Pollution cuts off the number of new born males

Jun 4, 2007 18:56 GMT  ·  By

Many proud fathers insist on passing their family name on their sons.

In the Chinese culture, it is considered that only the male offspring can celebrate the cult of the forbears. In India, having a daughter could mean the ruin of your family when you have to pay her dowry. Sadly, in China, India and other Asian countries, the parents' wish to have a boy has triggered a massive slaughter of the female embryo and severely unbalanced gender ratios in some areas.

To complicate the view, a new research shows that boys are getting harder to make. Naturally, there are more boys born for every 100 girls. But boys are much more sensitive to disease and more likely to die during infancy, so that at the time of the sexual maturity, the sex ratio is balanced.

The research team led by Devra Lee Davis of the University of Pittsburgh worked with data on U.S. birth ratios from the National Center for Health Statistics. The researchers discovered that from 1970 to 2001, the sex ratio at birth male:female dropped continuously from 105.5 (105.5 boys for every 100 girls) to 104.6. The drop was the most severe amongst American white in the case of male births, the ratio dropped from 105.9 to 104.7.

The team discovered a similar decline in Japan, another industrialized country which could provide excellent data on birth records. The researchers also discovered that the percentage of death among fetuses after the 20th week of pregnancy (before that, sex can be difficult to determine; a recent technique detects it at 6 weeks, but this is a novelty) has continuously increased in both countries.

Partially, the decline in male births can be blamed on fetal loss but the rest of the issue is determined by fewer conceived males.

"The falling sex ratio coupled with the disproportionately male fetal deaths supports the hypothesis that males are being culled in some systematic fashion," explained the researchers.

The cause of this is puzzling the researchers; they believe that the shift is highly due to exposure to gender-bending pollutants, like certain plastics and metals which were proven in laboratory tests to preferentially impair male-producing Y sperms or to induce female development in genetically male embryos.