Selected tag(s): model

New EPA model enables comparison of various sources of childhood exposure to lead

Tom Neltner, J.D.is Chemicals Policy Director and Dr. Ananya Roy is Health Scientist

This week, Environmental Health Perspectives published an important article by scientists at the Environmental Protection Agency (EPA) that sheds important light on the various sources of children’s lead exposure. Led by Valerie Zaltarian, the article shares an innovative multimedia model to quantify and compare relative contributions of lead from air, soil/dust, water and food to children’s blood lead level. The model couples existing SHEDS and IEUBK models to predict blood lead levels using information on concentrations of lead in different sources, intake and gut absorption. The predicted blood lead levels compared well with observed levels in the National Health and Nutrition Evaluation Survey population. Given the variety of independent sources of lead exposure, the model provides a critical tool that public health professionals can use to set priorities and evaluate the impact of various potential standards for all children and not just those with the greatest exposure.

This peer-reviewed article builds on a draft report EPA released in January 2017 evaluating different approaches to setting a health-based benchmark for lead in drinking water. The report has provided a wealth of insight into a complicated topic. Earlier this year, we used it to show that formula-fed infants get most of their lead exposure from water and toddlers from food, while the main source of lead for the highest exposed children is soil and dust. In our February blog, we provided our assessment of a health-based benchmark for lead in drinking water and explained how public health professionals could use it to evaluate homes. The information was also critical to identifying lead in food as an overlooked, but meaningful, source of children’s exposure to lead.

The new article reaffirms the analysis in the January 2017 EPA report and highlights that evaluating source contribution to blood lead in isolation versus aggregating across all sources can lead to very different answers and priorities. A health-based benchmark for lead in drinking water could vary from 0 to 46 ppb depending on age and whether all other sources of lead are considered. For example, a health-based benchmark for infants (birth to six months old) would be 4 ppb or 13 ppb depending on whether or not you consider all sources of exposure.

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Posted in Drinking Water, Emerging Science, EPA, Food, Health Policy, lead, Uncategorized| Also tagged , , , , , , , | Comments are closed

Perchlorate regulation: Critical opportunities for EPA and FDA to protect children’s brains

Tom Neltner, J.D.is Chemicals Policy Director

All Americans who have been tested have perchlorate in their bodies. Perchlorate threatens fetal and child brain development by impairing the thyroid’s ability to transport iodine in the diet into the gland to make a thyroid hormone, known as T4, that is essential to brain development. Both the Environmental Protection Agency (EPA) and the Food and Drug Administration (FDA) are scheduled to make decisions in 2017 that could significantly reduce exposure to this hazardous chemical.

Based on statements in a new report by EPA, we estimate that at least 20% of pregnant women are already iodine deficient, resulting in T4 levels that put the fetuses’ developing brains at risk. For this population of pregnant women, any perchlorate exposure results in an even greater risk of impaired brain development in their children and potentially a lifetime of behavioral and learning difficulties.

This is why it is critical that our public health agencies take actions to reduce exposure to perchlorate with a focus on this vulnerable population. There are three key decisions to be made in the coming year:

  1. EPA will decide in January 2017 whether hypochlorite bleach, an antimicrobial pesticide, degrades to perchlorate in significant amounts. If EPA agrees it does, the agency must set standards to limit that degradation as part of its 15-year update to the pesticide’s registration. Bleach is a widely-used disinfectant in food manufacturing facilities and likely a significant source of perchlorate in contaminated foods. Research shows that reducing hypochlorite concentration limits degradation and this, coupled with expiration dates on the product would significantly reduce exposure to perchlorate.
  2. FDA will decide whether perchlorate should continue allowing perchlorate to be added to plastic packaging for dry food at levels up to 12,000 ppm to reduce buildup of static charges. The agency has evidence that the perchlorate migrates from the packaging into food, especially when it flows in and out of the container. In response to a lawsuit filed by public interest organizations, FDA told a court that it aims to make a final decision by the end of March 2017. A 2008 report by FDA indicated that almost 75% of all food types are contaminated with perchlorate.
  3. EPA told a court that it will complete external peer review of a dose-response model in October 2017 and sign a proposed rule to regulate perchlorate in drinking water a year later. This model is a critical step in establishing a drinking water standard for perchlorate pursuant to its 2011 determination that an enforceable standard was necessary under the Safe Drinking Water Act. The perchlorate is most likely from contaminated source waters (e.g. from military and defense industry activities and some fertilizer use in agricultural regions) or from degradation of hypochlorite bleach used to disinfect water. EPA acted in response to a lawsuit by the Natural Resources Defense Council.

To guide their decision-making, FDA and EPA collaborated to develop a biologically-based dose-response model to predict T4 levels in pregnant women, fetuses, and infants exposed to perchlorate. EDF and NRDC submitted joint comments on the model and the summary report requesting that EPA ensure protection of fetuses during the first two trimesters for pregnant women with serious iodine deficiencies.  These fetuses are particularly vulnerable because their thyroids is not yet functioning. The current fetal model only considers the third trimester when the fetus has a functioning thyroid. The current model fails to adequately protect their vulnerable subpopulations, falling shot of both the EPA's Science Advisory Board recommendation and the Safe Drinking Water Act requirements.

For decades, federal agencies have been charged with protecting children from environmental health risks with the recognition that they are uniquely vulnerable to chemical exposures. The upcoming decisions on perchlorate present critical opportunities to protect what many of us value the most—our children’s health and their ability to learn and thrive to their fullest potential.

Posted in Drinking Water, Emerging Science, EPA, FDA, Food, Health Policy, perchlorate, Regulation, Uncategorized| Also tagged , , , , , , , | Comments are closed
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