granite and Lung-Neoplasms

IARC (2009; Metals, Particles and Fibres. IARC Monographs on the Evaluaton of Carcinogenic Risks to Humans. Volume 100C. Lyon, France: IARC) concluded that crystalline silica in occupational settings is a lung carcinogen. This conclusion is based primarily on studies with exposure-response (E-R) analyses and a pooled analysis of 10 major studies with about 1000 lung cancer cases. The purpose of this review is to critically assess this cancer classification based on E-R analyses in 18 studies from eight countries with about 2000 lung cancer cases and the same database used by IARC (2009) . The most appropriate exposure-response analysis is selected from latest study with least effect from bias, confounding, and presented graphically to assist individual assessment of the weight of evidence. Strength of association is consistently weak in the majority of studies. At the highest exposure level the mean relative risk (RR) is 1.5; four studies have strong associations (RRs > 2), three have moderate strong associations (RRs 1.5-2.0), six have weak-negligible associations (RRs 1-1.5), and five have no associations (RRs ≤1.0). Biological gradients were an inconsistent finding. Three studies had clear positive E-R trends; 3 had suggestive trends; and 12 had no E-R trends, 9 of which were flat or negative. There was a negative ER slope using RRs at the highest exposure of each study. Consistent findings of weak associations and lack of E-R trends does not support a causal association. Weight of evidence from occupational epidemiology does not support a causal association of lung cancer and silica exposure, which is contrary to the IARC conclusion using essentially the same data.

Topics: Adult; Aged; Air Pollutants, Occupational; Carcinogens; Ceramics; China; Crystallization; Dose-Response Relationship, Drug; Germany; Humans; Italy; Lung Neoplasms; Middle Aged; Mining; Occupational Diseases; Occupational Exposure; Silicon Dioxide

Silica is one of the most common occupational exposures worldwide. In 1997 the International Agency for Research on Cancer (IARC) classified inhaled crystalline silica as a human carcinogen (group 1), but acknowledged limitations in the epidemiologic data, including inconsistencies across studies and the lack of extensive exposure-response data. We have conducted a pooled exposure-response analysis of 10 silica-exposed cohorts to investigate lung cancer.. The pooled cohort included 65,980 workers (44,160 miners, 21,820 nominees), and 1,072 lung cancer deaths (663 miners, 409 nonminers). Follow-up has been extended for five of these cohorts beyond published data. Quantitative exposure estimates by job and calendar time were adopted, modified, or developed to permit common analyses by respirable silica (mg/m3) across cohorts.. The log of cumulative exposure, with a 15-year lag, was a strong predictor of lung cancer (p = 0.0001), with consistency across studies (test for heterogeneity, p = 0.34). Results for the log of cumulative exposure were consistent between underground mines and other facilities. Categorical analyses by quintile of cumulative exposure resulted in a monotonic trend with odds ratios of 1.0. 1.0, 1.3, 1.5, 1.6. Analyses using a spline curve also showed a monotonic increase in risk with increasing exposure. The estimated excess lifetime risk (through age 75) of lung cancer for a worker exposed from age 20 to 65 at 0.1 mg/m3 respirable crystalline silica (the permissible level in many countries) was 1.1-1.7%, above background risks of 3-6%.. Our results support the decision by the IARC to classify inhaled silica in occupational settings as a carcinogen, and suggest that the current exposure limits in many countries may be inadequate. These data represent the first quantitative exposure-response analysis and risk assessment for silica using data from multiple studies.

Topics: Air Pollutants, Occupational; Carcinogens, Environmental; Cohort Studies; Diatomaceous Earth; Follow-Up Studies; Gold; Humans; Linear Models; Lung Neoplasms; Maximum Allowable Concentration; Mining; Occupational Diseases; Risk Assessment; Silicon Dioxide; Silicosis

Radon is a noble gas derived from the decay of radium, which itself is a decay product of uranium. The decay products of radon can collect electrostatically on dust particles in the air and, if these particles are inhaled and attach to bronchial epithelium, produce a high local radiation dose. Alpha particles can induce DNA double-strand breaks and the development of cancer. A causal relation between lung cancer and radon exposure and its progeny has been demonstrated in epidemiological studies of miners. Radon exposure became a public health issue almost 15 years ago. Most radon exposure occurs indoors, predominantly in the home. There is however, a wide range of radon concentration values in different countries. The highest level occurs in areas with granite and permeable soils. The risk for smoking, the leading cause of lung cancer, is far greater than for radon, the second leading cause. The estimates obtained from case-control studies of indoor radon are very contradictory. Scientific knowledge of effects of low levels of exposure to radon and the role of cigarette smoking, as a combined factor, must be studied. Smoking and radon probably interact in a multiplicative fashion.

Topics: Air Movements; Air Pollutants, Radioactive; Carcinogens, Environmental; Case-Control Studies; Causality; Environmental Exposure; France; Housing; Humans; Lung Neoplasms; Public Health; Radon; Radon Daughters; Silicon Dioxide; Smoking; Soil

To understand why 2 studies relating crystalline silica exposure to lung-cancer mortality in Vermont granite workers yielded conflicting results.. Data used in the 2 studies were linked to identify discrepancies. Mortality data and employment histories from the earlier study were revised based on data obtained in the later study. SMR were computed and Poisson regressions corresponding to those in the earlier study were performed using the original and revised data. Analyses were repeated with the addition of workers omitted from the earlier study.. After correction of incomplete mortality and employment information in the original data, the overall SMR for the cohort in the earlier study increased from 1.17 (95% CI 1.03 to 1.36) to 1.39 (95% CI 1.22 to 1.59), and was similar to the SMR of 1.37 observed in the later study (95% CI 1.23 to 1.52). The exposure-response relationship was attenuated, particularly when person-years in all exposure categories were included in the analysis. Inclusion of additional workers had a smaller impact on the SMRs but further attenuated the exposure-response relationship.. Differing results from the 2 studies are partly attributable to incomplete vital status and work history information used in the earlier study, as well as differences in cohort inclusion criteria. However, differences in length of follow-up and other factors likely play a larger role.

Topics: Aged; Aged, 80 and over; Bias; Cohort Studies; Female; Humans; Lung Neoplasms; Male; Middle Aged; Occupational Diseases; Occupational Exposure; Regression Analysis; Silicon Dioxide; Vermont

To assess mortality in Vermont granite workers and examine relationships between silica exposure and mortality from lung cancer, kidney cancer, non-malignant kidney disease, silicosis and other non-malignant respiratory disease. Methods Workers employed between 1947 and 1998 were identified. Exposures were estimated using a job-exposure matrix. Mortality was assessed through 2004 and standardised mortality ratios (SMRs) were computed. Associations between mortality and exposure to silica were assessed by nested case-control analyses using conditional logistic regression. Results 7052 workers had sufficient data for statistical analysis. SMRs were significantly elevated for lung cancer (SMR 1.37, 95% CI 1.23 to 1.52), silicosis (SMR 59.13, 95% CI 44.55 to 76.97), tuberculosis (SMR 21.74, 95% CI 18.37 to 25.56) and other non-malignant respiratory disease (SMR 1.74, 95% CI 1.50 to 2.02) but not for kidney cancer or non-malignant kidney disease. In nested case-control analyses, significant associations with cumulative exposure to respirable free silica were observed for silicosis (OR 1.13, 95% CI 1.05 to 1.21 for each 1 mg/m(3)-year increase in cumulative exposure) and other non-malignant respiratory disease (OR 1.10, 95% CI 1.03 to 1.16) but not for lung cancer (OR 0.99, 95% CI 0.94 to 1.03), kidney cancer (OR 0.96, 95% CI 0.84 to 1.09) or non-malignant kidney disease (OR 0.95, 95% CI 0.84 to 1.08). Conclusions Exposure to crystalline silica in Vermont granite workers was associated with increased mortality from silicosis and other non-malignant respiratory disease, but there was no evidence that increased lung cancer mortality in the cohort was due to exposure. Mortality from malignant and non-malignant kidney disease was not significantly increased or associated with exposure.

Topics: Aged; Aged, 80 and over; Epidemiologic Methods; Humans; Kidney Diseases; Kidney Neoplasms; Lung Neoplasms; Male; Middle Aged; Mining; Occupational Diseases; Occupational Exposure; Respiratory Tract Diseases; Silicon Dioxide; Silicosis; Vermont

Radon gas ((222)Rn) is a natural constituent of the environment and a risk factor for lung cancer that we are exposed to as a result of radioactive decay of radium ((226)Ra) in stone and soil. Granite countertops, in particular, have received recent media attention regarding their potential to emit radon. Radon flux was measured on 39 full slabs of granite from 27 different varieties to evaluate the potential for exposure and examine determinants of radon flux. Flux was measured at up to six pre-selected locations on each slab and also at areas identified as potentially enriched after a full-slab scan using a Geiger-Muller detector. Predicted indoor radon concentrations were estimated from the measured radon flux using the CONTAM indoor air quality model. Whole-slab average emissions ranged from less than limit of detection to 79.4 Bq/m(2)/h (median 3.9 Bq/m(2)/h), similar to the range reported in the literature for convenience samples of small granite pieces. Modeled indoor radon concentrations were less than the average outdoor radon concentration (14.8 Bq/m(3); 0.4 pCi/l) and average indoor radon concentrations (48 Bq/m(3); 1.3 pCi/l) found in the United States. Significant within-slab variability was observed for stones on the higher end of whole slab radon emissions, underscoring the limitations of drawing conclusions from discrete samples.

Topics: Air Pollutants, Radioactive; Air Pollution, Indoor; Construction Materials; Environmental Exposure; Housing; Humans; Lung Neoplasms; Radiometry; Radon; Risk Assessment; Silicon Dioxide; United States

To explore the healthy worker survivor effect (HWSE) in a study of Vermont granite workers by distinguishing "prevalent" from "incident" hires based on date of hire before or after the start of follow-up.. Records of workers between 1950 and 1982 were obtained from a medical surveillance programme. Proportional hazards models were used to model the association between silica exposure and lung cancer mortality, with penalised splines used to smooth the exposure-response relationship. A sensitivity analysis compared results between the original cohort and subcohorts defined by restricting date of hire to include varying proportions of prevalent hires.. Restricting to incident hires reduced the 213 cases by 74% and decreased the exposure range. The maximum mortality rate ratio (MRR) was close to twofold in all subcohorts. However, the exposure at which the maximum MRR was achieved decreased from 4.0 to 0.6 mg-year/m3 as the proportion of prevalent hires decreased from 50% in the original cohort to 0% in the subcohort of incident hires.. Despite loss in power and restricted exposure range, decreasing the relative proportion of prevalent to incident hires reduced HWSE bias, resulting in stronger evidence for a dose-response between silica exposure and lung cancer mortality.

Topics: Aged; Bias; Cohort Studies; Employment; Follow-Up Studies; Healthy Worker Effect; Humans; Incidence; Industry; Lung Neoplasms; Middle Aged; Prevalence; Proportional Hazards Models; Silicon Dioxide; Silicosis; Survival Analysis; Time Factors; Vermont

This mortality study extends the period of observation of an article published in 1988 of 5414 workers in Vermont granite sheds and quarries to assess whether previously reported reductions in silicosis and tuberculosis mortality were maintained. The relationship between lung cancer and quartz exposure is also examined by comparing mortality in workers hired before and after 1940, when dust controls were introduced and exposures were reduced by 80% to 90%. Before 1940, general stone shed air contained 20 million particles/cubic foot (mppcf) (approximately equivalent to 0.2 mg/m of quartz), and pneumatic chisel workers were exposed on average to 60 mppcf (approximately equivalent to 0.6 mg/m of quartz). Other workers had variable exposures. After 1940, a period of decline occurred in dust levels and then stabilized in approximately 1955, when average dust levels were 5 to 6 mppcf (equivalent to 0.05-.06 mg/m of quartz). Dust exposures in the Vermont industry is considered to be free of confounding occupational substances such as arsenic, although cigarette smoking was common. By the end of 1996, 2539 workers, or 46.9% of the cohort, had died. There were no silicosis deaths in workers hired after 1940 who were exposed only in the Vermont granite industry, illustrating the effect of lowering quartz exposures. Tuberculosis caused 2 deaths in those hired after 1940 (standardized mortality ratio [SMR] = 0.52; not significant). Overall lung cancer mortality was elevated in shed workers who had been exposed both to high levels of quartz before 1940 and to the lower levels prevailing after 1940 (SMR = 1.32; P < 0.01). Quarry workers did not show an excess of lung cancer (SMR = 0.73; not significant). When shed workers with high and low exposure histories (before and after 1940) but with comparable latency and tenure were contrasted, lung cancer mortality was similar. Differing levels of quartz exposure, which resulted in large differences in the mortality experience from silicosis, did not result in differences in lung cancer mortality. The results do not support the hypothesis that granite dust exposure has a causal association with lung cancer.

Topics: Cause of Death; Cohort Studies; Environmental Exposure; Extraction and Processing Industry; Humans; Lung Neoplasms; Male; Occupational Diseases; Quartz; Silicon Dioxide; Silicosis; Tuberculosis, Pulmonary; Vermont

The study evaluated the possibility of a direct association between silica dust exposure and lung cancer.. Mortality and morbidity among 1026 granite workers was followed in 1940-1989. Regional census data for 1970-1985 and lung cancer incidence data were also linked. The cytotoxicity of different granite fractions and their capacity to induce reactive oxygen species (ROS) in human leukocytes was studied in vitro.. Excess lung cancer mortality was found during several follow-up periods. The rate ratios were 1.6-3.8 for different latency periods. Lung cancer risk increased with the length of exposure and latency. Lung cancer morbidity in 1953-1987 showed an excess for the red and grey granite areas, the rate ratio being 2.5 for > or = 20-year latency. Only one lung cancer case came from the black granite area. The cancer cases from the grey area had a shorter latency than those from the red area. The mineral composition differed for each area. The strongest ROS-inducing activity of grey and red granite was seen in the quartz-containing fractions. In the cytotoxicity tests the quartz-containing fractions of the grey and red granite also caused the strongest lactic dehydrogenase (LDH) release. However, plagioclase, the main constituent of black granite (60%), had approximately the same ability to induce ROS as the quartz-containing fractions of red and grey granite.. The cancer morbidity and mortality figures of the three different granite areas, combined with the found differences in biological activity of granite dusts and a hypothesis that there is a cancer-inducing mechanism for ROS, point to a direct role for quartz in cancer induction.

Topics: Adult; Aged; Case-Control Studies; Cohort Studies; Dust; Finland; Humans; Incidence; Lung Neoplasms; Male; Middle Aged; Morbidity; Neutrophils; Occupational Diseases; Occupational Exposure; Reactive Oxygen Species; Risk Factors; Silicon Dioxide; Survival Rate

Of the 184 cases of silicosis registered between 1 January 1970 and 31 December 1984 in Singapore, all the relevant information was available for 159, which were linked to the population-based National Cancer Register for lung cancer. Nine cases of lung cancer were found. The standardized incidence ratio (SIR) was computed with the age- and calendar-specific incidence of lung cancer rates of Chinese males in Singapore as a basis. Excess risk of lung cancer was found (SIR 2.01, 95% confidence interval 0.92-3.81). Adjustment for smoking showed that it alone could not account for the excess lung cancer risk. There was an increasing, but not significant, trend with increasing severity of silicosis and exposure duration. The results suggest that the severity of silicosis and possibly exposure to free silica may have contributed to the excess of lung cancer among the cases of silicosis studied.

Topics: Cohort Studies; Dust; Humans; Lung Neoplasms; Male; Middle Aged; Mining; Occupational Diseases; Racial Groups; Risk Factors; Silicon Dioxide; Silicosis; Singapore; Smoking

A cohort mortality study was carried out in Vermont granite workers who had been employed between the years 1950 and 1982. The cohort included men who had been exposed to high levels of granite dust prior to 1938-1940 (average cutters to 40 million parts/cubic foot), and those employed at dust levels after 1940, which on average were less than 10 million parts/cubic foot. Deaths were coded by a qualified nosologist and standardized mortality ratios were calculated. The results confirm previous studies that show that death rates from silicosis and tuberculosis, the major health threats in the years before 1940, were essentially eliminated after dust controls. However, we found excessive mortality rates from lung cancer in stone shed workers who had been employed prior to 1930, and hence had been exposed to high levels of granite dust. When information was available, 100% of those dying from lung cancer had been smokers.

Topics: Adult; Aged; Humans; Lung Neoplasms; Male; Middle Aged; Mortality; Risk Factors; Silicon Dioxide; Silicosis; Silicotuberculosis; Smoking; Vermont

The proportional mortality experience (1952-1978) of 969 deceased white male granite workers was compared with that of United States white males. Industrial hygiene information was combined with work histories to develop an estimate of lifetime granite dust exposure for each individual. Subjects were grouped into four cumulative exposure categories, and exposure-response relationships were examined. Trends of increasing silicosis and tuberculosis with increasing lifetime exposure were observed. These are consistent with earlier findings. With the exception of excess suicide among granite workers dying before 1970, there was little evidence of association between other causes of death and employment in the granite industry.

Topics: Adult; Humans; Lung Neoplasms; Male; Middle Aged; Neoplasms; Occupational Diseases; Regression Analysis; Silicon Dioxide; Silicosis; Silicotuberculosis; Suicide; United States; Vermont