On the death rates from cancer of the stomach and respiratory diseases in 1949-53 among coal miners and other male residents in counties of England and Wales

Mapping the Morbidity Risk Associated with Coal Mining in Queensland, Australia

The populations in the vicinity of surface coal mining activities have a higher risk of morbidity due to diseases, such as cardiovascular, respiratory and hypertensive diseases, as well as cancer and diabetes mellitus. Despite the large and historical volume of coal production in Queensland, the main Australian coal mining state, there is little research on the association of coal mining exposures with morbidity in non-occupational populations in this region. This study explored the association of coal production (Gross Raw Output—GRO) with hospitalisations due to six disease groups in Queensland using a Bayesian spatial hierarchical analysis and considering the spatial distribution of the Local Government Areas (LGAs). There is a positive association of GRO with hospitalisations due to circulatory diseases (1.022, 99% CI: 1.002–1.043) and respiratory diseases (1.031, 95% CI: 1.001–1.062) for the whole of Queensland. A higher risk of circulatory, respiratory and chronic lower respiratory diseases is found in LGAs in northwest and central Queensland; and a higher risk of hypertensive diseases, diabetes mellitus and lung cancer is found in LGAs in north, west, and north and southeast Queensland, respectively. These findings can be used to support public health strategies to protect communities at risk. Further research is needed to identify the causal links between coal mining and morbidity in non-occupational populations in Queensland.

Using human epidemiological analyses to support the assessment of the impacts of coal mining on health

The potential impacts of coal mining on health have been addressed by the application of impact assessment methodologies that use the results of qualitative and quantitative analyses to support their conclusions and recommendations. Although human epidemiological analyses can provide the most relevant measures of risk of health outcomes in populations exposed to coal mining by-products, this kind of studies are seldom implemented as part of the impact assessment methods. To review the use of human epidemiological analyses in the methods used to assess the impacts of coal mining, a systematic search in the peer review literature was implemented following the PRISMA protocol. A synthesis analysis identified the methods and the measures used in the selected publications to develop a thematic review and discussion. The major methodological approaches to assess the impacts of coal mining are environmental impact assessment (EIA), health impact assessment (HIA), social impact assessment (SIA) and environmental health impact assessment (EHIA). The measures used to assess the impacts of coal mining on health were classified as the estimates from non-human-based studies such as health risk assessment (HRA) and the measures of risk from human epidemiological analyses. The inclusion of human epidemiological estimates of the populations exposed, especially the general populations in the vicinity of the mining activities, is seldom found in impact assessment applications for coal mining. These methods rather incorporate HRA measures or other sources of evidence such as qualitative analyses and surveys. The implementation of impact assessment methods without estimates of the risk of health outcomes relevant to the potentially exposed populations affects their reliability to address the environmental and health impacts of coal mining. This is particularly important for EIA applications because these are incorporated in regulatory frameworks globally. The effective characterization of the impacts of coal mining on health requires quantitative estimates of the risk, including the risk measures from epidemiological analyses of relevant human health data.

Mortality and morbidity in populations in the vicinity of coal mining: a systematic review

BACKGROUND

Evidence of the association of coal mining with health outcomes such as increased mortality and morbidity in the general population has been provided by epidemiological studies in the last 25 years. Given the diverse sources of data included to investigate different health outcomes in the exposed populations, the International Classification of Diseases (ICD) can be used as a single classification standard to compare the findings of studies conducted in different socioeconomic and geographic contexts. The ICD classifies diagnoses of diseases and other disorders as codes organized by categories and chapters.

OBJECTIVES

Identify the ICD codes found in studies of morbidity and/or mortality in populations resident or in proximity of coal mining and assess the methods of these studies conducting a systematic review.

METHODS

A systematic database search of PubMed, EMBASE and Scopus following the PRISMA protocol was conducted to assess epidemiological studies from 1990 to 2016. The health outcomes were mapped to ICD codes and classified by studies of morbidity and/or mortality, and the categories and chapters of the ICD.

RESULTS

Twenty-eight epidemiological studies with ecological design from the USA, Europe and China were included. The exposed populations had increased risk of mortality and/or morbidity by 78 ICD diagnosis categories and 9 groups of ICD categories in 10 chapters of the ICD: Neoplasms, diseases of the circulatory, respiratory and genitourinary systems, metabolic diseases, diseases of the eye and the skin, perinatal conditions, congenital and chromosomal abnormalities, and external causes of morbidity. Exposed populations had non-increased risk of 9 ICD diagnosis categories of diseases of the genitourinary system, and prostate cancer.

CONCLUSIONS

There is consistent evidence of the association of coal mining with a wide spectrum of diseases in populations resident or in proximity of the mining activities. The methods of the studies included in this review can be integrated with individual-level and longitudinal studies to provide further evidence of the exposure pathways linked to increased risk in the exposed populations.

Cytogenetic monitoring of coal workers and patients with coal workers' pneumoconiosis in Turkey

Occupational exposure to coal dust causes coal workers' pneumoconiosis (CWP), which is a chronic inflammatory and fibrotic lung disease. Recently, chronic inflammation has been accepted as a crucial factor in the pathogenesis of neoplasia. The chronic inflammation provides dynamic setting for oxidative stress and formation of free radicals. Interaction of reactive oxygen species (ROS) with DNA augments the likelihood of DNA structural and transcriptional errors. The purpose of this study was to investigate the genotoxic risk in pneumoconiotic patients and in those with occupational exposure to coal dust. Therefore, sister chromatid exchange (SCE) and micronucleus (MN) tests were performed in Turkish CWP patients, coal workers, and an unexposed control group. Both SCE and MN frequencies in CWP patients were found significantly higher than in coal worker and unexposed groups. There were no differences between SCE and MN frequencies of coal worker and unexposed groups. On the other hand, no correlation between SCE frequency, duration of exposure, and age was observed in all three groups. There was also no effect of smoking on the frequencies of SCE and MN in the groups. Based on these results, it might be suggested that development of CWP leads to a significant induction of cytogenetic damage in peripheral lymphocytes of CWP patients. This is the first report on CWP patients with elevated cytogenetic endpoints. Further, a larger follow-up study is warranted.

Airborne exposures and risk of gastric cancer: A prospective cohort study

There is an unexplained male predominance among patients with gastric cancer, and many carcinogens are found in male-dominated dusty occupations. However, the relation between occupational exposures and risk of gastric cancer remains unclear. To investigate whether airborne occupational exposures might influence the risk of noncardia gastric cancer, we used a large, prospective cohort study of male Swedish construction workers. These workers were, during the period 1971-1993, regularly invited to health examinations by a nationwide occupational health service organization. Data on job titles and other variables were collected through self-administered questionnaires and forms completed by the health organization's staff. Industrial hygienists assessed 12 specific airborne occupational exposures for 200 job titles. Gastric cancer, death or emigration occurring during follow-up in 1971-2002 were identified by linkage to the Swedish registers of Cancer, Causes of Death and Total Population, respectively. Incidence rate ratios (IRR) and 95% confidence intervals (CI), adjusted for attained age, tobacco smoking, calendar period and body mass, were derived from Cox regression. Among 256,357 cohort members, contributing 5,378,012 person-years at risk, 948 noncardia gastric cancers were identified. Increased risk of this tumor was found among workers exposed to cement dust (IRR 1.5 [95% CI 1.1-2.1]), quartz dust (IRR 1.3 [95% CI 1.0-1.7]) and diesel exhaust (IRR 1.4 [95% CI 1.1-1.9]). Dose-response relations were observed for these exposures. No consistent positive associations were found regarding exposure to asbestos, asphalt fumes, concrete dust, epoxy resins, isocyanates, metal fumes, mineral fibers, organic solvents or wood dust. In conclusion, this study provides some support to the hypothesis that specific airborne exposures increase the risk of noncardia gastric cancer.

Occupation and gastric cancer

Gastric cancer is a cause of significant morbidity and mortality. There are several risk factors, with occupation emerging as one of these. There is considerable evidence that occupations in coal and tin mining, metal processing, particularly steel and iron, and rubber manufacturing industries lead to an increased risk of gastric cancer. Other "dusty" occupations-for example, wood processing, or work in high temperature environments have also been implicated but the evidence is not strong. The mechanism of pathogenesis of gastric cancer is unclear and the identification of causative agents can be difficult. Dust is thought to be a contributor to the pathological process, but well known carcinogens such as N-nitroso compounds have been detected in some environments. Further research on responsible agents is necessary and screening for detection of precursor gastric cancer lesions at the workplace merits consideration.

Mutagenicity of coal-dust and smokeless-tobacco extracts in Salmonella typhimurium strains with differing levels of O-acetyltransferase activities

Epidemiological studies have indicated an increased incidence of gastric neoplasia in coal miners. Because smokeless tobacco use is prevalent in the mining industry, nitrites or other components of these products may be etiologically associated with these gastric neoplasms. In this study both nitrosated and non-nitrosated coal-dust (from West Virginia and New Mexico) as well as smokeless-tobacco (snuff and chewing tobacco) extracts were examined for the presence of aromatic amines and nitroarenes by comparing the activities of these extracts in the pre-incubation variant of the Ames assay. Salmonella strains with differing O-acetyltransferase activities (TA98 and YG1024) were utilized in this investigation. The results of the examination of the coal-dust extracts indicated positive activity only in the nitrosated extracts. Both nitrosated extracts elicited an increased number of revertants (2-4-fold) on YG1024 without S9 in comparison to TA98, suggesting the presence of nitroarenes in these extracts. Additionally, the nitrosated West Virginia coal extract showed higher levels of activity on YG1024 with S9, indicating the possible presence of aromatic amines in this complex mixture. The non-nitrosated smokeless-tobacco extracts showed activity only on YG1024 in the presence of S9, with the highest amount of activity occurring in the snuff sample. Except for the chewing-tobacco extract on TA98 without S9, positive activity was found in both nitrosated tobacco extracts on YG1024 and TA98. As with the coal extracts, the presence of nitroarenes was inferred for these nitrosated materials. A comparative study of the non-nitrosated snuff extract across 5 tester strains with varying sensitivities to aromatic amines and nitroarenes (TA98NR, TA98/1,8-DNP6, TA98, YG1021 and YG1024) indicated that aromatic amines were a probable source of the mutagenic activity. The curing process and/or the addition of certain flavorants are potential sources of the mutagenic aromatic amines suggested to be present in the non-nitrosated snuff extract. These findings are consistent with an etiologic role supplementary to the nitroso compounds for mutagenic nitroarenes and aromatic amines in the development of gastric neoplasia in coal miners.

Occupational exposures as risk factors for gastric cancer in Italy

Occupational associations with gastric cancer were investigated in a multicenter case-control study in Italy involving interviews with 640 histologically confirmed male cases and 959 controls, randomly selected from the resident populations of the study areas. From information on the three jobs each person held the longest, risks were evaluated according to employment in 35 occupations (ever or 21+ years) and to estimated exposure (ever or 21+ years) to six chemicals using a job-exposure matrix. All risk estimates were adjusted by personal, demographic, and dietary variables identified as gastric-cancer risk factors in previous analyses. The only significantly increased risk was observed for sailors, seamen, and allied groups (ever employed: odds ratio [OR] = 2.9; 95 percent confidence interval [CI] = 1.1-8.0; 21+ years: OR = 3.1, CI = 0.8-13). Nonsignificant increases after 21+ years of employment were observed for forestry workers, miners, and janitors and cleaners. Crude ORs were elevated significantly among farmers, but adjusting for demographic and lifestyle factors largely eliminated the association: a nonsignificant 30 percent excess risk remained for farm laborers, but there was no rise in risk among long-term farm laborers and no excess among farm owners. Application of the job-exposure matrix revealed excess risks of borderline significance associated with potential exposure to mineral dusts and nitrogen oxides. For subjects with 21+ years of potential exposure, nonsignificantly increased risks were related to mineral dusts, asbestos, fertilizers, and nitrosamines.(ABSTRACT TRUNCATED AT 250 WORDS)

Screening for gastric carcinoma in coal miners

This study aimed to determine the prevalence of dyspeptic symptoms and premalignant gastric lesions in coal miners and sex matched population control subjects. Retired coal miners and men from the general population in north Nottinghamshire were sent a dyspepsia questionnaire to fill in, and those with upper gastrointestinal symptoms were invited for gastroscopy and biopsy. A total of 1272 men from the general population and 2099 retired coal miners aged 50-75 years took part in the study. Some 977 of 1272 (76.8%) control subjects and 1715 of 2099 (81.7%) miners replied to the questionnaire. A total of 308 of 977 (31.5%) controls and 620 of 1715 (36.2%) miners were positive for at least one symptom. There was a highly significant difference between the numbers of surface mine and underground workers who reported dyspeptic symptoms (66 of 300 (22%) v 425 of 1083 (32.2%) of p < 0.0001). Histology showed that significantly more miners than controls had acute on chronic gastritis (22 v 11%; p = 0.01) and intestinal metaplasia (23 v 8%; p = < 0.0001). Coal miners may be a suitable group for gastric premalignancy screening using an upper gastrointestinal symptom questionnaire and upper gastrointestinal endoscopy.

Long-term mortality in miners with coal workers' pneumoconiosis in The Netherlands: a pilot study

In order to investigate whether the prolonged exposure to coal mine dust increases the cancer risk for coal miners, a pilot study in a selected cohort of 334 Dutch miners with coal workers' pneumoconiosis (CWP), followed from 1956 until 1983, was conducted. In total, 165 miners had died (49.4%); for 162 (98.2%) the cause of death was traced. In comparison to the general Dutch male population, total mortality in the cohort was statistically significantly increased (SMR: 153). This was in general due to the significantly higher than expected cancer mortality (SMR: 163), cancer of stomach and small intestine (SMR: 401) and nonmalignant respiratory disease (SMR: 426). The lung cancer mortality was within the expected range.

Induction of morphological transformation by coal-dust extract in BALB/3T3 A31-1-13 cell line

The transforming activity of coal dust extracts was studied using BALB/3T3 clone A31-1-13 cells. Coal-dust extracts, both nitrosated and nonnitrosated, induced cell transformation in a dose-response manner. However, the transformation frequency was higher with the nitrosated than with the nonnitrosated extract. All transformed cell lines derived from coal-dust extract-induced foci showed biological characteristics of neoplastic transformation such as loss of contact inhibition and anchorage-independent growth. These results appear to support a hypothesis of coal mine dust causation of gastric cancer in coal miners.

Stomach cancer and work in dusty industries

The city of Stoke-on-Trent, whose major industries include coalmining, iron and steel, ceramics, and rubber, has death rates from stomach cancer some 80% above the national average. To explore the hypothesis that work in these dusty industries is responsible for the local excess of stomach cancer, we compared 95 incident cases with 190 age and sex matched community controls. Lifetime occupational histories and premorbid consumption of foods suspected of causing or protecting against stomach cancer were ascertained by a self administered questionnaire, supplemented at interview. Sixty eight cases had at some time held a manual job in one of the four dusty industries (relative risk = 1.4, 95% confidence interval 0.8-2.4). After allowance for diet, rubber manufacture was the industry most strongly associated with stomach cancer (relative risk = 2.5, 95% CI 1.0-6.4). Associations were also found with coal mining and ceramics but these were not statistically significant at a 5% level. The estimated proportion of stomach cancer attributable to the four dusty industries was 23%. It is concluded that the high incidence of stomach cancer in Stoke-on-Trent is unlikely to be explained solely by occupational exposure to dust.

Gastric cancer in coalminers: final report

A matched case-control study was conducted to investigate the risk of gastric cancer in coalminers in the southern part of Limburg, The Netherlands. All 683 male cases of gastric cancer were identified at the five pathology departments in the area, all histologically confirmed by a pathologist. For each case a control patient, free of gastric cancer, was selected from the same pathology department, matched on date of birth. Of the 1366 patients enrolled in the study, an occupational history was collected regarding previous employment in a Dutch coal mine. Of the patients with gastric cancer, 28% had been employed as underground workers in a coalmine compared with 25% of the control group. The odds ratio for underground coalmining and gastric cancer was 1.15 (95% confidence limits: 0.89-1.47). There was no evidence for the existence of a dose-response relation. It was concluded that the study did not provide support for the hypothesis that underground coalmining increases the risk of gastric cancer.

Dust exposure, pneumoconiosis, and mortality of coalminers

General mortality in approximately 25 000 British coalminers over 22 year periods ending in 1980 was 13% lower on average than in English and Welsh men in the same regions of Britain. There were significant within region variations between collieries, and standardised mortality ratios increased during the later years of the follow up, approaching or slightly exceeding 100 in most of the 20 coalmines studied. Age specific comparisons of 22 year survival rates were made in subgroups. Relative risks of death from all non-violent causes for men with the earliest stage of progressive massive fibrosis (PMF category A), compared with risks in miners with no pneumoconiosis (category O), ranged from 1.2 in those aged 55-64 initially to 3.5 for those aged 25-34. Mortality in miners with higher categories of PMF (B or C) was even more severe. Survival rates in men with category 1 simple pneumoconiosis were about 2% to 3% lower than in miners with radiographs classified as category O, but there was no consistent evidence of an increase in mortality with increasing category of simple pneumoconiosis. Mortality from all non-violent causes increased systematically with increases in estimates of exposure to dust before the start of the follow up. That gradient was attributable primarily to deaths certified as due to pneumoconiosis and those recorded as due to bronchitis and emphysema (p less than 0.001). There was some evidence of a dust related increase in deaths from cancers of the digestive system (p approximately equal to 0.05), but none of an association between exposure to coalmine dust and lung cancer. Lung cancer mortality, assessed over 17 year periods, was about 5.5 times higher in smokers than in life long non-smokers. Smokers with no pneumoconiosis had slightly higher lung cancer death rates than smokers with pneumoconiosis. We conclude that miners exposed to excessive amounts of respirable coalmine dust are at increased risk of premature death, either from progressive massive fibrosis or from chronic bronchitis or emphysema.

Gastric cancer in coal miners: a case-control study in a coal mining area

In collaboration with three pathology departments a case-control study was conducted in the southern part of the Netherlands to investigate the risk of gastric cancer in coal miners. Between 1 January 1973 and 31 December 1983, 323 male patients were diagnosed as having a malignant neoplasm of the stomach. For each case a control was selected from the same pathology department, matched on year of birth and regardless of diagnosis. The archives of the Central Coal Miners Pension Fund were searched to obtain information about whether or not a patient had ever worked for a coal mining company in the Netherlands. Twenty two per cent of the patients had been registered as an underground coal miner, compared with 20% of the control group (odds ratio of 1.14, 95% confidence interval: 0.33-1.73). Those with gastric cancer who had ever worked underground in a coal mine did so for an average period of 16.9 years compared with an average of 19.7 years in the control group. The study gives no indication that the underground workers of the Dutch coal mines had a raised risk of developing a malignant neoplasm of the stomach.

Induction of sister chromatid exchanges by coal dust and tobacco snuff extracts in human peripheral lymphocytes

The organic solvent extracts of sub-bituminous coal dust and tobacco snuff, both together and separately, were tested for the induction of sister chromatid exchanges (SCEs) in human peripheral lymphocytes. The results indicate that these extracts induced SCEs, and that when tested together synergistically induced SCEs in two of three donors. Studies with the organic solvent extracts of all five ranks of coal indicate that the extracts of bituminous, lignite, and peat, but not anthracite, induced SCEs. Similar experiments conducted with water extracts show that bituminous, lignite, and peat, but not sub-bituminous extracts, induced SCEs, and that anthracite was equivocal. To determine whether individuals differed in their SCE responses to coal dust extracts, lymphocytes from five donors were tested with organic solvent extracts of bituminous and sub-bituminous coal. An analysis of variance indicates that the SCE response was significantly influenced by the donor (p less than 0.0001) and each of the two coal extracts (p less than 0.0001). From studies of workers occupationally exposed to coal dust, it is known that inhaled coal dust is cleared from the lungs by mucociliary action and introduced into the stomach by swallowing. Coal dust, or coal dust plus snuff, may be responsible for the increased frequency of gastric cancer observed in coal miners. The findings presented here suggest that coal dust, with or without tobacco snuff, may play a role in the elevated incidence of gastric cancer in coal miners. Because water extracts of some ranks of coal induced SCEs, there exists the possibility of adverse environmental effects due to coal leachates.

Genotoxic activity of nitrosated coal dust extract in mammalian systems

The genotoxicity of coal dust extract nitrosated by NaNO2 was investigated because of an elevated incidence of gastric cancer in coal miners. Human peripheral lymphocytes were used to determine the frequency of sister chromatic exchanges (SCE) and chromosome aberrations. Chinese Hamster Ovary (CHO) cells were also used to measure SCEs. The mouse lymphoma forward mutation assay comprised the final in vitro system, while the micronucleus test on mouse bone marrow cells was used as an in vivo assay. The SCE frequency in human lymphocytes increased from 9.2 per cell in untreated cultures to 31.6 per cell in cultures treated with 10.0 microliter/ml of nitrosated coal dust extract (NCDE) (P less than .0001). Chromosome aberrations were tested during two phases of the cell cycle; the results indicate that NCDE causes an increase in aberrations in each cell phase tested. The SCE frequency in the CHO system increased from 9.0 per cell in untreated cultures to 18.0 per cell in cultures treated with 3.3 microliter NCDE per ml of medium (P less than .001). In the mouse lymphoma system, the background mutation frequency was tripled at 2.0 microliter NCDE per ml of medium. NCDE was not found to be active in the murine micronucleus assay. No consistent increase in genetic activity was observed with nonnitrosated coal dust extract alone or with NaNO2 alone. Metabolic activation greatly reduced or eliminated genetic activity. These results indicate that nitrosated coal dust extract is genetically active in in vitro mammalian systems without metabolic activation. These findings suggest that the nitrosation of ingested coal dust may be responsible for the elevated incidence of gastric cancer in coal miners.

Mutagenicity of tobacco snuff: possible health implications for coal miners

Mutagenicity of tobacco snuff extracts was studied using the Ames Salmonella/microsome assay system. No mutagenic activity was found for tobacco snuff extracts without S9 activation. However, mutagenic substances were formed from tobacco snuff extracts in an acidic environment. The mutagenic substances induced predominantly frameshift mutations and were direct-acting mutagens. Mutagenic activity of tobacco snuff extracts was enhanced in the presence of coal-dust extracts at low pH. Since tobacco snuff has been used by some coal miners to substitute for cigarettes, a possible risk for gastric cancer induction among coal miners is proposed.

Role of nitrosation in the mutagenic activity of coal dust: a postulation for gastric carcinogenesis in coal miners

The mutagenicity of coal dust solvent extracts with and without nitrosation was studied using the Salmonella/microsome assay system. Coal dust solvent extracts were either non-mutagenic or very weakly mutagenic with S9 activation. High mutagenic activities, however, were found when extracts of bituminous, subbituminous, and lignite coal dusts were reacted with nitrite under an acidic condition. Formation of mutagens from coal dust extracts by nitrosation was highest at pH 3.2 and decreased with increasing pH in the reaction mixture. Mutagenic activity appeared to be independent of metabolic activation. The mutagens formed from nitrosation of coal dust extracts induced frameshift mutations. The results reported here may have possible implications for the explanation of an elevated incidence of gastric cancer in coal miners.

Does coal mine dust present a risk for lung cancer? A case-control study of U.S. coal miners

This paper evaluates the relationship between the risk of lung cancer mortality and coal mine dust exposure under control by cigarette smoking status. Two case-control studies based on 317 white male lung cancer mortality cases are presented. A one-to-one matched-case design allows examination of the risk of coal mine dust exposure and cigarette smoking. A two-to-one matched-case design was employed to examine the lung cancer risk of coal mine dust exposure independent of cigarette smoking. Based upon these data, no evidence of a coal mine dust exposure-lung cancer risk was found, although the expected increased risk for lung cancer in cigarette smokers was observed. There was no evidence of an interactive effect between cigarette smoking and coal mine dust exposure.

Gastric cancer in coal miners: an hypothesis of coal mine dust causation

An hypothesis is proposed to explain the elevated incidence of gastric cancer among coal miners. Inhaled coal mine dust, especially the larger particles, is cleared from the lung and tracheobronchial tree by mucociliary function, swallowed, and introduced into the stomach. Organic and/or inorganic materials in the dust can undergo intra-gastric nitrosation and/or interaction with exogenous chemicals to form carcinogenic compounds which in turn may lead to precancerous lesions, which may subsequently develop into gastric cancer. This sequence of events, however, depends upon occupational exposures as well as life-style features and individual genetic predisposition.

Gastric cancer and coal mine dust exposure. A case-control study

Based on evidence that coal miners have elevated gastric cancer mortality rates, a case-control study was developed to assess the gastric cancer risk of coal mine dust exposure. Forty-six cases of US white male gastric cancer deaths from NIOSH coal miner cohorts were individually matched by age to controls. From these data we show that a statistically elevated gastric cancer risk exists for miners who have prolonged exposure to coal mine dust and prolonged exposure to cigarette smoke. Coal workers' pneumoconiosis, a disease defined in terms of coal dust deposition in the lungs, was not found to be a gastric cancer risk.

Health effects of coal mining and combustion: carcinogens and cofactors

Some polynuclear aromatics (PNA) have been found to be potent carcinogens for all tissues and organs of experimental animals that have been exposed to them, but different dose levels are needed for these effects. They have been known for decades to cause cancer at the site of application but also at certain sites distant from the area of contact. Although some hydrocarbons are potent and complete carcinogens, the majority of related hydrocarbons was originally found to be inactive. Since they generally appear together, it was important to know more about their interaction, particularly whether they would synergize, or antagonize. The polycyclic hydrocarbons have been studied by subcutaneous injection, where they prove very potent carcinogens. They are also very active on the skin of mice where they produce cancer on prolonged application. Inhalation studies, require larger doses yielded negative results until particulate matter was introduced which facilitated the development of lung tumors. Although iron oxide dust was used initially, other dusts were also capable of enhancing the response of the tissue to benzo(a)pyrene carcinogenesis. This point is of importance, particularly since the inhalation of PNA in situations of air pollution or coal mining involves particulates, although of a different type. Soot is not a homogenous substance and several factors determine its properties. Soots will lose some of the absorbed chemicals during their residence in air, but they retain their PNAs for long periods of time when they reach the soil. The carcinogenicity of PNAs in the adsorbed state may be completely absent, depending on particle size of the soot and availability of eluting capability of the tissues or cells in contact with the soot. Whenever the carcinogenic polynuclear aromatics can be eluted they will be active in producing cancer if their residence is adequate. There seems to be no reason to assume that a large increase in coal combustion in the future will by necessity lead to greater risks of cancer to the coal miners or the general urban dweller, because activities to be started now can take into consideration the requirements necessary for control of air pollution in mines as well as in cities. If new uses of coal will be developed, it will be a completely different situation, and statements about the carcinogenic risk from coal utilization do not apply there. Although some of the same carcinogenic PNAs are involved in the health hazards from those processes, other carcinogens and also cocarcinogens will be present, and the exposed workers will not have the apparent benefits of adsorption of PNAs on soot.

Occupational safety and health implications of increased coal utilization

An area of major concern in considering increased coal production and utilization is the health and safety of increased numbers of workers who mine, process, or utilize coal. Hazards related to mining activities in the past have been especially serious, resulting in many mine related accidental deaths, disabling injuries, and disability and death from chronic lung disease. Underground coal mines are clearly less safe than surface mines. Over one-third of currently employed underground miners experience chronic lung disease. Other stresses include noise and extremes of heat and cold. Newly emphasized technologies of the use of diesel powered mining equipment and the use of longwall mining techniques may be associated with serious health effects. Workers at coal-fired power plants are also potentially at risk of occupational diseases. Occupational safety and health aspects of coal mining are understood well enough today to justify implementing necessary and technically feasible and available control measures to minimize potential problems associated with increased coal production and use in the future. Increased emphasis on safety and health training for inexperienced coal miners expected to enter the work force is clearly needed. The recently enacted Federal Mine Safety and Health Act of 1977 will provide impetus for increased control over hazards in coal mining.