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Environmental Factor

Environmental Factor

Your Online Source for NIEHS News

February 2016

Papers of the month

Prenatal PFOA exposure linked to increased weight gain in childhood

Women exposed to higher levels of perfluorooctanoic acid (PFOA) while pregnant had children who had gained more weight by age 8 than children whose mothers were less exposed, according researchers funded by NIEHS.

To examine the link between PFOA and obesity, researchers studied 204 mother-child pairs who lived downstream of a chemical plant along the Ohio River in West Virginia. The plant produced PFOA, a toxic chemical found in many household products including nonstick pans and water-repellant clothing. The researchers used data from the HOME study (Health Outcomes and Measures of the Environment), an NIEHS-funded cohort established in 2003 at the University of Cincinnati to study the effects over time of low-level exposures in pregnant women and their children.

By looking at the children over time, researchers found that children of more highly exposed mothers generally had the lowest body mass index (BMI) at age 2. But between 2 and 8 years of age, those children gained more weight than children born to less-exposed mothers and had much higher BMI measures by age 8. This could explain why studies that measure only one moment in time have found mixed results for this association.

CitationBraun JM, Chen A, Romano ME, Calafat AM, Webster GM, Yolton K, Lanphear BP. 2015. Prenatal perfluoroalkyl substance exposure and child adiposity at 8 years of age: the HOME study. Obesity (Silver Spring) 24(1):231-237.

Early-life pesticide exposure associated with reduced breathing capacity

Children with higher levels of organophosphate metabolites in their urine were more likely to have decreased lung function, according to an NIEHS-funded study of children in California. The metabolites measured were products of organophosphate pesticides, which are heavily used in agriculture. The findings are the first to link low-level childhood exposures to organophosphate pesticides to lung health in children.

The children in the study were part of the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS), a long-term study in which the researchers follow children in California’s Salinas Valley from before birth to adolescence. Researchers collected urine samples five times, between 6 months and 5 years of age, and measured levels of organophosphate pesticide metabolites each time. At age 7, the children were given a spirometry test, which evaluates lung function by measuring the amount of air exhaled.

Each tenfold increase in organophosphate metabolite concentrations in the children’s urine was associated with a 159-millimeter decrease in lung function, or an average of about eight percent less air exhaled. This decreased lung function level is similar to the effects experienced by a child with secondhand smoke exposure in the household.

CitationRaanan R, Balmes JR, Harley KG, Gunier RB, Magzamen S, Bradman A, Eskenazi B. 2015. Decreased lung function in 7-year-old children with early-life organophosphate exposure. Thorax; doi: 10.1136/thoraxjnl-2014-206622 [Online 3 December 2015].

Mercury deposition and elimination in humans after eating fish

NIEHS grantees have developed a new way to measure how methylmercury changes in the body and how it is eliminated. Methylmercury exposure from fish consumption is a public health concern, and this new method is a step toward better understanding of different responses to methylmercury.

Researchers coupled laser ablation, a sampling method, with inductively coupled plasma-mass spectrometry, an advanced laboratory technique, to measure levels of methylmercury along the length of a single human hair. This method enabled them to detect the rate at which a person eliminated mercury from their body following even a single meal of fish.

They were also able to estimate demethylation status, or the rate at which methylmercury transforms into inorganic mercury, which is thought to be an integral step in removing mercury from the body. Because as much as 90 percent of mercury is excreted via feces, researchers measured mercury in feces and correlated it to the methylmercury elimination rate from their hair.

Elimination of methylmercury from the body occurs slowly and is a major determinant of the body burden of mercury resulting from fish consumption. This simplified and noninvasive approach can improve the understanding of mercury metabolism and elimination status, shedding light on genetic and dietary factors that influence methylmercury exposure.

CitationRand MD, Vorojeikina D, van Wijngaarden E, Jackson BP, Scrimale T, Zareba G, Love TM, Myers GJ, Watson GE. 2015. Methods for individualized determination of methylmercury elimination rate and de-methylation status in humans following fish consumption. Toxicol Sci; doi: 10.1093/toxsci/kfv241 [Online 15 November 2015].

Modifying the inflammasome to treat malignant mesothelioma

Chemotherapeutic drugs coupled with an inhibitor to reduce specific tumor-promoting components may play a beneficial role in malignant mesothelioma treatment, according to new research funded by NIEHS. Malignant mesothelioma, a type of cancer, is caused by exposure to asbestos, and inflammation plays an important role in its development. The drugs target the inflammasome, which is responsible for the activation of inflammatory processes in the body.

In human cell lines and tissue, researchers found that chemotherapeutic drugs elevate the levels of two components of the inflammasome that contribute to cell death — NLRP3 and caspase-1 — playing a beneficial role in malignant mesothelioma therapy. However, the drugs also increased the levels of pro-inflammatory molecules that promote tumor growth , most importantly interleukin-1-beta.

Based on these findings, they conducted cell line and mouse studies focusing on the effects of the inflammasome. They combined the chemotherapeutic drugs with a drug that inhibits interleukin-1 receptors, in an attempt to block the negative effects of inflammasome activation. The mouse studies showed that tumors were smaller in the combined treatment group compared to the group just treated with chemotherapeutics or untreated groups.

Taken together, the study’s findings provide the first step toward a possible strategy for inhibiting malignant mesothelioma growth using a combination of chemotherapeutics with interleukin-1 receptor agonists.

CitationWestbom C, Thompson JK, Leggett A, MacPherson M, Beuschel S, Pass H, Vacek P, Shukla A. 2015. Inflammasome modulation by chemotherapeutics in malignant mesothelioma. PLoS ONE 10(12): e0145404.

(Sara Mishamandani is a research and communication specialist for MDB Inc., a contractor for the NIEHS Division of Extramural Research and Training.)

Read the current Superfund Research Program Research Brief. New issues are published on the first Wednesday of every month.

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