On October 15th, the Lancet Respiratory Medicine Journal published a landmark study demonstrating a significant association among maternal exposure to pollution and traffic during pregnancy and an increased risk of low birthweight and a reduction in the head circumference of newborns. Though air pollution through ambient particulate matter was known to affect the health, especially the respiratory health, of adults and children, little was known as to how such pollution could affect fetal growth and development. In the study, entitled “Ambient air pollution and low birthweight: a European cohort study (ESCAPE),” researchers pooled fourteen different cohort studies conducted in twelve European countries. The research involved over 74,000 women and infant pairs, and the data spanned the course of seventeen years.
Air pollution can be measured in a number of ways, and in this study the researchers focused on the concentrations of particulate matter (“PM”) around each of the 74,178 maternal homes. They calculated ambient air pollution, as well as PM2.5 absorbance and concentrations of nitrogen dioxide and nitrogen oxide around the homes. In addition, the researchers investigated the traffic density and total traffic loads on the roads closest to each maternal home.
Ultimately the researchers were able to make a number of conclusions concerning particulate matter and traffic’s effects on fetal growth. First, a 5 microgram per cubic meter (“μg/m3”) increase in PM2.5 (fine particulate matter) during pregnancy was associated with an increased risk of low birthweight at term. Researchers found that mothers exposed to PM2.5 concentrations at considerably lower levels than the current European Union annual limit of 25 μg/m3 were linked to reductions in newborn head circumference and an increased risk of low birthweight. In addition, high levels of PM10, nitrogen dioxide, and greater traffic density on the nearest street were associated with an increased risk of low birthweight. Altogether, an estimated 22% of low birthweight cases could be avoided by a reduction of ambient PM2.5 concentration to 10 μg/m3 during pregnancy.
ESCAPE and similar studies could have great implications for international environmental law. The European Union has developed an extensive body of air quality law recognizing and attempting to address the health risks posed by particulate matter, but ESCAPE provides a strong indication that air quality laws in the European Union should be even more stringent. The European Union’s new air quality law, Directive 2008/50/EC, went into force in 2008. The “directive on ambient air quality and cleaner air” places limits on fine particulate matter for the first time, and directed all member states to not only respect the new PM2.5 limit of 25 μg/m3, but also introduce legislation to meet the standard by 2015. Yet the World Health Organization, critics, and scientific studies indicate that the European Union’s PM2.5 limit should be much closer to 10 μg/m3. As ESCAPE demonstrates, a reduction in particulate matter pollution in European urban areas could reduce the number of low birthweight infants, as well as the health risks, challenges, and costs associated with restricted fetal growth.
During the European Commission’s air pollution summit in January 2013, the World Health Organization’s Regional Office for Europe reviewed the latest health data as a key step in evaluating whether to update Europe’s air quality limit values. Perhaps ESCAPE and similar studies will increase the pressure on the European Parliament to draft a new, more restrictive air quality directive in the near future.