Chemical pollutants associated with fewer female births

The new study reveals that mainly two groups of related chemicals, i.e., polybrominated biphenyls (PBBs) and polychlorinated biphenyls (PCBs) can affect human reproduction.

PBBs were previously utilised as flame retardants in plastics, electronics and textiles. On the other hand, PCBs were used in almost everything ranging from home appliances to fluorescent lighting and insecticides etc.

Both of these chemicals were banned during the 1970s after being discovered that they are potentially dangerous to health. However, they are still a cause of concern as they have not been thrown out of the environment completely. They are accumulating in the fat of fish, mammals and birds.

Parents’ high exposure to PBB and PCB leads to increased chances of male birth

For conducting the current study, researchers took into account data from a group of Michigan residents who, in the early 1970s, had been unintentionally exposed to elevated levels of PBBs. These chemicals reached the humans through contaminated meat, eggs and milk when they accidentally got mixed with cattle feed.

After analysing the statistics, researchers noted that between the time period of 1975 to 1988, women in the study group had a higher-than-average rate of male births.

Also, there was an indication that increased odds of a male birth were very high when both the parents were exposed to PBB. This was in comparison to couples who had a lower PBB exposure.

Similarly, couples exposed to high PCB levels had a higher rate of male births.

Certain PBBs and PCBs can also change levels of male and female sex hormones. But whether they actually advance the survival of Y-bearing over X-bearing sperm is still not clear.

A thorough study analysis needs to be done

According to lead researcher Metrecia Terrell, of Emory University in Atlanta, how all these results can be generalised for everyone is still uncertain.

Terrell said, “This was a unique situation, so it’s very difficult to extend the findings to people with everyday exposures.”

She further added, “Exposure in the general population would be much lower and we just don’t know if there are effects on sex ratio.”

Many previous researches have found out that birth ratio is on a decline in the U.S. and elsewhere. A recent study showed that in the U.S. in 2001, the boys to girls ratio was 104.6:100. This disparity is less than what it was in 1970, when the ratio was 105.5:100.

The reason behind this difference in the ratio could be environmental toxins because many chemicals affect the possibility of sperm that bears the Y chromosome, which eventually determines male sex.

However, a continuing research on the potential effects of these chemicals on the reproductive system needs to be done to come to a concrete conclusion.

The latest study findings have been published in the journal Environmental Health.