| China has achieved the largest production and application of Indium(In)in the world,and has a large occupational population of In exposure.Case reports of In-related lung disease in workers that have emerged during the past decade have raised public concern regarding the human toxicity of In and its compounds.The occupational chemical poisoning caused by In and its compounds was listed as legal occupational disease in China in 2013.However,occupational epidemiological studies of workers from In smelting and application plants are rare in our country.In this study,we focused on In production and In application plants and chose In smelting plants and liquid crystal display panel production plants,with the main objective of characterizing In exposure in the plants by measuring concentrations in both air samples and biological samples;we also carried out occupational health risk assessment combined with the survey data and toxicological data,and explored the exposure biomarkers and the effect biomarkers of In exposure workers.The results provided basis data to formulate and revise related policies and standards of occupational health.1.Occupational exposure to In of In exposure workers from In smelting plantsWe selected four smelting plants of different sizes in different areas and recruited 494 subjects in total.(1)Exposure study:According to GBZ159-2004 "Specifications of air sa,mpling for hazardous substances monitoring in the workplace",we collected 219 personal breathing zone air samples from the workers,and the samples from office workers were considered as controls.The geometric mean concentrations of In in the air samples from the smelting workers and office workers were 1.22?g/m3 and 0.35?g/m3,respectively.The concentrations were significantly higher in smelting workers than those in office workers(P<0.05).In concentrations in the air samples from different work procedures were significantly different(P<0.05),with the higher concentrations in workers of ingot casting.metathesis,and electrolysis than in workers from other procedures.However,no concentration in air samples exceeded the permissible concentration-time weighed average(PC-TWA)of China(0.1 mg/m3).(2)Biomonitoring:We collected 424 blood,430 serum,and 477 urine samples from subjects in smelting plants.In concentrations in blood,serum and urine of the smelting workers were 0.09?g/L,0.07?g/L,and 0.16 ?g/L,respectively,which were significantly higher than those of office workers(P<0.05).Smoking,gender or work age had no significant effects on In concentrations in biological samples.In concentrations in the air samples from different work procedures were significantly different(P<0.05),with the higher concentrations in workers of ingot casting,and electrolysis than in workers from other procedures.The result was similar to that of air samples.2.Study of biomarkers of In and its compounds for In smelting workersWe calculated the correlations of In concentrations between bio samples from the smelting workers and the corresponding air samples.The result showed positive correlations between air In and urine In concentrations(r = 0.481,P<0.01)and between air In and blood In concentrations(r = 0.448,P<0.01).But no correlation was found between serum In and air In concentrations.In this study,no correlation was found between the concentration of serum In and the effect indicators such as KL-6,SP-A and SP-D.The results indicated that blood In and urine In have the potential to be the exposure biomarker to reflect the In exposure level of In smelting workers.3.Occupational exposure to In of workers from liquid crystal display panel manufacturing plants(1)Exposure study:the average concentrations of In in the inhalable dust and total dust were 0.39±0.17mg/m3 and 1.03±0.94mg/m3,respectively,both of which exceeded the PC-TWA.(2)Characterization of In contained particles:the particles produced by grinding operation mainly contained fine particles(particle size at 0.1?2.5?m),which accounted for more than 97%of the total particles.The particle number was 16264pt/L during the grinding operation,and 190pt/L for background value of workshop,with statistically significant difference(P<0.05);the real-time surface area concentration was 1.98?m2/cm3 during the grinding operation,and 0.13?m/cm3 for background value,with statistically significant difference(P<0.05);the real-time particle mass concentrations for grinding operation and background were 7.66?g/m3 and 1.86?g/m3,respectively,the difference was statistically significant(P<0.05).The concentration of particle number has a good correlation with that of surface area(r=0.581,P<0.01);there was a weak correlation between the number concentration and the mass concentration(r=0.367,P<0.01),and no significant correlation was observed between surface concentration and mass concentration.(3)Biomonitoring:The biomonitoring results of the liquid crystal display panel manufacturing plant indicated that In concentrations in all the bio samples were lower than the limit of detection(<0.03?g/L).The results of respirator fit test showed that the workers' individual respirators were befitting and has a good protective effect,this explain why the In was not detected in biosamples.4.ConclusionIn this study,we systemly studied the internal and external exposure levels of the workers from In smelting plants.No concentration in air samples from In smelting workers exceeded the permissible concentration-time weighed average(PC-TWA)of China(0.1 mg/m3),but the bio monitored results indicated that some workers had a higher internal exposure to In,which suggested that nondestructive biological monitoring should be conducted together with the routine air concentration monitoring.Thus we can observe the occupational disease and take the protection measures in time.In In smelting plants,workers from ingot casting,electrolysis and metathesis procedures belong to groups of high In exposure.So they should be considered as key working group to strengthen the monitoring and protection,and reduce In exposure level.The concentrations of blood In and urine In of In smelting workers have good correlations with those of air In,which indicated that blood In and urine In can reflect recent In exposure and be used as biological monitoring indicators of In smelting workers.In concentrations in the air samples from liquid crystal display panel manufacturing plants were higher than PC-TWA,but the dose of internal exposure was very low due to the effective personal protection of the plants.Particles generated in grinding operation were main fine particles(particle size of 0.1-2.5 ?m),which showed particle number concentration and surface area concentration in the workplace should be measured together with the mass concentration of In.Thus the exposure characteristics of particles in the workplaces can be accurately evaluated.A present,the studies on toxicology,toxicokinetics and epidemiology of In and its compounds are still inadequate.For low exposure population,longitudinal study should be conducted to determine the consequences of long-term exposure to In and its compounds,and then to explore effective strategies to prevent occupational diseases.For high exposure population,routine nondestructive monitoring frequency should be strengthened in order to observe related diseases and take protection measures in time.In addition,since the risk caused by In is not yet clear,we suggest that the plants should reduce the In exposure levels in working places as possible as they can,and take some prevention measures in time when related health damage is observed. |
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