Papers of the Month
By Megan Avakian
Children in smoke-free homes still exposed to tobacco residue
Nearly all children have nicotine on their hands, even those living in smoke-free environments, according to NIEHS-funded research. The children were exposed via thirdhand smoke (THS), or the residue that lingers on surfaces and in dust where tobacco was used.
The study included 504 children under the age of 12 from the Cincinnati area. The researchers analyzed child handwipe samples for nicotine, a marker of THS exposure. A child was considered protected from exposure if no household member smoked or vaped, smoking and vaping were banned in homes and cars, and there was no contact with tobacco users within the previous week.
Nicotine was detected on 98% of children living in exposed conditions and, surprisingly, on 95% of children in protected spaces. On average, exposures of about 3 nanograms per wipe were observed among children from protected households and 22 nanograms per wipe among children in exposed households.
Among children considered to be protected, children of Black parents had higher exposure than those with white or multiracial parents. Children from the lowest income families had about five-fold higher nicotine exposure compared to children from families with incomes greater than $30,000. The association between income and exposure points to a potential role of income-related disparities, such as housing type and quality.
According to the authors, results suggest that decades of permissive smoking policies have created significant THS reservoirs in many indoor environments. Smoking bans, exposure screening, and THS remediation are needed to help protect children.
Citation: Matt GE, Merianos AL, Quintana PJE, Hoh E, Dodder NG, Mahabee-Gittens EM. 2022. Prevalence and income-related disparities in thirdhand smoke exposure to children. JAMA Netw Open 5(2):e2147184.
Pine needles work as passive samplers for PFAS
NIEHS-funded researchers showed that pine needles can be used as a tool to monitor the presence and distribution of per- and polyfluoroalkyl substances (PFAS) over time. The pine needle’s waxy coating traps PFAS and other airborne pollutants, providing a record of contamination.
The study included 60 pine needle samples from six North Carolina counties. For historical comparison, the researchers examined 15 archived samples, dating back to the 1960s, collected from the same counties. The team analyzed each sample using a non-targeted, multidimensional approach that allowed them to distinguish between PFAS based on molecular structure.
More than 70 different PFAS were identified in the pine needles. The types of PFAS detected in samples correlated with known changes in PFAS use over time. For example, samples from the past three decades had an increasing number of newer PFAS, such as GenX, compared with samples collected before the newer substances had emerged. The pine needles, taken at varying distances from contamination sources such as airports, firefighter training sites, and chemical plants, revealed where specific PFAS were being used. For example, samples collected near a contamination source had extremely elevated levels of a type of PFAS commonly used in firefighting foams compared with samples collected further away.
According to the researchers, study results showed that using pine needles in combination with non-targeted multidimensional analyses is a viable method for monitoring the distribution of diverse PFAS.
Citation: Kirkwood KI, Fleming J, Nguyen H, Reif DM, Baker ES, Belcher SM. 2022. Utilizing pine needles to temporally and spatially profile per- and polyfluoroalkyl substances (PFAS). Environ Sci Technol 56(6):3441-3451.
Exposure to PCB mixture mimicking school air linked to range of health effects
Long-term exposure to polychlorinated biphenyl (PCB) mixtures in school air may affect the nervous and immune systems, according to an NIEHS-funded study in rats. Although PCBs were banned in the U.S. in the late 1970s, air in older schools may be contaminated with PCBs released from building materials. This study contributes to knowledge of the health effects of long-term PCB inhalation, which are poorly understood.
For 13 weeks, the researchers exposed female rats to a PCB mixture and dose representative of air in a Chicago school built in 1968. They used a combination of transcriptomics, metabolomics, and neurobehavioral tests to examine the effects of PBC exposure on the nervous, immune, reproductive, and endocrine systems.
PCBs were detected in the brain, liver, lung, serum, and adipose tissue. PCB exposure impaired memory, induced anxiety-like behavior, substantially reduced white blood cell counts, and disrupted plasma metabolite composition. Exposed rats had altered expression of genes in the brain that are important in neurotransmitter signaling, cognitive function, vascular function, and immune response.
Although the exposure level used in this study was higher than what is found in most new schools, it is similar to concentrations reported for some older schools. According to the authors, results indicate that this exposure level — 45.5 micrograms per cubic meter — may be close to the lowest dose in which airborne PCB exposure induces adverse health effects.
Citation: Wang H, Adamcakova-Dodd A, Lehmler HJ, Hornbuckle KC, Thorne PS. 2022. Toxicity assessment of 91-day repeated inhalation exposure to an indoor school air mixture of PCBs. Environ Sci Technol 56(3):1780-1790.
Data mining study sheds light on factors contributing to preterm birth disparities
NIEHS-funded researchers used a data mining approach to identify a diverse set of chemicals that may contribute to disparities in preterm birth among different populations. In the U.S., preterm birth occurs disproportionately in the Black population. Black women also face disproportionate exposure to chemicals in personal care products and from racial disparities in siting of polluting facilities.
The study included 19 chemicals observed at higher levels in the blood or urine of Black women compared with white women. The researchers obtained chemical-gene interactions from the Comparative Toxicogenomics Database and a list of genes involved in preterm birth from the Preterm Birth Database. They examined chemicals for enrichment with preterm birth genes and identified biological pathways affected by these genes.
All 19 chemicals were associated with enriched expression of genes involved in preterm birth. Exposure levels for several chemicals were at least 1.5-fold higher in Black women compared with white women. These chemicals, which included methyl mercury, methylparaben, propylparaben, diethyl phthalate, DDE, and bisphenol S, also had a higher degree of enrichment with preterm birth genes. The chemicals affected genes involved in pathways relevant to preterm birth, such as inflammation, aging, and estradiol response. Most chemicals impacted genes involved in all three pathways.
Study results suggest that exposure to a diverse array of chemicals contributes to racial disparities in preterm birth and that multiple chemicals drive these effects. According to the authors, results may help to prioritize chemicals for further study and exposure reduction in the fight against preterm birth disparities.
Citation: Harris SM, Colacino J, Buxton M, Croxton L, Nguyen V, Loch-Caruso R, Bakulski KM. 2022. A data mining approach reveals chemicals detected at higher levels in non-Hispanic Black women target preterm birth genes and pathways. Reprod Sci; doi:10.1007/s43032-022-00870-w [Online 2 Feb 2022].
(Megan Avakian is a science writer for MDB Inc., a contractor for the NIEHS Division of Extramural Research and Training.)