title: Polychlorinated biphenyls (PCBs) in relation to secondary sex ratio--a systematic review of published studies.
abstract: There is reasonably strong evidence linking reduced secondary sex ratio (proportion of males) and environmental exposures. Polychlorinated biphenyls (PCBs) are persistent contaminants of the environment and several studies have reported an association of PCBs with birth outcomes. A decrease in the male/female sex ratio at birth has been reported in some, but not all studies. The aim of this systematic review was to summarize and pool the research findings about the influence of PCBs on sex ratio. Several article databases and reference lists of identified articles were searched. Studies reporting the proportion of boys and girls born to individuals who were exposed to high PCB concentrations were included. The primary outcome measure was the proportion of males in groups exposed to high or low levels of PCBs. Studies with both direct and indirect surrogate PCB measurements were included. The search and selection resulted in 15 eligible studies on the association between the sex ratio and parental PCB exposures. Analyses of the high exposure groups showed that the sex ratio was not significantly altered from the historical reference range in 13 of the 15 articles. The majority of the exposure studies reported also internal comparisons between high and low PCB exposure levels. The pooled 95% confidence interval estimate for the difference in high and low maternal exposure with direct PCB measure was - 0.048 with 95% CI of (-0.121, 0.026). There was no strong or moderate indication that parental exposure to PCBs alters the sex ratio of the children.
authors.affiliation: Medical Informatics and Statistics Research Group, University of Oulu, P.O. Box 5000, FIN-90014 Oulu, Finland. pentti.nieminen@oulu.fi
authors.forename: Pentti
authors.initials: P
authors.lastname: Nieminen
authors.forename: Heli
authors.initials: H
authors.lastname: Lehtiniemi
authors.forename: Antti
authors.initials: A
authors.lastname: Huusko
authors.forename: Kirsi
authors.initials: K
authors.lastname: Vähäkangas
authors.forename: Arja
authors.initials: A
authors.lastname: Rautio
mesh_terms: D004785:Environmental Pollutants / Q000032:analysis*; D004787:Environmental Pollution / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008297:Male; D018811:Maternal Exposure / Q000706:statistics & numerical data*; D011078:Polychlorinated Biphenyls / Q000032:analysis*; D012744:Sex Ratio
chemical_list: D004785:Environmental Pollutants; D011078:Polychlorinated Biphenyls