Papers of the Month
Extramural
By Julie Leibach
Racially segregated children in North Carolina more exposed to lead
Black children living in racially segregated North Carolina neighborhoods are disproportionately exposed to lead, an NIEHS-funded study found. The trend has persisted since the 1990s, despite an overall decline in blood lead levels statewide.
One glaring indicator of structural racism is neighborhood segregation, which pushes minority races and ethnicities into areas where unhealthy social and environmental exposures tend to accumulate, according to the authors. They wondered if trends in childhood lead exposure — a risk factor for learning deficits that can persist into adulthood — reflected racial segregation among North Carolina youth.
Using records from the N.C. Department of Health and Human Services, the team analyzed data on blood lead levels for more than 300,000 non-Hispanic Black and non-Hispanic White children under age 7. Blood lead levels were collected between 1992–1996 or 2013–2015 across all 100 N.C. counties. The researchers examined associations between racial isolation — an indication of racial residential segregation that is tied to health — and childhood blood lead levels during the two time periods.
From the 1990s to 2015, blood lead levels declined almost everywhere across the state. However, the team observed an enduring relationship between highly segregated communities and childhood lead exposure. Children living in predominantly Black neighborhoods had higher blood lead levels, on average, than less racially isolated children. Within those highly segregated areas, Black children consistently showed higher blood lead levels than White children over the study period.
The results exemplify the environmental burdens affecting segregated communities, according to principal investigator Marie Lynn Miranda, Ph.D. Pediatric testing for lead exposure is still important, she noted, as is providing healthy and affordable housing, particularly for families with children.
Citation: Miranda ML, Lilienfeld A, Tootoo J, Bravo MA. 2023. Segregation and childhood blood lead levels in North Carolina. Pediatrics 152(3):e2022058661.
Emissions from indoor flooring reflect airborne PCB levels
Chemical emissions from flooring can predict polychlorinated biphenyl (PCB) concentrations in room air, according to NIEHS-supported research. The findings could inform targeted remediation strategies for indoor spaces.
For decades, manufacturers blended PCBs with other substances as plasticizers for use in caulks, adhesives, and other materials. Although the U.S. banned PCB production in 1976, tainted building materials can still off-gas, meaning they can release gaseous chemicals into indoor air people breathe. Inhaling PCBs may lead to cancer, hormone dysfunction, or learning disabilities.
Working in a university built in the 1970s, the researchers monitored airborne PCB levels by attaching sampling devices to ceiling tiles. They also placed samplers on tile, wood paneling, and carpet to measure PCB emissions at their source. Sampling occurred before and after wiping surfaces with hexane, a cleaning agent. In addition, the team removed chunks of carpet and wood paneling to analyze PCB concentrations in each material.
By applying gas chromatography-tandem mass spectrometry — used to parse chemical mixtures — the researchers identified 209 types of PCBs across the samples. Statistical analysis showed that emissions from flooring best predicted the magnitude and makeup of PCBs detected in room air, probably because certain compounds were added to adhesives used in flooring construction, the authors suggested. Meanwhile, PCB concentrations in the carpet and wood samples did not reflect PCB emissions from source material or indoor air PCB levels. Wiping surfaces with hexane reduced PCB emissions by more than 60% overall, suggesting that surface films are an important contaminant reservoir.
According to federal regulations, building materials containing PCB levels of 50 parts per million (ppm) or above must be removed from interiors. However, building materials containing lower levels can still emit PCBs at concentrations that could be harmful, according to the study. Coupling measurements of PCB emissions at their source with room air concentrations is a better way to gauge potential health risks than analyzing solid materials, the authors explained.
Citation: Bannavti MK, Marek RF, Just CL, Hornbuckle KC. 2023. Congener-specific emissions from floors and walls characterize indoor airborne polychlorinated biphenyls. Environ Sci Technol Lett 10(9):762-767.
Endocrine-disrupting chemicals linked to greater odds of past cancer diagnoses in women
Exposure to per- and polyfluoroalkyl substances (PFAS) and phenols is associated with past diagnoses of hormone-driven cancers, particularly in women, according to NIEHS-funded research. The findings could inform risk assessment and prevention efforts for susceptible groups.
People may encounter PFAS or phenols in food packaging and personal care products, among other items. Although research suggests these chemicals disrupt the endocrine, or hormonal, system, few studies have assessed their relationship to multiple hormone-driven cancers, such as melanoma, breast cancer, and prostate cancer.
The team leveraged data collected on men and women aged 20 and older between 2005–2018 by the long-running National Health and Nutrition Examination Survey. They compared self-reported diagnoses of melanoma and cancers of the thyroid, breast, ovary, uterus, and prostate to exposure data for seven PFAS, eight phenols, and four parabens, another endocrine-disrupting chemical.
Greater exposure to three PFAS chemicals was associated with higher odds of prior melanoma diagnosis among women, but not men. Increased likelihood of past ovarian cancer diagnosis in women was also tied to higher levels of three phenols and one PFAS. Additionally, racial differences appeared: Chances of past cancer diagnoses were higher among Black and Mexican American women with more exposure to certain phenols, whereas the likelihood of prior cancer diagnoses among White women was higher with greater PFAS exposure.
The findings highlight sex differences in melanoma risk and suggest the need for further exploration of a potential estrogen-dependent pathway for melanoma and ovarian cancer, the authors noted. Future work that investigates cancer mechanisms and risk should consider racial differences in exposure, they added.
Citation: Cathey AL, Nguyen VK, Colacino JA, Woodruff TJ, Reynolds P, Aung MT. 2023. Exploratory profiles of phenols, parabens, and per- and poly-fluoroalkyl substances among NHANES study participants in association with previous cancer diagnoses. J Expo Sci Environ Epidemiol 33(5):687-698.
Hair product availability may contribute to chemical exposure disparities
Hair products containing harmful chemicals may be more commonly sold in neighborhoods that are low-income or that comprise more people of color compared to affluent, predominantly White neighborhoods, an NIEHS-funded study suggested. The research is a step toward better understanding the role of personal care product availability in environmental health disparities.
Personal care products are a significant source of exposure to chemicals such as endocrine disruptors, which affect the hormonal system. However, research examining how safer hair product availability varies by neighborhood sociodemographic characteristics is limited.
The researchers catalogued more than 14,000 hair products — including shampoos, hair gels, hair oils, and hair relaxers — sold in 50 Boston-area stores. They focused on eight neighborhoods that reflected a range of socioeconomic levels and racial and ethnic compositions. Next, the team identified safety ratings for each product using the Skin Deep Cosmetics Database, a free consumer resource maintained by the nonprofit Environmental Working Group. Ratings depend on how ingredients relate to health and ecological outcomes, such as cancer, reproductive or developmental toxicity, endocrine disruption, and ecotoxicity.
Of 1,332 products assessed in Roxbury, a lower-income Boston community of color, more than 12% had high hazard scores. In another nearby low-income community called Mission Hill, more than 11% of 571 items were listed as high hazard. By contrast, in a higher-income, predominantly White neighborhood called Beacon Hill, less than 8% of 382 products earned high hazard ratings.
A dearth of safer hair products may contribute to the disproportionate burden of environmental exposures in communities of color and lower-income neighborhoods, the authors noted. The findings could inform efforts to reduce chemical exposure inequities and related health problems, as well as inspire retailers and manufacturers to offer less hazardous products, they added.
Citation: Chan M, Parikh S, Shyr D, Shamasunder B, Adamkiewicz G, James-Todd T. 2023. Evaluating neighborhood-level differences in hair product safety by environmental working group ratings among retailers in Boston, Massachusetts. Environ Health Perspect 131(9):97002.
(Julie Leibach is a senior science writer at MDB, Inc., a contractor for the NIEHS Division of Extramural Research and Training.)
