LINE1 methylation is differentially associated with lead exposure and job-tasks performed by electronic waste workers

Abstract

Background/Aim: Electronic waste (e-waste) is a pressing global public health concern due to high production volumes and inadequate management practices, which often occur in developing countries without appropriate recycling infrastructure. Exposure to a variety of chemical mixtures during informal e-waste recycling processes has been associated with adverse health outcomes affecting respiratory, cardiovascular, neurological, and reproductive systems. DNA methylation has been associated with toxic chemical exposures including heavy metals in epidemiological studies. Although e-waste contains a myriad of toxic chemicals with known health effects, DNA methylation profile of e-waste recyclers has not been studied. This study assessed the associations between cadmium (Cd), lead (Pb), and arsenic (As) concentration and methylation levels of the LINE1 gene among e-waste workers and non e-waste workers in Ghana.Methods: The study included 100 males e-waste workers and 51 males non e-waste workers. The participants provided extensive demographic and work-related data and biological samples. The metals were measured in blood and urine using Inductively Coupled Plasma Mass Spectrometry while LINE1 methylation levels were determined by pyrosequencing of bisulfite-converted DNA from whole blood.Results: There was no significant difference in LINE1 methylation between e-waste workers and non-e-waste workers (85.16% ±1.32 vs 85.17% ±1.11, p = 0.950). However, CpG1 showed significantly lower mean methylation among non-e-waste workers compared to the e-waste workers (81.70% ±1.86 vs 82.48% ±2.20, p = 0.034). In linear regression models, blood lead (B-Pb) level was significantly inversely associated with overall LINE1 methylation (β = -0.004; 95%CI: -0.008, -0.0002; p = 0.038), while e-waste collectors showed significantly reduced LINE1 methylation levels (β = -1.068; 95%CI: -2.040, -0.095; p = 0.032) when comparing across job-task for e-waste workers.Conclusion: Our results suggest that lead exposure may alter LINE1 methylation levels, and collectors, in particular, maybe at an increased risk of epigenetic alteration due to lead exposure.