Air Pollution + Parental Stress = Asthma?
by Bill Chameides | July 29th, 2009
posted by Erica Rowell (Editor)
We all know that air pollution is not good. But what does that have to do with IQ and stressed-out parents?
Before we get to the stressed-out parents part, here’s some not so good news about air pollution and IQ.
Intelligence and Air Pollution
As you no doubt know, air pollution is that noxious assortment of gases and tiny suspended particles that come from tailpipes and smokestacks and make for hazy skies and wheezy air. It includes many of the usual suspects such as ground-level ozone, sulfur and nitrogen oxides (also known by the little-kitty monikers of SOx and NOx), and carbon monoxide. For a more complete rundown check out EPA’s list, and if your interest tends towards the automobile this spreadsheet [pdf] might be of interest.
On both those long lists, you will find polycyclic aromatic hydrocarbons or PAHs. PAHs belong to a class of pollutants called toxic or hazardous air pollutants in the parlance of the Clean Air Act. This is an especially worrisome category because these pollutants can cause cancer and other serious, life-threatening maladies.
PAHs arise from the incomplete combustion of any fuel (e.g., gasoline, wood, tobacco), and, given the amount of fuel we burn, you would not be wrong if you concluded that PAHs are fairly ubiquitous. You would also not be wrong if you concluded that most of us, including pregnant women, are exposed to PAHs on a regular basis. Which brings us to the next part of the story.
PAHs Not Recommended for Babies
There is growing evidence that in utero exposure to high PAH levels can have a negative impact on a child — and not just at birth but for years after during the child’s development.
In 2006 scientists concluded that in utero exposure to PAHs resulted in developmental delays in inner-city minority children at age three. Now a new study, following the same group of children, builds on those earlier findings. Researcher Frederica Perera of the Columbia Center for Children’s Environmental Health and colleagues evaluated the effects of in utero exposure to elevated PAHs on IQ in 5-year-old children. The researchers found that such exposure lowered both full-scale and verbal IQ by a mean of almost five points — similar to the effect of high lead exposures on IQ. Their report is published in last week’s edition of Pediatrics.
Suffice it to say a reduction in IQ scores is not something parents would want for their kids at age five, especially since preschool IQ scores have been found to be good indicators of how well children do in elementary school. How long into his or her life does in utero PAH exposure follow a child? We don’t know yet, but to get a better picture of the long-term impact, follow-up testing with this cohort is planned through age 11.
Stress + Air Pollution Increases Asthma Risk
The next topic relates to asthma and stress and a new report published last week in the online edition of the Proceedings of the National Academy of Sciences. Ketan Shankardass of the Centre for Research on Inner City Health and colleagues just released their findings from a health study of 2,497 children that’s part of the larger Southern California Children’s Health Study,
Here, Shankardass et al. looked at the interplay of how poverty, pollution, and parental stress affected the likelihood of children getting asthma, a chronic inflammatory disease in which a narrowing of the lung’s airways causes wheezing and breathlessness. In general the authors found that exposure to traffic-related pollution increased the risk of asthma in children, as did in utero exposure to tobacco smoke. No surprise there, but what was surprising, at least for me, was the role of stress in causing asthma in children.
To assess the role of stress, Shankardass et al. compared the incidence of asthma in two groups of children both exposed to similar levels of traffic-related pollution. One group lived in stressed households and the other did not. OK, I can hear a lot of you saying, “How did they know which households were stressful and which not?” Good you should ask because that was exactly my question. Each household’s stress level was determined from a short survey in which parents gauged the degree to which their lives were unpredictable, uncontrollable, or overwhelming. Not exactly an ironclad measure of stress in households but not unreasonable either, provided people were honest.
Now back to the interesting part: the children in the stressed households were more at risk for developing asthma. Because both stress and air pollution can inflame airways in the lungs, the researchers speculate that both variables act synergistically, causing children in stressful households to be more susceptible to the effects of air pollution.
Having raised a bunch of kids, I am not sure which is easier: getting the government to regulate, restrict and reduce our exposure to PAHs and other atmospheric baddies or lowering the level of stress in one’s household. And generally trying to get the government to do anything has the potential to raise one’s level of stress. Even so, I suppose one could work on both — but I’m not promising anything on the stress thing in my home. …filed under: faculty, health, science
and: air pollution, asthma, children, IQ, research, stress, traffic