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Biomedical subjects

T Sorahan

Publications and source records attributed to T Sorahan.

At least 19 recordsLinked to original sources

A further cohort study of workers employed at a factory manufacturing chemicals for the rubber industry, with special reference to the chemicals 2-mercaptobenzothiazole (MBT), aniline, phenyl-beta-naphthylamine and o-toluidine.

OBJECTIVES: To investigate mortality and cancer morbidity in workers from a factory manufacturing chemicals for the rubber industry. METHODS: The mortality (1955-96) and cancer morbidity experience (1971-92) of a cohort of 2160 male production workers from a chemical factory in north Wales were investigated. All subjects had at least 6 months employment at the factory and some employment in the period 1955-84. Detailed job histories were abstracted from company computerised records and estimates of individual cumulative exposure to 2-mercaptobenzothiazole (MBT) and its derivatives were obtained, with a job exposure matrix derived by a former factory hygienist. Durations of employment in the aniline, phenyl-beta-naphthylamine (PBN) and o-toluidine departments were also calculated. Two analytical approaches were used, indirect standardisation and Poisson regression. RESULTS: Based on serial rates for the general population of England and Wales, observed mortality for the total cohort was close to expectation for all causes (observed (obs) deaths 1131, expected (exp) deaths 1114.5, standardised mortality ratio (SMR) 101), and for all cancers (obs 305, exp 300.2, SMR 102). There was a significant (p < 0.05) excess mortality from cancer of the bladder in the 605 study subjects potentially exposed to one or more of the four chemicals being investigated (obs 9, exp 3.25, SMR 277, 95% confidence interval (95% CI) 127 to 526). This excess was dependent primarily on deaths occurring > 20 years after first exposure in those who started employment before 1955 (obs 7, exp 1.25, SMR 560, 95% CI 225 to 1154, p < 0.001). There were 30 subjects in the total study cohort who, on the basis of death certificates or cancer registration particulars, had had malignant bladder cancer. In separate analyses of the four exposure history variables (after adjustment for age), Poisson regression showed significant positive trends for risk of notification of bladder cancer increasing with cumulative duration of employment in the PBN (p < 0.001) and o-toluidine departments (p < 0.01); similar findings were not obtained for cumulative exposure to MBT or for duration of employment in the aniline department. In a simultaneous analysis of all four chemical exposure variables, a significant positive trend remained for duration of employment with exposure to PBN (p < 0.05). Further analyses of all cases of bladder cancer (malignant and benign diagnoses) used employment histories lagged by 15 years; similar findings were obtained. CONCLUSIONS: It seems likely that some members of this cohort have had occupational bladder cancer. Confident interpretation is difficult because of small numbers in the exposed subcohorts, relatively crude measures of exposure assessment for the four chemicals under study, and presence of unconsidered potential chemical confounders. The simplest interpretation of the findings about bladder cancer may be that PBN (or a chemical reagent or chemical intermediate associated with its production at this factory in the 1930s and 1940s) is a bladder carcinogen. Priority should be given, however, to obtaining information on the cancer experience of other working populations exposed to PBN or to o-toluidine.

2-Naphthylamine

Maternal occupational exposure to electromagnetic fields before, during, and after pregnancy in relation to risks of childhood cancers: findings from the Oxford Survey of Childhood Cancers, 1953-1981 deaths.

BACKGROUND: The concern that maternal exposure to electromagnetic fields (EMF) might be related to childhood cancer risks, particularly leukemia risks. METHODS: Maternal occupational data already collected as part of the Oxford Survey of Childhood Cancers have been reviewed. Information on occupations held before, during, and after the pregnancy was sought for 15,041 children dying of cancer in Great Britain in the period 1953-1981, and for an equal number of matched controls. Each period of working was classified under one of five headings: (1) sewing machinist; (2) textile industry workers (other than sewing machinists) with likely exposures to EMF; (3) other machinists and other jobs with likely "higher" EMF exposure; (4) other jobs with likely exposure to some EMF, and (5) jobs with little potential for EMF exposure. RESULTS: Relative to risks in the children of mothers who held occupations with little potential for EMF exposure during pregnancy (a category that included housewives), risks of all childhood cancers were close to unity both for the children of sewing machinists (22 case and 31 control mothers, RR 0.72, 95% CI 0.42 to 1.25) and for the children of other machinists with likely "higher" EMF exposures (44 case and 47 control mothers, RR 0.93, 95% CI 0.61 to 1.41). Corresponding risks for all childhood leukemias and for all childhood brain cancers were similarly unexceptional. Simultaneous adjustment for social class, maternal age at birth of child, and sibship position had little effect. CONCLUSIONS: The study findings did not indicate that maternal occupational exposure to EMF during pregnancy is a risk factor for childhood leukemias, childhood brain cancers, or the generality of all childhood cancers.

Adolescent

Occupational urothelial tumours: a regional case-control study.

OBJECTIVE: To investigate the role of occupational exposures in the risk of developing urothelial cancer. MATERIALS AND METHODS: Occupational histories, obtained using a self-administered questionnaire, for 803 patients with urothelial cancer (first diagnosed 1991-93) were compared with similar information for 2135 matched controls. Relative risks (RRs) were estimated using conditional logistic regression. Comparisons were also made with historical regional employment information available from the 1971 census. RESULTS: There were many statistically significant positive associations for urothelial cancer risks and ever being employed in specified occupations (with or without statistical adjustment for smoking status in 1991). Smoking-adjusted RRs of > 2.0 were obtained for seven occupations; manufacture of fire lighters/ patent fuels (RR 4.30, 95% confidence interval 0.78-23.79), rodent extermination (3.71, 1.20-11.48), manufacture of dyestuffs (2.61, 0.98-7.00), leather work (2.51, 1.44-4.35), cable manufacturing industry (2.46, 1.20-5.04), textile printing and dyeing (2.32, 0.98-5.45), and sewage works (2.19, 1.16-4.11). Analyses of the occupations followed in 1971 (thus allowing for 20-year latency) indicated an elevated RR for workers in the plastics industry (5.22, 1.57-17.36). CONCLUSIONS: The historical legacy of exposure to aromatic amines in the rubber, cable-making, dyestuffs and other industries remains. An important proportion of patients presenting with urothelial tumours are likely to have had occupational exposure to urothelial carcinogens. A review of occupational exposures in the contemporaneous plastic, textile and leather industries is warranted.

Adult

Lung cancer mortality in nickel/chromium platers, 1946-95.

OBJECTIVES: To investigate mortality from lung cancer in nickel/chromium platers. METHODS: The mortality experience of a cohort of 1762 chrome workers (812 men, 950 women) from a large electroplating and light engineering plant in the Midlands, United Kingdom, was investigated for the period 1946-95. All subjects were first employed in chrome work at the plant during the period 1946-75, and had at least six months employment in jobs associated with exposure to chromic acid mist (hexavalent chromium). Detailed job histories were abstracted from original company personnel records and individual cumulative durations of employment in three types of chrome work were derived as time dependent variables (chrome bath work, other chrome work, any chrome work). Two analytical approaches were used--indirect standardisation and Poisson regression. RESULTS: Based on mortalities for the general population of England and Wales, male workers with some period of chrome bath work had higher lung cancer mortalities (observed deaths 40, expected deaths 25.41, standardised mortality ratio (SMR) 157, 95% confidence interval (95% CI) 113 to 214, p < 0.01) than did other male chrome workers (observed 9, expected 13.70, SMR 66, 95% CI 30 to 125). Similar findings were shown for female workers (chrome bath workers: observed 15, expected 8.57, SMR 175, 95% CI 98 to 289, p = 0.06; other chrome workers: observed 1, expected 4.37, SMR 23, 95% CI 1 to 127). Poisson regression was used to investigate risks of lung cancer relative to four categories of cumulative duration of chrome bath work and four categories of cumulative duration of other chrome work (none, < 1 y, 1-4 y, > or = 5 y). After adjusting for sex, age, calendar period, year of starting chrome work, period from first chrome work, and employment status (still employed v left employment), there was a significant positive trend (p < 0.05) between duration of chrome bath work and risks of mortality for lung cancer. Relative to a risk of unity for those chrome workers without any period of chrome bath work, risks were 2.83 (95% CI 1.47 to 5.45), 1.61 (95% CI 0.75 to 3.44), and 4.25 (95% CI 1.83 to 9.87) for the second, third, and fourth exposure categories, respectively. Duration of other chrome work was not a useful predictor of risks of lung cancer. Similar findings for both variables were obtained when adjustment was made for sex and age only. Similar findings for both variables were obtained relative to risk of chrome nasal ulceration. CONCLUSIONS: The findings are consistent with the hypothesis that soluble hexavalent chromium compounds are potent human lung carcinogens.

Adult

Cancer in the offspring of radiation workers: a record linkage study.

OBJECTIVES: To test the "Gardner hypothesis" that childhood leukaemia and non-Hodgkin lymphoma can be caused by fathers' exposure to ionising radiation before the conception of the child, and, more generally, to investigate whether such radiation exposure of either parent is a cause of childhood cancer. DESIGN: Case-control study. SETTING: Great Britain. SUBJECTS: 35,949 children diagnosed as having cancer, together with matched controls. MAIN OUTCOME MEASURES: Parental employment as radiation worker as defined by inclusion in the National Registry for Radiation Workers and being monitored for external radiation before conception of child; cumulative dose of external ionising radiation for various periods of employment before conception; dose during pregnancy. RESULTS: After cases studied by Gardner and colleagues were excluded, fathers of children with leukaemia or non-Hodgkin lymphoma were significantly more likely than fathers of controls to have been radiation workers (relative risk 1.77, 95% confidence interval 1.05 to 3.03) but there was no dose-response relation for any of the exposure periods studied; indeed, the association was greatest for those with doses below the level of detection. No increased risk was found for fathers with a lifetime preconception dose of 100 mSv or more, or with a dose in the 6 months before conception of 10 mSv or more. There was no increased risk for the group of other childhood cancers. Mothers' radiation work was associated with a significant increase of childhood cancer (relative risk 5.00, 1.42 to 26.94; based on 15 cases and 3 controls). Only four of the case mothers and no controls were radiation workers during pregnancy. CONCLUSIONS: These results do not support the hypothesis that paternal preconception irradiation is a cause of childhood leukaemia and non-Hodgkin lymphoma; the observed associations may be chance findings or results from exposure to infective or other agents. If there is any increased risk for the children of fathers who are radiation workers, it is small in absolute terms: in Britain the average risk by age 15 years is 6.5 per 10,000; our best estimate, using all available data, is that the increase is 5.4 per 10,000. For mothers, the numbers are too small for reliable estimates of the risk, if any, to be made.

Adolescent

Childhood cancer and parental use of tobacco: deaths from 1953 to 1955.

Parental smoking data have been abstracted from the interview records of the case-control study that first indicated that pregnancy radiographs are a cause of childhood cancer (Oxford Survey of Childhood Cancers, deaths from 1953 to 1955). Reported smoking habits for the parents of 1549 children who died from cancer were compared with similar information for the parents of 1549 healthy controls (matched pairs analysis). There was a statistically significant positive trend between paternal daily consumption of tobacco and the risk of childhood cancer (P< 0.001). This association could not be explained by maternal smoking, social class, paternal or maternal age at the birth of the survey child, sibship position or obstetric radiography. About 15% of all childhood cancers in this series could be attributable to paternal smoking.

Case-Control Studies

Childhood cancer and parental use of tobacco: deaths from 1971 to 1976.

Parental smoking data have been reabstracted from the interview records of the Oxford Survey of Childhood Cancers (deaths from 1971 to 1976). Reported smoking habits for the parents of 2587 children who died with cancer were compared with similar information for the parents of 2587 healthy controls (matched pairs analysis). Maternal daily consumption of cigarettes and paternal use of pipes or cigars were unimportant, but there was a statistically significant positive trend between paternal daily consumption of cigarettes and the risk of childhood cancer (P < 0.001). This association could not be explained by maternal smoking, social class, parental ages at the birth of the survey child, sibship position or obstetric radiography. Relations between maternal consumption of cigarettes and birth weights suggested that (maternal) smoking data were equally reliable for case and control subjects. About 14% of all childhood cancers in this series could be attributable to paternal smoking. These data were combined with smoking data from two previously published reports from the Oxford Survey (deaths from 1953 to 1955, deaths from 1977 to 1981) to obtain further information on risks for different types of cancer and different ages at onset of disease. Paternal cigarette smoking emerged as a potential risk factor both for the generality of childhood cancer and for all ages at onset.

Adolescent

A case-control study of percutaneous nephrolithotomy versus extracorporeal shock wave lithotripsy.

OBJECTIVES: To assess the relative efficacy of percutaneous nephrolithotomy (PCN) and extracorporeal shock wave lithotripsy (ESWL) in clearing stones and to examine factors which affected the results from each treatment. PATIENTS AND METHODS: The study comprised 390 patients treated with PCN who were compared to 618 patients treated with ESWL. Unconditional logistic regression analysis was used to compare the odds of success and failure in the PCN group with those in the ESWL group, whilst controlling for any potential effects of age, sex, laterality, presence of other stones, previous stone history, pre-operative treatment and centre. RESULTS: PCN was more successful in obtaining satisfactory results than ESWL with an odds ratio of 2.67 (P < 0.001, 95% confidence intervals 1.84-3.87). The odds ratio in favour of PCN was increased after controlling for differences by centre (odds ratio 5.18, 95% confidence intervals 2.89-9.16). No other factors significantly influenced the odds ratio. ESWL was less successful in treating stones > 2 cm in diameter compared to treating stones < 2 cm in diameter (P = 0.001). ESWL results were also affected by re-treatment rates, which were influenced by distance of the local hospital from the lithotripter. The results with PCN improved with experience. The results of ESWL were satisfactory and the treatment cheaper, with a lower morbidity and hospital stay than after PCN for stones < 2 cm in diameter, making it the treatment of choice. However for stones > 2 cm, the results of ESWL were not as good and costs of treatment, morbidity and hospital stay were much closer to those of PCN for similar sized stones. CONCLUSIONS: PCN is more effective than ESWL in clearing stones. However, ESWL is an effective treatment and is usually the treatment of choice for most stones. Nevertheless, PCN remains an important and extremely effective method of treatment. The choice of treatment for stones will be influenced by the distance of a centre from a static lithotripter, and the potential availability of a mobile lithotripter.

Adolescent

Occupational exposure to magnetic fields in relation to mortality from brain cancer among electricity generation and transmission workers.

OBJECTIVE: To investigate whether the risks of mortality from brain cancer are related to occupational exposure to magnetic fields. METHODS: A total of 112 cases of primary brain cancer (1972-91) were identified from a cohort of 84,018 male and female employees of the (then) Central Electricity Generating Board and its privatised successor companies. Individual cumulative occupational exposures to magnetic fields were estimated by linking available computerised job history data with magnetic field measurements collected over 675 person-workshifts. Estimated exposure histories of the case workers were compared with those of 654 control workers drawn from the cohort (nested case-control study), by means of conditional logistic regression. RESULTS: For exposure assessments based on arithmetic means, the risk of mortality from brain cancer for subjects with an estimated cumulative exposure to magnetic fields of 5.4-13.4 microT.y v subjects with lower exposures (0.0-5.3 microT.y) was 1.04 (95% confidence interval (95% CI) 0.60 to 1.80). The corresponding relative risk in subjects with higher exposures (> or = 13.5 microT.y) was 0.95 (95% CI 0.54 to 1.69). There was no indication of a positive trend for cumulative exposure and risk of mortality from brain cancer either when the analysis used exposure assessments based on geometric means or when the analysis was restricted to exposures received within five years of the case diagnosis (or corresponding period for controls). CONCLUSIONS: Although the exposure categorisation was based solely on recent observations, the study findings do not support the hypothesis that the risk of brain cancer is associated with occupational exposure to magnetic fields.

Brain Neoplasms

Lung cancer mortality in a cohort of workers employed at a cadmium recovery plant in the United States: an analysis with detailed job histories.

OBJECTIVES: To identify and measure any relations between occupational exposure to cadmium compounds (oxide, sulphide, and sulphate) and the risk of mortality from lung cancer. METHODS: The mortality experience of 571 male production workers from a cadmium recovery facility in the United States was investigated for the period 1940-82. All study subjects were first employed in the period 1926-69; they had all been employed for at least six months between 1 January 1940 and 31 December 1969. Newly abstracted detailed job histories for the period 1926-76 were combined with assessments of exposures to cadmium over time to develop individual estimates of cumulative exposure to cadmium (total exposure and exposures received both in the presence and absence of "high" exposures to arsenic trioxide). Poisson regression was used to investigate risks of mortality from lung cancer in relation to four concentrations of cumulative exposure to cadmium (< 400, 400-999, 1000-1999, > 2000 mg.m-3.days). RESULTS: After adjustment for age attained, year of hire, and Hispanic ethnicity, there was a significant positive trend (P < 0.05) between cumulative exposure to cadmium and risks of mortality from lung cancer. Relative to a risk of unity for the lowest exposure category (first level), risks were 2.30 (95% confidence interval (95% CI) 0.72 to 7.36), 2.83 (95% CI 0.75 to 10.72), and 3.88 (95% CI 1.04 to 14.46) for the second, third, and fourth categories, respectively. Similar findings were obtained after adjustment for age only. Trends were more pronounced when employment histories were lagged first by 10 years and then by 20 years. A separate analysis examined the independent effects of exposure to cadmium received in the presence of high exposures to arsenic trioxide (mainly cadmium oxide) and exposures to cadmium received without such exposure to arsenic (mainly cadmium sulphide and cadmium sulphate). A significant trend for a risk of lung cancer was found only for exposures to cadmium received in the presence of arsenic trioxide. CONCLUSIONS: Hypotheses which are consistent with the study findings include: (a) cadmium oxide in the presence of arsenic trioxide is a human lung carcinogen, (b) cadmium oxide and arsenic trioxide are human lung carcinogens and cadmium sulphate and cadmium sulphide are not (or they are less potent carcinogens), or (c) arsenic trioxide is a human lung carcinogen and cadmium oxide, cadmium sulphate, and cadmium sulphide are not. There were only 21 deaths from lung cancer available for this analysis and it is impossible to gauge which, if any, of these hypotheses are correct.

Arsenic Trioxide

Mortality study of nickel platers with special reference to cancers of the stomach and lung, 1945-93.

OBJECTIVES: To re-examine mortality patterns in a cohort of nickel platers with no history of chromium plating. METHODS: All 284 men first employed by the company in 1945-75 with a minimum employment of three months in the nickel plating department were identified. Workers who had worked in the chromium plating or nickel/chromium plating departments were excluded. Standardised mortality ratios (SMRs), P values, and 95% confidence intervals were calculated. Poisson regression was used to carry out statistical modelling of mortalities within the cohort (internal standard). Four variables were considered to have the potential to influence mortality within the cohort: attained age (age at follow up or age at death), year of starting nickel work, period of follow up (measured from the first period of work with nickel exposure), and duration of exposure to nickel. RESULTS: The only significant difference between observed and expected numbers, when investigated by site of cancer and by broad non-cancer groupings, was that for stomach cancer (observed eight, expected 2.49, SMR 322). CONCLUSIONS: The study provides only weak evidence that nickel plating is associated with an excess risk of stomach cancer. This cohort of nickel platers does not seem to have experienced any discernible risk of occupational lung cancer. Other studies of nickel platers rather than nickel/chromium platers would be useful.

Cohort Studies

Childhood cancer and paternal exposure to ionizing radiation: a second report from the Oxford Survey of Childhood Cancers.

Paternal occupational data already collected as part of the Oxford Survey of Childhood Cancers have been reviewed. Information on paternal occupation was available for 14,869 children dying from cancer in England, Wales, and Scotland in the period 1953-81 and for an equal number of matched controls. The importance of fathers working, at any time before or after conception of the survey child, in any of the following occupations was assessed: radiologists (clinical), surgeons and anesthetists, veterinary surgeons, dental surgeons, nuclear industry workers, industrial radiographers. There was no indication that preconception employment in any of these occupations was more important than postconception employment with regard to the risks of all childhood cancers or all childhood leukemias. Findings were consistent with neither paternal preconception exposure to external ionizing radiation nor exposure to unsealed sources of radionuclides being an important risk factor for childhood leukemia or for the overall grouping of all childhood cancers.

Case-Control Studies

Childhood cancer and parental use of alcohol and tobacco.

Reported consumptions of alcohol and tobacco for the parents of 1641 children who died with cancer in England and Wales during the period 1977 to 1981 were compared with similar information for the parents of 1641 control subjects. Consumption of alcohol by fathers was not associated with an increased risk of childhood cancer (relative risk (RR)) = 1.05; 95% confidence interval (CI): 0.86 to 1.28), but for daily consumption of cigarettes was not shown to be associated with an increased risk and consumption of alcohol was associated with a relatively low cancer risk (RR = 0.82; 95% CI: 0.70 to 0.96). Relations between maternal consumption of cigarettes and birth weights suggested that the smoking data were equally reliable for case patients and control subjects.

Alcohol Drinking

Determinants of fetal haemoglobin in newborn infants.

Percentage fetal haemoglobins (% HbF) were measured in 7081 newborns at the University Hospital, Nottingham, between 1990 and 1992 to assess the effects of a range of factors, and to determine if there was an association between % HbF at birth and risk of SIDS (sudden infant death syndrome). Data from the obstetric clinical records were analysed by multiple linear regression to establish the major determinants of % HbF. New findings were the identification of maternal smoking, twin pregnancy, ethnic origin, and season of birth as significant determinants. Alcohol use, drug and vitamin intake, and duration of labour were not found to be important. The previously reported correlations between % HbF and sex, gestational age, and birthweight were confirmed, and the relative effects quantified. Overall, the major determinants of an increase in % HbF in neonates are similar to the known antenatal risk factors for sudden infant death syndrome (SIDS).

Birth Weight

Mortality of copper cadmium alloy workers with special reference to lung cancer and non-malignant diseases of the respiratory system, 1946-92.

OBJECTIVES: To identify and quantify any relations between occupational exposure to cadmium oxide fume and mortalities from lung cancer and from chronic non-malignant diseases of the respiratory system. METHODS: The mortality experience of 347 copper cadmium alloy workers, 624 workers employed in the vicinity of copper cadmium alloy work (vicinity workers), and 521 iron and brass foundry workers (all men) was investigated for the period 1946-92. All subjects were first employed in these types of work in the period 1922-78 and for a minimum period of one year at one of two participating factories. Two analytical approaches were used, indirect standardisation and Poisson regression. RESULTS: Compared with the general population of England and Wales, mortality from lung cancer among copper cadmium alloy workers was close to expectation (observed deaths 18, expected deaths 17.8, standardised mortality ratio (SMR) 101, 95% confidence interval (95% CI) 60 to 159). A significant excess was shown for lung cancer among vicinity workers but not among iron and brass foundry workers (vicinity workers: observed 55, expected 34.3, SMR 160, 95% CI 121 to 209, P < 0.01; iron and brass foundry workers: observed 19, expected 17.8, SMR 107, 95% CI 64 to 167). Increased SMRs for non-malignant diseases of the respiratory system were shown for each of the three groups (alloy workers: observed 54, expected 23.5, SMR 230, 95% CI 172 to 300, P < 0.001; vicinity workers: observed 71, expected 43.0, SMR 165, 95% CI 129 to 208, P < 0.001; iron and brass foundry workers: observed 34, expected 17.1, SMR 199, 95% CI 137 to 278, P < 0.01). Work histories of the copper cadmium alloy workers were combined with independent assessments of cadmium exposures over time to develop individual estimates of cumulative exposure to cadmium; this being a time dependent variable. Poisson regression was used to investigate risks of lung cancer and risks of chronic non-malignant diseases of the respiratory system in relation to three levels of cumulative cadmium exposure (< 1600, 1600-4799, > or = 4800 micrograms.m-3.y). After adjustment for age, year of starting alloy work, factory, and time from starting alloy work, there was a significant positive trend (P < 0.01) between cumulative exposure to cadmium and risks of mortality from chronic non-malignant diseases of the respiratory system. Relative to a risk of unity for the lowest exposure category, risks were 4.54 (95% CI 1.96 to 10.51) for the middle exposure category and 4.74 (95% CI 1.81 to 12.43) for the highest exposure category. There was a non-significant negative trend between cumulative cadmium exposure and risks of mortality from lung cancer. Relative to a risk of unity for the lowest exposure category, risks were 0.85 (95% CI 0.27 to 2.68) for the middle exposure category and 0.81 (95% CI 0.18 to 3.73) for the highest exposure category. Similar findings were obtained when adjustment was made for age only. CONCLUSIONS: The findings are consistent with the hypothesis that exposure to cadmium oxide fume increases risks of mortality from chronic non-malignant diseases of the respiratory system. The findings do not support the hypothesis that exposure to cadmium oxide fume increases risks of mortality for lung cancer.

Alloys