Several pollutants influence whether a baby will be born a boy or a girl, according to study

The presence of certain pollutants in the air and water can influence whether a baby will be born a boy or a girl, according to the analysis of more than 6 million births in the United States and Sweden published this Thursday in the journal PLOS Computational Biology.

During this study, led by Andrey Rzhetsky of the University of Chicago (USA), researchers analyzed records of more than 3 million births in the United States from 2003 to 2011, as well as data from more than 3 million births in the Swedish National Patient Register from 1983 to 2013.

The experts crossed these data with information on the climate and different atmospheric and aquatic pollutants in the period of each birth.

In doing that analysis, the team led by Rzhetsky determined that several contaminants were associated with changes in the sex ratio at birth (SRB) during different stages, either increasing or decreasing the number of male babies relative to newborns of female gender.

According to their data, the presence of air pollutants such as polychlorinated biphenyls, iron, lead, mercury, carbon monoxide and aluminum, and aquatic pollutants such as chromium and arsenic, influenced the sex of the baby.

Additionally, experts found other factors associated with SRB, including extreme droughts and traffic accident rates.

When the researchers tried to determine links between two high-stress events in the US and SRB in nearby areas, they found no relationship between Hurricane Katrina in August 2005 and the local SRB, but a significant association in the area. Virginia Tech shooting case in April 2007.

Despite these findings, Rzhetsky said this study cannot determine whether these contaminants actually caused the observed changes in SRB.