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Pollution and Maternal Stress Harm Babies During Pregnancy

Fetal exposure to pollution and stress linked to behavioral problems and autism.

Researchers have found that maternal psychological stress combined with exposure to air pollution during pregnancy have an adverse impact on a child's behavioral development, according to researchers at the Columbia Center for Children's Environmental Health at the Mailman School of Public Health.

"This study shows that the combination of physical and psychosocial stressors during fetal development magnifies the effect of each exposure," says lead author Frederica Perera, DrPH, PhD, director of the Columbia Center. "The findings are of concern because attention problems and anxiety and depression have been shown to affect peer relationships, academic performance, and future well-being of children."

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The study, released on October 7, 2013, is the first to assess the interaction between Polycyclic aromatic hydrocarbons (PAH), combustion-related pollutants measured in air the mother breathed during pregnancy, and maternal demoralization on a variety of behavioral problems in childhood. Air pollution and demoralization create a vicious cycle that harms childhood development.

The study, which appears in the journal Pediatrics, reports that maternal demoralization, a measure of psychological distress capable of affecting a mother's ability to cope with stressful situations, was linked with a number of behavioral problems, including anxiety, depression, attention problems, rule-breaking, externalizing problems, and aggressive behavior. The effects of psychological demoralization were greatest among children with higher levels of prenatal exposure to PAH in air pollution.

PAH's are released to the air during incomplete combustion of fossil fuel, tobacco, and other organic material. In New York City (NYC) and other urban areas, traffic and residential heating are major sources of PAH. Urban, minority populations in the United States often have a disproportionately higher exposure to air pollution and are at greater risk for adverse health and developmental outcomes. In Krakow, Poland, where the Columbia study took place, as in many areas worldwide, coal burning is a major source of air pollution.

"Air pollution exposure is ubiquitous and often co-occurs with socioeconomic disadvantage and maternal psychological distress," notes Dr. Perera. Although Krakow has relatively high ambient concentrations of PAH from coal-burning and vehicle emissions, levels are within the range seen in many other urban areas worldwide. Anyone who has gotten stuck in a traffic jam on the Cross Bronx Expressway—or lives near any congested highway passage in a residential urban environment—has experienced first hand how potent vehicle emissions can be.

The relationship between prenatal air pollution and behavioral or cognitive problems in childhood have  been observed in other studies. This new Columbia study builds upon prior findings to examine the joint impact of maternal psychological distress and air pollution on behavioral problems.

Air Pollution Linked to Childhood Behavioral Problems

A June 2012 study in New York City found that prenatal exposure to environmental PAH at levels encountered in the air of NYC were linked to behavioral problems in 6-7 year olds. The results suggest an adverse impact of prenatal PAH exposure on child behavior that could impact cognitive development and a child’s ability to learn.

Anxiety, depression, and attention problems, were all associated with PAH exposure in the womb and were linked to poorer academic performance in early childhood. PAH are widespread in urban environments worldwide mostly due to fossil fuel combustion and vehicular emissions. Fortunately, we can reduce airborne PAH concentrations by: using currently available pollution controls, seeking greater energy efficiency, promoting the use of alternative energy sources, and urging policy makers to make regulatory intervention to remove sources of air pollution.

Dr. Perera concludes, “Understanding the interactions between the social and physical environment will help to explain health disparities and create interventions to prevent health and developmental problems in children. The findings support policy interventions to reduce air pollution exposure in urban areas as well as programs to screen women early in pregnancy to identify those in need of psychological or material support."

Air Pollution Linked to Autism

A June 2013 study from the Harvard School of Public Health (HSPH) found that American women who were exposed to high levels of air pollution while pregnant were up to twice as likely to have a child with autism as women who lived in areas with low pollution.

“Our findings raise concerns since, depending on the pollutant, 20% to 60% of the women in our study lived in areas where risk of autism was elevated,” said lead author Andrea Roberts, research associate in the HSPH Department of Social and Behavioral Sciences.

Exposure to diesel particulates, lead, manganese, mercury, methylene chloride and other pollutants are known to affect brain function and to affect the developing baby. Two previous studies also found associations between exposure to air pollution during pregnancy and autism in children.

The researchers examined data from Nurses’ Health Study II, a long-term study based at Brigham and Women’s Hospital involving 116,430 nurses that began in 1989. Among that group, the authors studied 325 women who had a child with autism and 22,000 women who had a child without the disorder. They looked at associations between autism and levels of pollutants at the time and place of birth. They used air pollution data from the U.S. Environmental Protection Agency to estimate women’s exposure to pollutants while pregnant. They also adjusted for the influence of factors such as income, education, and smoking during pregnancy.

The results concluded that women who lived in the 20% of locations with the highest levels of diesel particulates or mercury in the air were twice as likely to have a child with autism as those who lived in the 20% of areas with the lowest levels.

Other types of air pollution—lead, manganese, methylene chloride, and combined metal exposure—were associated with higher autism risk as well. Women who lived in the 20% of locations with the highest levels of these pollutants were about 50% more likely to have a child with autism than those who lived in the 20% of areas with the lowest concentrations.

Conclusion: The Lorax and an Inconvenient Truth

I gave my daughter Dr. Seuss’ book “The Lorax” for her fifth birthday. Reading that book is always a reminder that we have an obligation to protect our environment for generations to come. If you haven’t read it lately, here is a video reading of The Lorax.  

As parents, policy makers, and citizens we all have an obligation to reduce pollution and socioeconomic stratification that gives those with financial resources more access to clean air. Organizations like the “Fresh Air Fund”—which sends inner city children from NYC to host families or summer camp—do a terrific job of offering free experiences in the country for children from low-income communities. But these programs only offer a small respite from the long term impact of smog seen in many low income urban areas. Unfortunately, much of the damage of air pollution happens to the fetus which is why policy makers around the world need to make environmental protection a top priority.

As Al Gore said in an Inconvenient Truth, ”Future generations may well have occasion to ask themselves, ‘What were our parents thinking? Why didn't they wake up when they had a chance?’ We have to hear that question from them, now.”

Christopher Bergland is a world-class endurance athlete, coach, author, and political activist.

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