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Bulgaria has a very high incidence of cardiometabolic diseases and air pollution-related mortality rate. This study investigated the relationship between daily air pollution levels and hospital admissions for ischaemic heart diseases (IHD), cerebral infarction (CI), and type 2 diabetes mellitus (T2DM) in Sofia, Bulgaria. We obtained daily data on hospitals admissions and daily average air pollution levels from 2009 to 2018. Pollutants of interest were particulate matter (PM and PM ), nitrogen dioxide (NO ), sulphur dioxide (SO ), ozone (O ), and carbon monoxide (CO). Negative binomial regressions were fitted to study the effects of air pollution on hospital admission over the course of seven days prior to that event, accounting for autocorrelations and time trend in the data, day of the week, temperature, and relative humidity. Our findings confirm that higher air pollution levels generally increase the risk of hospital admissions for IHD and CI. For T2DM the association is less clear. Admissions often lagged several days behind and were more common in specific demographic subgroups or when pollution crossed a particular threshold. However, we did not expect to find the risk of hospital admissions increased in warmer rather than colder months of the year. Our findings are to be taken with reservation but do provide an idea about how air pollution could trigger acute episodes of related cardiovascular diseases, and our model may serve to investigate similar associations across the country.

Public health impacts of non-optimal temperatures and air pollution have received insufficient attention in Southeast Europe, one of the most air-polluted regions in Europe, simultaneously pressured by climate change. This study employed a multimodal approach to characterize the microclimate and air quality and conduct a health impact assessment in the three biggest cities in Bulgaria. Simulation of atmospheric thermo-hydrodynamics and assessment of urban microclimate relied on the Weather Research and Forecasting model. Concentrations of fine particulate matter (PM2.5) and nitrogen dioxide (NO2) were calculated with a land-use regression model. Ischemic heart disease (IHD) hospital admissions were linked to daily measurements at background air quality stations. The results showed declining trends in PM2.5 but persistent levels of NO2, especially in Sofia and Plovdiv. Distributed lag nonlinear models revealed that, in Sofia and Plovdiv, PM2.5 was associated with IHD hospitalizations, with a fifth of cases in Sofia attributable to PM2.5. For NO2, an increased risk was observed only in Sofia. In Sofia, the risk of IHD was increased at cold temperatures, while both high and low temperatures were associated with IHD in Plovdiv and Varna. Short-term effects were observed in response to heat, while the effects of cold weather took up to several weeks to become apparent. These findings highlight the complexity of exposure–health interactions and emphasize the need for integrated policies addressing traffic emissions, urban design, and disease burden.

Telomere length (TL) is a biomarker of biological aging, with shorter telomeres linked to age-related diseases and cancers. Benzene, a known carcinogen, may contribute to telomere shortening through oxidative DNA damage and other mechanisms. Previous studies gave conflicting results. The aim of this study is to investigate the association between benzene and TL in a study population characterized by a wide range of mostly low exposure levels. We enrolled 423 workers occupationally exposed to benzene and 190 non-occupationally exposed referents from three cities in Italy and one in Bulgaria. Participants wore passive and active samplers for an entire work shift to measure time-weighted average benzene exposure. TL was measured through real-time PCR. We applied multivariable mixed-effects models with a random intercept on the city, adjusted for sex, age, smoking, cigarettes/day, and alcohol consumption to evaluate the association between benzene and changes in TL. Exposure to environmental benzene ranged from 0.0013 to 21.14 ppm (min-max). For every ten-fold increase in benzene concentrations, TL decreased by 7.4% (95% confidence interval [CI]: -9.9; -4.7). A similar pattern was observed in never-smokers (-10.2%, 95%CI: -14.9; -5.3) and after additional adjustment for toluene (-6.5%, 95%CI: -9.7; -3.2). When data were available, we observed a negative association also between TL and urinary benzene (-5.8%, 95%CI: -8.7; -2.8 for each twofold increase in urinary benzene concentration). Our findings suggest that even low levels of benzene exposure may cause telomere shortening and accelerate biological aging.

Chronic occupational exposure to benzene is associated with an increased risk of hematological malignancies such as acute myeloid leukemia (AML), but the underlying mechanisms are still unclear. The main objective of this study was to investigate the association between benzene exposure and DNA methylation, both in repeated elements and candidate genes, in a population of 158 Bulgarian petrochemical workers and 50 unexposed office workers. Exposure assessment included personal monitoring of airborne benzene at work and urinary biomarkers of benzene metabolism (S-phenylmercapturic acid [SPMA] and trans,trans-muconic acid [t,t-MA]) at the end of the work-shift. The median levels of airborne benzene, SPMA and t,t-MA in workers were 0.46 ppm, 15.5 µg/L and 711 µg/L respectively, and exposure levels were significantly lower in the controls. Repeated-element DNA methylation was measured in Alu and LINE-1, and gene-specific methylation in MAGE and p15. DNA methylation levels were not significantly different between exposed workers and controls (P>0.05). Both ordinary least squares (OLS) and beta-regression models were used to estimate benzene-methylation associations. Beta-regression showed better model specification, as reflected in improved coefficient of determination (pseudo R(2)) and Akaike's information criterion (AIC). In beta-regression, we found statistically significant reductions in LINE-1 (-0.15%, P<0.01) and p15 (-0.096%, P<0.01) mean methylation levels with each interquartile range (IQR) increase in SPMA. This study showed statistically significant but weak associations of LINE-1 and p15 hypomethylation with SPMA in Bulgarian petrochemical workers. We showed that beta-regression is more appropriate than OLS regression for fitting methylation data.

ObjectiveTelomere length (TL) is a biomarker of biological aging, with shorter telomeres linked to age-related diseases and cancers. The aim of this study is to investigate the association between benzene and TL in a large study population, characterized by a wide range of mostly low exposures.MethodsWe enrolled 423 workers exposed to benzene and 190 non-exposed referents from three cities of Italy (Genoa, Milan, Cagliari) and one of Bulgaria (Burgas). Exposure to benzene was measured through passive (Italy) and active (Bulgaria) samplers the participants wore near the breathing zone during their work shift. TL was measured through real-time PCR. We applied multivariable mixed-effects models with a random intercept on the city, adjusted by sex, age, smoking, cigarettes/day, and alcohol consumption to evaluate the association between benzene and changes in TL.ResultsExposed subjects were selected from occupational categories exposed to low levels of benzene: 144 bus drivers (Genoa), 77 traffic police officers and 76 gas station attendants (Milan), 18 and 180 petrochemical workers (Cagliari and Burgas, respectively). In each city, exposed workers showed higher benzene values than referents, with the highest exposure levels measured among Bulgarian petrochemical workers (median: 0.17 ppm, IQR: 0.44; 1.44). We estimated a 6.9% reduction (95% confidence interval [CI]: -9.5; -4.3) in TL for each 10-fold increase in environmental benzene concentration. A similar pattern was observed in never smokers (-9.48%, 95%CI: -14.10; -4.60) and in the subgroup where urinary benzene was available (-8.27%, 95%CI: -12.34; -4.02).ConclusionsOur findings align with existing literature, suggesting that low levels of benzene exposure may accelerate biological aging, and underline the importance of monitoring occupational benzene exposure, even at concentrations below current regulatory limits.