In a review of all births in both countries, the University of Pittsburgh-led study found significantly fewer boys being born relative to girls in the U.S. and Japan, and that an increasing proportion of fetuses that die are male. They note that the decline in births is equivalent to 135,000 fewer white males in the U.S. and 127,000 fewer males in Japan over the past three decades and suggest that environmental factors are one explanation for these trends.
“The pattern of decline in the ratio of male to female births remains largely unexplained,” said Devra Lee Davis, Ph.D., M.P.H., lead investigator of the study, director of the University of Pittsburgh Cancer Institute’s Center for Environmental Oncology and professor of epidemiology, University of Pittsburgh Graduate School of Public Health. “We know that men who work with some solvents, metals and pesticides father fewer baby boys. We also know that nutritional factors, physical health and chemical exposures of pregnant women affect their ability to have children and the health of their offspring. We suspect that some combination of these factors, along with older age of parents, may account for decreasing male births.”
Dr. Davis explained that environmental factors, such as prenatal exposure to endocrine- disrupting environmental pollutants may impact the SRY gene – a gene on the Y chromosome that determines the sex of a fertilized egg. Other environmental factors that also may affect the viability of a male fetus include the parents’ weight, nutrition and the use of alcohol and drugs.
In the study, Dr. Davis and her colleagues reported an overall decline of 17 males per 10,000 births in the U.S. and a decline of 37 males per 10,000 births in Japan since 1970. They also found that while fetal death rates have generally decreased, the proportion of male fetuses that die has continued to increase. In Japan, among the fetuses that die, two-thirds are male, up from just over half in 1970.
The study also examined the ratio of African-American male to female births to that of whites in the U.S. The researchers found that while the number of African-American male births has increased modestly over time, the ratio of male to female births for African-Americans remains lower than that of whites. In addition, they noted that African-Americans have a higher fetal mortality rate overall and a higher proportion of male fetuses that die.
“These results are not surprising since the black-white ratio in terms of infant mortality has remained the same for almost 100 years,” said Lovell A. Jones, Ph.D., study co-investigator and professor and director, Center for Research on Minority Health, department of health disparities research, University of Texas M.D. Anderson Cancer Center. “Given the higher mortality rates for African-American males in the United States, these results reemphasize the need to determine all factors, including environmental contaminants, which are responsible for this continuing health disparity.”
“Given the importance of reproduction for the health of any species, the trends we observed in the U.S. and Japan merit concern,” added Dr. Davis. “In light of our findings, more detailed studies should be carried out that examine sex ratio in smaller groups with defined exposures as a potential indicator of environmental contamination.”
Clare Collins | EurekAlert!
Value from wastewater
16.08.2017 | Hochschule Landshut
Species Richness – a false friend? Scientists want to improve biodiversity assessments
01.08.2017 | Carl von Ossietzky-Universität Oldenburg
Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.
As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...
Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.
Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...
For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.
While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...
An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.
The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...
A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...
16.08.2017 | Event News
04.08.2017 | Event News
26.07.2017 | Event News
18.08.2017 | Life Sciences
18.08.2017 | Physics and Astronomy
18.08.2017 | Materials Sciences