Occupational Exposures And Epigenetics Alteration Among Electronic Waste Workers At Agbogbloshie, Ghana
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Date
2022-09
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University Of Ghana
Abstract
Background: The techniques used in the informal recycling of e-waste, particularly in low- and middle-income countries (LMICs), are unsophisticated and rudimentary without safeguards for the health and safety of humans and the environment. Particulate matter (PM), including toxic chemical components in the form of metallic and organic compounds are generated and released into the environment during informal e-waste recycling activities. Available data suggests that PM and metals are among the most important risk factors for developing many chronic diseases such as cardiovascular diseases, neurological diseases, reproductive toxicity, renal dysfunction, autoimmune diseases and cancers. Due to the deleterious effects of PM and metals on human health, as well as elevated levels detected in occupational environments, there is a need to determine the intermediate health outcomes associated with pollutants exposure before the onset of clinical occupational disease. Epigenetic modification such as DNA methylation are highly suspected as an intermediary between environmental and occupational exposures and adverse health outcomes. Although research has been carried out on the adverse health effects of e-waste recycling in Ghana and elsewhere, there is still little published data examining the effects of metals and PM on DNA methylation in occupationally exposed populations especially those in the informal sector such as e-waste recyclers.
Objective: The objective of this work was to examine the effects of personal particulate matter exposure and a mixture of metals on global DNA methylation among e-waste recyclers and a reference population.
Methods: This study made use of biological samples and exposure data collected during the first round of a parent/larger GEOHealth II study - a longitudinal study. One hundred (100) male e-waste workers and fifty-one (51) male non-e-waste workers serving as a reference
population were recruited at baseline. The participants provided survey data and blood samples for measurements of concentrations of metals as well as DNA methylation analysis. The methylation levels of long interspersed nucleotide repetitive elements-1 (LINE-1) was measured by pyrosequencing bisulfite-converted DNA from whole blood as a proxy for global DNA methylation. Personal PM2.5 and PM10 were measured over a 4-hour work-shift using real-time particulate matter monitors incorporated into a backpack and worn by study participants (e-waste workers and reference population). The concentrations of selenium (Se), zinc (Zn), manganese (Mn), cadmium (Cd) and lead (Pb) were measured in blood using inductively coupled plasma mass spectrometry (ICPMS). Descriptive statistics were used to determine differences in participant’s characteristics. Multiple linear regression model with robust standard errors (SE) from ordinary least squares (OLS) was used to evaluate the associations between PM and metals exposure on the one hand and LINE-1 DNA methylation on the other hand. Further, ccorresponding interaction terms were incorporated into the regression model to determine possible modification effect of selected toxic metals (Cd and Pb) on DNA methylation caused by essential metals (Mn, Se and Zn) concentrations. Lastly, a further sensitivity analysis using different variants of the outcome model (robust and cross-fit partialling-out least absolute shrinkage and selection operator (LASSO) linear regression models) were performed to compare with the results of the OLS with robust SEs.
Results: Personal median concentrations of PM2.5 and PM10 were significantly higher among the e-waste workers than the reference population (PM2.5: median (interquartile range) 77.32(34.08) μg/m3 vs 34.88 (16.55) μg/m3, p < 0.001 and PM10: median (interquartile range) 210.21 (93.32) μg/m3 vs 121.92 (82.93) μg/m3, p < 0.001, respectively). Overall, metals (Cd, Mn, and Se) were significantly higher in the reference group (geometric mean: Cd = 0.8μg/L, Mn = 14.7 μg/L, and Se = 190.5 μg/L) than those in the e-waste worker group (geometric mean: Cd = 0.6 μg/L, Mn = 11.4 μg/L, and Se = 147 μg/L). Only Pb was significantly higher
in the e-waste workers (geometric mean: Pb = 79.6 μg/L) compared to the reference group (geometric mean: Pb = 37.7 μg/L). There was no significant difference in LINE-1 methylation among the e-waste workers and the reference group (85.16 ± 1.32% vs 85.17 ± 1.11%, p=0.950). In the linear regression models controlling for confounders, the associations between PM2.5 and PM10, and LINE-1 DNA methylation were not statistically significant among the e- waste workers (βPM2.5 = 0.004; 95% CI; -0.001, 0.010, p = 0.114), and (βPM10 = 0.002; 95% CI;
-0.001, 0.005, p = 0.088), respectively and reference population. For metals exposure, the OLS results of multiple metals showed a significant inverse association between Zn and the LINE- 1 DNA methylation among only the e-waste workers (βZn = -1.180, 95% CI: -2.199, -0.161, p
= 0.024) which corresponds to a 0.012 decrease in LINE-1 DNA methylation (95% CI: -0.022,
-0.002, p = 0.024) for a 1% increase in Zn concentration. The linear regression results from OLS with robust SEs and those of the sensitivity analysis yielded similar estimates of the beta- coefficients. Potential interactions between toxic and essential metals on global DNA methylation were observed.
Conclusion: In conclusion, the high concentration of breathing zone PM and the body burden of metals detected in both the e-waste workers and reference population in Ghana shows the elevated levels of air pollutants in urban Ghana, particularly the capital city, Accra. Overall, PM concentration did not show significant association with LINE-1 DNA methylation in both the e-waste workers and the reference population. However, for metals exposure, increased blood zinc levels showed a significant decrease in LINE-1 methylation only among the e-waste workers. The results of this study further revealed that alteration of DNA methylation by toxic metals could be modified due to the concentration of essential metals. The alteration of LINE- 1 methylation by metals could serve as an early epigenetic marker for future adverse health outcomes in e-waste workers and other workers with similar exposure. Therefore, effective interventions to improve occupational safety for e-waste recycling workers are urgently needed.
Description
PhD. Public Health
Keywords
Agbogbloshie, Ghana, Occupational Exposures, Epigenetics Alteration