This is how pollution determines the sex ratio of babies born - Study

Mercury, chromium and aluminium pollution results in the birth of more boys, while lead pollution increased the number of baby girls born.

Pollution may have a say in the number of boys and girls being born. A new research has shown that some pollutants are linked to higher number of male births, while some determine the number of girls that are born.

Pollutants and Poverty Indicators

The study was conducted into the ratio of baby boys to girls born in the US and Sweden. Findings of the study show that a number of pollutants and poverty indicators can skew the sex ratio in these countries.

These findings were arrived at by examining over half of the US population of approximately 150 million for over eight years and the entire Swedish population of approximately 9 million for over 30 years.

Researchers tested more than 100 possible factors and found that increased levels of air and water pollutants were associated with lower SRBs - human sex ratio at birth (SRB) is defined as the ratio between the number of newborn boys to the total number of newborns. The researchers said:

Our present study is the first systematic investigation of numerous chemical pollutants and other environmental factors using large datasets from two continents.

Mercury, chromium and aluminium pollution coincided with the birth of more boys, while lead pollution increased the number of baby girls born.

Dispelling the Myths

Higher chemical exposures in farming communities also affected the sex ratio. However, the season of birth, weather temperature, unemployment and violent crimes were not shown to have impacted the ratio in any way.

Andrey Rzhetsky at the University of Chicago is the research lead. She said:

There are a lot of myths about sex ratio and birth, but when you dig into the research, it turns out that everything that was tested on real data was done on relatively small samples [risking spurious correlations], and some statements are not founded in observations at all.

However, the team believes more research needs to be done to examine the effects of chemicals on human cells or animal models in the laboratory to pin them as the direct cause. Rzhetsky said:

This is a list of suspects to investigate, and all the suspects have some credible evidence, but we’re very far from conviction.
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