Evaluating Exposure-Response Associations for Non-Hodgkin Lymphoma with Varying Methods of Assigning Cumulative Benzene Exposure in the Shanghai Women's Health Study

UBE2L3 promotes benzene-induced hematotoxicity via autophagy-dependent ferroptosis

Benzene is a common environmental pollutant and significant health hazard. Low-dose benzene exposure is common in most industrial settings, and some workers exhibit hematotoxicity characterized by impaired hematopoietic function. Consequently, understanding the early hematopoietic damage and biomarkers associated with low-dose benzene exposure is of critical importance for health risk assessment. Using data from a 5-year prospective cohort study on benzene exposure and the National Center for Biotechnology Information's Gene Expression Omnibus database, we detected significant downregulation of the ubiquitin-conjugating enzyme UBE2L3 (E2) in benzene-exposed subjects compared to control subjects. Liquid chromatography tandem mass spectrometry and co-immunoprecipitation experiments illustrated the binding interaction between UBE2L3 and the ubiquitin-protein ligase ZNF598 (E3). We applied deep learning algorithms to predict candidate interacting proteins and then conducted validation via co-immunoprecipitation experiments, which showed that ZNF598 engages in binding with the autophagy protein LAMP-2. Subsequent overexpression and knockdown of UBE2L3 coupled with immunofluorescence experiments and transmission electron microscopy revealed that UBE2L3 disrupts the ubiquitination-degradation of LAMP-2 by ZNF598, reduces GPX4 expression levels, and activates an autophagy-dependent ferroptosis pathway. It also leads to increased lipid peroxidation, thereby promoting ferroptosis and contributing to the hematotoxicity induced by benzene. In summary, our results suggest that UBE2L3 may be involved in early hematopoietic damage by modulating the autophagy-dependent ferroptosis signaling pathway in benzene-induced hematotoxicity.

Occupational exposure to benzene and risk of non-Hodgkin lymphoma in an extended follow-up of two population-based prospective cohorts of Chinese men and women

The carcinogenicity of benzene was reevaluated by the International Agency for Research on Cancer in 2017, with the Working Group reaffirming positive yet inconclusive associations with non-Hodgkin lymphoma (NHL). To extend our previous observation of a significant exposure-response for cumulative occupational benzene exposure and NHL risk among Chinese women in a population-based cohort in Shanghai, we extended follow-up of this cohort and pooled the data with a similarly designed population-based cohort of men in Shanghai. Cumulative exposure estimates were derived for 134,449 participants in the pooled analysis by combining ordinal job-exposure matrix intensity ratings with quantitative benzene measurements from an inspection database of Shanghai factories. Associations between benzene exposure metrics and NHL (n = 363 cases including multiple myeloma [MM]) were assessed using Cox proportional hazard models. Ever occupational exposure to benzene in the pooled population was associated with NHL risk (HR = 1.5, 95% CI = 1.2-2.0), and exposure-response relationships were observed for increasing duration (ptrend = .003) and cumulative exposure (ptrend = .003). Associations with ever exposure, duration, and cumulative exposure were similar for NHL with and without MM in the case definition, including lifetime cumulative exposures in the highest quartile (HR = 1.6, 95% CI = 1.1-2.4 with MM included; HR = 1.7, 95% CI = 1.1-2.7 with MM excluded). An elevated risk of the chronic lymphocytic leukemia subtype was suggested in the pooled analyses (HR for ever vs. never exposure = 2.3, 95% CI = 0.9-5.6). These observations provide additional support for a plausible association between occupational benzene exposure and risk of NHL.

LincRNA-p21 promotes p21-mediated cell cycle arrest in benzene-induced hematotoxicity by sponging miRNA-17-5p

Benzene is widely employed in manufacturing and causes hematotoxic effects and leukemia in humans. A long intergenic noncoding RNA (lincRNA)-microRNA (miRNA)-mRNA coexpression and competing endogenous RNA (ceRNA) regulatory network was constructed by bioinformatics analysis based on a benzene-induced aplastic anemia (BIAA) mouse model. In this population-based study, we observed a trend consistent with that in the BIAA mice: lincRNA-p21 and p21 were upregulated, while miRNA-17-5p expression was downregulated in benzene-exposed workers. Moreover, multiple linear regressions indicated that lincRNA-p21 was negatively associated with white blood cell (WBC) counts. Predictive thresholds of hematotoxicity were identified by ROC curve analysis with S-phenylmercapturic acid (SPMA) and lincRNA-p21 showing a better predictive ability than the other parameters and the combination of SPMA and lincRNA-p21 exhibiting the highest predictive value for hematotoxicity. LincRNA-p21 was predominantly present in the cytoplasm of bone marrow cells (BMCs) and K562 cells as assessed by fluorescence in situ hybridization (FISH). Upon exploring the underlying mechanism by which lincRNA-p21 mediates benzene-induced hematotoxicity, we observed that the negative regulation of 1,4-benzoquinone (1,4-BQ) on cell cycle arrest and inhibition of K562 cell proliferation was partially relieved by lincRNA-p21 knockdown, which can inhibit the expression of P21 and thereby suppress the toxic effects of 1,4-BQ. Finally, dual-luciferase reporter gene and RIP assay showed that, by acting as a sponge, lincRNA-p21 reduced the activity of miRNA-17-5p and consequently increased the expression of p21. In conclusion, our research suggested that benzene induces hematotoxicity via the lincRNA-p21/miRNA-17-5p/p21 signaling which might contribute to the underlying mechanism of lincRNA-p21 in benzene-induced hematotoxicity. Therefore, lincRNA-p21 can serve as a potential biomarker for the early detection of hematopoiesis inhibition in individuals with long-term exposure to low-dose benzene.

Estimating Historical Exposure to Respirable Crystalline Silica in the Mining Industry in Ontario, Canada Using a Newly Developed Exposure Database

OBJECTIVES

To use the recently developed Ontario Mining Exposure Database (OMED) to describe historical silica exposure in the Ontario metal mining industry and identify predictors of historical silica exposure.

METHODS

Personal respirable crystalline silica (RCS) data for metal mines were extracted from OMED and included both individual and summary measures, where multiple exposure measurements (n > 1) were aggregated and entered as a single exposure value (n = 1). Data were stratified by sample location (underground/surface) for analysis. Monte Carlo simulation was used to simulate individual measures from the summary measures. A fixed effects multiple linear regression model was used to assess the effects of commodity (ore mined), sample year, source of exposure data, and occupational group on RCS concentration. Parameter estimates (β), standard errors, and 95% upper and lower confidence intervals were reported.

RESULTS

The OMED contained 12 995 silica measurements. After limiting to RCS measurements in metal mines, and measures with sufficient information for analysis, 2883 RCS measurements collected from 1974 to 1991 remained, including 2816 individual and 67 summary measurements. In total, 321 individual RCS measurements were simulated from the 67 summary measures. The analysis database contained 2771 (12% simulated) underground measurements and 366 surface measurements (0% simulated). In the underground group, an overall geometric mean (GM) of 0.05 [geometric standard deviation (GSD) 3.09] mg m-3 was estimated with a 6% annual decrease over time. In this group, the commodity with the highest average RCS level was zinc mines (GM = 0.07 mg m-3) and the lowest was iron mines (GM = 0.01 mg m-3). In the surface group, an overall GM of 0.05 (GSD 3.70) mg m-3 was estimated with an 8% decreased over time. In this group, the commodity with the highest average RCS level was gold mines (GM = 0.07 mg m-3) and the lowest was zinc mines (GM = 0.03 mg m-3). In both groups, company collected data had lower estimated RCS compared with regulator collected data.

CONCLUSIONS

Historical RCS levels decreased over time. Mean measurements exceeded the American Conference of Governmental Industrial Hygienists current health-based threshold limit value (0.025 mg m-3). The main predictors of exposure were commodity, source of exposure data, and sample year. However, low R2 and high GSD values suggest additional predictors of RCS exposures in Ontario's metal mines exist that were unavailable in OMED.

Detection rates, trends in and factors affecting observed levels of selected volatile organic compounds in blood among US adolescents and adults

Data from National Health and Nutrition Examination Survey were analyzed to evaluate detection rates, trend in and factors affecting the observed levels of 1,4-dichlorobenzene, benzene, ethylbenzene, o-xylene, styrene, toluene, and m/p-xylene among US adolescents and adults over 2005-2012. Over 2005-20102, among adolescents, detection rates declined by more than 50% for benzene, ethylbenzene, and o-xylene, and among adults, detection rates declined by more than 50% for ethylbenzene and o-xylene and by a little less than 50% for benzene. Among adults, adjusted levels of 1, 4-dichlorobenzene, benzene, ethylbenzene, o-xylene, toluene, and m/p-xylene decreased by 13.7%, 17.1%, 20%, 17.7%, 23.2%, and 18.7% respectively for every two-year survey cycle. Among adolescents, percentage decline in the levels of 1, 4-dichlorobenzene, benzene, ethylbenzene, o-xylene, styrene, toluene, and m/p-xylene was 15.2%, 21.4%, 19.3%, 16.1%, 47.8%, and 17.7% respectively for every two year survey period. The ratio of adjusted geometric means for adult smokers as compared to adult nonsmokers was 10.7 for benzene, 3.5 for ethylbenzene, 2.0 for o-xylene, 3.4 for styrene, 3.5 for toluene, and 2.2 for m/p-xylene. Among adolescents, gender did not affect the adjusted levels of any of the seven VOCs, and the order in which adjusted levels for 1, 4-dichlorobenzene by race/ethnicity was observed was: non-Hispanic white (0.038ng/mL)<Mexican American (0.102ng/mL)<non-Hispanic black (0.178ng/mL) and most of the pairwise comparisons were statistically significantly different (p<=0.02) but race/ethnicity did not affect the adjusted levels for benzene, ethylbenzene, o-xylene, styrene, toluene, and m/p-xylene. For benzene, males had lower levels of adjusted geometric means (AGM) than females (0.021 vs. 0.025ng/mL). For adults, gender did not affect the adjusted levels of 1, 4-dicholorobenzene, ethylbenzene, o-xylene, styrene, toluene, and m/p-xylene.

New Opportunities in Exposure Assessment of Occupational Epidemiology: Use of Measurements to Aid Exposure Reconstruction in Population-Based Studies

PURPOSE OF REVIEW

Exposure assessment efforts in population-based studies are increasingly incorporating measurements. The published literature was reviewed to identify the measurement sources and the approaches used to incorporate measurements into these efforts.

RECENT FINDINGS

The variety of occupations and industries in these studies made collecting participant-specific measurements impractical. Thus, the starting point was often the compilation of large databases of measurements from inspections, published literature, and other exposure surveys. These measurements usually represented multiple occupations, industries, and worksites, and spanned multiple decades. Measurements were used both qualitatively and quantitatively, dependent on the coverage and quality of the data. Increasingly, statistical models were used to derive job-, industry-, time period-, and other determinant-specific exposure concentrations. Quantitative measurement-based approaches are increasingly replacing expert judgment, which facilitates the development of quantitative exposure-response associations. Evaluations of potential biases in these measurement sources, and their representativeness of typical exposure situations, warrant additional examination.