Response to ‘Comment on “Evaluation of Micronucleus in Exfoliated Human Buccal Epithelium Cells among E-Waste Exposed Residents in Payatas, Philippines”’

Abstract

We express our appreciation of the response to our micronucleus paper 1 and are glad that our research findings are relevant to other findings on e-waste issues from the plethora of literature that we have read. We understand that there are confounding factors to consider when it comes to micronucleus assays. Based on our reading of other related studies, the use of buccal micronucleus assay for biomonitoring of e-waste workers is definitely possible because the micronucleus (MN) assay in exfoliated buccal cells is a useful and minimally invasive method for monitoring genetic damage (as also experienced among e-waste workers) in humans. The MN assay in buccal cells has been used since the 1980's to demonstrate the cytogenetic effects of environmental and occupational exposures, lifestyle factors, dietary deficiencies, and different diseases, but important knowledge gaps remain about the characteristics of micronuclei and other nuclear abnormalities, with the basic biology explaining the appearance of various cell types in buccal mucosa samples and effects of diverse staining procedures and scoring criteria in laboratories around the world. With these uncertainties, the human micronucleus project (HUMN) 2 has initiated a new international validation project for the buccal cell MN assay. They advised that future research should explore sources of variability in the assay (e.g., between laboratories and scorers, as well as inter-and intra-individual differences in subjects), and resolve key technical issues, such as the method of buccal cell staining, optimal criteria for classification of normal and degenerated cells and for scoring micronuclei and other abnormalities. The harmonization and standardization of the buccal MN assay will allow more reliable comparison of data among human populations and laboratories, evaluation of the assay's performance, and consolidation of its worldwide use for biomonitoring of DNA damage. 3 In this regard, the buccal cell MN assay was first proposed in 1983 and continues to gain popularity as a biomarker of genetic damage in numerous applications. More than 40 laboratories from many countries either have used or are currently using this assay, and the number of articles published annually is steadily increasing. Different issues related to the buccal cell MN assay were reviewed in several publications over the last decade. 4 Since the publication of the previous e-waste monitor in 2017, the number of studies on the adverse health effects from e-waste have increased. These studies have continued to highlight the dangers to human health from exposure to well-studied toxins, such as lead. Recently, research has found that unregulated e-waste recycling is associated with increasing numbers of adverse health effects. These include adverse birth outcomes, altered neurodevelopment, adverse learning outcomes, 5 DNA damage, 6 adverse cardiovascular effects, 7 adverse respiratory effects, 8 and adverse effects on the immune system. Additionally, the Micronucleus Assay Expert Group reported s...