Papers of the Month
By Adeline Lopez
PM2.5 levels in subways sometimes exceed health guidelines
In a new study, NIEHS-funded researchers found that subway transit workers and commuters may be at increased risk for health problems due to exposure to high levels of air pollutants in subway stations.
The team monitored 71 subway stations across 12 transit lines in Philadelphia, Boston, New York City, New Jersey, and Washington, D.C. during morning and evening rush hours. They measured real-time concentrations of fine particulate matter (PM2.5) at stations — both aboveground and underground — and on trains. X-ray fluorescence spectroscopy was used to evaluate composition of the particulates.
Reported PM2.5 concentrations varied but were very high at some locations. In general, PM2.5 levels were lowest in aboveground stations, followed by inside trains, and were highest in underground stations. Morning rush hour levels tended to be higher than evening rush hour levels across cities. Levels measured in subway stations during rush hours were 2-7 times higher than health standards. Stations serviced by the New York City/New Jersey system had the highest PM2.5 concentrations ever reported for a subway system. Iron and total carbon accounted for approximately 80% of the PM2.5 mass, although composition varied by station and city.
According to the authors, the elevated PM2.5 concentrations measured across Northeastern subway systems during rush hours suggest commuters or transit workers may be at increased risk for death due to cardiovascular health problems.
Citation: 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 life exposure to PFOS alters zebrafish development
Exposure to perfluorooctanesulfonic acid (PFOS) early in development can alter metabolic programming and pancreas development in zebrafish, according to a new NIEHS-funded study. The changes persisted in juvenile fish, suggesting PFOS as a contaminant of interest in the developmental origins of diabetes and obesity, according to the authors.
Researchers exposed zebrafish embryos to PFOS from either 1-5 days post fertilization (dpf) or 1-15 dpf. They evaluated fish at different time points up to 30 dpf, or juvenile stage. The researchers looked at concentrations of lipids, triglycerides, protein, cholesterol, and glucose, as well as at pancreatic islet cell shape, body fat, and fish behavior. They also measured the expression of different forms of the peroxisome proliferator-activated receptor (PPAR), a pathway involved in nutrient metabolism and storage.
Comparing exposed with nonexposed fish, the team did not observe any differences in levels of protein, cholesterol, triglycerides, or glucose. However, in exposed fish 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 juvenile PFOS-exposed fish compared with unexposed fish. The researchers did not observe any difference in behavior.
According to the authors, these data suggest that PFOS exposures early in development can disrupt metabolic programming and result in changes that persist later in life.
Citation: Sant KE, Annunziato K, Conlin S, Teicher G, Chen P, Venezia O, Downes GB, Park Y, Timme-Laragy AR. 2021. Developmental exposures to perfluorooctanesulfonic acid (PFOS) impact embryonic nutrition, pancreatic morphology, and adiposity in the zebrafish, Danio rerio. Environ Pollut 275:116644.
New study sheds light on TCE bioremediation
NIEHS-funded researchers demonstrated that natural microbial communities amended with acetylene can break down chlorinated contaminants, and in the process, they discovered a new bacteria species. Acetylene, produced in aquifers when certain minerals interact with trichloroethene (TCE), usually interferes with the ability of microbes to dechlorinate TCE. TCE is a chlorinated compound that can contaminate the environment and has been linked to health outcomes like cancer.
Previous lab studies by the team showed that acetylene could act as an energy source for certain bacteria, which could then continue to degrade TCE. To explore this finding in natural systems, they combined laboratory studies of natural microbial communities with computational approaches and metagenomic analyses to characterize the community. The scientists examined microbe metabolism and community functions to determine which bacteria could use acetylene for energy while breaking down TCE.
First, they took samples from a site contaminated with TCE and used acetylene to enrich the microbes that could it as an energy source. They continued adding TCE to examine at 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 common than previously thought — useful for developing effective bioremediation strategies to clean up contaminated sites.
Citation: Gushgari-Doyle S, Oremland RS, Keren R, Baesman SM, Akob DM, Banfield JF, Alvarez-Cohen L. 2021. Acetylene-fueled trichloroethene reductive dechlorination in a groundwater enrichment culture. mBio 12(1):e02724-20.
Chemicals released in new cars increase cancer risk
People who spend a significant amount of time in their vehicles may have higher cancer risks from inhaling benzene and formaldehyde, which are used in car interiors, according to a recent NIEHS-funded study.
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 commute times. They compared these estimated exposure levels to those established by the California Office of Environmental Health Hazard Assessment to determine the probability of increased cancer risk. The team used a benchmark of 10% probability of exceeding cancer risk as a level of concern.
Benzene and formaldehyde were the only two chemicals with higher cancer risk estimates across any of the commute times, with a large proportion of commuters in the state of California estimated to have at least a 10% probability of having higher cancer risk. Specifically, the researchers estimated that 78% of Californians had higher risk of cancer due to formaldehyde exposure, and 63% were at higher risk due to benzene exposure. They also estimated that 11% of commuters had higher risk of poor reproductive or developmental health resulting from benzene exposure while commuting. According to the authors, people experiencing long commutes over years or decades likely represent a vulnerable subpopulation for exposure to these chemicals.
Citation: Reddam A, Volz DC. 2021. Inhalation of two Prop 65-listed chemicals within vehicles may be associated with increased cancer risk. Environ Int 149:106402.
(Adeline Lopez is a science writer for MDB Inc., a contractor for the NIEHS Superfund Research Program.)