Toxins blamed for baby boys declining in U.S. & Japan
NEW YORK - Mother Nature has always ensured that male births outnumber female ones, but the gap has been steadily narrowing over the past three decades in the U.S. and Japan, according to a new study.Researchers believe the decline in male births can be enlightened, at least in part, by fatherly exposure to environmental toxins, such as certain pesticides, heavy metals, solvents or dioxins - chemical byproducts produced during ignition or the manufacture of other chemicals.
Traditionally, it’s been estimated that for every 100 girls born, there will be about 105 boys. This balances out the higher death rate among male fetuses and infants. But since 1970, the U.S. and Japan have knowledgeable a descending shift in this male-to-female birth ratio, researchers report in the online edition of the journal Environmental Health Perspectives.
In the U.S., the share of boys dropped from 105.5 per 100 girls in 1970 to 104.6 in 2001; in Japan, the male-to-female ratio dropped from 106.3 boys for every 100 girls to just fewer than 105 per 100.
The changes may seem small, but the study authors suspect they are one manifestation of the effects of environmental poisons on the male reproductive system.
These other signs, she told Reuters Health, include lower testosterone levels and sperm counts, as well as boosts in testicular cancer, a disease that most frequently affects young men.
Environmental toxins may be a common denominator here, according to Davis and her colleagues. Such exposures may specifically lower rates of male, rather than female, births for a few reasons. They may, for example, affect the viability of sperm that bear the Y chromosome, which determines male sex — or the viability of male fetuses.
Reuters
Traditionally, it’s been estimated that for every 100 girls born, there will be about 105 boys. This balances out the higher death rate among male fetuses and infants. But since 1970, the U.S. and Japan have knowledgeable a descending shift in this male-to-female birth ratio, researchers report in the online edition of the journal Environmental Health Perspectives.
In the U.S., the share of boys dropped from 105.5 per 100 girls in 1970 to 104.6 in 2001; in Japan, the male-to-female ratio dropped from 106.3 boys for every 100 girls to just fewer than 105 per 100.
The changes may seem small, but the study authors suspect they are one manifestation of the effects of environmental poisons on the male reproductive system.
These other signs, she told Reuters Health, include lower testosterone levels and sperm counts, as well as boosts in testicular cancer, a disease that most frequently affects young men.
Environmental toxins may be a common denominator here, according to Davis and her colleagues. Such exposures may specifically lower rates of male, rather than female, births for a few reasons. They may, for example, affect the viability of sperm that bear the Y chromosome, which determines male sex — or the viability of male fetuses.
Reuters
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