Abstract
Inappropriate processing and disposal of electronic waste (e-waste) expose workers and surrounding populations to hazardous chemicals, including clastogens and aneugens. Recently, considerable literature hasgrown around e-waste recycling, associated chemical exposures and intermediate health outcomes, including DNA damage. Micronuclei (MN) frequency has been widely used as a biomarker to investigate DNA damage in human populations exposed to genotoxic agents. We conducted a systematic review of published studies to assess DNA damage in e-waste-exposed populations and performed a meta-analysis to evaluate the association between e-waste exposure and DNA damage. This systematic review with meta-analysis was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statement checklist. Articles published in English from January 2000 through December 2020 investigating the associations between e-waste exposure and DNA damage were retrieved from the following three major databases: MEDLINE, ProQuest, and Scopus. Studies that reported the use of MN assay as a biomarker of DNA damage were included for meta-analysis. Studies that also reported other DNA damage biomarkers such as chromosomal aberrations, comet assay biomarkers, 8-hydroxy-2'-deoxyguanosine (8-OHdG), telomere length, apoptosis rate were reported using narrative synthesis. A total of 20 publications were included in this review, of which seven studies were within the occupational setting, and the remaining 13 studies were ecological studies. The review found six biomarkers of DNA damage (micronuclei, comets assay parameters (tail length, % tailDNA, tail moment, and olive tail moment), 8-OHdG, telomere length, apoptosis rate and chromosomal aberrations) which were assessed using seven different biological matrices (buccal cells, blood, umbilical cord blood, placenta, urine and semen). Most studies showed elevated levels of DNA damage biomarkers among e-waste exposed populations than in control populations. The most commonly used biomarkers were micronuclei frequency (n=9) in peripheral blood lymphocytes or buccal cells and 8-OHdG (n=7) in urine. The results of the meta-analysis showed that electronic waste recycling has contributed toan increased risk of DNA damage measured using MN frequency with a pooled estimate of the standardized mean difference (SMD) of 2.30 (95% CI: 1.36, 3.24, p<0.001) based on 865 participants. Taken together, evidence from this systematic review with meta-analysis suggest that occupational and non-occupational exposure to e-waste processing is associated with increased risk of DNA damage measured through MN assay and other types of DNA damage biomarkers. However, more studies from other developing countries in Africa, Latin America, and South Asia are needed to confirm and increase these results' generalizability.
Highlights
IntroductionRecyclers often use basic tools such as a hammer, chisel and occasionally screwdrivers and spanners to dismantle and separate the different components [2] and a long metal rod to rotate/flip burning items such as insulated wires and circuit boards of various sizes [3, 4]
The techniques used in the informal recycling of e-waste, in lower- and middle-income countries (LMICs), are basic and primitive, with little or no regard for the health and safety of humans and the environment [1].This work is licensed under the Creative Commons Attribution 4.0Recyclers often use basic tools such as a hammer, chisel and occasionally screwdrivers and spanners to dismantle and separate the different components [2] and a long metal rod to rotate/flip burning items such as insulated wires and circuit boards of various sizes [3, 4]
A number of researchers have reported that high concentrations of heavy metals and organic pollutants from e-waste recycling sites are associated with increased cancer risks [1, 7,8,9]
Summary
Recyclers often use basic tools such as a hammer, chisel and occasionally screwdrivers and spanners to dismantle and separate the different components [2] and a long metal rod to rotate/flip burning items such as insulated wires and circuit boards of various sizes [3, 4]. These primitive recycling methods release multiple toxic pollutants into the environment that exposes recyclers and surrounding populations. A number of researchers have reported that high concentrations of heavy metals and organic pollutants from e-waste recycling sites are associated with increased cancer risks [1, 7,8,9]
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