title: Reduced fertility among women employed as dental assistants exposed to high levels of nitrous oxide.
abstract: BACKGROUND
  Fertility is reduced in female rats exposed to levels of nitrous oxide similar to those found in some dental offices. Epidemiologic studies have suggested an association between exposure to mixed anesthetic gases and impaired fertility. We investigated the effects of occupational exposure to nitrous oxide on the fertility of female dental assistants.
  
  
  METHODS
  Screening questionnaires were mailed to 7000 female dental assistants, ages 18 to 39, registered by the California Department of Consumer Affairs. Sixty-nine percent responded. Four hundred fifty-nine women were determined to be eligible, having become pregnant during the previous four years for reasons unrelated to the failure of birth control, and 91 percent of these women completed telephone interviews. Detailed information was collected on exposure to nitrous oxide and fertility (measured by the number of menstrual cycles without contraception that the women required to become pregnant).
  
  
  RESULTS
  After controlling for covariates, we found that women exposed to high levels of nitrous oxide were significantly less fertile than women who were unexposed or exposed to lower levels of nitrous oxide. The effect was evident only in the 19 women with five or more hours of exposure per week. These women were only 41 percent (95 percent confidence interval, 23 to 74 percent; P less than 0.003) as likely as unexposed women to conceive during each menstrual cycle.
  
  
  CONCLUSIONS
  Occupational exposure to high levels of nitrous oxide may adversely affect women's ability to become pregnant.
authors.affiliation: Epidemiology Branch, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709.
authors.forename: A S
authors.initials: AS
authors.lastname: Rowland
authors.forename: D D
authors.initials: DD
authors.lastname: Baird
authors.forename: C R
authors.initials: CR
authors.lastname: Weinberg
authors.forename: D L
authors.initials: DL
authors.lastname: Shore
authors.forename: C M
authors.initials: CM
authors.lastname: Shy
authors.forename: A J
authors.initials: AJ
authors.lastname: Wilcox
mesh_terms: D000293:Adolescent; D000328:Adult; D003726:Dental Assistants; D005260:Female; D005298:Fertility / Q000187:drug effects*; D006801:Humans; D009609:Nitrous Oxide / Q000009:adverse effects*; D016273:Occupational Exposure; D012189:Retrospective Studies; D011795:Surveys and Questionnaires
chemical_list: D009609:Nitrous Oxide