Selected category: Emerging Science

Children’s lead exposure: Relative contributions of various sources

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

Last week, we noted in our blog that the Environmental Protection Agency (EPA) dropped the statement that paint, dust and soil are the most common sources of lead in its “Protect Your Family from Lead in Your Home” booklet. Property owners provide this booklet to prospective homebuyers and tenants in housing built before 1978. The change implicitly recognizes that there is no safe level of lead in the children’s blood, and we must reduce all sources of lead exposure. It also acknowledges that the relative contribution of air, water, food, soil, dust, and paint to children’s blood lead levels is complicated. Exposure varies significantly based on age of the home, the child’s race and age, the family’s income-level, and region of the country. Any simplification obscures these important differences.

EPA’s scientists made this clear in a model published earlier this year that pulled together the available data, divided children into three age categories, and assigned children in each category into ten groups based on their overall lead exposure. For each group, they estimated the relative contribution of air, water, food, and soil/dust (from paint). Not surprisingly, children living in older homes with lead-based paint hazards by far have the most exposure to lead. For 1 to 6 year olds in the top 90-100 percentile, more than 70% of the lead in their blood is from soil and dust. The contribution from food is 20% and drinking water is 10%. For infants, soil and dust contributes to 50% of the lead in blood, while 40% is from water and 10% from food.

Since there is no known safe level of lead in blood, we must do even more to reduce children's exposure to lead-contaminated soil and dust.

However, to prioritize action at a national level, it is important to understand how different sources contribute to lead exposure in the average child as well as the most-exposed child. We used the underlying EPA data to calculate the average relative source contribution of different sources to blood lead levels for infants from birth to six months old, for toddlers 1 to 2 years old, and young children from 1 to 6 years old. The results indicate that infants have a much higher source contribution of lead from water in comparison to older children (Figure 1). For the average child 1 to 6 years old, food is the largest source of lead exposure, with 50%, followed by soil/dust then water.

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Also posted in Drinking Water, EPA, Health Policy, Health Science, lead, Public Health| Tagged , , , , , , | 1 Response

EPA’s latest analysis shows perchlorate risks to fetal brain development

Tom Neltner, J.D.is Chemicals Policy Director and Maricel Maffini, Ph.D., Consultant

Pursuant to a consent decree with the Natural Resources Defense Council (NRDC), the Environmental Protection Agency (EPA) is developing drinking water regulations to protect fetuses and young children from perchlorate, a toxic chemical that inhibits the thyroid’s ability to make the hormone T4 essential to brain development. The rulemaking is part of a long process that began in 2011 when the agency made a formal determination that Safe Drinking Water Act standards for perchlorate were needed. Under the consent decree, EPA should propose a standard by October 2018.

In the latest step in that process, EPA’s scientists released a draft report in September that, at long last, answers questions posed by its Science Advisory Board in 2013: does perchlorate exposure during the first trimester reduce production of T4 in pregnant women with low iodine consumption? Does reduction in maternal T4 levels in these women adversely affect fetal brain development? According to EPA’s scientists, the answers are Yes and Yes.

For several years, EPA and the Food and Drug Administration (FDA) have developed and refined a model that would predict the effect of different doses of perchlorate on levels of T4 in pregnant women. The latest version of the model addresses women during the first trimester, especially those with low iodine intake. This is important because iodine is essential to make T4 (the number four indicates the number of iodine atoms present in the hormone); perchlorate inhibits its transport from the blood into the thyroid. The risk of perchlorate exposure to fetuses in the first trimester is greatest because brain development starts very early and is fully dependent on maternal T4. If the mother gets insufficient iodine to offset the perchlorate inhibition, she will not produce enough T4 for the fetal brain to develop properly. When free T4 (fT4) levels are low but without increase in thyroid stimulating hormone (TSH), the condition is known as hypothyroxinemia. When T4 production is lowered further, the pituitary gland releases TSH to increase T4 production by a feedback loop mechanism.

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Also posted in Drinking Water, EPA, FDA, Food, Health Policy, perchlorate, Public Health, Regulation| Tagged , , , , , , , , , , , | Comments are closed

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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Also posted in Drinking Water, EPA, Food, Health Policy, lead, Uncategorized| Tagged , , , , , , , , | Comments are closed

Podcast: You Make Me Sick! The mysteries of the epigenome

Each type of cell in our body expresses our genes differently based on many things including what they are (skin or kidney cells) and how old we are (newborn or 65 years old). These differences are controlled by our epigenome – the set of molecular marks along our DNA that dictate which and when genes turn on and off. Turns out our environment can influence and alter these marks!

For this episode we talked to Dr. Dana Dolinoy of the University of Michigan about her work on the epigenome, including how twin mom mice can birth very different looking newborns—either yellow and obese or brown and normal weight—depending on what they ate during pregnancy.

Want more? Subscribe to us on iTunes or Google Play, or check out our SoundCloud to listen via desktop!

Also posted in Health Science| Tagged | Comments are closed

Podcast: You Make Me Sick! Cocaine in the Puget Sound!?!

After our episodes on the impact of lead on the developing brain and how microbes teeming inside us shape our health in unbelievable ways, EDF Health is proud to present the latest episode of our podcast, You Make Me Sick. On this episode, we interviewed Dr. James Meador of the National Oceanic and Atmospheric Agency about his research article where he found a soup of chemicals, including cocaine, in the waters of the Puget Sound. He explains how drugs and other chemicals of emerging concern can pass through wastewater treatment plants and end up in the surrounding waters and even the tissues of fish!

Click below to listen. Want more? Subscribe to us on iTunes or Google Play, or check out our SoundCloud to listen via desktop!

Also posted in Health Science| Tagged | Read 1 Response

EDF’s assessment of a health-based benchmark for lead in drinking water

Tom Neltner, J.D.is Chemicals Policy Director

Health professionals periodically ask me how they should advise parents who ask about what constitutes a dangerous level of lead in drinking water. They want a number similar to the one developed by the Environmental Protection Agency (EPA) for lead in dust and soil (which is the primary source of elevated blood lead levels in young children). I usually remind them that EPA’s 15 parts per billion (ppb) Lead Action Level is based on the effectiveness of treating water to reduce corrosion and the leaching of lead from plumbing; it has no relation to health. Then I tell them that EPA is working on one and to hold tight. Admittedly, that is not very satisfying to someone who must answer a parent’s questions about the results of water tests today.

On January 12, EPA released a draft report for public comment and external peer review that provides scientific models that the agency may use to develop potential health-based benchmarks for lead in drinking water. In a blog last month, I explained the various approaches and options for benchmarks that ranged from 3 to 56 ppb. In another blog, I described how EPA’s analysis provides insight into the amounts of lead in food, water, air, dust and soil to which infants and toddlers may be exposed. In this blog, I provide our assessment of numbers that health professionals could use to answer a parent’s questions. Because the numbers are only a start, I also suggest how health professionals can use the health-based benchmarks to help parents take action when water tests exceed those levels.

EDF’s read on an appropriate health-based benchmark for individual action on lead in drinking water

When it comes to children’s brain development, EDF is cautious. So we drew from the agency’s estimates calculated by its model to result in a 1% increase in the probability of a child having a blood lead level (BLL) of 3.5 micrograms of lead per deciliter of blood (µg/dL).

EDF's assessment of a health-based benchmark for individual action on lead in drinking water
Age of child in home and type of exposureHouses built before 1950¹Houses built 1950 to 1978²Tests show no lead in dust or soil³
Formula-fed infant3.8 ppb8.2 ppb11.3 ppb
Other children 7 years or younger5.9 ppb12.9 ppb27.3 ppb

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Also posted in Drinking Water, Flint, lead| Tagged , , , , , | Comments are closed
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