Breathing air pollution may be as toxic as cigarette smoke for pregnant women

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Breathing the air outside their homes may be just as toxic to pregnant women —if not more so — as breathing in cigarette smoke, increasing a mom-to-be’s risk of developing deadly complications such as preeclampsia, according to findings from a new University of Florida study.

UF researchers compared birth data with Environmental Protection Agency estimates of air pollution, finding that heavy exposure to four air pollutants led to a significantly increased risk for developing a high blood pressure disorder during pregnancy. The research was published in the January issue of the Journal of Epidemiology and Community Health.

The pollutants include two specific types of fine and coarse particulate matter, carbon monoxide and sulfur dioxide. According to the EPA, particulate matter includes acids, dust, metals and soil particles. These inhalable particles are released from industries and forest fires and can form when gases react with each other in the air. Sulfur dioxide is emitted from power plants and industries. Most carbon monoxide is produced by car exhaust.

“Fetal development is very sensitive to environmental factors,” said Xiaohui Xu, M.D., Ph.D., an assistant professor of epidemiology in the colleges of Public Health and Health Professions and Medicine. “That is why we wanted to do this research. Hypertension (high blood pressure), in particular, is associated with increased morbidity and mortality, causing a lot of problems for the mother and fetus, including preterm delivery.”

Hypertensive disorders such as gestational hypertension, preeclampsia and the deadly condition it leads to, eclampsia, affect about 10 percent of pregnancies. Despite the serious risks to mother and baby, little is known about what specifically causes these conditions to develop in pregnant women, the researchers say.

Although more studies are needed, the researchers hypothesize that exposure to air pollution during pregnancy may affect a woman’s normal pattern of blood pressure.

“We also want to look at preterm delivery and low birth-weight and find out what the effects of breathing contaminated air are on fetal development.” Xu said.

Large study finds exposure to even low levels of air pollution during pregnancy has risks

"Our findings suggest that a substantial proportion of cases of low birthweight at term could be prevented in Europe if urban air pollution, particularly fine particulate matter, was reduced", explains lead author Dr Marie Pedersen from the Centre for Research in Environmental Epidemiology in Barcelona, Spain.

The researchers estimate that for every increase of 5 micrograms per cubic metre (5µg/m³) in exposure to fine particulate matter during pregnancy, found in for example traffic fumes and industrial air pollutants, the risk of low birthweight at term rises by 18%. Importantly, this increased risk persists at levels below the existing EU annual air quality limit of 25µg/m³. 

Using data from the European Study of Cohorts for Air Pollution Effects (ESCAPE, coordinated by the University of Utrecht, the Netherlands), the investigators pooled data from 14 cohort studies in 12 European countries involving over 74 000 women who had singleton babies between Feb, 1994 and June, 2011.

Air pollution concentrations of nitrogen oxides and particulate matter were estimated at the home addresses using land-use regression models. Traffic density on the nearest road and total traffic load on all major roads within 100m of the residence were also recorded.

All air pollutants, particularly fine particulate matter (PM 2.5; with a diameter of 2.5 micrometers or less), and traffic density increased the risk of term low birthweight and reduced average head circumference at birth, after accounting for other factors like maternal smoking, age, weight, and education.

The researchers estimated that if levels of PM 2.5 were reduced,  22% of cases of low birthweight among term deliveries could be prevented.

According to Dr Pedersen, "The widespread exposure of pregnant women worldwide to urban ambient air pollution at similar or even higher concentrations than those assessed in our study provides a clear message to policy makers to improve the quality of the air we all share."

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Study shows air pollution has a direct impact on heart attacks

Researchers at Rice University in Houston have found a direct correlation between out-of-hospital cardiac arrests and levels of air pollution and ozone. Their work has prompted more CPR training in at-risk communities.

Given that the American Lung Association has ranked Houston eighth in the United States for high-ozone days, statisticians Katherine Ensor and Loren Raunthe set out to see if there is a link between ambient ozone levels and cardiac arrest.

For the new study, the authors analyzed eight years’ worth of data drawn from Houston’s extensive network of air-quality monitors and more than 11,000 concurrent out-of-hospital cardiac arrests (OHCA) logged by Houston Emergency Medical Services (EMS).

They found a positive correlation between cardiac arrests and exposure to both fine particulate matter (airborne particles smaller than 2.5 micrograms) and ozone.

The researchers found that a daily average increase in particulate matter of 6 micrograms per day over two days raised the risk of OHCA by 4.6 percent, with particular impact on those with pre-existing (and not necessarily cardiac-related) health conditions. Increases in ozone level were similar, but on a shorter timescale: Each increase of 20 parts per billion over one to three hours also increased OHCA risk, with a peak of 4.4 percent. Peak-time risks from both pollutants rose as high as 4.6 percent. Relative risks were higher for men, African-Americans and people over 65.

For the study, OHCA events were defined as cases where EMS personnel performed chest compressions. Ensor and Raun noted the patients died in more than 90 percent of the cases, which occurred more during the hot summer months (55 percent of total cases).

The researchers also looked at the effects of nitrogen dioxide, sulfur dioxide and carbon monoxide levels, none of which were found to impact the occurrence of OHCA.

The work is expected to help Houston EMS fine-tune its deployment of personnel and equipment and provide early warnings to health officials and the public when weather and/or incidents warrant an alert for high ozone levels in specific areas, Ensor said.

Co-author David Persse, Houston Fire Department EMS physician director and a public-health authority for the city, said it’s long been thought by EMS workers that certain types of air pollution, including ozone, have significant negative effects on cardiac and respiratory health. “But this mathematically and scientifically validates what we know,” he said.

Houston is already acting upon the results.

“The city has targeted educational resources to at-risk communities, where they’re now doing intensive bystander CPR training,” Raun said. Early intervention is seen as critical, as the chance of survival for a person suffering cardiac arrest drops 10 percent for every minute he or she is left unattended. She said statistics show one life is saved for every 26 to 36 people who receive cardiopulmonary resuscitation from a bystander.

Houston’s effort is part of a range of interventions to mitigate the consequences of poor air quality days, though none are substitutes for the primary strategy of improving air quality, according to the city’s Health and Human Services Department.