Karl Mathiesen “Air pollution causes low birth weight, Beijing study shows” http://www.theguardian.com/environment/2015/apr/28/air-pollution-causes-low-birth-weight-beijing-study-shows
2008年の北京オリンピック期間中、中国政府は工場の操業を停止させたり、建築工事を中断させたり、北京中心部への自動車の乗り入れを制限したりという介入を行い、その結果、北京の大気汚染は一時的に大幅に改善した。
さて、最近公刊されたローチェスター大学のDavid Rich*1を中心とした米中の研究者による研究によると、2008年に北京で出生し北京オリンピック期間中に妊娠後期の胎児だった赤ん坊（つまり、オリンピックの直後に生まれた子ども）は2007年や2009年に北京で生まれた子どもよりも出生時の体重が大きかった*2。出生時の体重の大きい子どもは乳幼児期の疾病の危険が低い。
The research surveyed the birth weights of 83,672 babies born in Beijing around the time of the 2008 Olympics, when the government closed down industry, raised vehicle emissions standards, stopped construction and introduced a license plate rotation to slash the number of vehicles on the road.The massive state intervention created a one-off natural laboratory in which air pollution levels in one of the most choked cities on Earth reduced by between 18% and 59% during the summer of 2008. Birth weights were an average of 23g higher for babies who were in the eight month of pregnancy during the summer of the Games than during the same period in 2007 and 2009 .
Mothers who were between one and seven months pregnant during the Beijing Olympics gave birth to babies of a similar size in all three years studied. Rich said the short period of lower pollution, and these mothers’ subsequent exposure to higher levels before giving birth, did not prove that no positive effect occurred from cleaner air during the early months of pregnancy.But the study showed that during late pregnancy air pollution was restricting the fastest phase of foetal development. Rich said this was likely due to a restriction of nutrient delivery through the placenta, but the precise reason was unknown.
“These findings not only illustrate one of the many significant health consequences of pollution, but also demonstrate that this phenomenon can be reversed,” said associate professor David Rich, a health scientist from the University of Rochester in the US.“Even a short term reduction in pollution in a community has a very large public health impact. Some of these babies will have fewer complications or diseases later in life. So any time we can improve or increase birth weight we’re protecting not only the babies when they are born, but also in later life,” he said.
Rich said that when the results were extrapolated beyond Beijing’s smoggy suburbs the total impact of air pollution was massive. “A major percentage of the world’s population lives in environments with pollution levels this high. You could name a lot of those cities in China and India. But this shouldn’t be thought of as only a problem in cites with very high air pollution. Even in cities that have lower pollution we see effects on birth weight.”
*1:See eg. https://www.urmc.rochester.edu/people/27458686-david-rich
*2:David Q. Rich, Kaibo Liu, Jinliang Zhang, Sally W. Thurston, Timothy P. Stevens, Ying Pan, Cathleen Kane, Barry Weinberger, Pamela Ohman-Strickland, Tracey J. Woodruff, Xiaoli Duan, Vanessa Assibey-Mensah, and Junfeng Zhang “Differences in Birth Weight Associated with the 2008 Beijing Olympic Air Pollution Reduction: Results from a Natural Experiment” http://ehp.niehs.nih.gov/1408795/
