Lung cancer risks among lead smelter workers also exposed to arsenic.

Recent publications indicate an increased incidence of lung cancer in non-ferrous smelter workers exposed to lead. The present study provides further data on selected subgroups in one such cohort. The cohort was based on 3979 smelter workers employed for at least 1 year between 1928 and 1979, and also exposed to lead and included in the Blood Lead Register that was started at the smelter in 1950. Two subcohorts were formed from the original cohort. One consists of 710 workers employed at the lead departments (Lead subcohort 1), and the other of 383 workers employed at the lead departments (Lead subcohort 2), but never at other works where an excess lung cancer risk was previously identified. Standardized Cancer Incidence Rates (SIR) 1958-1987 were calculated relative to county rates. In the subcohorts, arsenic exposure in lung cancer cases was assessed in detail based on occupational hygiene information from the company. Lung cancer incidence was raised in both subcohorts (Lead subcohort 1: SIR 2.4; 95% CI 1.2-4.5; Lead subcohort 2: SIR 3.6; 95% CI 1.2-8.3). Total cancer incidence in the cohorts was not increased. A detailed study of arsenic exposure in the 10 lung cancer cases in these two subcohorts revealed that all but one of these cases had a significant exposure also to arsenic. An elevated incidence of lung cancer was observed in smelter workers exposed to lead. However, considerable arsenic exposure also occurred in a majority of the lung cancer cases in the investigated subcohorts. In this multifactorial exposure situation it has not been possible to separate the carcinogenic effects of lead and arsenic, but a possible interaction between these metals may be involved in explaining the carcinogenic risks.

Cumulative lead exposure in relation to mortality and lung cancer morbidity in a cohort of primary smelter workers.

OBJECTIVES: The purpose of this study was to determine the mortality and cancer incidence of long-term lead smelter workers at a primary smelter. METHODS: A cohort of 3979 workers employed for at least 1 year during 1928-1979 and a subcohort of 1992 workers employed in lead-exposed departments (lead only workers) was formed. The expected mortality in 1955-1987 and cancer incidence in 1958-1987 were calculated relative to the county rates, specified for cause, gender, 5-year age groups, and calendar year. A cumulative blood-lead index was used for the dose-response analyses. RESULTS: The lung cancer incidence of the total cohort [standardized incidence ratio (SIR) 2.8, 95% confidence interval (95% CI) 2.1-3.8] and the group with the highest exposure (SIR 3.1, 95% CI 2.0-4.6) was high. Similar risk estimates were observed with a latency of 15 years. The workers hired before 1950 had higher lung cancer risk estimates (SIR 3.6, 95% CI 2.6-5.0) than the workers hired later (SIR 1.3, 95% CI 0.6-2.6, no latency period). The risk estimates for lung cancer were further elevated in the subcohort of lead-only workers (SIR 5.1, 95% CI 2.0-10.5 in the highest exposed subgroup; latency period of 15 years). No excesses of other malignancies were noted. CONCLUSIONS: The increased relative risks were probably mainly due to interactions between lead and other carcinogenic exposures, including arsenic. Further study is required concerning such possible interactions before a role in the induction of lung cancer can be ascribed to lead.

Lead in tissues of deceased lead smelter workers.

Smelter workers are exposed to a number of metals and other substances in dust, fumes and gases. The concentrations of lead in liver, lung, kidney, brain, hair and nails were determined in 32 deceased, long-term exposed male lead smelter workers, and compared with those of 10 male controls. The lead levels in liver, lung, kidney and brain were analyzed by atomic absorption spectrophotometry. X-ray fluorescence was used for the determinations in hair and nails. Lead in blood had been determined repeatedly in the lead workers since 1950, which made it possible to calculate a time-integrated blood lead index for each worker. The highest lead levels in soft tissues were found in liver, followed in order of concentration by kidney, lung and brain, among both exposed workers and controls. These organ lead concentrations were all significantly higher among the workers as compared with the control group (p < or = 0.02). The largest difference between workers and controls was found in brain tissue (ratio between median values = 5.6). The lead levels in hair and nails were of the same magnitude in the two groups. The workers showed positive correlations between lead concentrations in liver and kidney (Spearman's rho = rs = 0.59; p < 0.001), liver and hair (rs = 0.51; p = 0.003), liver and nails (rs = 0.52; p = 0.002) and hair and nails (rs = 0.52; p = 0.002). Lead concentrations in kidney correlated well with lead levels in hair (rs = 0.57; p = 0.001) and nails (rs = 0.51; p = 0.003), respectively. The positive correlation between the lead concentrations in liver and kidney indicates that these organs belong to the same soft tissue lead pool in the body. In retired lead workers, positive correlations were observed between the lead concentrations in liver and the cumulative blood lead index (CBLI) (rs = 0.50; p = 0.016), as well as between lead levels in kidney and CBLI (rs = 0.51; p = 0.014).

Biological specimen bank for smelter workers.

The biological specimen bank was initiated by the department of Environmental Medicine and the department of Medicine at the University of Umeå in 1975. The aims of the bank are to collect information on trace elements in human organs. Special attention is focused on the influence of occupational exposure. Tissue samples are taken from deceased workers from a copper and lead smelter in northern Sweden. Control specimens have been collected from deceased normal individuals from four control areas. Lung, liver and kidney samples are collected with quartz instruments and stored in quartz ampoules to avoid contamination. Other samples, e.g. bone, brain, fat, hair, heart muscle, nails, skin and stomach are taken with common autopsy instruments and stored in acid-washed polyethene vessels. The samples are stored at -20 degrees C. The elements Sb, As, Cd, Cr, Co, La and Se are analyzed by neutron activation analysis, Pb and Zn by atomic absorption spectrophotometry. The findings over time can be related to a number of factors: normal values in tissues, airborne exposure and causes of death. Special attention is paid variation over time, reevaluation of threshold limit values and risk assessment.

In vivo measurements of lead in bone in long-term exposed lead smelter workers.

In-vivo measurements of lead concentrations in calcaneus (mainly trabecular bone) and tibia (mainly cortical bone) were performed by x-ray fluorescence (XRF) in 70 active and 30 retired lead smelter workers who had long-term exposure to lead. Comparison was made with 31 active and 10 retired truck assembly workers who had no known occupational exposure to lead. After physical examination, all participants provided blood and urine samples and answered a computerized questionnaire. Since 1950, blood lead has been determined repeatedly in lead workers at the smelter, which made it possible to calculate a time-integrated blood lead index for each worker. Lead concentrations in blood, urine, calcaneus, and tibia in active and retired lead workers were significantly higher than in the corresponding control groups (p < .001). The highest bone lead concentrations were found among retired lead workers (p < .001), which was the result of considerably higher lead exposure during 1940 to 1960. Lead concentrations in calcaneus in active lead workers were significantly higher than in tibia when expressed in ug of lead per gram of bone mineral, which suggests a quicker absorption over time in this mainly trabecular bone. The estimated biological half-times were 16 y in calcaneus (95% confidence interval [95% CI] = 11-29 y) and 27 y in tibia (95% CI = 16-98 y). A strong positive correlation was found between lead concentrations in calcaneus and tibia for all lead workers (r = 0.54; p < .001). A strong positive correlation was also found between the bone lead concentrations and the cumulative blood lead index. Blood lead, at the time of study, correlated well with bone lead concentrations in retired--but not in active--workers, reflecting the importance of the endogenous (skeletal) lead exposure. The findings in this study indicate that bone lead measurements by XRF can give a good index of long-term lead exposure. Tibia measurements offer a higher precision than calcaneus measurements. The method is of particular interest in epidemiologic studies of adverse health effects caused by long-term lead exposure.

Mortality and lead exposure: a retrospective cohort study of Swedish smelter workers.

The study is based on the work histories and mortality data for 3832 male workers first employed before 1967 at a copper smelter in northern Sweden and followed up from 1950 to 1981. From the 3832 workers a lead cohort consisting of 437 workers employed for at least three years at sites with considerable lead exposure during 1950-74 was selected. These workers had regularly had blood lead measurements performed since 1950. Based on the cumulative blood lead dose 1950-74 and peak blood lead values, the cohort was subdivided into high mean, low mean, high peak, and low peak groups. Standardised mortality ratios (SMR) were calculated for the six groups using general and local reference populations. The original cohort of 3832 workers showed considerable excess of deaths for total mortality, malignant neoplasms especially lung and stomach cancer, ischaemic heart diseases, and cerebrovascular diseases when compared with the general population. In the lead cohort where the workers had been subjected to a considerable lead exposure only the raised SMR for lung cancer was sustained (SMR = 162; not significant). No significant differences were found between high lead and low lead exposed smelter workers.