Smelter Workers Research Articles

Relationship between cardiopulmonary mortality and cancer risk and quantitative exposure to polycyclic aromatic hydrocarbons, fluorides, and dust in two prebake aluminum smelters

We examined the risk of mortality and cancer incidence with quantitative exposure to benzene-soluble fraction (BSF), benzo(a)pyrene (BaP), fluoride, and inhalable dust in two Australian prebake smelters. A total of 4,316 male smelter workers were linked to mortality and cancer incidence registries and followed from 1983 through 2002 (mean follow-up: 15.9 years, maximum: 20 years). Internal comparisons using Poisson regression were undertaken based on quantitative exposure levels. Smoking-adjusted, monotonic relationships were observed between respiratory cancer and cumulative inhalable dust exposure (trend p = 0.1), cumulative fluoride exposure (p = 0.1), and cumulative BaP exposure (p = 0.2). The exposure-response trends were stronger when examined across the exposed categories (BaP p = 0.1; inhalable dust p = 0.04). A monotonic, but not statistically significant trend was observed between cumulative BaP exposure and stomach cancer (n = 14). Bladder cancer was not associated with BaP or BSF exposure. No other cancer and no mortality outcomes were associated with these smelter exposures. The carcinogenicity of Söderberg smelter exposures is well established; in these prebake smelters we observed an association between smelter exposures and respiratory cancer, but not bladder cancer. The exploratory finding for stomach cancer needs confirmation. These results are preliminary due to the young cohort and short follow-up time.

Increased lung cancer risks are similar whether arsenic is ingested or inhaled.

In 1980, the International Agency for Research on Cancer (IARC) determined there was sufficient evidence to support that inorganic arsenic was a human lung carcinogen based on studies involving exposure through inhalation. In 2004, IARC listed arsenic in drinking water as a cause of lung cancer, making arsenic the first substance established to cause human cancer through two unrelated pathways of exposure. It may initially seem counterintuitive that arsenic in drinking water would cause human lung cancer, and even if it did, one might expect risks to be orders of magnitude lower than those from direct inhalation into the lungs. In this paper, we consider lung cancer dose-response relationships for inhalation and ingestion of arsenic by focusing on two key studies, a cohort mortality study in the United States involving Tacoma smelter workers inhaling arsenic, and a lung cancer case-control study involving ingestion of arsenic in drinking water in northern Chile. When exposure was assessed based on the absorbed dose identified by concentrations of arsenic in urine, there was very little difference in the dose-response findings for lung cancer relative risks between inhalation and ingestion. The lung cancer mortality rate ratio estimate was 8.0 (95% CI 3.2-16.5, P<0.001) for an average urine concentration of 1179 microg/l after inhalation, and the odds ratio estimate of the lung cancer incidence rate ratio was 7.1 (95% CI 3.4-14.8, P<0.001) for an estimated average urine concentration of 825 microg/l following ingestion. The slopes of the linear dose-response relationships between excess relative risk (RR-1) for lung cancer and urinary arsenic concentration were similar for the two routes of exposure. We conclude that lung cancer risks probably depend on absorbed dose, and not on whether inorganic arsenic is ingested or inhaled.

Manganese exposure among smelting workers: blood manganese–iron ratio as a novel tool for manganese exposure assessment

Unexposed control subjects (n = 106), power distributing and office workers (n = 122), and manganese (Mn)-exposed ferroalloy smelter workers (n = 95) were recruited to the control, low and high groups, respectively. Mn concentrations in saliva, plasma, erythrocytes, urine and hair were significantly higher in both exposure groups than in the controls. The Fe concentration in plasma and erythrocytes, however, was significantly lower in Mn-exposed workers than in controls. The airborne Mn levels were significantly associated with Mn/Fe ratio (MIR) of erythrocytes (eMIR) (r = 0.77, p < 0.01) and plasma (pMIR) (r = 0.70, p < 0.01). The results suggest that the MIR may serve as a useful biomarker to distinguish Mn-exposed workers from the unexposed, control population.

Arsenic and other trace elements contamination in groundwater and a risk assessment study for the residents in the Kandal Province of Cambodia

Concentrations of arsenic and other trace elements in groundwater were examined at three villages (PT, POT and CHL) in the Kandal Province of Cambodia. Concentrations of arsenic in the groundwater ranged from 6.64 (in POT village) to 1543 μg/L (in PT village), with average and median concentrations of 552 and 353 μg/L, respectively. About 86% out of fifteen samples contained arsenic concentrations exceeding the WHO drinking water guidelines of 10 μg/L. Concentrations of arsenic (III) varied from 4 (in POT village) to 1334 μg/L (in PT village), with an average concentration of 470 μg/L. In addition, about 67%, 80% and 86% of the groundwater samples had higher concentrations for, respectively, barium, manganese and lead than the WHO drinking water guidelines. These results reveal that groundwater in Kandal Province is not only considerably contaminated with arsenic but also with barium, manganese and lead. A risk assessment study found that one sample (PT25) had a cumulative arsenic concentration (6758 mg) slightly higher than the threshold level (6750 mg) that could cause internal cancer in smelter workers with chronic exposure to arsenic from groundwater. High cumulative arsenic ingestion poses a health threat to the residents of Kandal Province.

Respiratory cancer and inhaled inorganic arsenic in copper smelters workers: a linear relationship with cumulative exposure that increases with concentration.

BackgroundInhalation of high levels of airborne inorganic arsenic is a recognized cause of respiratory cancer. Although multiple epidemiologic studies have demonstrated this association, there have been few analyses of the mathematical relationship between cumulative arsenic exposure and risk of respiratory cancer, and no assessment as to whether and how arsenic concentration may modify this association.ObjectivesThe objective is an evaluation of the shape of the relationship between respiratory cancer mortality and cumulative inhaled arsenic exposure among copper smelter workers, and the modification of that relationship by arsenic concentration.MethodsWe used Poisson regression methods to analyze data from a cohort of arsenic-exposed copper smelter workers under a linear-exponential model for the excess relative risk.ResultsWithin categories of arsenic concentration, the association between respiratory cancer and cumulative arsenic exposure was consistent with linearity. The slope of the linear relationship with cumulative exposure increased with increasing arsenic concentration category.ConclusionsOur results suggested a direct concentration effect from inhaled inorganic arsenic, whereby the excess relative risk for a fixed cumulative exposure was greater when delivered at a higher concentration and shorter duration than when delivered at a lower concentration and longer duration.

Occupational and environmental risks in and around a smelter in northern Sweden. VII. Reanalysis and follow-up of chromosomal aberrations in workers exposed to arsenic.

A reanalysis of data on chromosomal aberrations among 33 copper smelter workers exposed to arsenic revealed no significant variations due to age, smoking habits or degree of arsenic exposure although the observed deviations were in the expected direction. The arsenic exposed workers showed, however, significantly increased frequencies of chromosomal aberrations when compared with referents without known occupational exposure to genotoxic agents. Eight workers were studied at three different occasions, viz. 1976, 1978 and 1979. The levels of urinary arsenic decreased significantly between 1976 and 1978. There was also a significant decrease of chromosomal aberrations between 1976 and 1978 when group data were analysed. Two individuals showed a significant decrease of breaks with time. One of them had changed from full time to half time work in 1977. Thus, in the follow-up study there is some evidence that decreased exposure leads to a lowered frequency of aberrations.

Beryllium Sensitization in Aluminum Smelter Workers

To determine whether beryllium-related disease exists among aluminum smelter workers. A total of 1278 employees from four aluminum smelters determined to have significant beryllium exposure based on 5 years of sampling were invited to participate in medical surveillance that included a respiratory symptoms questionnaire, spirometry, and blood beryllium lymphocyte proliferation test. Of these, 734 employees participated in the program. Beryllium exposure from 965 personal samples ranged from 0.002 to 13.00 microg/m time-weighted average, with a median of 0.05 microg/m, geometric mean of 0.05 microg/m, and arithmetic mean of 0.22 microg/m. Only two employees had confirmed beryllium sensitization (0.27%). There is evidence of beryllium sensitization among aluminum smelter workers. When compared with beryllium-exposed workers in other industries, aluminum smelter workers had lower rates of sensitization. The low beryllium sensitization rate observed may be related to work practices and the properties of the beryllium found in this work environment.

Early neurotoxic effects of inhalation exposure to aluminum and/or manganese assessed by serum levels of phospholipid-binding Clara cells protein

Little is known on the disturbances of lung epithelium function in aluminum casting smelters and shipyard welders exposed by inhalation to irritant occupational pollutants, dust and fumes. The exact mechanism of aluminum and manganese toxicity is not known, but it is thought that they may potentiate oxidative and inflammatory stress, leading to impaired neurological function. The aim of the study was to investigate the subclinical effects of aluminum and manganese exposure on the nervous system and to assess their relationship to the biomarkers of exposure and effect in workers exposed to neurotoxic fumes. The relationship between the neurological and respiratory effects was investigated in 50 workers at aluminum casting smelters exposed to xGM = 0.29 Al2O3 mg m− 3, and 59 shipyard welders exposed to xGM = 0.16 Mn mg m− 3, and the reference group. Serum anti-inflammatory, phospholipid-binding Clara cell protein (CC16) as a peripheral marker of the bronchiolar epithelium function measured. The lowest CC16 concentrations were found in workers showing subjective CNS symptoms and abnormal neurophysiological findings: EEG and visual evoked potentials. A strong inverse relationship was found between serum Al (Al-S) and CC16 concentrations (p = 0.006). Younger smelter workers and welders, with a shorter exposure duration, presented a higher number of VEPs than the workers employed for a longer period of time. The sub-clinical neurological symptoms (VEP) and low CC16 level can be associated with an internalization of Al ions with lipid fractions of the lung epithelium, which in turn may help Al ions overcome the blood–brain barrier. The inhibited secretion of anti-inflammatory Clara cell protein and low respiratory performance in younger Mn welders was found to enhance subclinical neurotoxic symptoms, especially VEPs, related to exposure to airborne Mn and Mn-B.

Mortality and Cancer Experience of Quebec Aluminum Reduction Plant Workers, Part 4: Cancer Incidence

To describe the cancer experience of Quebec aluminum smelter workers. Cancer incidence was compared with that of the Quebec general population and examined in relation to benzo[a]pyrene (B[a]P) and smoking exposure indices. There was a statistically significant increased incidence of stomach (two cohorts), pancreatic (one cohort), laryngeal (one cohort), lung (three cohorts), and bladder (four cohorts) cancers. Unlike lung and bladder cancers, pancreatic and stomach cancer risks do not relate meaningfully to cumulative B[a]P exposure. Laryngeal and buccal cavity cancer standardized incidence ratios (SIRs) seem to increase with increasing B[a]P exposure. SIRs from lung cancer have greatly diminished whereas bladder cancer SIRs remain elevated in all but one cohort. The cancer incidence results are consistent with those from mortality studies, but identify other cancers that deserve scrutiny in future follow-ups.

Mortality and Cancer Experience of Quebec Aluminum Reduction Plant Workers, Part 2: Mortality of Three Cohorts Hired on or Before January 1, 1951

To describe the mortality of Quebec aluminum smelter workers employed before 1951. The mortality of 5,977 men hired at three plants on or before January 1, 1951 was compared with that of Quebec men. Relationships to benzo[a]pyrene, benzene-soluble material, and smoking were examined. Statistically significant causes of death were lung cancer (three plants); bladder cancer; chronic obstructive lung disease (two plants each); cancers of the stomach, digestive system unspecified, rectum and rectosigmoid, pancreas, and larynx; Alzheimer's disease (one plant); and cerebrovascular disease (one plant). Not significant increases were also observed. Mortality from cancer of the lung and bladder and chronic obstructive pulmonary disease are related to exposure in Söderberg smelters. The cause of increased stomach cancer mortality is unclear. Excess mortality from some other diseases may be explained by factors other than coal tar pitch volatiles exposure.

Smelter workers’ environment—a hazard for respiratory disease?

Smelter workers’ environment—a hazard for respiratory disease?

Mortality and Cancer Experience of Quebec Aluminum Reduction Plant Workers. Part I: The Reduction Plants and Coal Tar Pitch Volatile (CTPV) Exposure Assessment

This paper presents the exposure assessment and job-exposure matrix (JEM) used to estimate coal tar pitch volatile (CTPV) exposure for a study of mortality and cancer incidence in aluminum smelter workers in Quebec, Canada. Historical CTPV exposure was assessed by estimating benzene-soluble material (BSM) and benzo[a]pyrene (B[a]P) levels for combinations of job and time period. Estimates were derived by using several procedures including averaging measurement data, a deterministic mathematical model using process-related correction factors, and expert-based extrapolation. The JEM comprised 28,910 jobs, covering 7 facilities from 1916 to 1999. Estimated exposures ranged from 0.01 microg/m(3) to 68.08 microg/m(3) (B[a]P) and 0.01 mg/m(3) to 3.64 mg/m(3) (BSM) and were lowest before 1940 and after 1980. This methodology constitutes an improvement compared with methods used for previous studies of the Quebec cohort.

State-of-the-Science Review: Does Manganese Exposure During Welding Pose a Neurological Risk?

Recent studies report that exposure to manganese (Mn), an essential component of welding electrodes and some steels, results in neurotoxicity and/or Parkinson's disease (PD) in welders. This “state-of-the-science” review presents a critical analysis of the published studies that were conducted on a variety of Mn-exposed occupational cohorts during the last 100 yr, as well as the regulatory history of Mn and welding fumes. Welders often perform a variety of different tasks with varying degrees of duration and ventilation, and hence, to accurately assess Mn exposures that occurred in occupational settings, some specific information on the historical work patterns of welders is desirable. This review includes a discussion of the types of exposures that occur during the welding process—for which limited information relating airborne Mn levels with specific welding activities exists—and the human health studies evaluating neurological effects in welders and other Mn-exposed cohorts, including miners, millers, and battery workers. Findings and implications of studies specifically conducted to evaluate neurobehavioral effects and the prevalence of PD in welders are also discussed. Existing exposure data indicate that, in general, Mn exposures in welders are less than those associated with the reports of clinical neurotoxicity (e.g., “manganism”) in miners and smelter workers. It was also found that although manganism was observed in highly exposed workers, the scant exposure-response data available for welders do not support a conclusion that welding is associated with clinical neurotoxicity. The available data might support the development of reasonable “worst-case” exposure estimates for most welding activities, and suggest that exposure simulation studies would significantly refine such estimates. Our review ends with a discussion of the data gaps and areas for future research.

Impact of cognitive reserve on the relationship of lead exposure and neurobehavioral performance

Cognitive reserve (CR)--a construct studied in many neurologic disorders--refers to the maintenance of cognitive performance in spite of ongoing underlying brain pathology. We hypothesized that a dose-effect relationship would exist between chronic occupational lead exposure and cognitive effects in workers with low CR but not in workers with high CR and identical lead exposure, and that level of CR would not influence the relationship between lead exposure and motor performance. We stratified currently employed lead smelter workers by Wide Range Achievement Test-R for reading (WRAT), a recognized measure of CR, into loCR and hiCR groups. From these two groups we matched 56 pairs on working lifetime weighted blood lead (TWA). We performed a factor analysis on 14 neuropsychological outcome variables. Within each CR group regression analyses after adjusting for age, alcohol use, and depression scale score tested for dose-effect relationships between TWA and outcome variables. Both CR groups had comparable age, years employed, alcohol use, and current blood lead levels. Factor analysis provided three factors and five tests used in the regression analyses. Significant dose-effect relationships between TWA and cognitive tests present only in the loCR group included Attention Factor and Digit Symbol. Both CR groups demonstrated significant dose-effect relationships on the Motor Factor. This study found that cognitive reserve protects against the effect of chronic lead exposure on select measures of cognitive performance but not on motor performance.

High exposure of Chinese mercury mine workers to elemental mercury vapor and increased methylmercury levels in their hair

The aim of this study was to determine the level of exposure of mercury (Hg) miners and smelter workers to elemental mercury (Hg(0)) vapor in China, who work in Hg mines without using protective equipment against Hg(0) vapor. In addition, the level of methylmercury (MeHg) intake by the workers was estimated from the MeHg concentration in their hair. Urinary total mercury (THg) and hair THg and MeHg concentrations were measured in 26 Hg miners and smelter workers (i.e., exposed group), and 48 unexposed people (unexposed group). The exposed group showed high geometric mean THg concentrations in urine (258 ng/ml, 226 μg/g creatinine) and hair (20.0 μg/g). The urinary THg concentration of the smelter workers in particular was extremely high (338 μg/g creatinine in urine). The highest urine THg concentration reached 4577 μg/g creatinine. THg concentrations in urine and hair showed a significant correlation in the exposed group (r=0.62), indicating the adhesion of Hg(0) vapor to hair. However, no such significant correlation was found in the unexposed group. Hair MeHg concentration in the exposed group (1.97 μg/g) was about threefold higher than that in the unexposed group (0.60 μg/g). This study shows that smelter workers in a Chinese Hg mine are exposed to extremely high levels of Hg(0) vapor, and that Hg miners are exposed to higher levels of MeHg than the unexposed subjects. Further study is needed to determine the cause of the higher hair MeHg concentration in the exposed group.

Estimation of Benchmark Dose for Pancreatic Damage in Cadmium-Exposed Smelters

The aim of this study was to estimate the benchmark dose (BMD) for pancreas dysfunction caused by cadmium (Cd) exposure in smelters. Smelter workers who had been exposed to Cd for more than 1 year and matching nonoccupationally exposed subjects were asked to participate in this study. Urinary cadmium (UCd) was used as a biomarker for exposure, serum insulin and amylase were used as biomarkers for pancreatic effects. In this study, serum insulin and amylase were lower in the smelter workers than in the nonoccupationally exposed subjects. A significant dose-response relationship with UCd was displayed. BMDs in terms of urinary Cd corrected for creatinine were calculated by use of BMDS (version 1.3.2). The benchmark dose lower limit of a one-sided 95% confidence interval (BMDL) for 10% excess risk was also determined. It was found that the BMDL10 for serum insulin and serum amylase was 3.7 and 5.3 microg/g Cr, respectively. Compared to the BMDL for renal damage caused by Cd exposure, identified by the effect biomarkers urinary beta2-microglobulin, urinary N-acetyl-beta-glucosaminidase, and urinary albumin (UALB), it was shown that BMDL10 for serum insulin is the lowest among all values and UALB gave the highest value (5.8 microg/g Cr). This study indicates that Cd exposure can result in pancreatic dysfunction and the effect appears at lower urinary Cd level than renal dysfunction. The endocrine function of the pancreas was affected at lower urinary levels of Cd, compared to the exocrine function, which was seen at higher urinary levels of Cd than those giving rise to renal tubular dysfunction.

Micronucleus frequency in peripheral blood lymphocytes and buccal mucosa cells of copper smelter workers, with special regard to arsenic exposure

Occupational exposure in copper smelters may produce various adverse health effects including cancer which, according to available epidemiologic data, is associated mainly with exposure to arsenic. Despite a number of well-documented studies reporting an increased risk of cancer among copper smelters workers, the data on genotoxic effects in this industry are scarce. In view of the above, an assessment of micronuclei (MN) frequency in peripheral blood lymphocytes and buccal epithelial cells from copper smelter workers was undertaken. Additionally, the clastogenic/aneugenic effect in lymphocytes was assessed with the fluorescence in situ hybridization (FISH). The study was conducted in three copper smelters in southwestern Poland. The subjects (n = 72) were enrolled among male workers at departments where As concentration in the air was up to at 80 microg/m(3). Exposure was assessed by measurement of arsenic concentration in urine and toenail samples. The control group (n = 83) was recruited from healthy male individuals living in central Poland who did not report any exposure to known genotoxins. The results of our study showed a significant increase in MN frequency in peripheral blood lymphocytes and in buccal epithelial cells of smelter workers, compared to the controls (7.96 +/- 4.28 vs. 3.47 +/- 1.70 and 0.98 +/- 0.76 vs. 0.50 +/- 0.52, respectively). The FISH technique revealed the presence of clastogenic and aneugenic effects in peripheral blood lymphocytes in both groups. The clastogenic effect was slightly more pronounced in the smelter workers; however, the difference was not statistically significant. The mean arsenic concentrations in urine (total arsenic species) and in toenail samples in the exposed group were 54.04 +/- 42.26 microg/l and 7.63 +/- 7.24 microg/g, respectively, being significantly different from control group 11.01 +/- 10.84 microg/l and 0.51 +/- 0.05 microg/g. No correlation between As content in urine or toenail samples and the genotoxic effect was found under study.

Lead Exposure and Spine Bone Mineral Density

The purpose of this study was to assess changes in spine BMD over time in relation to changes in bone and blood lead levels and baseline risk factors among female former smelter workers in Bunker Hill, Idaho. Spine BMD was measured using Norland XR-26 X-Ray bone densitometer. Cd109 K XRF system was used to estimate tibia bone lead content. Blood lead levels were analyzed using graphite furnace atomic absorption with Zeeman effect background correction. Information about risk factors was obtained through a questionnaire. In the final backward stepwise multivariate regression model after controlling for baseline BMD, baseline blood lead measured in 1994 and time since menopause; spine bone density in 2000 decreased with increasing blood lead levels in 2000 in all these women, especially if they worked in a technical job (miner) most of the time at the smelter. Blood lead may adversely affect bone mineral density.

The association of lead exposure and motor performance mediated by cerebral white matter change

The goals were to determine if lead exposure is associated with cerebral white matter changes (WMC) and if so, does WMC mediate the relation between lead and psychomotor slowing as measured by Grooved Pegboard (GP). In the literature, age is the strongest predictor of WMC and therefore 61 lead smelter workers age 50 and under were included in the study population. Mean (range) age was 40 (23–50) years, years of education was 9 (0–13), duration of employment was 19 (1–26), current blood lead (PbB) was 29 (16–42) μg/dl, working lifetime weighted integrated blood lead (IBL) was 826 (65–1451) μg year/dl, working lifetime weighted average blood lead (TWA) was 42 (17–59) μg/dl, and bone lead (PbBn) was 39 (−12–90) μg Pb/g bone mineral. WMC, recorded as hyperintensities on T2-weighted MRI of the brain were graded. Lead variables were entered in a logistic regression attempting to differentiate normal versus abnormal MRI, after controlling for age and cerebrovascular risk factors. Direct effects of lead on GP and indirect effects of lead on GP through WMC was modeled using multiple linear regression analyses after controlling for the covariates. WMC were present in 23% of MRIs. Logistic regression of WMC on lead exposure metrics demonstrated significantly elevated odds ratios for IBL, TWA, and PbBn after the covariates. Of the lead exposure variables, IBL ( β = 0.339, p < 0.10) had a larger direct effect on GP after adjusting for the covariates than PbBn ( β = 0.265, p < 0.10). After adjusting for the lead term and covariates WMC accounted for an additional effect on GP performance after PbBn ( β = 0.261, p < 0.10) and after IBL ( β = 0.278, p < 0.05). Path analysis demonstrated that some of the relationship of both PbBn and IBL with GP is mediated by WMC.

Lung Cancer Development in Primary Smelter Workers: A Nested Case-Referent Study

The objective of this study was to study the impact of work-related exposure to mainly arsenic and lead versus smoking in primary smelter workers developing lung cancer. In a cohort of 3979 primary smelter workers, 46 subjects had contracted respiratory malignancies. They were compared with 141 age-matched male referents by conditional logistic regression analysis. Cases showed a significantly higher smoking rate as compared with referents: odds ratio (OR) = 4.0; 95% confidence interval (CI) = 1.6-10.1; P = 0.003. When restricted to smokers (33 cases, 63 referents), the cumulative air arsenic exposure index, but not the lead exposure indices, was significantly higher among the cases: OR = 1.07; 95% CI = 1.02-1.11; P = 0.005. Cumulative arsenic exposure and smoking were identified as risk factors for the development of lung cancer; lead exposure, however, was not.