The risk of occupational exposure to mercury vapor in some public dental clinics of Baghdad city, Iraq

Occupational exposures in low- and middle-income countries: A scoping review

Exposure to high levels of harmful agents in the workplace can significantly impact workers' health, contributing to morbidity and mortality. Levels of these exposures are often measured in high-income countries in research studies and, in some places, to monitor levels in line with health and safety regulations. However, less is known about workplace exposure levels in low- and middle-income countries (LMICs). Our aim was to describe the quantitative exposure measurements of different occupational agents across industries within LMICs. We conducted a scoping review of peer-reviewed publications available on Web of Science and PubMed from inception to 1 September 2023. Our search focused on quantitative occupational exposure measurements across industries in LMICs. We identified a total of 8,676 publications. After screening, 58 studies from 25 countries were retained for final review. China, Iran, and Tanzania contributed the greatest number of studies. Manufacturing, mining, and agriculture were the most studied sectors, with factory workers and miners being the most common job titles. Exposure measurements included vapour, gases, dust, and fumes (VGDF), solvents, metals, pesticides and particulate matter. Occupational exposure levels for the same industry varied widely across geographical regions. This review provides a comprehensive overview of occupational exposures in LMICs and highlights the absence of data in certain geographical areas and industries. The study contributes valuable insights for directing future research, and the need to optimise the assessment of occupational exposures in LMICs with the aim ultimately of reducing disease.

A multiple and comprehensive approach to assess health risk in amalgam-exposed Chinese workers

Fluorescent lamp manufacturing workers have been extensively exposed to mercury (Hg). Our aim was to assess their health risks using several approved occupational health risk assessment methods, and to find out which method was more suitable for identification of occupational health risks. Work locations, and air and urine samples were collected from 530 exposed workers in Zhejiang, China. Based on the calculated exposure doses, health risks and risk ratios (RRs) as health risk indices, were evaluated using: Environmental Protection Agency (EPA), Australian, Romanian, Singaporean, International Council on Mining and Metals (ICMM), and Control of Substances Hazardous to Health (COSHH) methods. Among the workers, 86.0% had higher Hg levels than the Chinese occupational exposure limits of 0.02 mg/m3, and 16.7% urine samples were higher than the biological exposure limits of 35.0 μg/g·creatinine. Among workers at the injection, etc. locations, their average RRs, evaluated by the EPA, COSHH and Singaporean methods were 0.97, 0.76, and 0.60, respectively, and were significantly higher than the ICMM (0.39), Australian (0.30) and Romanian (0.29) methods. The RRs from the Singaporean method showed significant correlations with the urinary Hg levels (P < 0.01). In conclusion, the Singaporean method was more appropriate than the others for health risk evaluation because the excessive risks were significantly associated with urinary Hg levels among the workers.

Bee venom Apis mellifera lamarckii rescues blood brain barrier damage and neurobehavioral changes induced by methyl mercury via regulating tight junction proteins expression in rat cerebellum

The objective of the current study is to investigate the protective effect of Egyptian bee venom (BV) against methyl mercury chloride (MMC) induced blood-brain barrier (BBB) damage and neurobehavioral changes. Eighty male Sprague-Dawley rats were randomly grouped into 1st control (C), 2nd BV (0.5 mg/kg S/C for14 days), 3rd MMC (6.7 mg/kg orally/14 days), and 4th MMC + BV group. MMC exposure significantly altered rat cognitive behavior, auditory startle habituation, and swimming performance, increased the exploratory, grooming, and stereotypic behavior. MMC significantly impaired BBB integrity via induction of inflammation, oxidative stress, and down-regulation of tight junction proteins genes (TJPs) mRNA expression levels: Occludin (OCC), Claudins-5 (CLDN5), Zonula occludens-1 (ZO-1), while up-regulated the transforming growth factor-beta (TGF-β) mRNA expression levels. MMC revealed a significantly higher percentage of IgG positive area ratio, a higher index ratio of Iba1, Sox10, and ss-DNA, while index ratio of CD31, neurofilament, and pan neuron showed a significant reduction. Administration of BV significantly regulates the MMC altered behavioral responses, TJPs relative mRNA expression, and the immune-expression markers for specific neural cell types. It could be concluded for the first time that BV retains a promising in vivo protection against MMC-induced BBB dysfunction and neurobehavioral toxicity.

Removal efficiency of central vacuum system and protective masks to suspended particles from dental treatment

BACKGROUND

High levels of suspended particulate matters (PMs) and bioaerosols are created by dental procedures. The present study aimed to evaluate the size and concentration of PMs produced by drilling and grinding teeth, and to assess the efficiency of central vacuum system and protective masks for the removal of PMs.

METHODS

A total of 20 extracted permanent teeth were collected. A novel experimental system and particle counter were used to evaluate the PMs produced by dental procedures and the PM removal efficiency of a central vacuum system and surgical/N95 masks.

RESULTS

The number concentration of total PMs produced by drilling and grinding teeth was significantly higher than the indoor background concentration. The average aerodynamic diameter of particle was generally less than 1 μm. The average number concentration of ultrafine particles was 2.1x1011 particles/m3 during tooth drilling and grinding. The efficiency of the central vacuum system was 35.74% for PM≥0.5 and 35.41% for PM10. For PM≥0.5, the ratios of inside and outside masks were 0.8-1.34 without vacuum and 1.18-1.36 with vacuum. No difference was found with the use of surgical/N95 masks during dental therapy, with or without vacuum use.

CONCLUSIONS

High levels of PMs were found during tooth drilling and grinding procedures, especially among PM1. The PM removal efficiency of a central vacuum system and surgical/N95 masks were limited.

Mercury exposure and its effects on fertility and pregnancy outcome

Mercury (Hg), a highly toxic environmental pollutant, shows harmfulness which still represents a big concern for human health, including hazards to fertility and pregnancy outcome. Research has shown that Hg could induce impairments in the reproductive function, cellular deformation of the Leydig cells and the seminiferous tubules, and testicular degeneration as well as abnormal menstrual cycles. Some studies investigated spontaneous abortion and complicated fertility outcome due to occupational Hg exposure. Moreover, there is a relation between inhaled Hg vapour and reproductive outcome. This MiniReview evaluates the hypothesis that exposure to Hg may increase the risk of reduced fertility, spontaneous abortion and congenital deficits or abnormalities.

Comparisons among Machine Learning Models for the Prediction of Hypercholestrolemia Associated with Exposure to Lead, Mercury, and Cadmium

Lead, mercury, and cadmium are common environmental pollutants in industrialized countries, but their combined impact on hypercholesterolemia (HC) is poorly understood. The aim of this study was to compare the performance of various machine learning (ML) models to predict the prevalence of HC associated with exposure to lead, mercury, and cadmium. A total of 10,089 participants of the Korea National Health and Nutrition Examination Surveys 2008–2013 were selected and their demographic characteristics, blood concentration of metals, and total cholesterol levels were collected for analysis. For prediction, five ML models, including logistic regression (LR), k-nearest neighbors, decision trees, random forests, and support vector machines (SVM) were constructed and their predictive performances were compared. Of the five ML models, the SVM model was the most accurate and the LR model had the highest area under receiver operating characteristic (ROC) curve of 0.718 (95% CI: 0.688–0.748). This study shows the potential of various ML methods to predict HC associated with exposure to metals using population-based survey data.

Vascular Dysfunction Induced by Mercury Exposure

Methylmercury (MeHg) causes severe damage to the central nervous system, and there is increasing evidence of the association between MeHg exposure and vascular dysfunction, hemorrhage, and edema in the brain, but not in other organs of patients with acute MeHg intoxication. These observations suggest that MeHg possibly causes blood-brain barrier (BBB) damage. MeHg penetrates the BBB into the brain parenchyma via active transport systems, mainly the l-type amino acid transporter 1, on endothelial cell membranes. Recently, exposure to mercury has significantly increased. Numerous reports suggest that long-term low-level MeHg exposure can impair endothelial function and increase the risks of cardiovascular disease. The most widely reported mechanism of MeHg toxicity is oxidative stress and related pathways, such as neuroinflammation. BBB dysfunction has been suggested by both in vitro and in vivo models of MeHg intoxication. Therapy targeted at both maintaining the BBB and suppressing oxidative stress may represent a promising therapeutic strategy for MeHg intoxication. This paper reviews studies on the relationship between MeHg exposure and vascular dysfunction, with a special emphasis on the BBB.