welding activities (pre-shift) and immediately after the exposure period (post-shift). The percentage of methylated cytosines (%mC) in LINE-1, Alu, and inducible nitric oxide synthase gene (iNOS) were quantified using pyrosequencing. Personal PM2.5 (particulate matter with an aerodynamic diameter ≤ 2.5 μm) was measured over the work-shift. A questionnaire assessed job history and years worked as a boilermaker. Linear mixed models with repeated measures evaluated associations between DNA methylation, PM2.5 concentration (acute exposure), and years worked as a boilermaker (chronic exposure).
  
  
  RESULTS
  PM2.5 exposure was associated with increased methylation in the promoter region of the iNOS gene (β = 0.25, SE: 0.11, p-value = 0.04). Additionally, the number of years worked as a boilermaker was associated with increased iNOS methylation (β = 0.03, SE: 0.01, p-value = 0.03). No associations were observed for Alu or LINE-1.
  
  
  CONCLUSIONS
  Acute and chronic exposure to PM2.5 generated from welding activities was associated with a modest change in DNA methylation of the iNOS gene. Future studies are needed to confirm this association and determine if the observed small increase in iNOS methylation are associated with changes in NO production or any adverse health effect.
authors.forename: Molly L
authors.initials: ML
authors.lastname: Kile
authors.forename: Shona
authors.initials: S
authors.lastname: Fang
authors.forename: Andrea A
authors.initials: AA
authors.lastname: Baccarelli
authors.forename: Letizia
authors.initials: L
authors.lastname: Tarantini
authors.forename: Jennifer
authors.initials: J
authors.lastname: Cavallari
authors.forename: David C
authors.initials: DC
authors.lastname: Christiani
mesh_terms: D000328:Adult; D000395:Air Pollutants, Occupational / Q000032:analysis / Q000633:toxicity*; D019175:DNA Methylation; D006801:Humans; D008297:Male; D008875:Middle Aged; D052247:Nitric Oxide Synthase Type II / Q000235:genetics* / Q000378:metabolism; D016273:Occupational Exposure / Q000009:adverse effects* / Q000032:analysis; D052638:Particulate Matter / Q000032:analysis / Q000633:toxicity*; D011401:Promoter Regions, Genetic; D014896:Welding; D055815:Young Adult
chemical_list: D000395:Air Pollutants, Occupational; D052638:Particulate Matter; C496319:NOS2 protein, human; D052247:Nitric Oxide Synthase Type II