Mortality of white South African gold miners.

Objectives: This two part study aimed to determine whether there was an excess mortality generally or for some diseases among middle aged white South African gold miners on the Witwatersrand and whether the underground dust exposure of these miners contributed to the development of lung cancer, chronic obstructive pulmonary disease (COPD), or ischaemic heart disease (IHD).

Methods: A cohort of 4925 white miners in South Africa, born between 1 January 1916 and 31 December 1930 who were alive and working in the vicinity of Johannesburg on 1 January 1970, then aged between 39 and 54, was followed up for 20 years by which time 2032 had died. Most were gold miners (about 87% had worked 85% or more of their shifts in gold mines).

Investigation of the relative contributions of cigarette smoking and mineral dust exposure to activation of circulating phagocytes, alterations in plasma concentrations of vitamin C, vitamin E, and beta carotene, and pulmonary dysfunction in South African gold miners.

Objectives: To determine the relative effects of cigarette smoking and mineral dust exposure on numbers and activity of circulating phagocytes, plasma nutritional antioxidant state, and pulmonary function in South African gold miners.

Methods: Pulmonary function was assessed spirometrically, whereas reactive oxidant generation by circulating phagocytes, and plasma concentrations of the nutritional antioxidative nutrients vitamin C and vitamin E and beta carotene were measured with chemiluminescence, spectrophotometry, or high performance liquid chromatography respectively.

Results: Cigarette smoking, but not mineral dust exposure, was associated with increased numbers and pro-oxidative activity of circulating neutrophils and monocytes, decreased plasma concentrations of vitamin C, and pulmonary dysfunction.

Emphysema and airway obstruction in non-smoking South African gold miners with long exposure to silica dust.

Objective: Occupational exposure to silica dust is associated with significant impairment of lung function. The present study investigates which pathological changes in the lung are associated with impairment of lung function in silica dust exposed workers who were life-long non-smokers.

Methods: 242 South African white gold miners who were lifelong non-smokers and who had a necropsy at death were studied.

Occupational noise exposure and blood pressure: longitudinal and cross-sectional observations in a group of underground miners.

The question of an association between occupational noise exposure and blood pressure has important public health implications. The harmful effects of hypertension are well known, and noise is considered the most pervasive of all occupational exposures. Most previous studies have looked cross-sectionally at blood pressure and noise exposures in workers.

Risk of silicosis in a cohort of white South African gold miners.

The risk of silicosis was investigated in a cohort of 2,235 white South African gold miners who had, on average, 24 years of net service from 1940 to the early 1970s and who were followed up to 1991 for radiological signs of onset of silicosis (ILO category 1/1 or more). There were 313 (14%) miners who developed signs of silicosis at an average age of 55.9 years.

Correlation between radiological and pathological diagnosis of silicosis: an autopsy population based study.

The radiological findings for the profusion of rounded opacities were compared to pathological findings for parenchymal silicosis in 557 gold miners who had, on average, 2.7 years between the radiological and pathological examination. Three readers read the radiographs, and ILO category 1/1 or more was defined as a positive diagnosis of silicosis.

The mortality of amphibole miners in South Africa, 1946-80.

A cohort was established in 1981 of all 7317 white male employees in the amosite and crocidolite mines in South Africa whose names had appeared in the personnel records (initiated between 1945 and 1955) of the major companies. Some of the men had been employed as early as 1925, but only 8% had had more than 10 years of service. Three subcohorts were defined: 3212 men whose only exposure to asbestos was to amosite; 3430 exposed to crocidolite; and 675 to both amphiboles.

Distribution of silicotic collagenization in relation to smoking habits.

Controversy regarding the association between silicosis and lung cancer has been clouded by the fact that studies examining this association generally do not include information on smoking. A causal association between smoking and silicosis would seriously confound the association between silicosis and lung cancer. The current analysis assessed the association between silicosis and smoking using data on deceased white gold miners who underwent postmortem examination between 1976 and 1981.

Emphysema type in relation to silica dust exposure in South African gold miners.

The relationship between silica dust exposure in gold mines and the type of emphysema was studied in a group of 1,553 white gold miners who had undergone autopsy examination between 1974 and 1987. Of particular interest was the contrast between centriacinar and panacinar emphysema as they relate to silica exposure and the presence of silicosis. Subjects with significant emphysema, that is, with an emphysema score of 30% or more, were classified as having predominantly panacinar or predominantly centriacinar emphysema, and compared to those without emphysema (emphysema score less than or equal to 10%).

Asbestos disease at low exposure after long residence time in amphibole miners.

Short reports of several studies carried out in South Africa which have a bearing on the health effects of low exposures to asbestos are presented. It is stressed that the findings refer solely to amphibole asbestos. Average fiber exposure of 1 or less or a cumulative exposure of less than 2-5 fibers/ml years is associated with the development of asbestosis increasing in frequency with residence time.

Silica exposure, silicosis, and lung cancer: a mortality study of South African gold miners.

The effects of exposure to gold mining dust with a high concentration of free silica and tobacco smoking on mortality from lung cancer was assessed in a sample of 2209 white South African gold miners who started mining exposure during 1936-43, and were selected for a study of respiratory disorders in 1968-71 when they were aged 45-54. The mortality follow up was from 1968-71 to 30 December 1986. The relative risk for the effect of dust cumulated to the start of the follow up period was estimated as 1.

Combined effect of silica dust exposure and tobacco smoking on the prevalence of respiratory impairments among gold miners.

The combined effect of underground gold mining dust with a high content of free silica and tobacco smoking on the prevalence of respiratory impairment was examined among 2209 South African gold miners and 483 nonminers. The subjects were grouped as having normal function; minimal, moderate or marked obstruction; marked obstruction with restriction; or pure restriction on the basis of their lung function profiles. Each profile group was compared with the normal group for exposure prevalences, and additive and multiplicative relative risk models were applied to test for departure from the additivity of individual effects.

Evidence for an amphibole asbestos threshold exposure for asbestosis assessed by autopsy in South African asbestos miners.

In an attempt to determine whether there exists a threshold asbestos dose below which asbestosis does not occur, data on 807 men who had worked on amphibole asbestos mines and undergone autopsy were analysed. When exposure was expressed as fibre-years no asbestosis was found at autopsy when exposure was up to 2 fibre-years, even after 31-45 years of residence time. In the group exposed to greater than 2-5 fibre-years asbestosis was found.

Silica exposure, silicosis, and lung cancer: a necropsy study.

Recent studies of the association between lung cancer and silicosis and silica dust have been inconclusive; some showing positive association and some showing none. The present study matched 231 cases of lung cancer with 318 controls by year of birth. Subjects were selected from the necropsy records of the National Centre for Occupational Health.

Progression of irregular opacities in asbestos miners.

All white and mixed race men who were employed in South African asbestos mines and mills between 30 November 1970 and 30 November 1975 were studied. The men who had two radiographs available, the first taken some time between the above two dates and the latest available radiograph which had to be at least two years after the first one numbered 1454: 793 continued exposure after the first radiograph and 661 did not. The films were read by a panel of three readers.

Prediction equations for lung function in black industrial workers at Palabora Mining Company.

In the course of a study on the health effects of vermiculite, 653 black rural industrial workers had their lung function measured. Since the study revealed no health effects of their industrial environment, the group was used to determine prediction equations for black men. Vital capacity, forced vital capacity, forced expiratory volume in 1 second, and peak flow were appreciably higher than the predicted values for blacks in the USA.

Relation between asbestosis and bronchial cancer in amphibole asbestos miners.

In a necropsy series of 339 amphibole asbestos miners heavy smoking, age, and the presence of asbestosis were significantly associated with the presence of bronchial cancer. Of the 35 cases of bronchial cancer, 24 were associated with asbestosis. Eleven cases of bronchial cancer occurred in men without asbestosis; all were smokers.

Factors influencing the reading of small irregular opacities in a radiological survey of asbestos miners in South Africa.

A cross-sectional radiological survey of 2,245 men who were employed in South African asbestos mines was conducted in 1976. Since 1976, the lungs of 172 of these men who died have been examined to establish the presence of asbestosis or other pneumoconiosis. The x-ray readings (ILO/UC 1971) were compared with the pathological findings.

Stannosis. A report of 2 cases.

Stannosis is a condition in which tin-oxide is deposited in lung tissue after inhalation. Tin-oxide is radiologically visible although there is no tissue reaction to its presence. Two examples of the condition are described.

X-ray findings, lung function, and respiratory symptoms in black South African vermiculite workers.

Health effects have been documented among American vermiculite workers who mined and processed vermiculite contaminated with amphibole asbestos, viz., tremolite-actinolite. Workers mining and processing South Africa vermiculite (N = 172), which contains very little asbestos, underwent x-ray examination and lung function testing and completed a respiratory symptom questionnaire.