Air pollution ‘as bad as smoking’ for increasing risk of miscarriage United States
Air pollution is as bad for pregnant women as smoking in raising the risk of miscarriage, according to a new scientific study.
The researchers said the finding was upsetting, and that toxic air must be cut to protect the health of the next generation.
Air pollution is already known to harm foetuses by increasing the risk of premature birth and low birth weight. Recent research has also found pollution particles in placentas.
The effect of long-term exposure to dirty air on the risk of miscarriage has been analysed previously. Studies from Brazil to Italy to Mongolia found a link, but others failed to do so.
However, the latest study is the first to assess the impact of short-term exposure to air pollution. It found that raised levels of nitrogen dioxide (NO2) pollution that are commonplace around the world increased the risk of losing a pregnancy by 16 per cent.
‘‘It’s pretty profound,’’ said Dr Matthew Fuller of the University of Utah’s department of emergency medicine, a member of the research team. ‘‘If you compare that increase in risk to other studies on environmental effects on the foetus, it’s akin to tobacco smoke in first trimester pregnancy loss.’’
NO2 is produced by burning fuel, particularly in diesel vehicles.
The research, published in the journal Fertility and Sterility, was conducted in Salt Lake City and surrounding urban areas. But Fuller said the results were applicable elsewhere. ‘‘This is a problem we are all facing.’’
NO2 levels in Salt Lake City are similar to those in cities such as London and Paris.
Fuller was initially alerted to the issue when a family member miscarried during a particularly poor period of air quality in 2016. He teamed up with the population health scientist Claire Leiser and others to see if the effect was real. They analysed the records of more than 1300 women after miscarriages from 2007 and 2015.
A woman’s exposure to air pollution at the time of the miscarriage was compared with similar times when she did not miscarry, meaning that age, weight, income and other personal factors were accounted for. The strongest link with a lost pregnancy was the level of NO2 in the seven days before the miscarriage.
The mechanism by which air pollution could harm a foetus has not yet been established but a likely hypothesis is that the pollutants cause oxidative stress and inflammation.
Dr Sarah Stock of the University of Edinburgh, who was not part of the research team, said: ‘‘Air pollution is clearly detrimental to the health of millions of mothers, babies and children worldwide. Measures to reduce the impact of air pollution are crucial to ensure the health of future generations.’’
But she noted that the risk of miscarriage varied substantially with the number of weeks of pregnancy, and that the study had not been able to record this information, potentially introducing a bias into the result.
‘‘If we were able to get the gestation stage, that would be a real benefit, to get a sense of when the woman is most at risk,’’ Leiser said.
Fuller said women could time their pregnancies to avoid the most polluted times of year, avoid exertion on polluted days, and consider buying indoor air filters. ‘‘But in the developing world, these are luxuries many people can’t afford.’’
Dr Sarah Stock, University of Edinburgh