Increased lymphocyte sister chromatid exchange frequency in workers with exposure to low level of ethylene dichloride

Impacts associated with the plastic polymers polycarbonate, polystyrene, polyvinyl chloride, and polybutadiene across their life cycle: A review

Polymers are the main building blocks of plastic, with the annual global production volume of fossil carbon-based polymers reaching over 457 million metric tons in 2019 and this figure is anticipated to triple by 2060. There is potential for environmental harm and adverse human health impacts associated with plastic, its constituent polymers and the chemicals therein, at all stages of the plastic life cycle, from extraction of raw materials, production and manufacturing, consumption, through to ultimate disposal and waste management. While there have been considerable research and policy efforts in identifying and mitigating the impacts associated with problematic plastic products such as single-use plastics and hazardous chemicals in plastics, with national and/or international regulations to phase out their use, plastic polymers are often overlooked. In this review, the polymer dimension of the current knowledge on environmental release, human exposure and health impacts of plastic is discussed across the plastic life cycle, including chemicals used in production and additives commonly used to achieve the properties needed for applications for which the polymers are generally used. This review focuses on polycarbonate, polystyrene, polyvinyl chloride, and polybutadiene, four common plastic polymers made from the hazardous monomers, bisphenol, styrene, vinyl chloride and 1,3-butadiene, respectively. Potential alternative polymers, chemicals, and products are considered. Our findings emphasise the need for a whole system approach to be undertaken for effective regulation of plastics whereby the impacts of plastics are assessed with respect to their constituent polymers, chemicals, and applications and across their entire life cycle.

Genotoxicity and immunotoxic effects of 1,2-dichloroethane in Wistar rats

Dichloroethane is widely used as a solvent, degreasing agent and in a variety of commercial products, and is known for being a ubiquitous contaminant in the environment. Important sources principally include the emissions from industrial processes, improper consumption, storage, and disposal methods. In view of the fact that the mechanism of its genotoxicity has not been satisfactorily elucidated, the acute in vivo toxicological impact is assessed in Rattus norvegicus. A systematic investigation has been made involving the use of conventional methods along with molecular and flow cytometric approaches. The micronucleus and chromosomal aberration frequencies were significantly elevated in bone marrow cells exposed to three concentrations at multiple treatment durations indicating positive time- and dose-response relationships. The mitotic index significantly decreased in similar concentrations in contrast to normal control. Separate studies were performed on blood cells for comet assay. It revealed dichloroethane-induced DNA damage in all exposures readily explainable in a dose- and time-dependent manner. Recent molecular techniques were further employed using leukocytes for the cell apoptosis/cycle and mitochondrial membrane potential employing propidium iodide staining and rhodamine-123, respectively. The effect on mitochondrial membrane permeability, cell cycle phases, and the DNA damage was analyzed through flow cytometry. These indicators revealed dichloroethane treatment decreased the mitochondrial membrane potential, affected the cell cycle, and confirmed the DNA damage, leading to apoptosis of the cells of the immune system responsible for immunotoxic effects of dichloroethane on rat leukocytes.

Differential induction of micronuclei in peripheral lymphocytes and exfoliated urothelial cells of workers exposed to 4,4'-methylenebis-(2-chloroaniline) (MOCA) and bitumen fumes

Cytogenetic end-points used to estimate risk of genotoxic events in workers include the measurement of micronuclei (MN) in exfoliated cells, lymphocytes, and other tissues. Micronuclei are chromatin-containing bodies outside the cell nucleus resulting from contaminant-induced DNA damage. A review of 71 reports of human genotoxic responses to chemical or physical agents published between 1999 and 2001 revealed that 14% of such studies measured genotoxicity endpoints in specific target tissues relevant to the site of disease for the agent examined; 18% used endpoints in surrogate or non-target tissues but considered the relations between endpoints in surrogate and disease target tissues, and 68% measured genotoxicity endpoints in accessible tissues without reference to specific targets for disease. Methylenebis-(2-chloroaniline) (MOCA), used in polyurethane manufacture, is a suspected bladder carcinogen. Bitumen, used in road surfacing, contains skin and lung carcinogens. In this study, we aimed to compare genotoxicity in urothelial cells and in lymphocytes of workers exposed to these materials. Twelve men employed in polyurethane manufacture, twelve bitumen road layers, and eighteen hospital stores personnel (controls) were recruited and all provided blood and urine samples on the same day. Blood cultures were prepared using a cytochalasin B-block method. Exfoliated urothelial cells were collected from urine and stained for light microscopy. The number of MN in urothelial cells was higher in MOCA-exposed (14.27 +/- 0.56 MN/1000, 9.69 +/- 0.32 MN cells/1000) than in bitumen exposed workers (11.99 +/- 0.65 MN/1000, 8.66 +/- 0.46 MN cells/1000) or in control subjects (6.88 +/- 0.18 MN/1000, 5.17 +/- 0.11 MN cells/1000). Conversely, in lymphocytes, MN were higher in bitumen-exposed (16.24 +/- 0.63 MN/1000, 10.65 +/- 0.24 MN cells/1000) than in MOCA-exposed workers (13.25 +/- 0.48 MN/1000, 8.54 +/- 0.14 MN cells/1000) or in control subjects (9.24 +/- 0.29 MN/ 1000, 5.93 +/- 0.13 MN cells/1000). The results of this study suggest that genotoxins can cause different rates of micronuclei formation in different tissues. Thus, the sensitivity and relevance to cancer risk may be greater if the tissues selected for genotoxicity studies reflect the target tissue for the chemicals concerned.

Synergistic effect of hepatitis virus infection and occupational exposures to vinyl chloride monomer and ethylene dichloride on serum aminotransferase activity

AIMS

To study the synergistic effect of occupational chemical exposure and hepatitis virus infection on serum aminotransferase activity.

METHODS

A total of 568 male workers who were employed in five polyvinyl chloride (PVC) or four vinyl chloride monomer (VCM) manufacturing factories were studied. Information relating to current job title, alcohol consumption, and cigarette smoking was obtained. Exposure level of chemical mixtures was classified by hygienic effect (a summation of personal time weighted average/reference permissible exposure level of each chemical) into high, moderate, and low exposure groups. Serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT), hepatitis B surface antigen (HBsAg), hepatitis B e antigen (HBeAg), and anti-hepatitis C antibody were assayed.

RESULTS

Hepatitis virus infection and increased body mass index were associated with abnormal serum aminotransferase activity. In workers with hepatitis virus infection, those with high exposure had a higher prevalence of abnormal AST and ALT compared to low exposure; among those without hepatitis virus infection, the differences of prevalence of abnormal AST and ALT were not significant between different chemical exposure groups. There was a significant trend of increasing risks of increased AST and ALT in moderate and high exposure groups with hepatitis virus infection. Such a synergistic effect was more prominent among HBeAg-positive workers.

CONCLUSIONS

Mixed exposures to 1,2-ethylene dichloride and VCM have a positive synergistic effect with hepatitis virus infection on liver damage. Assessment of fitness for work should be considered in workers with hepatitis B and C infection, when they have potential exposure to hepatotoxins in the workplace.