Toxicology and Industrial Health

Octamethylcyclotetrasiloxane (D4; CAS No. 556-67-2) is used as a monomer in the manufacture of polymeric materials, which are widely used in various industrial and/or medical applications, such as breast implants. D4 has a relatively low order of toxicity following acute administration via the oral, dermal, and inhalation routes of exposure and is not considered to be a dermal or eye irritant or to be a dermal sensitizer. There is no appreciable dermal absorption of D4 based on results from in vivo and in vitro studies. D4 has not been shown to be genotoxic/mutagenic when tested in a number of short-term in vitro and in vivo assays. Overall, studies have demonstrated adverse effects on specific female reproductive endpoints at higher exposure concentrations; however, no D4 exposure-specific effects were noted with respect to developmental endpoints. Inhalation exposure of rats to 700 ppm D4 for up to 24 months produced effects in the liver, kidney, and uterus (weight changes, hepatocellular hypertrophy, endometrial hyperplasia, and nephropathy). Changes in the nasal epithelium (eosinophilic globules) were also noted at 150 and 700 ppm. Despite 24 months of exposure, only mild to minimal inflammatory responses were found at 150 ppm, and overall, the basic integrity of the respiratory tract was unchanged at this dose. At 700 ppm, there was an increased incidence of endometrial adenomas in female rats. Based on the adverse changes in the respiratory tract, kidney, and female reproductive tract in the chronic inhalation study, 150 ppm was determined to be the no-observed-adverse-effect level (NOAEL) and was selected as the point of departure for the derivation of the workplace environmental exposure level (WEEL®) value. The inhalation NOAEL was adjusted to account for interindividual variability and residual uncertainty regarding upper respiratory tract changes still occurring at 150 ppm. An 8-h time-weighted average WEEL value of 10 ppm is expected to provide a significant margin of safety against any potential adverse health effects in workers exposed to airborne D4.

Decamethylcyclopentasiloxane (D5; CAS No. 541-02-6) is a precursor in the production of siloxane polymers for industry and medicine and is a carrier ingredient in many toiletries and cosmetics. D5 has a relatively low order of toxicity following acute administration via the oral, dermal, and inhalation routes of exposure. It is not considered to be a dermal or eye irritant or a dermal sensitizer. There is no appreciable dermal absorption of D5 based on results from in vivo and in vitro studies. It has not been shown to be genotoxic/mutagenic when tested in a number of short-term in vitro and in vivo assays and did not cause reproductive or developmental toxicity in rats. Inhalation exposure of rats to 160 ppm D5 for up to 24 months produced adverse effects in the liver (weight changes and hepatocellular hypertrophy) and uterus (increased incidence of endometrial adenocarcinoma, endometrial adenoma, and adenomatous polyps in several animals); however, the results of recent mode-of-action studies are consistent with a uterine tumorigenesis mechanism that is not relevant for humans. Based on the results of the chronic inhalation study, 160 ppm was determined to be the no-observed-adverse-effect level (NOAEL) and was selected as the point of departure for the derivation of the workplace environmental exposure level (WEEL®) value. This NOAEL was adjusted to account for interindividual variability and residual uncertainty regarding upper respiratory tract changes still occurring at 160 ppm. The resulting 8-h time-weighted average WEEL value of 10 ppm is expected to provide a significant margin of safety against any potential adverse health effects in workers exposed to airborne D5.

Zinc (Zn) is known to interact with lead (Pb) and cadmium (Cd) reversing their toxicity and reducing their concentrations. However, lactating women are at high risk of developing Zn deficiency, which may result in Pb and Cd intoxication or increased exposure of breast-fed infants to Pb and Cd from breast milk. The aim of this study was to determine Zn, Pb, and Cd concentrations and examine their relationship in serum and breast milk of lactating women in Ibadan, Nigeria. Ninety-two lactating women were recruited into this study. Anthropometric measurements were assessed by standard methods while serum and breast milk concentrations of Zn, Pb, and Cd were assessed by atomic absorption spectrophotometry. Data analyzed statistically by Student’s t test, Pearson’s correlation coefficient, and a multiple regression model were significant at p < 0.05. Zn deficiency was observed in 12 (17.1%) of lactating women. Breast milk levels of Zn, Pb, and Cd were significantly higher than their levels in serum, whereas the ratios Zn:Pb and Zn:Cd in milk were significantly less than serum ratios. Significant negative correlation was observed between milk Pb and serum Zn:Pb while milk Cd correlated positively with milk Zn. Significant positive correlations were observed between serum Zn and serum Zn:Pb, serum Zn and serum Zn:Cd, as well as serum Zn:Cd and serum Zn:Pb. Serum Cd and serum Zn were significantly negatively related. Significant negative correlations between serum Pb and serum Zn:Pb as well as milk Zn:Pb. Serum Cd and serum Zn:Pb as well as serum Zn:Cd correlated negatively. Milk Cd and Zn/Cd positively related with milk Pb while milk Zn was a negatively related with milk Pb in a multiple regression model (R ² = 0.333; p = 0.023). Breast milk may be contaminated by toxic metals. However, Zn supplementation in deficient mothers may protect maternal and infant health.

The health effects of bisphenol A (BPA) have become a great concern in recent years. In this study, the reproductive toxicity of BPA was investigated. Male CD-1 mice were orally administrated with BPA (0, 100, 300 and 600 mg kg⁻¹ body weight) for 56 consecutive days. Results showed that relative testis weight to total body weight was significantly lower in the high-dose group (p < 0.01, p < 0.05). Microscopic examination under light and transmission electron microscopes showed disorders of spermatogenesis after BPA exposure, including rough basal lamina of seminiferous tubules and damage of tight junctions between Sertoli cells. Further study by terminal-deoxynucleoitidyl transferase–mediated nick end labelling assay showed a significant induction of apoptosis in the testis tissue of the BPA groups (p < 0.01). Immunohistochemical study found that the expression of androgen-binding protein (ABP) was significantly decreased in BPA-treated mice (p < 0.01). Our results indicated that impairment of the basal lamina of seminiferous tubules and tight junctions may contribute to BPA-induced cell injury. A decrease in the level of ABP could be the possible mechanism for the reproductive toxicity of BPA. These findings provided direct evidence and novel insight into the reproductive toxicity of BPA and may have implications for understanding the toxicity of other endocrine disruptors.

Currently, in India, air pollution is widespread in urban areas where vehicles are major contributors. The aim of this study was to investigate the level of exposure in traffic police officers exposed to vehicle exhaust for less than 8 h/day. The specific objective of the study was to determine the levels of carboxyhaemoglobin (COHb) in these officers. The effect of exposure for 8 h/day is known, but shorter durations of chronic exposure need to be investigated, and there is a need to explore the policy options in this exposed population. This cross-sectional study, included non-smoking traffic police officers between 30 and 50 years of age working for more than 2 years in busy traffic junctions. The cases were sex matched with controls of same age group, working in offices at a teaching hospital. Venous blood was collected at the end of 3 h of duty for estimation of COHb among both the groups. The COHb levels were expressed as percentage values. Differences between the COHb levels among the traffic police officers and office workers were analysed using the Mann-Whitney U test and considered significant at p < 0.05. Traffic police officers had significantly elevated COHb levels compared with the controls; 76.5% of traffic police officers had COHb >2.5% compared with no office workers at this level and 41.2% of the police officers had COHb levels >4%. Overall, 53.8% of officers with COHb >2.5% reported headaches compared with 15.8% of officers with COHb <2.5%.

Carbon monoxide (CO) is a colourless and odourless gas appearing as a result of incomplete combustion of carbon-containing fuels. Many domestic or occupational poisonings are caused by CO exposure. Malfunctioning heating systems, improperly ventilated motor vehicles, generators, grills, stoves and residential fires may be listed in the common sources of CO exposure. The aim of this study was to emphasize the significance of early diagnosis of CO poisoning with non-invasive measurement of CO levels of the patients with non-specific symptoms using a pulse oximeter device in the triage. Our study was a cross-sectional study. Patients who presented to the emergency department (ED) due to non-specific symptoms and had a Canadian Triage and Acuity scale level of 4 or 5 were included in the study; 106 (5.9%) of 1788 patients admitted during the study period were diagnosed with CO poisoning. Patients with CO poisoning and the other patients had statistically significant differences in terms of presenting symptoms, namely, headache, dizziness, nausea, and vomiting. More CO poisoning cases were admitted in the fall and winter compared to the spring and summer. The number of CO poisoning victims can be decreased if preventive measures like CO monitoring systems and well-designed ventilation systems are generalized at homes and workplaces. Measurement of carboxyhaemoglobin levels of patients presenting to ED due to non-specific symptoms like headache and dizziness during cold seasons and winter months using a pulse CO-oximeter should be a part of the routine of emergency medicine triage.

The purpose of this study is the evaluation of possible toxicological effects on dental personnel, who are exposed to the production materials of prostheses during their entire working life. In this study, the level of methyl methacrylate (MMA) in ambient air was measured as an indicator of external exposure on the personnel. In order to evaluate the possible toxic effects of oxidative stress, which is thought to play an important role in the formation process of many diseases such as cancer, blood samples of volunteers were examined via the ultraviolet-spectroscopic determination of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase antioxidant enzyme activities, comparing occupationally MMA-exposed (n = 69) and control (n = 67) groups. In these groups, malondialdehyde (MDA) and glutathione levels were also determined by the same method. The results showed that SOD activity and MDA and glutathione levels were significantly higher in the exposed group when compared with the control group (p < 0.001). A significant decrease was determined in the glutathione peroxidase activities of the exposed group (p < 0.05). No significant difference in CAT activities between the groups has been found. When the results obtained in the study are considered, it is suggested that an adaptive response might be developed by dental technicians against low-level MMA exposure.

This cross-sectional study examined whether people who are exposed to mercury (Hg) vapours in ongoing artisanal gold mining activities have alteration in kidney function monitoring parameters. The study enrolled 164 miners and 127 participant controls. The Hg concentrations for miners and control participants were measured in blood (B-Hg; median 7.0 vs. 2.5 µg/L), urine (U-Hg; median 3.9 vs. 1.5 µg/g creatinine) and hair (H-Hg; median 0.8 vs. 0.4 µg/g hair). The biomarkers of renal function were creatinine, albumin and excretion of β-2 microglobulin. Glomerular filtration rate (eGFR) was calculated using the chronic kidney disease epidemiology collaboration equation. Significant statistical differences were found in Hg concentrations and eGFR levels between the two study groups (p < 0.01) but not with the other biomarkers of renal function. A multiple regression model was applied to explore the relationship of eGFR levels and Hg concentrations. However, no association was found between the prevalence of reduced eGFR (<71.96 mL/min/1.73 m²) and the B-Hg or U-Hg levels after adjustment for covariates. Nevertheless, it was observed that having B-Hg levels above 10 µg Hg/L decreased the eGFR by 1.7 mL/min/1.73 m² (confidence interval 95% −5.1 to 1.7) compared to having levels below 2.0 µg Hg/L. Our results found no support for kidney damage associated with Hg vapour exposure in ongoing artisanal gold mining, whose population has a level of Hg exposure from low to moderate (B-Hg from 3.4 to 11.0 µg/L and U-Hg from 1.3 to 9.6 µg/g creatinine).

Heavy metal determination in ambient air is an important task for environmental researchers because of their toxicity to human beings. Some heavy metals (hexavalent chromium (Cr), arsenic (As), cadmium (Cd) and nickel (Ni)) have been listed as carcinogens. Furthermore, heavy metals in the atmosphere can accumulate in various plants and animals and enter humans through the food chain. This article reviews the determination of heavy metals in the atmosphere in different areas of the world since 2006. The results showed that most researchers concentrated on toxic metals, such as Cr, Cd, Ni, As and lead. A few studies used plant materials as bio-monitors for the atmospheric levels of heavy metals. Some researchers found higher concentrations of heavy metals surrounding industrial areas compared with residential and/or commercial areas. Most studies reported the major sources of the particulate matter and heavy metals in the atmosphere to be industrial emissions, vehicular emissions and secondary aerosols.