Benchmark dose estimation for coke oven emissions based on oxidative damage in Chinese exposed workers

Associations of coke oven emission exposure with pulmonary function, blood pressure, blood cell parameters, and biochemical indices in coking workers: a cross-sectional pilot study

Background and objective: Coke oven emissions (COEs) are formed in the process of coking production, mainly composed of polycyclic aromatic hydrocarbons (PAHs) and benzene; however, the health impacts of COE exposure in coking workers are not fully clear so far. We aimed to explore the associations of occupational COE exposure with pulmonary function, blood pressure, blood cell parameters, and blood biochemical indices, and to bolster health surveillance and disease prevention and control in coking workers. Methods: We investigated 566 coking workers at a large state-owned enterprise coking plant in Taiyuan, Shanxi, China, measured the concentrations of plasma 16 PAHs and urinary phenol, assessed the health outcomes including pulmonary function, blood pressure, the levels of peripheral hematologic parameters and biochemical indices, and examined the associations of PAH and phenol concentrations with the health outcomes using multiple linear regressions, least absolute shrinkage and selection operator regression (LASSO), and Bayesian kernel machine regression (BKMR). Results: After adjustment for confounders, plasma ∑15PAH concentration was significantly associated with increases in hemoglobin (HGB) and triglyceride (TG) levels in coking workers, and urinary phenol concentration was significantly associated with increases in the diastolic blood pressure (DBP) level, and decreases in platelet (PLT) count. When phenol concentration and PAH concentration were simultaneously included in the multiple linear regression model, both of them were associated with the level of HGB. LASSO and BKMR indicated that the PAHs with four rings and above contributed to the HGB level. Conclusion: PAH exposure could damage hematological parameters and blood lipids, and benzene exposure could increase blood pressure and decrease PLT count.

Coke oven emissions exacerbate allergic asthma by promoting ferroptosis in airway epithelial cells

Epidemiological studies have shown that coke oven emissions (COEs) affect the deterioration of asthma, but has not been proven by experimental results. In this study, we found for the first time that COEs exacerbate allergen house dust mite (HDM)-induced allergic asthma in the mouse model. The findings reveal that airway inflammation, airway remodeling and allergic reaction were aggravated in the COE + HDM combined exposure group compared with the individual exposure group. Mechanism studies indicated higher levels of iron and MDA in the COE + HDM combined exposure group, along with increased expression of Ptgs2 and reduced GPX4 expression. Iron chelator deferoxamine (DFO) effectively inhibited ferroptosis induced by COE synergistically with HDM in vitro. Further studies highlighted the role of ferritinophagy in the COE + HDM-induced ferroptosis. 3-methyladenine (3-MA) could inhibit ferroptosis in the COE + HDM exposure group. Interestingly, we injected DFO intraperitoneally into mice in the combined exposure group and found DFO could significantly inhibit the COE-exacerbated ferroptosis and allergic asthma. Our findings link ferroptosis with COE-exacerbated allergic asthma, implying that ferroptosis may have important therapeutic potential for asthma in patients with occupational exposure of COE.

An emission model for inhalable chemicals from children's play mats based on partition coefficients

Inhalable chemicals found in children's play mats can be slowly released into indoor environments and consequently threaten human health. In this study, the partition coefficients of seven inhalable chemicals between play mats and air were calculated by headspace gas chromatography-mass spectrometry based on the law of conservation of mass and the principle of equilibrium of headspace bottles. Furthermore, an emission source model for the residual ratio of the inhalable chemicals in play mats was established. Most substances found in play mats have large partition coefficients owing to the complex void structure of the mats, which adsorbs a large number of organic pollutants. The partition coefficient is not only related to the boiling point and environmental temperature, but also the specific material and the adsorption of the organic pollutant onto the material. The emission source model for children's play mats developed in this study can characterize the decay of the inhalable chemicals over time. The data showed that after eight days of placing the play mat in a ventilated environment, the residual ratio of seven inhalable chemicals did not exceed 15 %.

The polymorphisms in cGAS-STING pathway are associated with mitochondrial DNA copy number in coke oven workers

OBJECTIVE

To evaluate the interaction effects of Polycyclic aromatic hydrocarbons (PAHs) exposure and variants in cGAS-STING genes on mitochondrial DNA copy number (mtDNAcn) in workers.

METHODS

The mtDNAcn was determined by real-time quantitative polymerase-chain reaction in 544 PAHs-exposed workers and 238 office workers. The polymorphisms were detected by flight mass spectrometry.

RESULTS

The mtDNAcn in PAHs exposure group was significantly lower than non-occupational exposure population (P < 0.00). The cGAS rs610913 CA+AA had significant interaction effects with STING rs11554776 GG+GA (P = 0.035), rs7380824 CC+CT (P = 0.026), and rs78233829 GC+CC (P = 0.034) on mtDNAcn. The generalized linear model results showed that the influencing factors of mtDNAcn include PAHs exposure (P < 0.001) and the interaction of PAHs exposure and cGAS rs 311678 AA+AG (P = 0.047).

CONCLUSION

The influencing factors of mtDNAcn include PAHs exposure and the interaction of PAHs exposure and cGAS rs 311678 AA+AG.

Chain-mediating effect of interaction between telomeres and mitochondria under oxidative stress in coke oven workers

Coke oven emissions (COEs) exposure leads to oxidative stress, an imbalance between oxidant production and antioxidant defence in the body, which then leads to shortened relative telomere length (RTL) and reduced mitochondrial DNA copy number (mtDNAcn), ultimately leading to ageing and disease. By analysing the relationship among COEs, oxidative stress, RTL and mtDNAcn, we investigated the chain-mediating effects of oxidative stress and telomeres on mitochondrial damage and mitochondria on telomere damage in coke oven workers. A total of 779 subjects were included in the study. Cumulative COEs exposure concentrations were estimated, and the RTL and mtDNAcn of peripheral blood leukocytes were measured using real-time fluorescence quantitative PCR. Total antioxidant capacity (T-AOC) was measured to reflect the level of oxidative stress. The data were statistically analysed using SPSS 21.0 software and discussed using mediation effect analysis. After adjusting for age, sex, smoking, drinking and BMI, generalised linear model revealed dose-response associations between COEs and T-AOC, RTL and mtDNAcn, respectively. (Ptrend < 0.05). The results of chain-mediating effect showed that the proportion of the chain-mediating effect of "CED-COEs→T-AOC→ RTL→mtDNAcn" was 0.82% (β = -0.0005, 95% CI = [-0.0012, -0.0001]), and the proportion of the chain-mediating effect of "CED-COEs→T-AOC→ mtDNAcn → RTL ″ was 2.64% (β = -0.0013, 95% CI = [-0.0025, -0.0004]). After oxidative stress is induced by COEs, mitochondria and telomeres may interact with each other while leading further to potential bodily damage. This study provides clues to explore the association between mitochondria and telomeres.

Benchmark dose estimation based on oxidative damage in Chinese workers exposed to benzene series compounds

This study evaluated the effects of BTEX exposure on oxidative stress; it analyzed the correlation between oxidative stress and peripheral blood counts and estimated the benchmark dose (BMD) of BTEX compounds. This study recruited 247 exposed workers and 256 controls; physical examination data were collected and serum oxidative stress levels were measured. Relationships between BTEX exposure and biomarkers were analyzed using Mann-Whitney U, generalized linear model, and chi-square trend tests. Environmental Protection Agency Benchmark Dose Software was used to calculate the BMD and lower confidence limit of the BMD (BMDL) for BTEX exposure. The total antioxidant capacity (T-AOC) correlated positively with peripheral blood counts, and negatively with the cumulative exposure dose. On using T-AOC as the outcome variable, the estimated BMD and BMDL for BTEX exposure were 3.57 mg/m³ and 2.20 mg/m³, respectively. Based on T-AOC, the calculated occupational exposure limit of BTEX was 0.055 mg/m³.

Risk assessment of chemical mixtures by benchmark dose-principle component analysis approach in occupational exposure

Mixtures of organic solvents are widely used in industrial processes. Risk assessment for chemical co-exposure has always been a challenge in past years. The present study aims to employ principle component analysis (PCA) to produce an entry for benchmark dose approximation in shoemakers based on the color vision effect. A total of 134 subjects consisting of 67 shoemakers and 67 staff workers were employed for Benchmark Dose (BMD) evaluation. Occupational exposure to benzene, toluene, xylene, and n-hexane was evaluated using NIOSH 1501 and OSHA ID-07 methods. The color vision effect was quantified using Lanthony D-15 desaturated test (D-15d). PCA was run for cumulative exposure dose (CED) of the solvents by MATLAB 2018. Finally, the lowest 95% confidence limit of the benchmark dose (BMDL) was determined using US EPA benchmark dose software (BMDS) version 3.2.1. The color confusion index (CCI) level in shoemakers increased from 1 to 1.15 by a median of 1.07. There was a significant difference in the CCI level (p value<0.0001) between exposed and control subjects. The first score of PCA was used as intake dose level (IDL) in solvents co-exposure. Using BMD analysis, the log-logistics model was fitted with a p-value> 0.1 and the lowest BMDL level. BMDL level was evaluated at 1.63, 10.25, 2.21, and 3.35 ppm for benzene, toluene, xylene, and n-hexane, respectively. The results showed a risk of color vision effect with co-exposure to solvents at different levels in the occupational exposure standards. In conclusion BMDL-PCA approach has been suggested for the risk assessment of chemical co-exposure.

Benchmark dose analysis for PAHs hydroxyl metabolites in urine based on mitochondrial damage of peripheral blood leucocytes in coke oven workers in China

OBJECTIVES

The aim was to explore the dose-response relationship between occupational polycyclic aromatic hydrocarbons (PAHs) exposure and mitochondrial damage in coke oven plants workers.

METHODS

544 workers and 238 healthy people were recruited. The ultra-high performance liquid chromatography was used to determine the level of 1-hydroxypyrene, 1-hydroxynaphthalene, 2-hydroxynaphthalene and 3-hydroxyphenanthrene. The real-time fluorescence quantitative polymerase chain reaction was used to determine the mitochondrial DNA copy number (mtDNAcn). The benchmark dose software was used to analyze the benchmark dose.

RESULTS

The mtDNAcn in the exposure group was lower than that in the control group. The concentrations of 1-hydroxypyrene, 1-hydroxynaphthalene, 2-hydroxynaphthalene and 3-hydroxyphenanthrene in the exposure group were higher than those in the control group. There is a dose-response relationship between 1-hydroxypyrene, 3-hydroxyphenanthrene and mitochondrial DNA damage. The benchmark dose lower confidence limit (BMDL) of 1-hydroxypyrene were 0.045, 0.004, and 0.058 pg/μg creatinine in the total, male, and female population, respectively. The BMDL of 3-hydroxyphenanthrene were 5.142, 6.099, and 2.807 pg/μg creatinine in the total, male, and female population, respectively.

CONCLUSIONS

The BMDL of 1-hydroxypyrene and 3-hydroxyphenanthrene initially explored can provide a reference to establish occupational exposure biological limits.

Impact of environmental mercury exposure on the blood cells oxidative status of fishermen living around Mundaú lagoon in Maceió - Alagoas (AL), Brazil

Mercury in the aquatic environment can lead to exposure of the human population and is a known toxic metal due to its capacity for accumulation in organs. We aimed to evaluate the mercury level in the blood and urine of fishermen and correlate it with the level of oxidative stress in blood cells. We show in this case-control study that the fishermen of the exposed group (case) of Mundaú Lagoon (Maceió - Alagoas, Brazil) have higher concentrations of total mercury in the blood (0.73-48.38 μg L^-1) and urine (0.430-10.2 μg L^-1) than the total mercury concentrations in blood (0.29-17.30 μg L^-1) and urine (0.210-2.65 μg L^-1) of the control group. In the blood cells of fishermen, we observed that the lymphomononuclear cells produced high levels of reactive oxygen species (61.7%), and the erythrocytes presented increased lipid peroxidation (151%) and protein oxidation (41.0%) and a decrease in total thiol (36.5%), GSH and the REDOX state (16.5%). The activity of antioxidant system enzymes (SOD, GPx, and GST) was also reduced in the exposed group by 26.9%, 28.3%, and 19.0%, respectively. Furthermore, hemoglobin oxygen uptake was decreased in the exposed group (40.0%), and the membrane of cells presented increased osmotic fragility (154%) compared to those in the control group. These results suggest that mercury in the blood of fishermen can be responsible for causing impairments in the oxidative status of blood cells and is probably the cause of the reduction in oxygen uptake capacity and damage to the membranes of erythrocytes.

Estimations of benchmark dose for urinary metabolites of coke oven emissions among workers

Coke oven emissions (COEs), usually composed of polycyclic aromatic hydrocarbons (PAHs) and so on, may alter the relative telomere length of exposed workers and have been linked with adverse health events. However, the relevant biological exposure limits of COEs exposure has not been evaluated from telomere damage. The purpose of this study is to estimate benchmark dose (BMD) of urinary PAHs metabolites from COEs exposure based on telomere damage with RTL as a biomarker. A total of 544 exposed workers and 238 controls were recruited for participation. High-performance liquid chromatography and qPCR were used to detect concentrations of urinary mono-hydroxylated PAHs and relative telomere length in peripheral blood leukocytes for all subjects. The benchmark dose approach was used to estimate benchmark dose (BMD) and its lower 95% confidence limit (BMDL) of urinary OH-PAHs of COEs exposure based on telomere damage. Our results showed that telomere length in the exposure group (0.75 (0.51, 1.08)) was shorter than that in the control group (1.05 (0.76,1.44))(P < 0.05), and a dose-response relationship was shown between telomere damage and both 1-hydroxypyrene and 3-hydroxyphenanthrene in urine. The BMDL of urinary 1-hydroxypyrene from the optimal model for telomere damage was 1.96, 0.40, and 1.01 (μmol/mol creatinine) for the total, males, and females group, respectively. For 3-hydroxyphenanthrene, the BMDL was 0.94, 0.33, and 0.49 (μmol/mol creatinine) for the total, males, and females. These results contribute to our understanding of telomere damage induced by COEs exposure and provide a reference for setting potential biological exposure limits.

Global H3K79 di-methylation mediates DNA damage response to PAH exposure in Chinese coke oven workers

Polycyclic aromatic hydrocarbons (PAHs) are the main contaminants of coke oven emissions which can induce serious genetic damage in coke oven workers. Epigenetic alternations play essential roles in the regulation of DNA damage effect of PAHs. Previous studies indicate that H3K79 di-methylation (H3K79me2) is integral in DNA damage repair. However, the potential role of H3K79me2 in DNA damage response (DDR) following PAHs exposure is still unclear. In this study, we recruited 256 male coke oven workers and control workers, and examined H3K79me2 and DNA damage in their peripheral blood lymphocytes (PBLCs). The results showed that global H3K79me2 of coke oven workers was 29.3% less than that of the controls (P < 0.001). The H3K79me2 was negatively correlated with the concentration of urinary 1-hydroxypyrene (1-OHP) (β = -0.235, P < 0.001) and level of genetic damage evaluated by comet assay (β_{Tail DNA %} = -0.313, P < 0.001; β_OTM = -0.251, P = 0.008). Consistently, we found that benzo(a)pyrene (BaP) inhibited H3K79me2 in immortalized human bronchial epithelial (HBE) cells in a time-dependent manner. In order to explore the function of H3K79me2 in PAHs DDR, we established histone 3.1/3.3 K79A mutant cells (H3K79 A) to suppress H3K79me2. H3K79 A cells showed more serious DNA damage and decreased cell viability than control cells after BaP treatment. In addition, we also found that the expression of DOT1L, the only methyltransferase in H3K79, was repressed by BaP dose-dependently. DOT1L knockdown resulted in decreased H3K79me2 level and aggravated DNA damage after BaP exposure. This suggests that BaP induces H3K79me2 repression via inhibiting DOT1L expression. In conclusion, these findings indicate that PAH exposure decreases the level of global H3K79me2, which is integral for DNA damage response regulation of PAHs.