Pregnant Moms + Air Pollution = Stupid Kids

Children of women with high exposure to air pollution from traffic during the third trimester of pregnancy have IQs that are on average 4.5 points lower in kindergartners. The standard deviation of an IQ score (the mean of which is set at 100 for the general population) is 15-16 points depending upon the test.

The results are consistent with the general finding that pregnant women are especially sensitive to environmental conditions, and that neo-natal and childhood pollutant exposure can lower IQ. The effect is "in the range of what might be triggered by exposures to high levels of lead or by fetal alcohol syndrome."

The final data included 249 predominantly English speaking children from 1998 to 2003"from inner-city neighborhoods in New York: Washington Heights, Harlem or the South Bronx. Each woman got a backpack fitted with a PAH [polycyclic aromatic hydrocarbons] sampler to wear continuously for two days during her last trimester of pregnancy. Traffic, which doesn’t vary much by season, was the primary source of PAHs that these women encountered — indoors and out[.]" Effects with observed by age 3 and IQ tests were taken at age 5. There was "an independent effect on IQ even after accounting for other factors that can influence intellect, such as prenatal exposure to lead or tobacco smoke, gender, ethnicity, mom’s IQ, her education and measures of the quality of in-home child care."

How much pollution is a concern to pregnant moms? Pretty much any amount.

The moms’ PAH exposures ranged from 0.5 to 34.5 nanograms per cubic meter of air. Anything above 2.26 ng/m3 — the mean value — was considered high, and kids whose moms had those exposures were compared with kids in the less exposed group. . . . Significantly, Perera notes, when all of the kids were compared individually, “we didn’t see any evidence of a threshold” below which PAHs had no effect on IQ. The same no-threshold effect is seen with lead.

Possible Responses

Perhaps, we should be doing spot testing within the city of PAH levels to evaluate this risk and abate it where it is excessive, much as cities do spot checks of high risk areas for lead. While pollution from vehicles is largely a matter of federal regulation (which may need to be tightened based upon this new information), traffic levels and pedestrian traffic patterns can heavily influence exposure to traffic based pollution and are largely a matter of local control. The findings may also suggest that greater regulatory measures, like applying California emissions standards nationally, may be in order.

The findings also highly a benefit of plug-in electric vehicles. While these vehicles don't always reduce aggregate air pollution, particularly in places where coal based power plants are the predominant source of electricity, electric vehicles can move the location of that air pollution from traffic which pregnant women, young children and other especially vulnerable populations like immuno-suppressed and elderly people cannot avoid, to distant locations that are less intensely populated and can have access restrictions in the highest exposure areas.

The findings also suggest that pre-natal care should include specific warnings about the risks associated with exposure to traffic pollution for pregnant women, similar to current fetal alcohol and tobacco use warnings. To the extent that exposure is linked to occupation, it may also be appropriate to institute warnings about the risks for pregnant women at risk of occupational exposure to traffic pollution.

The underlying references for the linked story are:

F.P. Perera et al. 2009. Prenatal airborne polycyclic aromatic hydrocarbon exposure and child IQ at age 5 years. Pediatrics. August. Vol. 124, p.E195.
doi: 10.1542/peds.2008-3506

F.P. Perera et al. 2004. Biomarkers in maternal and newborn blood indicate heightened fetal susceptibility to procarcinogenic DNA damage. Environmental Health Perspectives. Vol 112. July. p. 1133
doi: 10.1289/ehp.6833