Ratio male female high low, why?

In a work published in Environmental Health , the authors question whether the contamination of some industrial chemicals has been banned, causing gender imbalance (low female to male ratio). .

The negative effects of organic chemicals containing halogenated elements such as bromine and chlorine, in particular polibrombiphenyl (PBB for short) and polysaccharide (abbreviated PCB), have negative effects on health. People, right from the 70s of the last century, many countries have banned use.

PCBs have been widely used as flame retardants as additives for plastics, as well as in the textile and electronics manufacturing industries, PCBs are also widely used from lighting devices and fluorescent lamps. Optical to insulating materials and pesticides.

Seeing the potential danger of detecting them too durable, undamaged, persistent in the environment and accumulating residues in fish fat, mammals and birds, the world has eliminated the This is in the list of industrial chemicals.

Recently, when long-term imbalance in the US infant sex imbalance is seen, researchers have raised the problem by Metrecia Terrel, Emory University in Atlanta (USA). are these substances.

(Artwork: Blogspot)

They relied on a study by the University of Michigan team on unintentional cases of high levels of PBB exposure because they were mixed into animal feed, leading to infection by humans. meat, milk and eggs must be sold on the market.

It is found that the rate of male births in couples exposed to PBB is much higher than those of low-exposed parents (average PBB content).

When considering couples exposed to PCBs, the results are similar.

The proportion of boys born, by law, is always higher than girls but not much. So in the 1970s (the US period has not banned PBB and PCBs), in the US the rate of male sex surged (105.5 males per 100 females).

By 2001 (after the substances were banned for 15 years, the residual content in the environment was less) the proportion of boys born decreased, but still slightly higher at 104.6 males per 100 females.

The researchers explained that chemicals in the environment play a certain role. For example, chemicals can affect the vitality of Y chromosome-bearing sperms - determine the male sex - or the vitality of male embryos.

In this case, it is the negative impact of PCB and PBB, which currently does not explain the mechanism.

Researcher Terrell and colleagues added that some substances in the PBB group and PCBs have also been shown to alter sex hormones. But whether they ' kill ' the Y chromosome sperm or negatively affect the baby embryo is still unknown.

Currently, this research group is still pursuing the impact of environmental chemicals on the sex ratio of newborns.