Fine particulate matters less than 2.5 µm (PM_2.5) in the ambient atmosphere are strongly associated with adverse health effects. However, it is unlikely that all fine particles are equally toxic in view of their different sizes and chemical components. Toxicity of fine particles produced from various combustion sources (diesel engine, gasoline engine, biomass burning (rice straw and pine stem burning), and coal combustion) and non-combustion sources (road dust including sea spray aerosols, ammonium sulfate, ammonium nitrate, and secondary organic aerosols (SOA)), which are known major sources of PM_2.5, was determined. Multiple biological and chemical endpoints were integrated for various source-specific aerosols to derive toxicity scores for particles originating from different sources. The highest toxicity score was obtained for diesel engine exhaust particles, followed by gasoline engine exhaust particles, biomass burning particles, coal combustion particles, and road dust, suggesting that traffic plays the most critical role in enhancing the toxic effects of fine particles. The toxicity ranking of fine particles produced from various sources can be used to better understand the adverse health effects caused by different fine particle types in the ambient atmosphere, and to provide practical management of fine particles beyond what can be achieved only using PM mass which is the current regulation standard.

In order to control the spread of COVID-19, social distancing measures were implemented in many countries. This study investigated changes in air pollution during the social distancing after the COVID-19 outbreak in Korea. Ambient PM2.5, PM10, NO2, and CO that are particularly related to industrial activities and traffic were reduced during the social distancing in response to the COVID-19 outbreak. In March 2020, immediately after social distancing, mean levels of PM2.5, PM10, NO2, and CO decreased nationwide from last year's mean levels by 16.98 μg/m3, 21.61 μg/m3, 4.16 ppb, and 0.09 ppm, respectively (p-value for the year-to-year difference <0.001, =0.001, =0.008, <0.001), a decrease by 45.45%, 35.56%, 20.41%, and 17.33%, respectively. Changes in ambient O3 or SO2 were not observed to be attributable to social distancing. Our findings, that such effort for a short period of time resulted in a significant reduction in air pollution, may point toward reducing air pollution as a public health problem in a more sustainable post-COVID-19 world.

Ji W, et al. J Korean Med Sci. 2020 May;35(25):e237. https://doi.org/10.3346/jkms.2020.35.e237

The prevalence of hearing loss increases rapidly with aging. Hearing loss is common in all age groups, even in young adults and adolescents. A growing body of evidence has suggested that heavy metals have ototoxic effects, yet few epidemiological studies have investigated the association between heavy metals and hearing loss in a general population that includes adults and adolescents. We examined the association between environmental exposures to lead, mercury, and cadmium and the risk of hearing loss in adults and adolescents while controlling for potential confounding factors, including noise exposures and clinical factors. We analyzed cross-sectional data from 5,187 adults and 853 adolescents in the Korean National Health and Nutrition Examination Survey 2010-2012. Pure-tone average (PTA) of hearing thresholds at high frequency (3, 4, and 6 kHz) were computed, and hearing loss was defined as a PTA>25 dB in adults and PTA>15 dB in adolescents. In adults, the highest (vs. lowest) quartiles of blood lead and cadmium were associated with 1.70 (95% CI: 1.25, 2.31) and 1.47 (95% CI: 1.05, 2.05) odds ratios for high-frequency hearing loss (p-trend<0.001 and=0.007), respectively. In adolescents, the highest quartile (vs. lowest) of blood cadmium had an odds ratio of 3.03 (95% CI: 1.44, 6.40) for high-frequency hearing loss (p-trend=0.003), but blood lead was not associated with hearing loss. No significant association between blood mercury and hearing loss was suggested in either adults or adolescents. The results of the present study suggest that exposure to environmental lead and cadmium in adults and exposure to environmental cadmium in adolescents may play a role in the risk of hearing loss. https://doi.org/10.1289/EHP565.