Environmental degradation may increase microplastics' toxicity

Environmental factors, such as ultraviolet (UV) light, can alter the chemistry of miniscule plastic fragments, potentially increasing their toxicity on lung cells, according to an NIEHS-funded study. The findings offer clues into the health risks of exposure to plastic debris.

Varying environmental conditions, such as sunlight, humidity, and temperature, can erode plastic into tiny fragments called microplastics. Those small plastic pieces can end up in dust, water, and food. As a result, people can be exposed to them through inhalation and ingestion.

The researchers sought to understand how weathering might render plastic debris toxic to respiratory health. They treated commercially available polystyrene microspheres — a type of microplastic commonly found in the environment — with UV light for five weeks to promote weathering. Then, they exposed lung cells to the aged microspheres and to pristine spheres, which had not been treated.

Using state-of-the-art spectroscopy techniques, the study showed that UV exposure affected the particle’s chemical structure and reactivity. Aged microspheres caused more biological responses in lung cells than pristine microspheres. Notably, aged microspheres slowed how cells healed in response to wounds, altered cell metabolism, and increased the number of cells in earlier stages of growth and division — a biological marker, or sign, that lung cancer could develop. The researchers noted that as radiation dose and microplastic size and concentration increased, the adverse effects of the particles on cell health also increased.

Understanding the influence of weathering, along with that of size, shape, and chemistry, across the lifespan of plastic products may be an important consideration for the types of plastics incorporated into products.

Citation: El Hayek E, Castillo E, In JG, Garcia M, Cerrato J, Brearley A, Gonzalez-Estrella J, Herbert G, Bleske B, Benavidez A, Hsiao H, Yin L, Campen MJ, Yu X. 2023. Photoaging of polystyrene microspheres causes oxidative alterations to surface physiochemistry and enhances airway epithelial toxicity. Toxicol Sci, 193(1):90-102.

New technology can remove PFAS from water

A small business funded by NIEHS developed a novel technology to clean up water contaminated with PFAS. Their materials can be reused multiple times and are potentially less expensive than current remediation technologies, the authors said.

PFAS have been detected in drinking water sources throughout the U.S. The substances are difficult to break down by traditional water treatment processes because they include a series of strong chemical bonds between carbon and fluorine atoms. Current technologies to filter contaminants from water, such as activated carbon and reverse osmosis, are not effective at trapping all PFAS and can discharge toxic waste.

Researchers created 12 materials, each with a unique surface chemistry and structural configuration, made of silica and fluorine. Silica, a mineral known for its porous structure and large surface area, is commonly used in water filtering technologies. The fluorine component allows the materials to attract the fluorine atoms that make up PFAS and collect the substances from polluted water onto the material’s surface.

The team tested the efficiency of each material at removing different types of PFAS from water samples taken from contaminated sites. The best-performing material removed more than 90% of PFAS tested, including new varieties of PFAS — called short-chain PFAS — that other technologies have trouble removing. In addition, the researchers noted that their materials could be reused at least five times without losing integrity.

The small business plans to continue testing the most effective material's performance in the lab, as well as determining operational costs for its use in pilot projects and full-scale water treatment facilities.

Citation: Singh A, Lynch R, Solomon J, Weaver JD, May AR. 2023. Development of novel fluor mop materials for remediation of perfluoroalkyl substances (PFAS) from groundwater. J Hazard Mater 448:130853.

Green space may reduce postpartum depression risk

Exposure to green space and increased physical activity may lower a mother’s risk of postpartum depression (PPD), NIEHS-funded researchers found. Approximately 13% of U.S. mothers experience PPD, which, if left untreated, can harm maternal health and may cause sleeping, eating, and behavioral problems for their babies.

The researchers gathered data on PPD and physical activity from electronic health records on 415,000 mothers who gave birth in Southern California between 2008 and 2018. For this study, PPD was defined as a depression diagnosis along with medications prescribed specifically for depression during the first 12 months after delivery. To assess green space exposure, the team used high-resolution street-view image data to determine the extent of street-level tree cover, low-lying vegetation like shrubs and bushes, and grass in participants’ residential areas. They also measured proximity of maternal street addresses to the nearest park.

Through statistical analysis, the team estimated the association between green space and PPD and whether physical activity played a mediating role in the effect of green space on PPD. They found that PPD risk decreased as street-level tree coverage increased. Other types of green space, such as proximity to a park and grass, had little to no effect on PPD risk. The authors also observed that physical activity during pregnancy was higher in areas with more green space, suggesting that physical activity is a possible link between green space and mental well-being.

These findings may help inform policies and interventions aimed at increasing tree coverage to improve the benefits for maternal mental health, the team noted.

Citation: Sun Y, Molitor J, Benmarhnia T, Avila C, Chiu V, Slezak J, Sacks DA, Chen J-C, Getahun D, Wu J. 2023. Association between urban green space and postpartum depression, and the role of physical activity: a retrospective cohort study in Southern California. Lancet Reg Health Am 21:100462.

DNA-based sensor rapidly detects pesticide contamination

Researchers funded by NIEHS developed a DNA-based sensor that can detect trace amounts of organophosphate pesticides in food products. The tool could address the limitations of traditional detection methods, such as liquid chromatography-tandem mass spectrometry, which are expensive, time-consuming, and require extensive training, the authors wrote.

The organophosphate pesticides triazophos, parathion, and chlorpyrifos are highly toxic and have been linked to adverse health outcomes, such as cancer. Although many countries have banned or restricted their use, the chemicals are still components of pesticide mixtures used in daily agricultural production around the world.

The sensor incorporates a fluorescent immunoassay, which is a type of test that uses antibodies to identify pesticide residues. In this study, gold nanomaterials and pesticide molecules were chemically bonded to single strands of DNA, known as bio-barcodes. Then, a DNA structure called a hairpin was introduced into the system to initiate a reaction in which two single DNA strands bonded together, which resulted in a double-stranded molecule. The double-stranded structure fluoresced upon detection of the residues so organophosphates could be quantified.

The team used the sensor to measure traces of triazophos, parathion, and chlorpyrifos in samples from contaminated fruit, vegetables, and grain and compared their results to findings from traditional liquid chromatography-tandem mass spectrometry. They found that their DNA-based sensor detected the three pesticides in the mixtures as accurately as the mass spectrometry method.

According to the authors, their device is easier to use, more reliable, faster, and a more cost-effective alternative to traditional methods of pesticide detection.

Citation: Wang Y, Abd El-Aty AM, Wang S, Cui X, Zhao J, Lei X, Xu L, She Y, Jin F, Eun JB, Shim JH, Wang J, Jin M, Hammock BD. 2023. Competitive fluorescent immunosensor based on catalytic hairpin self-assembly for multiresidue detection of organophosphate pesticides in agricultural products. Food Chem 413:135607.