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Environmental Factor

Environmental Factor

Your Online Source for NIEHS News

July 2023

Papers of the Month

PFAS exposure may interfere with dieting success

Exposure to PFAS can hinder dieting efforts to lose weight, according to an NIEHS-funded study. PFAS, which are found in numerous industrial and consumer products, have been linked to various health problems, including metabolic changes and obesity. 

For their study, the researchers gathered data on people with obesity who had participated in a large European clinical trial on weight loss strategies. They focused on a subset of nearly 400 individuals who had lost at least 8% of their body weight. After this initial dieting period, individuals were randomly selected to follow one of five diets for at least 26 weeks. 

The team analyzed participant blood samples, collected at the beginning of the clinical trial, for five different PFAS. Then the researchers used statistical methods to explore associations between baseline PFAS concentrations and weight fluctuations over time. They also considered other factors that might influence body weight.

They observed a significant positive relationship between weight gain and blood levels of PFAS perfluorooctanoic acid (PFOA) and perfluorohexanesulfonic acid (PFHxS), regardless of which diet participants followed. For example, at 26 weeks, the highest weight gain — over 3 pounds — was associated with a doubling of PFOA in the blood. 

At 52 weeks, participants with the highest concentrations of PFOA and who had followed a healthy diet had gained an average of about 10 pounds, which was on par with individuals with low PFOA levels who had been assigned the least healthy diet. 

The findings support mounting evidence that PFAS may contribute to the rising global trend in obesity and could help explain the variable success of some diet regimens, according to the authors.

Citation: Grandjean P, Meddis A, Nielsen F, Sjödin A, Hjorth MF, Astrup A, Budtz-Jørgensen E. 2023. Weight loss relapse associated with exposure to perfluorinated alkylate substances. Obesity (Silver Spring) 31(6):1686–1696.

Outdoor heat associated with mental health emergencies in young people

On higher temperature days, hospital visits for mental health emergencies may increase among young people, according to a study funded by NIEHS. 

Juvenile mental health is a growing public health crisis in the U.S. Various studies have uncovered links between temperature and acute mental health problems among people of all ages. To study this association in young people, the researchers gathered data on emergency room and hospital visits in New York City for each summer from 2005-2011. They evaluated visits among children ages 6-11 years old, adolescents ages 12-17, and young adults ages 18-25.

Next, they gathered corresponding daily temperatures from several local weather stations to determine annual summer trends. Through statistical analysis, they calculated how temperature related to clinical visits for mental health. The team further sorted the data by mental health categories and socioeconomic factors to identify vulnerable populations.

Higher temperature days were associated with more clinical visits across all age groups, particularly among children and adolescents. A diagnosis of reaction disorder — an excessive emotional or behavioral response to a stressful event — among children, and of anxiety or bipolar disorder among adolescents, had the strongest ties to temperature. Of those groups, children who were Black or who represented another race or ethnicity were at greater risk than White children for heat-related mental health emergencies.

Because emergency room and hospital encounters represent more severe mental health cases, the results may underestimate the toll of heat on mental health, according to the researchers. They added that their findings could inform targeted strategies to improve mental health during  extreme heat events in vulnerable youth populations.

Citation: Niu L, Girma B, Liu B, Schinasi LH, Clougherty JE, Sheffield P. 2023. Temperature and mental health-related emergency department and hospital encounters among children, adolescents and young adults. Epidemiol Psychiatr Sci 32:e22.  

Disinfectant reduces toxic byproduct levels in algae-affected water

Adding the chemical chloramine, rather than the common disinfectant chlorine, to water contaminated by toxic algae can result in lower levels of harmful byproducts, an NIEHS-funded study found. 

Certain types of algae produce harmful chemicals that can taint drinking water supplies. In addition, water disinfection processes can interact with algae in other ways, resulting in hazardous byproducts that have been implicated in cancer, miscarriages, and other health problems. 

Treating water with chloramine — formed by combining chlorine and ammonia — can significantly reduce byproduct levels. However, most studies on chloramine involve the algae Microcystis aeruginosa, the most common toxin-producing freshwater species. For their work, the researchers investigated how chloramine interacted with other kinds of algae currently spreading in southern waters. 

The team collected samples of Microseira wollei and Phormidium algal strains from several South Carolina lakes and treated them with either chloramine or chlorine. They also added naturally occurring bromide and iodide to some samples. Bromide and iodide are known to interact with chlorine or chloramine and other organic matter to form particularly hazardous disinfection byproducts. 

Next, the researchers analyzed the byproducts in each treated sample, then calculated toxicity. Overall, chloramine reduced disinfection byproduct levels three to five times more than chlorine. However, in samples in which bromide and iodide concentrations were high, chloramine treatment resulted in disinfection byproducts that were more toxic than those in chlorinated samples.

The results suggest that chloramine can be a superior disinfectant to chlorine in some cases, especially in waters that contain low concentrations of bromide and iodide. However, the choice depends on the kinds of algal species and other compounds present in the source water, according to the authors.

Citation: Aziz MT, Granger CO, Ferry JL, Richardson SD. 2023. Algae impacted drinking water: does switching to chloramination produce safer drinking water? Sci Total Environ 877:162815.  

Benefits of lower air pollution vary by racial identity and income

Black Americans of all incomes and White Americans with lower incomes may benefit more from reduced exposure to air pollution than affluent White Americans, according to an NIEHS-funded study. The results suggest that federal air quality regulations may insufficiently protect populations marginalized by race or socioeconomic class. 

The U.S. government sets national air quality standards for fine particulate matter (PM2.5) — a notoriously harmful form of air pollution — based on scientific estimates of how exposures will affect health. Although some studies have included populations classified by race or ethnicity or by socioeconomic status, none have defined groups by both categories. 

The researchers analyzed data collected by the Centers for Medicare and Medicaid Services from 2000-2016 on nearly 73 million people over age 65 years. They grouped individuals by whether they identified as Black or White and by income level. Using a model that projects daily air pollution levels across the U.S., they estimated annual PM2.5 exposure for each person based on residential zip code. 

Lower PM2.5 exposure was associated with lower death rates across all study participants. However, various statistical analyses suggested that Black individuals, regardless of income, as well as White individuals with lower incomes, may benefit most from reduced PM2.5. For example, when air pollution was reduced by a third below national standards, there were nearly half as many deaths among higher income Black individuals compared to White individuals in the same category.

The findings underscore the importance of considering both race and income when assessing health inequities, according to the authors. In addition, the work suggests that lowering federally acceptable levels for PM2.5 would protect a wider array of older Americans.

Citation: Josey KP, Delaney SW, Wu X, Nethery RC, DeSouza P, Braun D, Dominici F. 2023. Air pollution and mortality at the intersection of race and social class. N Engl J Med 388(15):1396–1404.

(Julie Leibach is a senior science writer at 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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