The Relationships Between Blood Pb Levels and Blood Pressure Among Lead-Exposed Workers in China: A Repeated-Measure Study.

OBJECTIVES: To explore the differences in the increase of systolic blood pressure (SBP) and diastolic blood pressure (DBP) in 3 consecutive years among lead (Pb) workers. METHODS: Four hundred forty-eight Pb workers were enrolled in this repeated-measure study. Blood Pb, SBP, and DBP were measured in 2015 to 2017. Repeated measure of analysis of variance was used to compare the differences in the increase of SBP and DBP. RESULTS: The mean SBP values were 124.0/125.5/126.9 mm Hg, and the mean DBP values were 75.4/77.4/77.8 mm Hg from 2015 to 2017. The differences in the increase of SBP and DBP were 2.94/2.42 mm Hg during the 3-year period. The average annual increase of SBP or DBP showed an upward trend in different Pb dose groups ( F = 4.904, P = 0.002; F = 3.612, P = 0.013). CONCLUSIONS: Lead exposure caused average annual increases in SBP and DBP with 0.98 and 0.81 mm Hg, which provided basic data for health surveillance.

An exploration of biomarkers for noise exposure: mitochondrial DNA copy number and micronucleus frequencies in Chinese workers.

Few studies have been conducted that use biomarkers as early warning signals for noise-associated health hazards. To explore potentially effective biomarkers for noise-exposed populations, we recruited 218 noise-exposed male workers in China. We calculated cumulative noise exposure (CNE) through noise intensity and noise-exposed duration. When the model was fully adjusted, ln-transformed relative mitochondrial DNA copy number (mtDNAcn) decreased by 0.014 (95% confidence interval (CI): -0.026, -0.003) units with each 1 dB(A)∙year increase in CNE levels. CNE was further included in the model as a grouping variable, and the results showed a negative dose-effect relationship between relative mtDNAcn and CNE (P-trend = 0.045). However, we did not find a correlation between CNE and micronucleus (MN) frequencies. Our findings suggest that CNE in workers was associated with a decrease in relative mtDNAcn which may provide a potential biomarker for noise and for certain health risk but not with MN frequencies.

Benchmark dose estimation for benzene-exposed workers in China: Based on quantitative and multi-endpoint genotoxicity assessments.

Based on previous exposure studies, benzene (BZ) has been classified as a human carcinogen and occupational exposure limit (OELs) for BZ has been set to be about 1 ppm around the world. However, health hazards have still been reported with exposure below the OEL. Thus, the OEL needs to be updated to reduce health risk. The overall aim of our study was therefore to generate new OEL for BZ via a benchmark dose (BMD) approach and based on quantitative and multi-endpoint genotoxicity assessments. Genotoxicities were determined using the novel human PIG-A gene mutation assay, the micronucleus (MN) test and the COMET assay in benzene-exposed workers. Among the 104 workers with below current OELs, they exhibited significantly higher PIG-A mutant frequencies (MFs) (15.96 ± 14.41 × 10-6) and MN frequencies (11.55 ± 6.83‰) than those among the controls (PIG-A MFs: 5.46 ± 4.56 × 10-6, MN frequencies: 4.51 ± 1.58 ‰), but no difference in the COMET assay. A significant association was also observed between BZ exposure doses and PIG-A MFs and MN frequencies (P < 0.001). Our results indicate that health hazards were induced among workers with below OEL exposures. Based on results from the PIG-A and MN assays, the lower confidence limit of the BMD (BMDL) were calculated to be 8.71 mg/m3-year and 0.44 mg/m3-year, respectively. Based on these calculations, the OEL for BZ was determined to be lower than 0.07 ppm. This value can be considered by regulatory agencies to set new exposure limits and to better protect workers.

Associations between DNA methylation and genotoxicity among lead-exposed workers in China.

Studies have shown that lead (Pb) exposure caused genotoxicity, however, the underlying mechanisms remain unclear. A mechanism may be via DNA methylation which is one of the most widely studied epigenetic regulations for cellular activities. Whether this is involved in Pb-induced genotoxicity has rarely been studied. Our study aimed to examine whether DNA methylation was associated with Pb exposure and genotoxicity, and to explore its potential mediating roles. A total of 250 Pb-exposed workers were enrolled. Blood lead levels (BLLs) and genotoxic biomarkers (Micronuclei and Comet) were analyzed. Methylation levels at CpG sites of LINE1 and Alu and promoter region of P53, BRCA1, TRIM36 and OGG1 were measured by pyrosequencing. Generalized linear model (GLM) combined with restricted cubic splines (RCS) were used to analyze relationships between Pb exposure, DNA methylation and genotoxicity. Mediation effect was used to explore mediating roles of DNA methylation. The distribution of BLLs was right-skewed and showed wide ranges from 23.7 to 636.2 µg/L with median (P25, P75) being 218.4 (106.1, 313.9) µg/L among all workers. Micronuclei frequencies showed Poisson distribution [1.94 ± 1.88‰] and Comet tail intensity showed normal distribution [1.69 ± 0.93%]. GLM combined with RCS showed that Alu methylation was negatively associated with BLLs, while P53 and OGG1 methylation were positively associated with BLLs. Micronuclei were negatively associated with Alu and TRIM36 methylation but positively with P53 methylation. Comet was positively associated with P53 and BRCA1 methylation. Mediation effect showed that Alu methylation mediated 7% effects on association between Pb exposure and micronuclei, whereas, P53 methylation mediated 14% and BRCA1 mediated 9% effects on association between Pb exposure and Comet. Our data show that Pb exposure induced changes of global and gene-specific DNA methylation which mediated Pb-induced genotoxicity.

Lymphocyte-based challenge DNA-repair assays for personalized health risk assessment.

Combinations of genetic and environmental factors are responsible for the development of many human diseases, such as cancer, as demonstrated using various biomarkers. Within this scenario, DNA repair holds a gate-keeper position which determines outcomes after appearance of DNA damage and, therefore, adverse cellular consequences, e.g., initiation of carcinogenesis. DNA repair deficiency and some of the subsequent events can be validated from studies using live cells from cancer patients. However, these deficiencies/events are difficult to demonstrate in live cells from normal individuals because individual variations in DNA repair capacities (DRC) are too low to be measured easily. Such lack of information has been hindering progress in developing personalized disease prevention and intervention protocols, especially among exposed populations. However, using a variety of challenge assays as biomarkers, variations in individual's DRC can be amplified in live cells and be determined. Furthermore, evidence indicates that DRC are not only inherited but can also be modified by environmental factors (e.g., nutritional status and exposure to genotoxic substances). Using these challenge assays, e.g., in live lymphocytes, individual's DRC can be holistically and functionally determined as well as quantitated. With the more precise information, assessment of health risk can be better determined on an individual rather than on a population basis. This review provides a succinct summary on the development and application of recent challenge assays in lymphocytes which can provide measurements of individuals' DRC, and on the latest data for more precise disease prevention and intervention.

Occupational lead exposure on genome-wide DNA methylation and DNA damage.

Lead (Pb) exposure can induce DNA damage and alter DNA methylation but their inter-relationships have not been adequately determined. Our overall aims were to explore such relationships and to evaluate underlying epigenetic mechanisms of Pb-induced genotoxicity in Chinese workers. Blood Pb levels (BLLs) were determined and used as individual's Pb-exposure dose and the Comet assay (i.e., % tail DNA) was conducted to evaluate DNA damage. In the screening assay, 850 K BeadChip sequencing was performed on peripheral blood from 10 controls (BLLs ≤100 µg/L) and 20 exposed workers (i.e., 10 DNA-damaged and 10 DNA-undamaged workers). Using the technique, differentially methylated positions (DMPs) between the controls and the exposed workers were identified. In addition, DMPs were identified between the DNA-undamaged and DNA-damaged workers (% tail DNA >2.14%). In our validation assay, methylation levels of four candidate genes were measured by pyrosequencing in an independent sample set (n = 305), including RRAGC (Ras related GTP binding C), USP1 (Ubiquitin specific protease 1), COPS7B (COP9 signalosome subunit 7 B) and CHEK1 (Checkpoint kinase 1). The result of comparisons between the controls and the Pb-exposed workers show that DMPs were significantly enriched in genes related to nerve conduction and cell cycle. Between DNA-damaged group and DNA-undamaged group, differentially methylated genes were enriched in the pathways related to cell cycle and DNA integrity checkpoints. Additionally, methylation levels of RRAGC and USP1 were negatively associated with BLLs (P < 0.05), and the former mediated 19.40% of the effect of Pb on the % tail DNA. These findings collectively indicated that Pb-induced DNA damage was closely related to methylation of genes in cell cycle regulation, and methylation levels of RRAGC were involved in Pb-induced genotoxicity.

Associations of changes in late-life blood pressure with cognitive impairment among older population in China.

BACKGROUND: The cognitive impact of changes in late-life blood pressure is less clear. We aimed to investigate the association between late-life blood pressure changing pattern and risk of cognitive impairment. METHODS: Using data from the community-based Chinese Longitudinal Healthy Longevity Survey, change in systolic (SBP) or diastolic (DBP) blood pressure was calculated as the difference between follow-up and baseline, cognitive impairment was defined based on both the Mini-Mental State Examination and education level. The generalized additive model with penalized spline and multivariate logistic regression model were used, respectively, to examine the associations between continuous and categorized blood pressure changes with cognitive impairment at the follow-up wave. RESULTS: A total of 8493 Chinese elderly without cognitive impairment were included, with mean (standard deviation) age 80.6 (10.7) years. U-shaped associations between late-life blood pressure changes and risk of cognitive impairment were found, with only stable optimal blood pressure related to the lowest risk. For participants with baseline SBP around 130-150 mmHg, the adjusted odds ratio was 1.48 (1.13-1.93) for increasing follow-up SBP (> 150 mmHg), 1.28 (1.02-1.61) for decreasing follow-up SBP (< 130 mmHg), compared to stable follow-up SBP (130-150 mmHg). For participants with relative lower baseline DBP (< 80 mmHg), increasing their DBP to 80-90 mmHg during follow-up was associated with lower cognitive impairment risk (0.73 (0.58-0.93)), compared to steady low follow-up DBP (< 80 mmHg). Sex-specific analysis suggested that men were more vulnerable in term of SBP change. CONCLUSIONS: Adhering to a stable optimal level of blood pressure in late-life is related to lower risk of cognitive impairment in Chinese elderly.

Changes in late-life systolic blood pressure and all-cause mortality among oldest-old people in China: the chinese longitudinal healthy longevity survey.

BACKGROUND: Blood pressure targets for oldest-old people have been long debated due to the concern that more stringent targets are associated with increased mortality. We aimed to investigate the association between changes of late-life systolic blood pressure (SBP), mean SBP and SBP variability (SBPV), and all-cause mortality in oldest-old. METHODS: Based on the community-based Chinese Longitudinal Healthy Longevity Survey with follow-up conducted in the 3-year interval, we assembled a retrospective cohort of 6639 participants ≥ 80 years with available blood pressure measurements at baseline and second wave. The primary exposures were mean SBP and SBPV (defined as the annual difference in SBP divided by mean SBP) measured between baseline and second wave. The primary outcome was all-cause mortality assessed from the second wave. RESULTS: During 21443.1 person-years of follow-up, 4622 death was recorded. U-shaped associations of mortality with mean SBP and SBPV were identified; the value of 137 mmHg and 4.0 %/year conferred the minimum mortality risk, respectively. The associations of a larger SBPV with an increased mortality risk were observed for both rises and large falls in SBP. The hazard ratio was 1.11 (comparing lowest versus middle quintile; 95 % CI: 1.01, 1.22) with large falls in SBPV and 1.08 (comparing highest versus middle quintile; 95 % CI: 0.98, 1.18) with large rises in SBPV. CONCLUSIONS: U-shaped associations between late-life SBP and SBPV and all-cause mortality were found. Our study suggests that a stable SBP level in the middle range is related to lower mortality risk in the oldest-old.

Gene-Environment Interactions Between Environmental Response Genes Polymorphisms and Mitochondrial DNA Copy Numbers Among Benzene Workers.

OBJECTIVE: To determine the effect of mitochondrial DNA copy number (mtDNAcn) as a biomarker of benzene exposure. METHODS: A total of 294 benzene-exposed workers and 102 controls were recruited. Biomarkers of mtDNAcn, cytokinesis-block micronucleus (MN) frequency, and peripheral blood white blood cells (WBC) were detected. Eighteen polymorphism sites in DNA damage repair and metabolic genes were analyzed. RESULTS: Benzene exposure increased mtDNAcn and indicated a dose-response relationship (P < 0.001). mtDNAcn was negatively correlated with WBC count and DNA methylation and positively correlated with MN frequency. The AG type in rs1695 interacted with benzene exposure to aggravate mtDNAcn (ß = 0.006, 95% CI: 0, 0.012, P = 0.050). rs13181, rs1695, rs1800975, and GSTM1 null were associated with benzene-induced mtDNAcn. Rs1695 interacted with benzene to increase mitochondrial damage. CONCLUSIONS: Benzene exposure increases mtDNAcn levels in benzene-exposed workers.

Occupational Health Risk Assessment of Benzene, Toluene, and Xylene in Shanghai.

OBJECTIVE: This study was designed to conduct a retrospective and systematic occupational health risk assessment (OHRA) of enterprises that used benzene, toluene, and xylene (BTX) in Shanghai, China. METHODS: All data for the study were obtained from 1,705 occupational health examination and evaluation reports from 2013 to 2017, and a semiquantitative model following Chinese OHRA guidelines (GBZ/T 298-2017) was applied for the assessment. RESULTS: The selected enterprises using BTX were mainly involved in manufacturing of products. Using the exposure level method, health risk levels associated with exposure to BTX were classified as medium, negligible, or low. However, the risk levels associated with benzene and toluene were significantly different according to job types, with gluers and inkers exhibiting greater health risks. For the same job type, the health risk levels assessed using the comprehensive index method were higher than those using the exposure level method. CONCLUSION: Our OHRA reveals that workers who are exposed to BTX still face excessive health risk. Additionally, the risk level varied depending on job categories and exposure to specific chemicals. Therefore, additional control measures recommended by OHRA guidelines are essential to reduce worker exposure levels.

Early occupational exposure to lead on neutrophil-to-lymphocyte ratio and genotoxicity.

BACKGROUND: Lead (Pb) is known to induce detrimental health effects in exposed populations, including hematotoxicity and genotoxicity. Complete blood count (CBC) is a cost-effective and easy way to determine toxicity, and variations in proportion of different types of leukocytes: neutrophil-to-lymphocyte ratio (NLR) and lymphocyte-to-monocyte ratio (LMR) are further evidence of hematotoxicity. However, few studies have been conducted to systematically evaluate effects of occupational Pb exposure on NLR and LMR, and their associations with genotoxicity. OBJECTIVES: Our study was aimed to systematically assess the effects of current occupational Pb exposure on NLR and LMR, and their associations with genotoxicity. METHODS: Our investigation was performed on 1176 workers from a newly built battery factory in North China. The workers had just entered their current job position in recent years and most of them had no previous history of occupational exposure to Pb. Blood lead levels (BLLs) and leukocytes indices were detected for all participants. Cytokinesis-blocked micronucleus assay (MN; n = 675) and alkaline comet assay (% tail DNA; n = 869) were used to assess genotoxicity. Multivariate linear and Poisson regression analyses were conducted to examine associations between leukocytes indices, genotoxic biomarkers and BLLs with adjustment for covariates. Spearman correlation and mediation analyses were used to investigate relationships between NLR and genotoxicity. RESULTS: Among all the exposed workers, NLR increased with increasing BLLs. However, WBC and LMR did not change significantly. Significant and dose-dependent increases in both MN frequencies and % tail DNA were observed among groups with different exposure doses. Compared with the normal NLR group (1.48 ≤ NLR < 4.58), the high NLR group (NLR ≥ 4.58) had higher % tail DNA. In addition, there was a significant and positive association between NLR and % tail DNA among all the workers, and % tail DNA mediated 15% of the effect of Pb on increasing NLR. CONCLUSION: Our large-scale population study shows that Pb exposure increased NLR and induced genotoxicity. There was an association between elevated NLR and DNA damage. In addition, the mediation effect of % tail DNA on the relationship between BLLs and NLR provided mechanistic evidence that certain mechanisms, e.g. inflammation, may be involved in elevation of NLR from Pb exposure. Therefore, NLR may be a convenient and sensitive biomarker for indication of Pb toxicity. Further studies are needed to validate the proposed mechanism and NLR as a biomarker.

Changes in miR-222 expression, DNA repair capacity, and MDM2-p53 axis in association with low-dose benzene genotoxicity and hematotoxicity.

Mechanisms for hematotoxicity and health effects from exposure to low doses of benzene (BZ) remain to be identified. To address the information gap, our investigation was focused onto using appropriate populations and cell cultures to investigate novel BZ-induced effects such as disruption of DNA repair capacity (DRC). From our study, abnormal miRNAs were identified and validated using lymphocytes from 56 BZ-poisoned workers and 53 controls. In addition, 173 current BZ-exposed workers and 58 controls were investigated for key miRNA expression using RT-PCR and for cellular DRC using a challenge assay. Subsequently, the observed activities in lymphocytes were verified using human HL-60 (p53 null) and TK6 (p53 wild-type) cells via 1,4-benzoquinone (1,4-BQ) treatment and miR-222 interferences. The targeting of MDM2 by miR-222 was validated using a luciferase reporter. Our results indicate induction of genotoxicity in lymphocytes from workers with low exposure doses to BZ. In addition, miR-222 expression was up-regulated among both BZ-poisoned and BZ-exposed workers together with inverse association with DRC. Our in vitro validation studies using both cell lines indicate that 1,4-BQ exposure increased expression of miR-222 and Comet tail length but decreased DRC. Loss of miR-222 reduced DNA damage, but induced S-phase arrest and apoptosis. However, silencing of MDM2 failed to activate p53 in TK6 cells. In conclusion, our in vivo observations were confirmed by in vitro studies showing that BZ/1,4-BQ exposures caused genotoxicity and high expression of miR-222 which obstructed expression of the MDM2-p53 axis that led to failed activation of p53, abnormal DRC and serious biological consequences.

Development of a benchmark dose for lead-exposure based on its induction of micronuclei, telomere length changes and hematological toxicity.

BACKGROUND: Excessive lead exposure is associated with adverse health effects. However, there is a lack of systematic investigation using large populations to ascertain acceptable exposure limits. OBJECTIVES: Our study was aimed to identify human exposure-response relationships between lead exposure and health-related outcomes, and to determine a benchmark dose (BMD). METHODS: A total of 1896 participants from a lead-acid battery plant were recruited. Blood lead levels (BLLs) were detected for all participants. Hematological parameters (n = 1896), micronuclei (MN) frequencies (n = 934), and relative telomere length (rTL) (n = 757) were also determined. Multivariate linear/Poisson regression analyses were performed to examine associations between BLLs and these health outcomes. Restricted cubic splines were used to identify dose-response relationships. Three BMD approaches were used to calculate BMD and its 95% lower confidence limit (BMDL). RESULTS: Among all participants, BLLs show a right-skewed distribution (median, 185.40 µg/L; 25th - 75th percentile, 104.63-271.70 µg/L). There existed significant differences for red blood cell (RBC), hemoglobin (Hb), MN and rTL among different BLL dose groups. After adjusting for possible confounders, all indicators were significantly associated with BLLs. Restricted cubic splines show that there were linear dose-response relationships for RBC and Hb with BLLs, while non-linear for MN and rTL. Results from the three BMD approaches indicate that the dichotomous models were better than continuous models to calculate BMD and BMDL of BLLs. The conservative BMDL obtained from RBC data was 135 for total, 104 for male and 175 µg/L for female. The corresponding BMDL obtained from Hb data was 105 for total, 116 for male and 70 µg/L for female. As for MN data, the BMDL estimate was 66 for total, 69 for male and 64 µg/L for female. Finally, the BMDL from rTL data was 35 for total, 32 for male and 43 µg/L for female. CONCLUSIONS: Our data show significant dose-response relationships between lead exposure and expressions of hematological toxicity and genotoxicity. The new BMDLs of 135 and 105 µg/L based on RBC and Hb, and even more strict level of 66 and 35 µg/L based on MN and rTL are lower than current exposure limits in China. Therefore, the four values can be considered as novel exposure limits. In addition, sex effect should be taken into account when setting occupational health standard. Considering that different biomarkers have different sensitivities, better understanding their relationships will certainly improve the current emphasis on precision health risk assessment.

Dataset on the effect of Benzene exposure on genetic damage, hematotoxicity, telomere length and polymorphisms in metabolic and DNA repair genes.

In this paper, we present an occupational dataset to evaluate benzene exposure on the effective biomarkers of genetic damage, indicated as cytokinesis-block micronucleus (MN) frequency, hematotoxicity, indicated as white blood cells (WBC) counts, and molecular marker of telomere length (TL). And we further to eliminate the mechanism of benzene induced damage. Then evaluate the effects of sites polymorphism in environmental response genes, including 18 sites in metabolic and DNA repair genes, and the interaction between gene polymorphism and benzene exposure. This dataset is supplementary to the submitted research by [1] focused on the biomarkers TL, and a detailed description of the subjects sampling, biomarkers detection, data analysis and discussion are discussed in detail.

Aberrant lncRNA Profiles Are Associated With Chronic Benzene Poisoning and Acute Myelocytic Leukemia.

OBJECTIVE: This study investigates the mechanisms of benzene hematotoxicity. METHODS: We used microarray to detect expression profiles of long non-coding RNAs (lncRNAs) and mRNAs in peripheral lymphocytes from chronic benzene poisoning, acute myelocytic leukemia, and healthy controls. The lncRNAs and mRNAs were validated using real-time quantitative PCR (RT-qPCR). Cytokinesis-block micronucleus assay was used to analyze chromosomal aberration. RESULTS: We found 173 upregulated and 258 downregulated lncRNAs, and 695 upregulated and 804 downregulated mRNAs. The lncRNA CUST_40243 and mRNA PDGFC and CDKN1A associated with chronic benzene poisoning. Relevant inflammatory response, hematopoietic cell lineage, and cell cycle may be important pathways for the sifted lncRNAs and mRNAs. Furthermore, micronuclei frequency was significantly higher in off-post chronic benzene poisoning patients. CONCLUSIONS: Chromosomal aberration induced by benzene exposure is irreversible. The lncRNA CUST_40243 and mRNA PDGFC and CDKN1A are related to chronic benzene poisoning.

Interaction effects of environmental response gene polymorphisms and benzene exposure on telomere length in shoe-making workers.

Benzene is a globally occurring environmental and occupational pollutant that causes leukemia. To better understand telomere length (TL) as a function of benzene toxicity, we recruited 294 shoe-making workers and 102 controls from Wenzhou, China in 2011. Biomarkers of TL, cytokinesis-block micronucleus (MN) frequency, and white blood cells (WBC) were measured. In total, 18 polymorphic sites in environmental response genes, including metabolic and DNA repair genes, were analyzed. Results indicate that benzene exposure led to a longer TL at a threshold of 32 mg/m3-year of cumulative exposure dose (CED). Furthermore, the TL was longer in members of the damaged group, when evaluated for MN frequency (P < 0.001) and reduced WBC (P < 0.001), than in those of the normal group. Workers carrying genotype TT (ß = 0.32, P = 0.042) in rs3212986 of ERCC1 and genotype TC (ß = 0.24, P = 0.082) in rs1051740 of mEH exon3 were associated with a longer TL as compared to the wild-type group. TA (ß = -0.53, P < 0.001) in rs6413432 of CYP2E1 was associated with a shorter TL. Benzene exposure interacted with the TA type in rs6413432 (ß = 0.003, 95% CI: 0, 0.006, P = 0.042) and the CC type in rs1051740 (ß = 0.007, 95% CI: 0.001, 0.013, P = 0.015) after adjusting for confounding factors. Our results indicate that benzene induces an increase in TL at a threshold of CED ≥32mg/m3-year. Rs1051740, rs3212986, and rs6413432 were found to be involved in benzene-induced telomere growth; in particular, rs1051740 and rs6413432 interacted with the benzene exposure, resulting in an extended TL.

Promoter hypermethylation in CSF3R induces peripheral neutrophil reduction in benzene-exposure poisoning.

Benzene is a global pollutant and has been established to cause leukemia. To better understand the role of DNA methylation in benzene toxicity, peripheral blood mononuclear cells were collected from six benzene-poisoning patients and six matched controls for genome-wide DNA methylation screening by Illumina Infinium Methylation 450 BeadChip. The Gene Chip Human Gene 2.0 ST Array (Affymetrix) was used to analyze global mRNA expression. Compared with the corresponding sites of controls, 442 sites in patients were hypermethylated, corresponding to 253 genes, and 237 sites were hypomethylated, corresponding to 130 genes. The promoter methylation and mRNA expression of CSF3R, CREB5, and F2R were selected for verification by bisulfite sequencing and real-time PCR in a larger data set with 21 cases and 23 controls. The results indicated that promoter methylation of CSF3R (p = .005) and F2R (p = .015) was significantly higher in cases than in controls. Correlation analysis showed that the promoter methylation of CSF3R (p < .001) and F2R (p < .001) was highly correlated with its mRNA expression. In the poisoning cases, neutrophil percentage was significantly different among the high, middle, and low CSF3R-methylation groups (p = .002). In particular, the neutrophil percentage in the high CSF3R-methylation group (48.10 ± 9.63%) was significantly lower than that in the low CSF3R-methylation group (59.30 ± 6.26%) (p = .012). The correlation coefficient between promoter methylation in CSF3R and the neutrophil percentage was -0.445 (p = .020) in cases and - 0.398 (p = .060) in controls. These results imply that hypermethylation occurs in the CSF3R promoter due to benzene exposure and is significantly associated with a reduction in neutrophils.

A Systematic Review and Meta-Analysis of Short-Term Ambient Ozone Exposure and COPD Hospitalizations.

Chronic obstructive pulmonary disease (COPD) is the third leading cause of death globally and ozone exposure is a main cause of its disease burden. However, studies on COPD hospitalizations from short-term ambient level ozone exposure have not generated consensus results. To address the knowledge gap, comprehensive and systematic searches in several databases were conducted using specific keywords for publications up to February 14, 2020. Random-effect models were used to derive overall excess risk estimates between short-term ambient-level ozone exposure and COPD hospitalizations. The influence analyses were used to test the robustness of the results. Both meta-regression and subgroup analyses were used to explore the sources of heterogeneity and potential modifying factors. Based on the results from 26 eligible studies, the random-effect model analyses show that a 10 µg/m3 increase in maximum 8-h ozone concentration was associated with 0.84% (95% CI: 0.09%, 1.59%) higher COPD hospitalizations. The estimates were higher for warm season and multiple-day lag but lower for old populations. Results from subgroup analyses also indicate a multiple-day lag trend and bigger significant health effects during longer day intervals. Although characteristics of individual studies added modest heterogeneity to the overall estimates, the results remained robust during further analyses and exhibited no evidence of publication bias. Our systematic review and meta-analysis indicate that short-term ambient level ozone exposure was associated with increased risk of COPD hospitalizations. The significant association with multiple-day lag trend indicates that a multiple-day exposure metric should be considered for establishing ambient ozone quality and exposure standards for improvement of population health. Future investigations and meta-analysis studies should include clinical studies as well as more careful lag selection protocol.

Effects of Micronucleus Frequencies and Mitochondrial DNA Copy Numbers among Benzene-Exposed Workers in China.

To provide a more comprehensive understanding of genotoxic effects from benzene exposure, its effects on induction of mitochondrial DNA copy number (MtDNAcn) and of micronucleus (MN) were investigated using peripheral blood from workers in China. Changes in mtDNAcn and MN were determined using quantitative real-time polymerase chain reaction (PCR) and cytokinesis-block micronucleus assays (CBMN), respectively, in 58 control and 174 benzene-exposed workers in Shanghai, China. Among the exposed workers, relative mtDNAcn increased and then decreased with increasing doses of benzene exposure. Significant and dose-dependent increase in MN frequencies were observed among the different exposure groups. In addition, the relative mtDNAcn were significantly associated with the MN frequencies in the low-level exposure group (P = 0.046), but not in the high dose groups. Therefore, the mechanisms for induction of MtDNAcn and MN by benzene may be similar from exposure to low doses but different from high doses. Similar increase of MN frequencies and MtDNAcn may be due to oxidative stress induced by benzene at low concentrations, while higher concentrations may start to initiate the cell death pathway. The pathway may be associated with excessive MtDNAcn which can initiate apoptosis while MN can continue to be induced. However, the differential mechanisms need to be investigated because they may represent different levels of risk for different health consequences. On the other hand, our data indicate that induction of MtDNAcn may be a sensitive genotoxic biomarker for workers with exposure to low dose of benzene. Environ. Mol. Mutagen. 61:355-360, 2020. © 2020 Wiley Periodicals, Inc.

Associations of blood lead levels with multiple genotoxic biomarkers among workers in China: A population-based study.

Carcinogenic effects from low doses of lead (Pb) exposure to populations have been suspected but not concluded. Therefore, a large-scale cross-sectional study was conducted by us to investigate genotoxic effects from Pb exposure during 2016-2018 in North China. Blood lead levels (BLLs) and cumulative blood lead levels (CBLLs) were measured. Multiple relevant biomarkers were used to assess genotoxicity of Pb: mitochondrial DNA copy number (mtDNAcn, n = 871), Comet Tail Intensity (n = 872), γ-H2AX (n = 345), relative telomere length (rTL, n = 757), micronuclei (MN, n = 934) and phosphatidylinositol glycan class A mutation (PIG-A, n = 362). The BLL data show right-skewed distribution, with increase of the median (P25, P75) from 17.4 (8.9, 26.4) µg/dl in 2016 to 18.5 (10.5, 27.2) µg/dl in 2017, and to 20.8 (11.3, 31.0) µg/dl in 2018. Multivariate regression analyses show that mtDNAcn was non-linearly associated with BLLs or CBLLs, i.e. decreased at low levels but increased at the higher levels. Comet and Micronuclei data show positive dose-response relationships with BLLs as well as CBLLs. γ-H2AX data show an overall increased trend with BLLs while rTL data show a shortening trend. No associations were found for PIG-A mutation with Pb exposure. Our findings indicate that current low dose exposure to Pb can still cause health hazards to occupational populations, and the mechanism may be via the induction of DNA & chromosome damage rather than via the mutagenesis pathway.