Quantcast
Environmental News for a Healthier Planet and Life

Help Support EcoWatch

Estimating Chemical Risk to Neurodevelopment of Children

Environmental Defense Fund

By Jennifer McPartland, Ph.D.

Earlier this month Dr. David Bellinger at Boston Children’s Hospital published a very interesting paper in Environmental Health Perspectives offering a new way to consider the importance of various risk factors for child neurodevelopment—such as pre-existing medical conditions, poor nutritional status or harmful chemical exposures—at the population level. “A Strategy for Comparing the Contributions of Environmental Chemicals and Other Risk Factors to Neurodevelopment of Children” argues that, in evaluating the contribution of a risk factor to a health outcome, it is critical to consider not only the magnitude of its effect on the health outcome, but also the prevalence of that risk factor in the population.

Dr. Bellinger argues: “Although a factor associated with a large impact would be a significant burden to a patient, it might not be a major contributor to the population if it occurs rarely. Conversely, a factor associated with a modest but frequently occurring impact could contribute significantly to population burden.”  The former “disease-oriented” approach has generally been used to estimate the burden of harmful chemical exposures to population health, rather than the latter “population-oriented” approach. Relying solely on the former approach, he contends, may result in an underestimation of the impact of a chemical exposure or other risk factor on public health.

Dr. Bellinger illustrates his point by examining the impact of various risk factors on neurodevelopment in U.S. children. He first estimates the drop in full-scale IQ (FSIQ) score (the size of the risk factor’s effect) associated with various risk factors, ranging from congenital heart disease to lead exposure. He then multiplies the effect size of each risk factor by the prevalence at which that risk factor occurs in U.S. children aged 0 to 5 years (a total of 25.5 million children), to determine the total cumulative impact of each risk factor on FSIQ loss in these children. 

The eye-opening results are shown in the table below.

Dr. Bellinger notes that the cumulative population burdens associated with chemical exposures (methylmercury, organophosphate pesticides and lead) are “surprisingly” large—due not so much to their effect sizes (degree of FSIQ loss), but rather to the prevalence at which children in the U.S. experience these exposures.

Dr. Bellinger emphasizes that the estimates of FSIQ loss associated with the various risk factors should not be over-interpreted, pointing to several limitations in his calculations. For example, some of the effect-size estimates for the risk factors were derived from studies conducted on non-U.S. samples. There could be regional differences that modify effect size in these populations versus U.S. populations. 

Nevertheless, the take-home message stands: Population burden needs to be considered just as much individual burden when evaluating the impact of a risk factor to a health outcome.

In EDF's chemicals policy work, we emphasize that the effects of chemical exposures on human health can vary across individuals and sub-populations, and hence, we need policies that protect the most vulnerable among us, such as children and pregnant women. Such vulnerabilities can be considered to represent the “depth” of a chemical exposure. This paper points out the other side of the same coin, namely that the “breadth”—or prevalence at which a chemical exposure occurs—is just as important in judging its significance to public health.

For more information, click here.

EcoWatch Daily Newsletter

More than 1,000 people were told to evacuate their homes when a wildfire ignited in the foothills west of Denver Monday, Colorado Public Radio reported.

Read More Show Less

Accessibility to quality health care has dropped for millions of Americans who lost their health insurance due to unemployment. mixetto / E+ / Getty Images

Accessibility to quality health care has dropped for millions of Americans who lost their health insurance due to unemployment. New research has found that 5.4 million Americans were dropped from their insurance between February and May of this year. In that three-month stretch more Americans lost their coverage than have lost coverage in any entire year, according to The New York Times.

Read More Show Less
Heat waves are most dangerous for older people and those with health problems. Global Jet / Flickr / CC by 2.0

On hot days in New York City, residents swelter when they're outside and in their homes. The heat is not just uncomfortable. It can be fatal.

Read More Show Less
Nearly 250 U.S. oil and gas companies are expected to file for bankruptcy by the end of next year. Joshua Doubek / Wikimedia Commons / CC by 3.0

Fracking companies are going bankrupt at a rapid pace, often with taxpayer-funded bonuses for executives, leaving harm for communities, taxpayers, and workers, the New York Time reports.

Read More Show Less
Trump introduces EPA Administrator Andrew Wheeler during an event to announce changes to the National Environmental Policy Act, in the Roosevelt Room of the White House on Jan. 9, 2020 in Washington, DC. The changes would make it easier for federal agencies to approve infrastructure projects without considering climate change. Drew Angerer / Getty Images

A report scheduled for release later Tuesday by Congress' non-partisan Government Accountability Office (GAO) finds that the Trump administration undervalues the costs of the climate crisis in order to push deregulation and rollbacks of environmental protections, according to The New York Times.

Read More Show Less
The American Federation of Teachers (AFT), National Education Association (NEA), and AASA, The School Superintendents Association, voiced support for safe reopening measures. www.vperemen.com / Wikimedia Commons / CC-BY-SA

By Kristen Fischer

It's going to be back-to-school time soon, but will children go into the classrooms?

The American Academy of Pediatrics (AAP) thinks so, but only as long as safety measures are in place.

Read More Show Less

Trending

Critics charge the legislation induces poor communities to sell off their water rights. Pexels

By Eoin Higgins

Over 300 groups on Monday urged Senate leadership to reject a bill currently under consideration that would incentivize communities to sell off their public water supplies to private companies for pennies on the dollar.

Read More Show Less