The results of a new scientific study has found a link between toxic environmental chemicals in the air and water and sex ratio at birth (SRB)*. More specifically, several environmental toxins were linked to higher SRBs. In short, this means that the gender of newborns may be affected by the level of toxins (including endocrine-disrupting chemicals) in the air and water that parents are exposed to. The takeaway is that according to the study results, changes in the human sex ratio at birth—defined as the percentage of newborns that are boys—are associated with the presence of air and water pollutants.
The new study evaluated over six million births in the US and Sweden. Scientists analyzed records from the IBM Health MarketScan insurance claim dataset on more than three million births in the US from 2003 to 2011, as well as records on more than 3 million births in the Swedish National Patient Register from 1983 to 2013.
They also assessed additional data on weather and pollutants at the time of each birth that was available from other national databases.
What are the specific toxic chemicals linked with affecting SRB?
Levels of pollutants including iron, lead, mercury, carbon monoxide, polychlorinated biphenyls (PCBs), aluminum in the air and chromium and arsenic in water were all linked to changes in SRB. How is this possible? At a biological level, the researchers said SRB is affected by hormonal factors that specifically terminated female or male embryos during pregnancy.
The scientists have called for further studies to understand the link between pollution and changes in SRB, adding that the findings could encourage policymakers to “decide to make steps toward reducing environmental pollution.”
*SRB was defined by the study as the percentage of newborns who are boys.
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Journal Reference: Long, Y., Chen, Q., Larsson, H. & Rzhetsky, A. Observable variations in human sex ratio at birth. PLoS Computational Biology Journal, 17(12): e1009586.