Environmental Factor – April 2021: Extramural Paper of the Month

PM2.5 levels on subways sometimes exceed health guidelines

In a new study, NIEHS-funded researchers found that subway transit workers and commuters may be at increased risk of health problems due to the high levels of air pollution in subway stations.

The team monitored 71 subway stations on 12 transit lines in Philadelphia, Boston, New York, New Jersey and Washington, DC during morning and evening rush hours. They measured real-time concentrations of fine particulate matter (PM2.5) at above-ground and underground stations and in trains. X-ray fluorescence spectroscopy was used to assess the composition of the particles.

Reported PM2.5 concentrations varied but were very high in some places. In general, PM2.5 levels were lowest in above-ground stations, followed by inside trains, and highest in underground stations. Morning rush hours tended to be higher in cities than evening rush hours. Values ​​measured in subway stations during rush hour were 2-7 times higher than health standards. Stations served by the New York City / New Jersey system had the highest PM2.5 concentrations ever reported for a subway system. Iron and total carbon made up about 80% of the PM2.5 mass, although the composition varied by station and city.

According to the authors, the increased PM2.5 concentrations measured during rush hour in northeastern metro systems suggest that commuters or transit workers are at increased risk of death due to cardiovascular health problems.

Quote:: Luglio DG, Katsigeorgis M., Hess J., Kim R., Adragna J., Raja A., Gordon C., Fine J., Thurston G., Gordon T., Vilcassim MJR. 2021. PM2.5 Concentration and Composition in Subway Systems in the Northeastern United States. Environ Health Perspect 129 (2): 27001.

Early exposure to PFOS alters the development of zebrafish

According to a new NIEHS-funded study, exposure to perfluorooctanesulfonic acid (PFOS) early in development can alter metabolic programming and pancreatic development in the zebrafish. The changes persisted in fry, which the authors suggests suggests that PFOS is a contaminant of interest in the development of diabetes and obesity.

The researchers exposed zebrafish embryos to PFOS either 1-5 days after fertilization (dpf) or 1-15 dpf. They rated fish at different times up to 30 dpf or in the youth stage. The researchers examined the concentrations of lipids, triglycerides, proteins, cholesterol and glucose as well as the shape of the pancreatic islet cells, body fat and fish behavior. They also measured the expression of various forms of the peroxisome proliferator activated receptor (PPAR), a pathway involved in nutrient metabolism and storage.

Compared to exposed and non-exposed fish, the team found no differences in protein, cholesterol, triglyceride or glucose levels. In exposed fish, however, they found higher concentrations of certain saturated fatty acids and lower PPAR gene expression. The team reported more abnormal pancreatic islet cells and increased body fat in both 15-dpf and young PFOS-exposed fish compared to unexposed fish. The researchers saw no difference in behavior.

According to the authors, these data suggest that exposure to PFOS early in development can disrupt metabolic programming and lead to changes that persist later in life.

Quote:: Sant KE, Annunziato K., Conlin S., Teicher G., Chen P., Venezia O., Downes GB, Park Y, Timme-Laragy AR. 2021. Developmental exposure to perfluorooctanesulfonic acid (PFOS) affects embryonic nutrition, pancreatic morphology and obesity in the zebrafish Danio rerio. Environ Pollut 275: 116644.

New study sheds light on TCE bioremediation

Researchers funded by NIEHS showed that natural microbial communities modified with acetylene can break down chlorinated contaminants, thereby discovering a new species of bacteria. Acetylene, which is formed in aquifers when certain minerals interact with trichlorethylene (TCE), usually affects the ability of microbes to dechlorinate TCE. TCE is a chlorinated compound that can contaminate the environment and has been linked to health effects such as cancer.

Previous laboratory studies by the team indicated that acetylene can act as an energy source for certain bacteria, which can then further break down TCE. To investigate this finding in natural systems, they combined laboratory studies of natural microbial communities with computational approaches and metagenomic analyzes to characterize the community. Scientists studied microbial metabolism and community functions to determine which bacteria could use acetylene for energy in breaking down TCE.

First, they took samples from a location contaminated with TCE and used acetylene to enrich the microbes that could use it as a source of energy. They continued to add TCE to study dichlorination and observed unique metabolic interactions previously only reported in synthetic laboratory settings. The researchers also identified novel acetylene-eating bacteria in the phylum Actinobacteria.

According to the authors, native bacteria that can use acetylene as an energy source may be more abundant than previously thought – useful for developing effective bioremediation strategies to clean up contaminated sites.

Quote:: Gushgari-Doyle S., Oremland RS, Keren R., Baesman SM, Akob DM, Banfield JF, Alvarez-Cohen L.. 2021. Reductive trichloroethene dechlorination operated with acetylene in a groundwater enrichment culture. mBio 12 (1): e02724-20.

Chemicals released in new cars increase the risk of cancer

According to a recent NIEHS-funded study, people who spend a lot of time in their vehicles may have a higher risk of cancer from inhaling benzene and formaldehyde, which are used inside cars.

Researchers estimated exposure to benzene, formaldehyde, phthalates, and other chemicals in vehicle interiors using a meta-analysis of chemical concentrations measured in other studies and commuting times. They compared these estimated exposure levels to those set by the California Environmental Impact Assessment Office to determine the likelihood of an increased risk of cancer. The team used a benchmark with a 10% chance of exceeding cancer risk as a cause for concern.

Benzene and formaldehyde were the only two chemicals with higher estimates of cancer risk in all commute times. A large proportion of California commuters estimated the likelihood of a higher risk of cancer to be at least 10%. In particular, the researchers estimated that 78% of Californians were at higher risk of cancer from exposure to formaldehyde and 63% were at higher risk from benzene exposure. They also estimated that 11% of commuters were at a higher risk of poor reproductive or developmental health due to benzene exposure while commuting. According to the authors, people who travel long distances for years or decades are likely to be a subpopulation at risk for exposure to these chemicals.

Quote:: Reddam A, Volz DC. 2021. Inhaling two Prop 65-listed chemicals in vehicles may be linked to an increased risk of cancer. Environ Int 149: 106402.

(Adeline Lopez is a research and communications specialist at MDB Inc., a contractor for NIEHS ‘extramural research and education division.)

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