Papers of the Month
By Julie Leibach
Latina mothers in Los Angeles express concern and frustration over environmental health burdens
Latina mothers in Los Angeles County have unique concerns about environmental health that could inform policy changes that consider their perspectives, according to researchers from the University of Southern California MADRES Center for Environmental Health Disparities. The center is funded by NIEHS, the National Institute on Minority Health and Health Disparities, and the U.S. Environmental Protection Agency.
Environmental health risks disproportionately burden Latina mothers and pregnant Latinas. However, little research has explored how urban Latinas perceive environmental health or how their views align with the priorities of public health efforts to reduce environmental health disparities.
For their study, the researchers worked with community organizations to recruit and interview 36 Latina mothers, including pregnant women and mothers of young children. The participants, who ranged in age from 18 to 45, lived primarily in the low-income neighborhoods of South-Central Los Angeles and East Los Angeles. The interviews, conducted in English and Spanish, explored the women’s perceptions of local environmental risks, preventative actions, and information sources, among other topics.
Responses comprised three broad categories: descriptions of home and neighborhood environments; connections between environment and health; and social and political factors affecting well-being. Participants consistently mentioned foul odors, trash, and other visible blights as signs of environmental hazards, and revealed fear and uncertainty about how their surroundings could affect health. The women saw environmental health as a collective concern and showed interest in improving their knowledge on the topic. However, they expressed frustration over the lack of control to change their environments because of power imbalances.
The results suggest that existing public health priorities and environmental risk communication strategies may not reflect concerns among low-income Latina mothers, according to the researchers. They also noted policies and regulations designed to reduce environmental hazards can be an effective way to protect the health of pregnant people and children in overburdened communities.
Citation: Kamai EM, Calderon A, Van Horne YO, Bastain TM, Breton CV, Johnston JE. 2023. Perceptions and experiences of environmental health and risks among Latina mothers in urban Los Angeles, California, USA. Environ Health 14;22(1):8.
DNA mapping reveals genetic variants involved in arsenic metabolism in diverse populations
By analyzing DNA from people of different ancestries, NIEHS-funded researchers identified several inherited genetic variants that could influence individual sensitivity to arsenic exposure. The findings point to potential biological mechanisms underpinning arsenic toxicity.
Chronic exposure to arsenic — a naturally occurring groundwater contaminant — increases the risk of bladder, kidney, lung, and other cancers. Variation in and around AS3MT, a gene involved in arsenic metabolism, is associated with individual sensitivity to arsenic exposure. However, the specific genetic differences underlying that association are unknown.
For their study, the team used genetic data from three health studies — the Health Effects of Arsenic Longitudinal Study (HEALS), the Strong Heart Study (SHS), and the New Hampshire Skin Cancer Study (NHSCS) — representing Bangladeshi, American Indian, and European American populations, respectively, that had experienced arsenic exposure.
Using a technique called fine mapping, the researchers looked for genetic variants in a region called 10q24.32, containing AS3MT, that could be responsible for differences in arsenic metabolism. They found evidence of three such variants in Bangladeshi participants, two in American Indian participants, and one in the European American participants. One of the variants appeared to be shared across all three populations. Further analysis revealed that several variants fell within genes that regulate AS3MT protein expression, suggesting that they might interfere with proper protein production.
Together, the analyses indicated that multiple variants in the 10q24.32 region likely affect arsenic metabolism efficiency. The study paves the way for future work with cells or animals to directly assess the impact of specific variants on arsenic metabolism, the authors wrote.
Citation: Chernoff MB, Delgado D, Tong L, Chen L, Oliva M, Tamayo LI, Best LG, Cole S, Jasmine F, Kibriya MG, Nelson H, Huang L, Haack K, Kent J, Umans JG, Graziano J, Navas-Acien A, Karagas MR, Ahsan H, Pierce BL. 2023. Sequencing-based fine-mapping and in silico functional characterization of the 10q24.32 arsenic metabolism efficiency locus across multiple arsenic-exposed populations. PLoS Genet 19(1)e1010588.
Paternal exposure to phthalates could have intergenerational effects on metabolic health
Researchers funded by NIEHS found that paternal exposure to chemicals called phthalates may cause adverse metabolic health effects in two generations of offspring. The findings could improve understanding of how chemical exposures in parents contribute to chronic diseases in progeny, according to the team.
Among various uses, phthalates add flexibility to plastic products and bring fragrance to personal care items. Research suggests that phthalate exposure can contribute to metabolic disorders like obesity and diabetes, with potential health effects in subsequent generations. However, most studies have focused on the impact of maternal exposure, not paternal exposure, on offspring health.
The team first exposed male mice to a common phthalate called dicyclohexyl phthalate (DCHP) for four weeks, then mated the mice with nonexposed females. They also mated nonexposed males and females to serve as controls. Then they fed the pups in each group either a high-fat or normal diet and measured their growth over several weeks.
Compared to control pups, first-generation male and female pups of DCHP-exposed mice exhibited glucose intolerance and insulin resistance — both risk factors for diabetes — despite having similar weights and fat composition. Subsequent genetic tests revealed changes in gene expression in the liver associated with insulin resistance and metabolic disorders.
In addition, the researchers observed impaired glucose tolerance in second-generation female mice but not in males, suggesting that paternal DCHP exposure can have sex-specific effects on the metabolic health of progeny.
The team also explored mechanisms underlying connections between paternal DCHP exposure and offspring health. Using an innovative genetic sequencing approach that they developed, the researchers found changes in several classes of small RNAs in paternal sperm that could have contributed to the health effects observed in pups, according to the study.
Citation: Liu J, Shi J, Hernandez R, Li X, Konchadi P, Miyake Y, Chen Q, Zhou T, Zhou C. 2023. Paternal phthalate exposure-elicited offspring metabolic disorders are associated with altered sperm small RNAs in mice. Environ Int 172:107769.
Air pollution exposure linked to dementia, Alzheimer’s disease risk in older adults
Long-term exposure to major constituents of air pollution is associated with higher rates of dementia and Alzheimer’s disease (AD) among older adults, according to a study funded by NIEHS and others. The researchers noted the findings could inform air pollution control strategies that target the sources of specific pollutants.
Growing evidence suggests that exposure to air pollution, specifically fine particulate matter (PM2.5), plays an important role in the development of AD and related dementias. However, the influence of individual PM2.5 components on neurodegeneration remains largely unknown.
Using the Chronic Conditions Warehouse, a research database of Medicare claims nationwide, the team gathered information on AD and dementia diagnoses from 2000 to 2017. They also collected high-resolution air pollution data from two independent sources for the same time period. The data included information on the following PM2.5 chemical components: black carbon, organic matter, nitrate, sulfate, ammonium, and soil dust.
Through statistical analyses, the team assessed whether associations exist between PM2.5 exposure and dementia and AD. They observed that higher exposure to four of the six major constituents — black carbon, organic matter, sulfate, and ammonium — was consistently associated with higher rates of dementia and AD. Sulfate and black carbon showed the strongest connections, perhaps because they are intrinsically toxic or because they co-occur with other toxic pollutants, the authors suggested.
The researchers also found stronger associations for AD than dementia, which is possibly because dementia encompasses a variety of disorders with different causes, some of which may not be influenced by air pollution.
According to the authors, the findings suggest that policies aimed at reducing particulate pollutants from sources such as traffic and sulfur-containing fossil fuel combustion could have a significant public health impact.
Citation: Shi L, Zhu Q, Wang Y, Hao H, Zhang H, Schwartz J, Amini H, van Donkelaar A, Martin RV, Steenland K, Sarnat JA, Caudle WM, Ma T, Li H, Chang HH, Liu JZ, Wingo T, Mao X, Russell AG, Weber RJ, Liu P. 2023. Incident dementia and long-term exposure to constituents of fine particle air pollution: A national cohort study in the United States. Proc Natl Acad Sci USA 120(1):e2211282119.
(Julie Leibach is a contractor for the NIEHS Division of Extramural Research and Training.)