The July 2023 EMM Editor’s Choice Article “Chromosome damage in regions with different levels of air pollution, “ by Musilova et al. https://onlinelibrary.wiley.com/doi/10.1002/em.22562 examines the chromosomal damage induced in Czech Republic policemen in two different urban and one rural area of the Czech Republic. Police officers actively patrol outdoors during the year and are subject to varying amounts of air pollution through their occupational exposures. Environmental exposure to air pollution affects the global population. Still, due to their high variability in geospatial location, distribution, and concentration, there are challenges to understanding passive and occupational exposures to particulates in air pollution. Air pollution has been attributed to various diseases, such as chronic respiratory illness, cancer, stroke and cardiovascular disease. However, the mechanisms underlying these effects are still being explored due to the high exposure variability and particulate components. Genomic instability results in chromosomal and DNA damage that contributes to cell death, fibrosis and tumorigenesis. Chromosomal aberrations and damage measurements can reflect genomic instability in an exposed population. Measuring chromosomal damage in peripheral blood lymphocytes has been previously used as a biomarker for cancer and air pollution exposures. In this Editor’s Choice Article, Musilova et al. used fluorescence in situ hybridization (FISH) to paint chromosomes 1, 2, 3, and 4 in a standard cytogenetic assay to measure chromosomal instability induced by air pollution exposures. City police officers were recruited from the industrial Ostrava with high levels of benzo[a]pyrene, automobile and heavy traffic containing Prague with large emissions of nitrogen oxides, and the more agricultural Ceske Budejovice. In the spring and autumn, 250 blood samples were collected from 125 recruited male nonsmokers with no history of cancer in the three distinct regions, Ostrava n=54, Prague n=55, and Ceske Budejovice n=16. Quarterly air pollution levels were extracted from air quality data in Ostrava, Prague, and Ceske Budejovice using automated air quality monitoring stations available at www.chmi.cz for 2019, when the study was conducted. Exposure levels to selected pollutants, PM2.5, benzene, benzo-[a]-pyrene, and nitrogen dioxide, were averaged quarterly for each district. In the spring, when the air pollution levels are shown to be more concentrated after the winter quarter in Ostrava and Prague, the frequency of unstable chromosomes increased compared to Ceske Budejovice. The frequency of chromosomal changes was higher in the spring than in the autumn, and the levels were always elevated in Ostrava and Prague but not Ceske Budejovice. No difference in levels was observed between the two urban cities. The findings of this work suggest there may be times of greater exposure during the winter months, which is reflected in abnormal chromosomes with two centromeres or dicentric chromosomes. However, they did not observe significant changes in chromosomal rearrangements. Earlier work in the late 2000s showed that these urban regions showed more significant chromosomal damage and rearrangements. However, this work examined changes in exposure throughout the year and has the advantage of using a more sensitive detection schema. While the work here has some limitations in sample size, it suggests that occupational exposure to air pollutants increases in the winter and impacts genetic stability in urban police officers. The changes observed throughout the exposure year offer new insight into exposure windows for air pollution. Natalie R. Gassman, PhD | Associate Professor The University of Alabama at Birmingham