title: A cohort study of in utero polychlorinated biphenyl (PCB) exposures in relation to secondary sex ratio.
abstract: BACKGROUND
  Polychlorinated biphenyls (PCBs) are ubiquitous industrial chemicals that persist in the environment and in human fatty tissue. PCBs are related to a class of compounds known as dioxins, specifically 2,3,7,8-TCDD (tetrachloro-dibenzodioxin), which has been implicated as a cause of altered sex ratio, especially in relation to paternal exposures.
  
  
  METHODS
  In the 1960's, serum specimens were collected from pregnant women participating in the Child Health and Development Study in the San Francisco Bay Area. The women were interviewed and their serum samples stored at -20 degrees C. For this study, samples were thawed and a total of eleven PCBs were determined in 399 specimens. Secondary sex ratio, or sex ratio at birth, was evaluated as a function of maternal serum concentrations using log-binomial and logistic regression, controlling for hormonally active medications taken during pregnancy.
  
  
  RESULTS
  The relative risk of a male birth decreased by 33% comparing women at the 90th percentile of total PCBs with women at the 10th percentile (RR = 0.67; 95% CI, 0.48-0.94; p = 0.02), or by approximately 7% for each 1 mug/L increase in total PCB concentration. Although some congener-specific associations with sex ratio were only marginally statistically significant, all nine PCB congeners with < 30% of samples below the LOQ showed the same direction of association, an improbable finding under the null hypothesis.
  
  
  CONCLUSIONS
  Maternal exposure to PCBs may be detrimental to the success of male sperm or to the survival of male embryos. Findings could be due to contaminants, metabolites or PCBs themselves.
authors.affiliation: Department of Public Health Sciences, School of Medicine, TB #168, University of California-Davis, Davis, CA 95616, USA. ihp@ucdavis.edu
authors.forename: Irva
authors.initials: I
authors.lastname: Hertz-Picciotto
authors.forename: Todd A
authors.initials: TA
authors.lastname: Jusko
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Willman
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: Baker
authors.forename: Jean A
authors.initials: JA
authors.lastname: Keller
authors.forename: Stuart W
authors.initials: SW
authors.lastname: Teplin
authors.forename: M Judith
authors.initials: MJ
authors.lastname: Charles
mesh_terms: D000328:Adult; D015331:Cohort Studies; D004781:Environmental Exposure / Q000009:adverse effects*; D004785:Environmental Pollutants / Q000032:analysis / Q000097:blood / Q000633:toxicity*; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D007407:Interviews as Topic; D016015:Logistic Models; D008297:Male; D011078:Polychlorinated Biphenyls / Q000032:analysis / Q000097:blood / Q000633:toxicity*; D012495:San Francisco; D012744:Sex Ratio
chemical_list: D004785:Environmental Pollutants; D011078:Polychlorinated Biphenyls