Cancer mortality of workers exposed to lead:A retrospective cohort study in a smeltery

Abstract

Objective To determine the mortality of cancer and relative risk of long-term lead exposure workers and to study the relation between occupational lead exposure and cancer. Methods A cohort study including 6 971 male workers employed for at least one year before Jan 1,1985 and still alive at this time,and a subcohort of 3 344 of them worked at lead-exposed workshop was conducted.The study was followed up from Jan 1,1985 to Dec 31,1997.Standardized mortality ratios(SMR) and relative risks(RR) were calculated.Cumulative exposure dose was used for a dose-response analysis. Results For 6 971lead exposure workers,SMR and its 95%CI for lung cancer were 128.0(101.1～159.7).SMR for lung cancer was 463.7(P<0.01) among lead exposure workers employed after Jan 1,1965.SMR for nasopharyngeal cancer was 408.0(P<0.01),lung cancer 156.6(P<0.01),among workers with lead-exposed history and length of more than 20 years.RR and 95%CI for neoplasms(in total),malignant neoplasms(in total),oesophageal cancer,stomach cancer,liver and biliary tract cancer,lung cancer,bladder cancer were 3.25(2.43～3.89),3.28(2.54～4.32),3.57(1.08～10.47),2.93(1.15～4.87),4.58(2.03～9.97),8.58(4.82～15.11),6.66(2.83～13.01) respectively.RR for malignant neoplasms at medium (0.1～0.5 mg*m-3*a-1) and high(0.5～ mg*m-3*a-1) cumulative exposure doses were 1.62(P<0.05) and 1.70(P<0.05) respectively and there was an increasing trend of RR as the doses raised.RR for lung cancer at medium and high exposure doses were 2.55 (P<0.05) and 2.31(P<0.05) respectively. Conclusions The increased death risks may relate to lead exposure.However,further study under controlling the harmful factors of other occupational exposure and non-occupational exposure is necessary.