Determination of benchmark dose based on adduct and micronucleus formations in formaldehyde-exposed workers

Global and gene-specific promoter methylation, and micronuclei induction in lead-exposed workers: A cross-sectional study

Perturbation of epigenetic regulation is a well-established mechanism for cancer but its role for lead (Pb)-associated toxicity has not been adequately investigated. We aimed to investigate whether occupational Pb exposure is associated with micronuclei (MN) frequency and to further explored the mediating roles of epigenetic gene regulation. All the Pb-exposed workers recruited from a Chinese acid battery factory, blood lead levels (BLLs) and MN frequency in lymphocytes were measured. In addition, methylation levels of seven genes (Line-1, RASSF1A, RUNX3, p16, CYP26C1, hMLH1, p15) were examined among 230 workers. Robust Poisson regression model was used to investigate the association between BLLs and MN frequency. Mediation analysis was used to explore the mediating role of specific DNA methylation. Among total 677 participants, 71% were male, median BLLs was 229.1 μg/L (P₂₅  = 155.5, P₇₅  = 319.3; ranged from 8.9 to 647.7 μg/L), mean MN frequency was 2.5‰ (SD = 1.8‰; ranged from 0 to 9‰). Results from base model, adjusted for age, sex, and body mass index, showed that MN frequency would increase 1.38 (95%confidential interval: 1.34, 1.43) per 100 μg/L increment in BLLs. Using categorized exposure variable analyses, a BLLs dose-response increase in MN frequency was observed: 2.74 (2.13, 3.51), 3.43 (2.73, 4.32), 4.41 (3.89, 5.01) to 6.86 (6.02, 7.81). Mediation analysis indicated that Line-1 methylation significantly mediated 3.6% of the association of BLLs with MN frequency. Occupational Pb exposure induces MN frequency in a dose-response relationship. Part of this association was mediated by Line-1 promotor methylation.

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.

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.

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

Coke oven emissions (COEs) can cause oxidative stress of the body, which in turn induces the occupational lung disease and also increases the risk of other diseases. COEs are the major occupational hazard factors for coke oven workers. The aim of the study is to explore the influences of COEs exposure on oxidative damage and estimate the benchmark dose (BMD) of COEs. A group of 542 workers exposed to COEs and 237 healthy controls from the same city were recruited in this study. The corresponding measuring kits were used to determine the plasma biomarkers of oxidative damage level. Generalized linear models and trend tests were used to analyze the relationship between COEs exposure and biomarkers. EPA Benchmark Dose Software was performed to calculate BMD and the lower confidence limit of the benchmark dose (BMDL) of COEs exposure. A significant association was observed between COEs exposure and oxidative damage with T-AOC as a biomarker. The BMD of COEs exposure were 2.83 mg/m³ and 1.39 mg/m³ for males and females, respectively, and the corresponding BMDL were 1.47 mg/m³ and 0.75 mg/m³, respectively. Our results suggested that the exposure level of COEs below the current national occupational exposure limits (OELs) would induce oxidative damage, and the OEL of COEs based on the T-AOC damage was suggested at 0.03 mg/m³ in this study.