The Effects of Air Pollution on Prenatal Health

By Molly Rauch

What a pregnant mom eats, drinks, and breathes can obviously affect her baby. We know this from studies of alcohol consumption and cigarette smoking, among other things. But how does air pollution affect her baby? Can the pollution a pregnant mom inhales, such as fine particles or soot, unknowingly cause health problems years down the line, when that baby is a teenager?

Dr. Frederica Perera, a professor at Columbia University’s Mailman School of Public Health and director of the Columbia Center for Children’s Environmental Health, focuses her research on just this question. She has been examining the effects of environmental exposures on pregnant women and their children for 15 years. Using personal air monitoring “backpacks” combined with ambient air monitors, Dr. Perera has been investigating the effects of air pollution on more than 700 mothers and their children in Northern Manhattan, with other ongoing studies in Poland and China.

Dr. Perera’s research explores the relationship between air pollution – specifically, exposure to polycyclic aromatic hydrocarbons (PAHs) – and birth weight, cancer markers, asthma, learning and behavior, obesity, and other health effects. PAHs are a group of chemicals released into the air when organic matter is burned, such as coal, gasoline, diesel fuel, firewood, and tobacco.

I spoke with her recently about her research.

Why do you study air pollution?

I study air pollution because it is a common and widespread exposure, in this country and of course globally. We have learned during the last several decades that exposure to air pollution has multiple adverse outcomes. Our work is focused on the prenatal window of susceptibility and the early period of child development because we know from many lines of evidence that this is a particularly important period for the potential disruption of normal development by environmental exposures. That’s been shown experimentally [in laboratory animals] and also in some studies, such as ours, in humans.

What are the major sources of air pollution for the population that you study?

We can talk about indoor and outdoor air pollution and sometimes people think that they’re completely separate, but they’re not. There is a great deal of exchange of air between the outdoor and indoor environment. Buildings are quite permeable, surprisingly so. The major sources of air pollution are combustion of organic material. Of course, fossil fuel combustion is a major source in urban areas. We’re talking about diesel, oil for heating, gasoline for vehicles, and coal burning. In addition, tobacco smoking causes air pollution. That’s a major indoor source, and it’s an indoor source of some of the very pollutants found in outdoor air from these other combustion sources.

Correlations between the levels of indoor and outdoor pollutants indicate that there is a considerable transfer from the outdoor to the indoor environment.

What are the health effects that you’re looking for?

Birth outcomes is the first thing we look at – birth weight, length, head circumference – and then we look at child development using standardized, validated measurements and instruments. We do the assessments periodically from the time the child is born all the way through adolescence. Our oldest children in the study are now 14. Of course the instruments change over time. They are age-appropriate tests and we’re able to gather more and more information, more refined information, on child development in different domains that are not accessible or would not have emerged at the early ages. Neurobehavioral development and cognitive development are important outcomes of interest for us in our research.

[What are Dr. Perera's findings on fetal growth and developmental effects? From her Center's website:]

• Prenatal exposure to PAH reduced birth weight and head circumference in African-American babies born to women who were more highly exposed to the air pollutants. Several studies have reported that reduction in head circumference at birth or during the first year of life correlates with poorer cognitive functioning and school performance in childhood.
• Children with high prenatal exposure to PAH had significantly lower test scores at age 3 on the Bayley test for cognitive development and were more likely to be developmentally delayed.
• Prenatal exposure to PAH at levels encountered in NYC air can adversely affect child IQ scores at 5 years of age. After adjustment for potential confounders, highly exposed children had Full-scale and Verbal IQ scores that were 4.31 and 4.67 points lower compared to less exposed children. These reductions are similar in magnitude to the effects of low-level lead exposure.

Also we’re looking at asthma as an outcome. We have been publishing results on our findings with respect to both prenatal and postnatal exposure to Polycyclic Aromatic Hydrocarbons [PAHs] and asthma in childhood. We’re continuing to follow the kids to be able to look at whether these conditions are persisting, are resolving, or even worsening. So respiratory health is a major outcome.

[What are Dr. Perera's findings on asthma and air pollution? From her Center's website:]

• Combined prenatal exposure to airborne PAHs and postnatal secondhand smoke results in the increased likelihood of respiratory and asthma-like symptoms at one and two years of age and at five to six years of age.
• CCCEH has linked epigenetic alterations associated with prenatal exposure to PAH in cord blood with parental report of asthma by age 5. Epigenetic changes may disrupt the normal functioning of genes by affecting how they are expressed, but do not cause structural changes or mutations in the genes.
• Exposure shortly after birth to ambient metals such as nickel, vanadium, and carbon is associated with wheeze and cough in children aged two and younger.

We’re also interested in potential risk of cancer. In our cohort we’re not able to look at cancer as an outcome because we don’t have the very large sample sizes needed for such studies. But we are able to look at what we call “procarcinogenic biomarkers.” We’re evaluating those particular chromosomal abnormalities, or chromosomal changes, attributable to or associated with the exposures. We look at this prenatally, we look at cord blood, and then we take repeat blood samples as the children are getting older, and are looking further at the chromosomal abnormalities in those older samples.

Research from our center has shown that in newborns, PAHs were associated with chromosomal aberrations. It’s not cancer per se, but it is a biomarker that has been shown in adults to be related to risk of cancer, so it’s a biomarker of concern.

[What are Dr. Perera's findings on cancer and air pollution? From her Center's website:]

• Approximately 40% of babies in the study were born with DNA damage associated with PAH. In other studies such damage has been tied to an increased risk of cancer. Of particular concern, newborns had higher (approximately 10-fold) levels of adducts than mothers per unit of estimated exposure, indicating greater fetal susceptibility and potential risk from these pollutants.
• Prenatal exposure to PAH was linked to structural changes in babies’ chromosomes. Such genetic alterations have been related in other studies to increased risk of cancer in children and adults.
• Prenatal maternal exposure to polycyclic aromatic hydrocarbons (PAH) from polluted air is associated with chromosomal abnormalities in cord blood. Chromosomal aberrations have been associated with increased risk of cancer in adults. These results suggest that the carcinogenic process may begin in the womb.

The other endpoints that we’re looking at are obesity and metabolic disorder. We are following up on some work in laboratories that had suggested that air pollution we’re interested in, the PAH, might be associated with increased weight and obesity. We have published from the Center the first finding that in fact there was a significant link between prenatal PAH exposure as we measured it and later body mass index of the children.

Next: what are the possible solutions?