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- Blue death | Life and style | The Guardian
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The evidence from studies of South African cases of mesothelioma is consistent in showing that the dominant fibre type responsible is Cape crocidolite. The data for Transvaal crocidolite is sparse. The Transvaal crocidolite mines were smaller operations and were often excluded from studies, or pooled with amosite mines Sluis-Cremer et al.
These environmentally exposed cases, in particular, appear to be the result of exposure to crocidolite. An important feature of the South African experience in respect of malignant mesothelioma is the prominence of environmental exposure.
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This has been identified since the very first published paper Wagner, on the association of blue fibre and malignant mesothelioma. The section on amosite makes it clear at the outset that determining exposure to a specific fibre only in the Pietersburg field is difficult. This is clear from detailed mapping, from west to east, of the geological transition from a succession of crocidolite and amosite seams at Malips River, to the dominance of amosite at the Mohlapitse River, to amosite only at Penge mine Figures 7 and 8 and at Kromellenboog mine Coetzee, The vast majority of occupational medicine studies are carried out and published without environmental measurements.
In this respect the Pietersburg field is unusual as there are reliable measurements of both occupational and environmental exposure. The two studies summarized in this chapter are unique in their attention to detail and the spread of the findings. This account seeks to add new data to the inconclusive situation in the Pietersburg field and the studies of amosite miners, as opposed to insulators and laggers.
The health effects of amosite mining and milling in South Africa have been reviewed in detail Murray and Nelson, There is sound evidence of occupational and environmental exposure to airborne amosite fibre in the Pietersburg asbestos field for more than fifty years. It was then one of the largest asbestos mines in the world and the source of most of the supply of amosite. Labour was drawn, in the main, from the rural areas surrounding the mines Davies et al. The Penge group of mines Penge, Weltevrede and Kromellenboog operated a recruiting depot in the Eastern Cape, in what was formerly the Transkei, which was used to recruit additional labour when labour shortages occurred locally.
Rendall, working at the National Institute for Occupational Health, carried out a detailed survey of Penge mine in Rendall and Davies, He collected full-shift personal samples from underground and surface workers at Penge mine in The average of 94 personal samples collected from individuals working underground was 1. This low level and narrow range of exposure is attributed to the fact that the underground workings at Penge mine are kept constantly wet by water dripping from the hanging walls and running down the side walls, acting as a dust suppressant.
The ore leaving the underground workings is saturated. The median value for the individuals grouped by task or work station and averaged 24 groups was The highest fibre level was associated with hand tamping in the packing process — exactly the situation described by Schepers see Felix except for the fact that there were no children jumping up and down in the bags.
Rendall also measured the total dust levels and calculated the number of fibres per milligram of dust, showing that the total dust level did not correlate well with the fibre exposure. In the assay laboratory the total dust level was 2. This illustrates the importance of the relationship between the process and the fibre content of the dust. Simultaneously Cape Asbestos, the owners of Penge, operated a smaller mine or set of mines known as Egnep at Malipsdrift towards the western extremity of the Pietersburg field 60 kilometres west of Penge Mine.
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Officially Penge and Egnep were considered as one mine, and the product from these mines, well to the west of the Mohlapitse River, was transported to Penge for shipment via the railway siding at Apiesdoring near Burgersfort. The association of the mining operation at Malipsdrift with that at Penge and the uncertainty as to where deposits of Transvaal crocidolite end and pure amosite begins implies a possibility, if not of admixture in the product, at least of mixed exposure of workers.
Production of amosite from Penge and the smaller mines along the northern bank of the Olifants River peaked in at , tonnes. At that stage 7, men were employed at Penge. This adds a further complication to the accurate determination of exclusive fibre type exposure.
Some experienced foremen were also moved from the crocidolite to the amosite mines and vice versa. Environmental exposure was investigated in detail as part of the study of the villages round Mafefe. The results are recorded here to make the point that one would expect a significant number of environment only cases from Mafefe and the many similar groups of villages situated in close proximity to asbestos mines in the Pietersburg field. Their tailings dumps were close to one or more of the 30 settlements which fall under the jurisdiction of the traditional ruler kgosi in the Mafefe area.
The population of Mafefe in November was 11, Tailings were frequently dumped on the banks of the Mohlapitse River or the streams draining into it. Deposits high in the Strydpoort Mountains were worked from adits and the waste rock and tailings tipped down the hillside — to this day the resulting environmental contamination cannot be abated in this rugged terrain.
This doctoral thesis is a rich source of historical and contemporary information, and includes detailed maps and lists of fibre levels measured by government inspectors over the years — it would be instructive to reproduce more of the detail in the thesis but this would make the account unwieldy. Thorough investigations of asbestos exposure in communities living around asbestos mines, such as this one, are rare. Ninety-two personal samples were collected by adults and children going about their usual tasks.
The highest mean concentration of fibres was School attendance exposed children to a mean of Usual activities such as building and gardening entailed exposure to Walking about the village exposed subjects to The tailings dumps on the bank of streams feeding the Mohlapitse River have been mentioned.
The seasonally dry bed of this river is used as a source of building sand. Needless to say nothing is known about asbestos-related diseases among the riparian population living downstream of the asbestos mines in the Pietersburg asbestos field. These levels were judged to be aberrant and no explanation could be found. The mean of 44 outdoor strategic samples was On days when vehicles used the road, the mean of 12 strategic samples taken at the roadside was Finally, the extent and variability of environmental asbestos exposure is clearly established by two series of strategic measurements made in 7 villages in close proximity less than 1 kilometre to tailings dumps and 11 villages far more than 1.
The mean fibre concentration in ambient air collected by strategic sampling in villages close to the dumps 21 samples was It is reasonable to conclude that residents of Mafefe were exposed intermittently to levels higher than this, and regularly to lowerlevels. Given this degree of occupational and environmental exposure of the labour force, and the communities from which they were drawn, one might be justified in assuming that a situation comparable to that described in the study of the crocidolite-exposed Prieska birth cohort might be found in the area.
This is not the case. Felix Felix, analysed the available data from two studies of autopsy findings in cardio-respiratory organs submitted from Penge Mine and from mines in the Northern Cape Sluis-Cremer, , The figures presented show a higher prevalence of asbestosis at Penge and, in addition, a much smaller improvement over time at Penge. The numbers of autopsies analysed, the age and length of service of the two groups do not differ significantly. There is a significant body of evidence of widespread benign pleural and parenchymal asbestos related respiratory disease among occupationally and environmentally exposed individuals.
There are sporadic, unconfirmed reports of mesotheliomas.
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In a random sample of adults from a census of Mafefe, where a number of small mines worked deposits of amosite and crocidolite, were examined. Reports from doctors working in the hospitals and clinics in and around the Pietersburg asbestos field were very uncommon prior to When a clinic was established at Groothoek Hospital to service the need for compensation examinations at Mafefe, no reports had ever been received from that hospital by the MBOD. Sustained attempts were made from November onwards to interview and examine former asbestos miners for compensation purposes, with the assistance of local activists.
In the period , reports for former asbestos miners were submitted to the MBOD. During an intensive case finding project in more than former miners were examined and reported Davies et al. A number of publications resulted and these show a high prevalence of benign asbestos-related diseases, but did not identify any substantial number of proven malignant mesotheliomas or lung cancers Davies et al. The first report of a malignant mesothelioma from the area of the Pietersburg asbestos field, which has overlapping seams ofamosite and crocidolite fibres, is contained in a review of females and 53 males admitted to the medical wards of the Jane Furse Memorial Mission Hospital situated about 60 kilometres south-west of Penge Mine Edginton et al.
At the time the hospital was estimated to be responsible for the medical care of , people. Forty-eight per cent of the diagnoses in women were respiratory disease - tuberculosis 98, other respiratory infections Non-infective respiratory disorders were found in only three women — one autopsy proven malignant pleural mesothelioma, and one possible but unproven lung cancer, and one case of asthma. Despite the proximity of asbestos mining, asbestos-related disease is not mentioned in the discussion.
The high incidence of respiratory disease and a single mesothelioma in a series of fewer than female patients is surely remarkable, and worthy of comment. Further unverified evidence of mesotheliomas from the Pietersburg field is included in the Felix thesis. No details of occupation or exposure are given. In a 44 year old migrant worker who worked for 2 years from to on an asbestos mine in the Pietersburg asbestos field, was diagnosed as having a mesothelioma at the Rand Mutual Hospital, Johannesburg Felix, No details of the mine on which he was employed are available.
The first proviso is that related to the overlapping fibre types in the Pietersburg field. Additional reservations include the inaccessible area in which amosite was mined, the rudimentary medical services in the area surrounding the amosite mines and the apparent neglect by the mine itself, all of which hamper us in getting conclusive data about amosite exposure. In the dust rooms of the National Centre for Occupational Health non-human primates were exposed to specific dusts, including amosite, and kept in the laboratory for many years in order to determine the long term effects of the dusts to which they had been exposed.
The non-human primates used in the experiments were locally captured baboons Papioursinus. At the time, there was no evidence that South African baboons were natural hosts for SV40 Malherbe, In one study, 12 baboons were exposed to amosite for a period of between days and days. Exposures were high, ranging between and fibres per cc. Ten survived the exposure period and lived for a further 1.
Five of these 10 baboons developed mesothelioma: 3 were peritoneal and 2 were pleural tumours Webster et al. This amosite standard reference sample has been used in asbestos-exposure related research studies worldwide Timbrell and Rendall, ; Rendall, It is possible that the milling of the fibre may alter its physical properties thereby increasing its toxicity, in contrast to the freshly mined fibres.
This may provide another possible explanation for the apparent rarity of malignant mesotheliomas among miners exposed to freshly mined amosite fibre. Rees debates the role of amosite in the causation of malignant mesothelioma in the course of a case-control study of cases and cancer controls and medical controls. This, together with the contention by Felix Felix et al. Cross-sectional surveys are inappropriate for a rare disease with short life expectancy following diagnosis, so alternatives are necessary. One approach would be to allocate the task to the regional health authority which would be in a position to identify cases by encouraging pathologists to submit suspect tissue for expert review.
Since this was written many thousands of former asbestos workers have been examined for compensation purposes in the Pietersburg asbestos field Davies et al. The Maandagshoek Project set up a network of clinics in co-operation with a number of community-based activists following five years of preliminary work at Groothoek Hospital.
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Workers who had been certified by the MBOD were subsequently denied compensation by an administrative decision making written records of mining employment obligatory. Among the thousands of applicants for benefits interviewed and examined as part of the Maandagshoek Project there were no proven mesotheliomas. The study of asbestos fibre type and mesothelioma carried out on cases autopsied at the NIOH demonstrates a residual burden of exclusively amosite fibres in only one of 43 cases examined. The remainder of the cases were attributable to crocidolite Nolan R P, Occupational and environmental exposures to asbestos in the Pietersburg field were high and high rates of benign asbestos-related disease have been described Murray and Nelson, But mesothelioma is rarely reported from the hospitals and clinics in and around the Pietersburg asbestos field.
The reporting of asbestos-related disease is extremely poor in South Africa, particularly in the areas that supplied labour to the mines Talent et al. There is an underlying problem in attributing cases of mesothelioma to amosite because of the geological relationship between deposits of amosite and Transvaal crocidolite.