氯乙烯装置防护设施改进对接触人群肝脏损伤状况的影响

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

目的比较氯乙烯单体(vinyl chloride monomer,VCM)装置关键控制点的接触人群于防护设施改进前、后的肝脏功能指标及B超结果的变化情况,评估防护设施改进对促进劳动者健康和提高生产安全的有效性,并分析影响因素。方法于2020年7月收集天津某电石法聚氯乙烯厂防护设施改进前(2013年)与改进后(2016年)VCM装置区防护设施的改进情况,获得职业病危害因素监测资料及员工职业健康体检结果。选择涉及8种VCM接触岗位的227名劳动者为接触组,选取无化学有害因素接触史的179名该企业的其它部门劳动者为对照组。通过比较防护设施改进前后VCM岗位接触水平、尿亚硫基二乙酸(thiodiglycolic acid,TDGA)含量、肝功、生化指标、肝脏B超结果的差异,评估关键控制点防护设施改进的有效性;同时以二分类Logistic回归分析影响肝脏B超结果异常的贡献因素;以单因变量一般线性回归模型分析各影响因素间是否存在可能的显著交互作用。结果防护设施改进前,8种岗位接触VCM的C_(TWA)均已超过1~2倍职业接触限值(OEL=10 mg/m^(3)),合成外操工和现场采样工接触1,2-DCE的C_(TWA)处于50%~1OEL,其它职业病危害因素均符合限值要求;接触组尿中TDGA含量与岗位VCM平均水平间呈较强正相关性(r=0.79,P<0.05)且接触组尿中TDGA含量、丙氨酸氨基转移酶(alanine aminotransferase,ALT)、γ-谷氨酰转肽酶(γ-glutamyl transpeptidase,GGT)及肝脏B超结果异常率均显著高于对照组(P<0.05或P<0.001)。改进后,8种岗位接触VCM、1,2-DCE及NH_(3)的C_(TWA)及TDGA水平均显著低于改进前水平,且符合卫生限值要求,接触组在ALT、GGT及B超中肝脏内钙化灶及肝回声增粗、肝脏周围纤维化、肝脏多发囊肿等结果的异常率上略低于改进前水平,但仍显著高于对照组(P<0.05或P<0.001)。性别、工龄、周接触时间、VCM岗位接触水平、尿中TDGA含量于防护设施改进前、后均为接触组肝脏B超结果异常的独立影响因素(P<0.05或P<0.001)。其中性别与工龄(F=4.028,P=0.044)、周接触时间与尿中TDGA含量(F=2.183,P=0.046)于防护设施改进前、后在肝脏B超异常率的贡献上存在显著交互作用(P<0.05)。结论该厂对VCM装置区防护设施实施的改进有效降低了空气中以VCM为主的职业病危害因素接触水平,但即使在低浓度接触水平下VCM仍对劳动者的肝脏造成损伤,这与劳动者的周接触时间较长、接害工龄较长及日常高脂饮食有关。

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.