By Miriam Stix, November 1, 2013
(Reuters Health) -
Women exposed to even low levels of urban air pollution during
pregnancy may be at heightened risk of having a low-birthweight baby,
according to a review of evidence from Europe.
Based on data for more
than 74,000 women in 12 European countries over a 15-year period,
researchers say that if pollution levels were lowered to limits set by
the World Health Organization (WHO), 22 percent of cases of low
birthweight would be avoided.
is similar to the number of cases that would be prevented by cessation
of maternal smoking during pregnancy in this European population," said
lead author Dr. Marie Pedersen from the Centre for Research in
Environmental Epidemiology in Barcelona, Spain.
who weigh less than 5.5 pounds at birth are at increased risk of
respiratory problems in childhood, as well as other disorders later in
looked at 14 studies of pregnant women who had a child at full term
between 1994 and 2011. She told Reuters Health the researchers
specifically focused on areas "where people live" - as opposed to
industrial locations - and selected cities that are much smaller, with
less dense traffic than the average American city.
researchers were able to obtain detailed birth records, including home
addresses during pregnancy, infant birthweight and gestational age and
sex, from maternal health centers in Scandinavia, Western Europe,
England, Lithuania and Greece.
also developed their own intensive air-monitoring network, sending
teams to residential areas in the study and measuring pollution levels
over three different seasons. Pedersen and her colleagues also used data
from air monitoring stations and combined it with information on
traffic density and land use.
they looked at women's exposure during pregnancy to the type of fine
particles in vehicle exhaust and some industrial air pollution, they
found that for every increase of 5 micrograms per cubic meter of air, the risk of low birthweight at term rises by 18 percent.
addition to the babies' weight at birth, the study looked at their head
circumference because of its potential effect on brain development,
according to Pedersen. They found reductions in the head size of babies
whose mothers were exposed to average small particle concentrations of
more than 15 micrograms per square meter.
researchers took into account factors like maternal smoking, age,
height and weight and education, and still concluded that all air
pollutants, especially fine particulates, as well as traffic density,
were tied to an increased risk of low birthweight and reduced average
head circumference at birth.
the women studied, the average exposure levels to fine particulates
during pregnancy ranged from less than 10 micrograms per cubic meter of air to nearly 30 micrograms.
The results were published in The Lancet Respiratory Medicine.
European Union air quality standards recommend limiting a person's
average fine particulate exposure over the course of a year to no more
than 25 micrograms per cubic meter.
United States Environmental Protection Agency (EPA) sets an upper limit
for a 24-hour period of 35 micrograms per cubic meter, but in 2013 EPA
lowered the annual exposure limit to 12 micrograms per cubic meter. The
WHO standard is no more than an average of 10 micrograms per cubic
If the women in
the study had all been exposed to only the WHO standard for
particulates, Pedersen said, 145 cases of low birthweight among 50,151
babies would have been prevented.
setting new more stringent standards for ambient air pollution, the
United States has taken a leadership role," said Tracey Woodruff,
director of the Program on Reproductive Health and the Environment at
the University of California, San Francisco. But most cities in the
United States are currently out of compliance.
Europe has better regulations on toxic chemicals, the United States has
been a leader in this area, and it could be that this study will be
more evidence for the Europeans to take action," added Woodruff, who has
researched the effects of pollution exposure during pregnancy.
said pregnant women worldwide are exposed to air pollution at similar
or even higher concentrations than those found in her group's study, and
the results "provide a clear message to policymakers to improve the
quality of the air we all share."
need cars and we need to heat our homes, but I think it is possible to
develop cleaner cities," she said. "It's a change that can happen and I
really hope it will, because there are so many bad health outcomes
related to air pollution."
Jonathan Grigg from Queen Mary University of London, UK, said,
"‘acceptable' levels (of air pollution) may well need to be revised
downward in the light of this and other studies."
this would involve weighing costs and benefits, "policy makers also
have to take a precautionary approach when considering children's
health," said Grigg, who wrote a commentary accompanying Pedersen's
study and is co-chair of the Royal College of Physicians Working Party
on air quality and life effects.
a London resident, told Reuters Health in an email that he would like
to place cell-phone size personal monitors onto pregnant women to see
what determines how much particulate pollution they're exposed to. That
could suggest generic precautions, like avoiding walking right next to
heavily used roads, that do not "either impact on lifestyle or make
women feel guilty," he said.
also suggested that policymakers take steps to reduce urban air
pollution by requiring reductions in emissions by cars, taxis and buses.
Development of stop/start technology to prevent idling, and requiring
fuel cell power for buses, would also help.
SOURCE: bit.ly/1gFSOkP and bit.ly/1iy8Yep The Lancet Respiratory Medicine, online October 15, 2013.