Occupational Exposure to Silica Dust and Silicosis Risk in Chinese Noncoal Mines: Qualitative and Quantitative Risk Assessment.

BACKGROUND: Despite increasing awareness, silica dust-induced silicosis still contributes to the huge disease burden in China. Worryingly, recent silica dust exposure levels and silicosis risk in Chinese noncoal mines remain unclear. OBJECTIVE: We aimed to determine recent silica dust exposure levels and assess the risk of silicosis in Chinese noncoal mines. METHODS: Between May and December 2020, we conducted a retrospective cohort study on 3 noncoal mines and 1 public hospital to establish, using multivariable Cox regression analyses, prediction formulas of the silicosis cumulative hazard ratio (H) and incidence (I) and a cross-sectional study on 155 noncoal mines in 10 Chinese provinces to determine the prevalence of silica dust exposure (PDE), free silica content, and total dust and respirable dust concentrations. The qualitative risk of silicosis was assessed using the International Mining and Metals Commission's risk-rating table and the occupational hazard risk index; the quantitative risk was assessed using prediction formulas. RESULTS: Kaplan-Meier survival analysis revealed significant differences in the silicosis probability between silica dust-exposed male and female miners (log-rank test χ21=7.52, P=.01). A total of 126 noncoal mines, with 29,835 miners and 4623 dust samples, were included; 13,037 (43.7%) miners were exposed to silica dust, of which 12,952 (99.3%) were male. The median PDE, free silica content, total dust concentration, and respirable dust concentration were 61.6%, 27.6%, 1.30 mg/m3, and 0.58 mg/m3, respectively, indicating that miners in nonmetal, nonferrous metal, small, and open-pit mines suffer high-level exposure to silica dust. Comprehensive qualitative risk assessment showed noncoal miners had a medium risk of silicosis, and the risks caused by total silica dust and respirable silica dust exposure were high and medium, respectively. When predicting H and I over the next 10, 20, and 30 years, we assumed that the miner gender was male. Under exposure to current total silica dust concentrations, median I10, I20, and I30 would be 6.8%, 25.1%, and 49.9%, respectively. Under exposure to current respirable silica dust concentrations, median I10, I20, and I30 would be 6.8%, 27.7%, and 57.4%, respectively. These findings showed that miners in nonmetal, nonferrous metal, small, and open-pit mines have a higher I and higher qualitative silicosis risk. CONCLUSIONS: Chinese noncoal miners, especially those in nonmetal, nonferrous metal, small, and open-pit mines, still suffer high-level exposure to silica dust and a medium-level risk of silicosis. Data of both total silica dust and respirable silica dust are vital for occupational health risk assessment in order to devise effective control measures to reduce noncoal mine silica dust levels, improve miners' working environment, and reduce the risk of silicosis.

Association of IL-8 and CXCR2 with AST/ALT Ratio in Liver Abnormalities Screening during Oxidative Stress Injury Caused by VCM.

Liver impairment caused by VCM has been linked to irreversible damage such as fibrosis, necrosis, hepatocellular carcinoma, and liver angiosarcoma. However, the ability to detect abnormalities during initial phase have not been achieved so far. Thus, this study aimed to investigate the effect of interleukin 8 (IL-8) and C-X-C chemokines 2 (CXCR2) on screening for a VCM-exposed group (n = 227) from a PVC manufacturing factory compared to a control group (n = 110) in Tianjin City in 2020 with influence factors evaluation. Ambient concentrations of VCM and health archives from 2012 to 2018 were collected for establishing the dose-effect trend. A cross-sectional survey in 2020 was performed to measure TDGA, IL-8, CXCR2, 8-OHdG, SOD, GPX, CAT, MDA, and ROS levels. Results indicated a continuous increased incidence on liver abnormalities despite a fluctuated downward trend in cumulative time-weighted average (CTWA) VCM concentrations over the years. ALT, AST, and AST/ALT ratio all contributed to liver abnormalities that contained fatty liver, liver calcification, and liver cysts, IL-8 and CXCR2 correlated with each other strongly and showed significant associations with oxidative stress markers, even AST/ALT ratio. IL-8 (>1547 µg/m3) or CXCR2 (<139 µg/m3) influenced the AST/ALT ratio through reciprocal interactions under oxidative stress injury, CXCR2 (>222 µg/m3), working years of 21 to 30 (a) and 11 to 20 (a), TDGA (>1.52 mg/L), alcohol consumption, smoking habit, and a less sleeping duration of <4 h per day would also be potential factors affecting the AST/ALT ratio. In conclusion (1) even with decreased VCM concentrations in PVC manufacturing factories liver abnormalities that contained fatty liver, liver calcification, and liver cysts could still occur due to oxidative stress injury with involvement of IL-8 and CXCR2. The status of protective measure and appropriate mask types also play a role; (2) the AST/ALT ratio could be a specific indicator for detecting abnormalities when combined with liver B ultrasonography results before impairment altered from bad to worse; and (3) factors such as definite medication history, fully broken protective facilities, alcohol consumption, less sleeping duration, inappropriate mask types, and longer working years could also influence AST/ALT ratio alterations through complex interactions.

[Liver impairment status toward workers exposed to vinyl chloride under different techniques].

OBJECTIVE: To analyse potential differences towards liver impairment status on vinyl chloride monomer(VCM) exposed population from technique under acetylene hydrochlorination to the one of ethylene oxychlorination respectively and to explore the possible reasons, which will pave the way for occupational health promotion in terms of hazard reduction. METHODS: a cross-sectional study was initiated between June and September in 2022 towards 2 groups of VCM exposed population from the facility of acetylene hydrochlorination(n=78) and the one of ethylene oxychlorination(n=69) in a PVC petrochemical complex enterprise(abbreviation of H) in Tianjin City. The demographic information concerning age, gender, messages on occupational history, field investigation were inquired through questionnaire interview. Then, venous blood(4 mL/person) and urine(10-50 mL/person) were collected during the physical exam phase and indices of 8-hydroxy-2 deoxyguanosine(8-OHdG) in blood and thiodiglycolic acid(TDGA) in urine were detected through ELISA and solid phase extraction-ion chromatography respectively. RESULTS: The 2 groups of population were matched well in terms of average age distribution and gender composition ratio, with significant differences on population composition ratio were found on variables of working years, alcohol consumption and daily sleeping duration(P<0.01 or P<0.05). It was found that the average content of TDGA in acetylene hydrochlorination group was(0.81±0.05)mg/L while the content in ethylene oxychlorination group reached to(0.83±0.06)mg/L, noteworthy differences were only found among 6 posts in the acetylene hydrochlorination group and 5 others in the ethylene oxychlorination group after classification for specific posts, however, the average concentration of 8-OHdG in acetylene hydrochlorination group(122(78.3, 168.8) µg/m~3) was different from the one in ethylene oxychlorination group(101.7(79.6, 149.7) µg/m~3)(Z=6.82, P<0.05). Moreover, a series of positive correlations in moderate intensity between 8-OHdG concentration and TDGA content were observed among posts of polymerization cleaners(r=0.53), aggregation operators(r=0.47), maintenance repairers(r=0.45), sampling operators(r=0.41) in acetylene hydrochlorination group(P<0.05) and posts of cracking reactants(r=0.64), DCS operators(r=0.51), oxychlorination operators(r=0.50) and chemical loaders(r=0.44) in ethylene oxychlorination group(P<0.05). Liver function indices such as content on ALT(χ~2=15.41, P<0.01), AST(χ~2=9.95, P<0.01) and ALP(χ~2=3.79, P<0.01) were different in the 2 groups population with statistical significance, then proportions on population composition ratio that exceeded normal ranges of indices on ALT, AST, AST/ALT ratio, ALP and Alb/Glb ratio were higher in acetylene hydrochlorination group than ones in ethylene oxychlorination group with great significance(P<0.05), so as to the abnormalities in liver B altrosonography test between groups(χ~2=17.33, P<0.01). Binary logistic regression model indicated that 8-OHdG concentration in blood that exceed 90 µg/m~3, TDGA content in urine that exceed 0.60 mg/L, working years that were over 10a, alcohol consumption, sleeping duration less than 6 h per day and male workers were potential risky factors for liver impairment(P<0.05). CONCLUSION: The degree on liver impairment status was higher in acetylene hydrochlorination group than ones in in ethylene oxychlorination group under the same PVC factory, which might be associated with the oxidative stress injury induced from the combination of higher VCM concentration at workplaces, longer cumulative exposure time, longer working years, alcohol consumption habits and sleep shortage caused by shift work patterns.

[Improvement of protective facilities in vinyl chloride units on liver injury status of occupational exposed group].

OBJECTIVE: To comprehensively evaluate the effectiveness of improvement of protective facilities in a vinyl chloride monomer(VCM) on promotion toward health status of occupational exposed group and safety production at poly-vinyl chloride(PVC) by comparing the liver function indicators and inspection result before and after the improvement, and to analyze the possible influential factors. METHODS: The information collection concerning facilities improvement in 2013 and 2016, identification toward critical controlling points, data or detection result from occupational on-site survey and physical examination were originated in July 2020, and 227 VCM exposed workers and 179 others without chemical reagents exposure history from production factory with calcium carbide process in Tianjin City were selected as objects. The effectiveness toward improvement of protective facilities in critical controlling points that occupational exposed workers usually involve in were evaluated through comparison toward VCM concentration result, thiodiglycolic acid(TDGA) content in urine, indicators on liver function and biochemistry and liver ultrasound. At the mean time, both binary Logistic regression analysis was used to screen the possible factors that contributed to abnormal symptoms and single dependent variable general linear regression model was used to find out the mutual interaction among influential factors. RESULTS: Prior to improvement on protective facilities, the C_(TWA)of VCM exposed by all 8 positions in G had exceeded 1 to 2 folds of occupational exposure limit(OEL=10 mg/m~3) and the position of synthetic operator and field sampling man were ones exposed to 1, 2-DCE with the range from 50% to 1 OEL, others hazard factors were found to meet relative OELs. Next, the content of TDGA in urine of exposed group was found to correlate strongly to the average concentration of VCM(r=0.79, P<0.05), and result of TDGA content, alanine aminotransferase(ALT), γ-glutamyl transpeptidase(GGT) and abnormal rate toward liver ultrasound test in exposed group were much higher than ones in control group with significant differences(P<0.05 or P<0.001). By contrast, after the improvement, the exposure level toward all identified hazard factors were declined to meet OEL levels with significant differences in TDGA content, and result of ALT, GGT and abnormal rates toward symptoms in liver ultrasound test such as liver calcification with thickened liver echo, peripheral fibrosis of the liver, multiple hepatic cysts were markedly lower than ones before improvement and still were higher than ones in control group(P<0.05 or P<0.001). Further, parameters of gender, length of employment, weekly contact time, VCM exposed level, TDGA content were all important contributing factors to abnormal symptoms in liver ultrasound test before and after improvement on protective facilities(P<0.05 or P<0.001), in which a significant interaction effect between gender and length of employment(F=4.028, P=0.044), weekly contact time and TDGA content(F=2.183, P=0.046) in urine were found in contribution analysis to abnormal symptoms in liver ultrasound test(P<0.05). CONCLUSION: The improvement measure carried out in VCM facilities by this PVC production factories with calcium carbide process effectively reduced the ambient concentration of hazard factors mainly led by VCM, but workers might still be at risk of liver injury even under VCM exposure at relative lower level, which may referred to factors of long weekly contact time, long length of employment and high fat diet.

Improvements in protective measures in factories with acetylene hydrochlorination and ethylene oxychlorination techniques declined risk assessment levels and affected liver health status.

Acetylene hydrochlorination and ethylene oxychlorination are the two most common methods of producing vinyl chloride monomer (VCM), which has been linked to liver impairment, hepatocellular carcinoma (HCC), and angiosarcoma of the liver (ASL) in occupational settings. However, whether and how these impairments could be effectively improved from workplace root causes has yet to be discovered. This study aimed to evaluate whether improvements in protective measures in groups Y (408 subjects) and Z (349 subjects) could have an influential impact on the alleviation of liver impairment by comparing risk assessment levels under several semi-quantitative models and results from liver ultrasound detection and liver function tests before and after the improvement. Importantly, significant differences in constituent ratio involved in parameters among age, length of employment, weekly exposure time, smoking status, alcohol consumption, and sleeping quality were found between Y and Z before improvement took place in 2020 (P < 0.05 or P < 0.001), and population distribution by gender between Y and Z was in a large homogeneity with differences in age and length of employment. CSTE involves ore breaking, acetylene generation, steam stripping, outward processing, and welding maintenance, was disqualified in 2020 compared to OEL, and was said to have declined to meet OEL requirements by 2021. Further, a negative correction of fresh air requirement and ventilation air changing rate with ambient concentration toward hazards in Y was stronger in 2021 than in 2020. Significant differences in risk levels in Y between 2020 and 2021 were found as ore breaking, acetylene generation, steam stripping, outward processing, VCM polymerization, welding, and repairing, decreasing to relatively lower risk levels in 2021 from the original ones in 2020 only under the semi-quantitative comprehensive index model. Abnormal rates toward other hepatic symptoms decreased in the majority of positions after the improvement, as referred to by alterations such as ALT, AST, and GGT. Overall, the effect of improvements on protective measures effectively reduced positions' risk assessment levels through ventilation enhancement and airtight strengthening, which further affected abnormal rates toward other hepatic symptoms, and alterations such as ALT, AST, and GGT were much more significant in Y than effect in Z.

[Occupational risk assessment levels before and after improvement on fueling devices in ammoniation facilities from 2 nuclear plants].

OBJECTIVE: To evaluate and compare possible changes of individual health risk levels for ammonia exposed positions from ammoniation facilities in 2 nuclear power plants(X and Y) through occupational risk assessment models(OHRA) before and after devices improvement. METHODS: This study tried to understand the improvement of fueling devices in ammoniation facilities, to identify the ammonia exposed positions and their working content, to collect information on protective measures and personal protective equipment situation through on-sites survey and detailed records of work days. Next, detection on C_(STE) of ammonia at different worksites and C_(TWA) of 10 involved positions were conducted, fresh air requirement and ventilation air changing rates were calculated through wind speed detection or collected directly. Finally, a semi-quantitative comprehensive index model and a quantitative non-carcinogenic model from standard GBZ/T 298-2017 were utilized to assess risk levels before and after improvement. RESULTS: After devices improvement, a series of innovations were observed, followed by:(1) ammonia steal tanks in stacking storage were replaced by metal pressure sealing tanks for reduction of exposure frequency and long time storage. (2) manual filling pattern was totally substituted by automatic filling devices with new installed ventilation systems and alarming apparatus. (3) increasing ventilation effect by doors opening when ammonia was filling. In this regard, conentration levels(C_(STE)) referred to positions of chemical analysis engineers, chemical sampling engineers, nuclear maintenance workers at 3# unit from X, and regular island operators at 1#unit, patrolling operators at 2# unit from Y were declined to qualified levels after improvement from unqualified levels before that, and significant difference of C_(STE )detected before and after improvement were found statistically(Z=10.856, P<0.001). C_(TWA )were all within the qualified ranges before and after improvement for relatively short cumulative exposure time. Moreover, the ventilation air changing rates from related indoor sectors were increased to 13.0 to 30.9 times/h after improvement which indicated a statistical difference as compared to quantitative ranges before started(Z=11.670, P<0.001). Further, a relative negative correlation was observed between C_(STE )and ventilation air changing rates(r=-0.39, P<0.05) while no correlation between them was spotted after improvement(r=-0.051, P>0.05). In addition, most positions like chemical analysis engineers and others changed their risk levels to a lower one from that they used to be after improvement with an observed significant difference(Z=1.345, P<0.05), by contrast, risk levels of positions like nuclear maintenance workers at 3#unit or patrolling operators at 4#unit increased a level or remained the same before and after improvement might be result ed from enhancement of cumulative exposure time. No significant difference among position risk levels under the quantitative non-carcinogenic model was observed(Z=0.447, P>0.05). CONCLUSION: The measure of devices improvement indeed decreased the ambient ammonia concentrations at workplaces of ammoniation facilities in X and Y and changed individual risk levels for most involved positions. The semi-quantitative comprehensive index model was more appropriated for self-contrast risk assessment application than quantitative non-carcinogenic model did, especially when improvement occurred.

[Risk assessment of noise-induced hearing loss among workers in railway transportation equipment manufacturing enterprises].

OBJECTIVE: To analyze the noise exposure and hearing loss of workers in railway transportation equipment manufacturing enterprises, and to assess the risk of hearing loss caused by noise. METHODS: From 2018 to 2020, an investigation was carried out on 3 railway transportation equipment manufacturing enterprises in Hubei Province and Hunan Province. A total of 840 noise-exposed workers were selected, the individual noise exposure level(L_(Aeq·8 h)) and hearing loss level were measured, the cumulative noise exposure(CNE) was calculated, and the relationship between hearing loss and technological process, working time and CNE were analyzed. ISO1999:2013 was used to calculate the change of hearing threshold and the risk of noise-induced hearing loss after 40 years old. RESULTS: The median age of workers was 32 years old, and the median working age for noise exposure was 10 years. The distribution of positions is mainly welding, machining, assembly and painting.79.5%(120/151) of the individual noise exposure doses exceeded 85 dB(A), and the average L_(Aeq.8 h) was 89.9(A). There were significant differences in the proportion of hearing loss among workers in different process units(χ~2= 29.597, P<0.001), and the proportion of hearing loss in the preparation and steel structure units was higher. The proportion of hearing loss showed an upward trend with the increase of working years(χ~2=164.462, P<0.001), and the high-frequency combined speech-frequency hearing loss(26.7%) increased significantly after working for more than 20 years. With the increase of CNE, the proportion of high-frequency hearing loss and the proportion of high-frequency combined speech-frequency hearing loss increased accordingly(χ~2=192.544, P<0.001). The proportion of high frequency combined speech frequency hearing loss increased significantly in the group with CNE greater than 105 dB(A)·years. It is predicted that the risk of hearing loss caused by noise in assemblers appears earliest and the risk is the greatest. The risk of high noise-induced frequency hearing loss of assemblers was 3.6%-8.6% at the age of 40, 20.2% at the age of 50, 22.0% at the age of 60. The risk of high-frequency combined speech-frequency hearing loss of assemblers was 1.2%-6.2% at the age of 50 and 8.6% at the age of 60. CONCLUSION: The noise hazard is serious and widely distributed in railway transportation equipment manufacturing enterprises, and the proportion of hearing loss increases with the increase of working time and CNE. Although ISO1999:2013 predicts that there may be an underestimation of noise-induced hearing loss in workers, it can be used as an early warning of hearing loss to identify the potential risk of hearing loss in the population.

Noise exposure assessment of non-coal mining workers in four provinces of China.

Objective: This study aimed to understand the noise exposure of non-coal mines in China to take appropriate controls to protect workers' health. Methods: An assessment of non-coal miners' noise exposures was conducted in four provinces in China. Individual noise exposure levels were measured, and the survey on the hearing protector device (HPD) equipment was administered. Results: 423 noise dosimeter measurements were obtained, including drilling, blasting, ore drawing, transportation, winching, crushing, screening and ball milling, and auxiliary (air pressure, pump, and maintenance). A total of 31.9% of the individual noise levels (LEX,8h) exceeded 85 dB(A), and the median dosages of non-coal miners with high noise exposure were: excavation workers-89.1 dB(A), mill operators-88.7 dB(A), and crusher operators-87.0 dB(A). The noise dose of underground mine workers is higher than that of surface mine workers (P < 0.001). A total of 53.7% of non-coal mining enterprises are not equipped with HPD for workers, mainly small and micro enterprises. Conclusions: High levels of hazardous noise exposure are typical in non-coal mines. Noise exposure data can help to develop more feasible noise controls.

Occupational Dust Hazards and Risk Assessment of Coal-Fired Thermal Power Plants of Different Capacities - China, 2017-2019.

WHAT IS ALREADY KNOWN ABOUT THIS TOPIC?: Silica dust and coal dust are the main occupational hazards in coal-fired thermal power plants, which mainly exist in coal transportation workplaces, combustion milling workplaces, and ash removal workplaces. WHAT IS ADDED BY THIS REPORT?: The overall environmental and personal dust exposure levels decrease with an increase in the capacity of coal-fired thermal power plants, the overall dust hazard risk level of the workforce in coal-fired is Medium. WHAT ARE THE IMPLICATIONS FOR PUBLIC HEALTH PRACTICE?: Dust management should be conducted in the coal-fired thermal power plant in 300 million watt units because it has the highest dust exposure level, and ash removal workplaces and combustion milling workplaces are key control points for dust hazards.