Papers of the Month
Extramural
By Adeline Lopez
Interaction of toxic metals in the digestive system revealed
NIEHS-funded researchers revealed how arsenic and cadmium may interact inside the human body, potentially altering their toxicity. The two metals frequently occur together in contaminated soil, but little is known about how combined exposure may affect health.
Using an simulated gastrointestinal (GI) tract in the lab, the team measured arsenic and cadmium bioaccessiblity, which is the amount of arsenic or cadmium that could be released during digestion and absorbed into the bloodstream. They exposed the artificial GI tract to cadmium only, arsenic only, or to a mixture of both metals. They also explored the effects of ferrihydrite, an iron mineral commonly found in dust, and pepsin, an enzyme responsible for protein digestion, to better replicate conditions inside the human body.
The team reported that cadmium bioaccessibility increased when arsenic was present. Arsenic bioaccessibility decreased with the addition of cadmium, but the arsenic present was transformed into a more toxic form. Both metals formed complexes with ferrihydrite, which promoted the release of cadmium but inhibited the release of arsenic. Pepsin formed soluble complexes with both metals, increasing their bioaccessibility.
According to the authors, these findings highlight the importance of understanding how exposure to contaminant mixtures affects their potential toxicity and may inform more protective regulatory strategies for soil and dust when cadmium and arsenic are both present.
Citation: Bai B, Kong S, Root RA, Liu R, Wei X, Cai D, Chen Y, Chen J, Yi Z, Chorover J. 2024. Release mechanism and interactions of cadmium and arsenic co-contaminated ferrihydrite by simulated in-vitro digestion assays. J Hazard Mater 467:133633.
Prenatal exposure to glyphosate linked to neurodevelopmental delays
An NIEHS-funded study found that glyphosate exposure during pregnancy may alter early brain development in children. According to the authors, this is one of the first studies to examine the relationship between exposure to the common herbicide before birth and neurodevelopment in young children.
The scientists studied 143 mother-baby pairs from Puerto Rico. To assess exposure, they collected urine samples from the mothers during pregnancy and measured levels of glyphosate and a common breakdown product of the herbicide. Then, they evaluated the children’s brain development at 6, 12, and 24 months using the Battelle Developmental Inventory. This test measures how well babies communicate, move, learn, and socialize. Using statistical models, they assessed potential links between the levels of glyphosate and the breakdown product in the mothers’ urine and their children’s performance on the test.
Children of mothers with higher glyphosate exposure scored lower in communication skills at 12 and 24 months. At 24 months, children with higher prenatal glyphosate exposure also scored lower in other areas, such as the ability to adapt to and understand new situations, attention, and memory.
These findings suggest that exposure to glyphosate during pregnancy may affect early neurodevelopment, with more pronounced delays by the time children reach 24 months, according to the authors. Because glyphosate is widely used, they noted that more research is needed to fully understand potential impacts on children’s neurodevelopment as they grow older.
Citation: Jenkins HM, Meeker JD, Zimmerman E, Cathey A, Fernandez J, Montañez GH, Park S, Pabón ZR, Vélez Vega CM, Cordero JF, Alshawabkeh A, Watkins DJ. 2024. Gestational glyphosate exposure and early childhood neurodevelopment in a Puerto Rico birth cohort. Environ Res 246:118114.
Maternal air pollution exposure, telomere length, and child sex interact to affect birthweight
NIEHS-funded researchers discovered that the length of a mother’s telomeres and the sex of her child complicate the effects of prenatal air pollution exposure on birthweight. Telomeres are regions of repetitive DNA sequences at the end of chromosomes that shorten with age. Several factors, including stress and exposure to environmental contaminants, can accelerate telomere shortening and biological aging.
The researchers explored whether premature aging of the placenta, reflected by telomere length, modifies the relationship between air pollution exposure and birthweight. Abnormal birthweight is associated with higher risk for health problems later in life. They looked at data from 306 mothers and their babies who participated in an urban health study in the Northeast U.S. Using mathematical models, the team assessed the effects of air pollution exposure during pregnancy and placental telomere length at delivery on birthweight while accounting for the length of the pregnancy and the baby’s sex.
Results differed by exposure window, air pollutant, sex, and placental telomere length. For boys, exposure to fine particulate matter during the third trimester was associated with lower birthweight if their mothers had longer telomeres. In contrast, exposure to ozone during the first trimester or nitrogen dioxide in the third trimester was associated with higher birthweight if mothers had shorter telomeres. For girls, exposure to a mix of pollutants during the second trimester was associated with lower birthweight if their mothers had longer placental telomeres.
According to the authors, the results suggest that exploring the complex relationships between exposure timing, air pollutant exposure, placental telomere length, and a baby’s sex may help researchers identify women at higher risk for adverse birth outcomes, informing targeted interventions.
Citation: Zhang X, Colicino E, Cowell W, Enlow MB, Kloog I, Coull BA, Schwartz JD, Wright RO, Wright RJ. 2024. Prenatal exposure to air pollution and BWGA Z-score: Modifying effects of placenta leukocyte telomere length and infant sex. Environ Res 246:117986.
Sorbent materials decrease movement and toxicity of PFAS in soil
A strategy developed by NIEHS-funded scientists may trap PFAS in soil and prevent the chemicals from spreading to plants or water. Immobilizing the chemicals in soil is one remediation strategy to reduce human exposure.
The scientists evaluated the ability of six different sorbent materials, made up of activated carbon or specialized clays, to trap four PFAS chemicals in soil. They measured how much PFAS solution leaked out of soil — a proxy for how much could be absorbed by plants or animals, called bioavailability — when each sorbent was added. They also explored how changes in PFAS bioavailability translated to toxicity by exposing worms and aquatic plants to soil or water following extraction.
Overall, adding any of the sorbent materials reduced PFAS bioavailability in soil by 58-97%. Activated carbon was the most effective at trapping PFAS, reducing the bioavailable amount by 73-97%, depending on the amount of sorbent used. Their method was effective in trapping PFAS for up to 21 days, even when the soil samples were exposed to different conditions, including simulations of acid rain, fresh water, and brackish water. Mirroring the reduced bioavailability of PFAS, the team reported a dose-dependent decrease in toxicity to plants and worms in the presence of any of the six individual sorbents — some modified clays promoted plant growth due to added nutrients.
According to the authors, adding a combination of activated carbon and modified clays is a practical approach to help reduce the spread of PFAS in soils while protecting surrounding plants and animals.
Citation: Wang M, Rivenbark KJ, Nikkhah H, Beykal B, Phillips TD. 2024. In vitro and in vivo remediation of per- and polyfluoroalkyl substances by processed and amended clays and activated carbon in soil. Appl Soil Ecol 196:105285.
(Adeline Lopez is a science writer for MDB Inc., a contractor for the NIEHS Division of Extramural Research and Training.)
