Cancer among the black labour force of the platinum group metals and the gold mining industries in South Africa, 1989-96

Aim. This paper aims to quantify for the first time the cancer occurrence among black employees of the platinum group metals (PGM) industry and to compare these figures with those of the well-recorded and long established gold mining industry. Patients and methods. Data on cancer incidence have been obtained from records of hospitals which serve the two industries for the period 1989-96. The PGM industry employs about one quarter of the labour force of the gold mines and both industries employ men from several areas across southern Africa. The PGM industry recruits especially from Bophuthatswana; both industries employ Mozambique men and gold miners also come especially from Lesotho and Transkei. Results. For total cancers of all sites, PGM workers record very significantly few cases: 149 observed whereas 385 were expected. Significant deficits of cancer amongst PGM men apply to twelve specific sites, including the three most numerous cancers of gold miners, respiratory system, liver and oesophagus which are all very significantly (p <0.01) under-represented in PGM employees. Studies show that cancer of the buccal cavity has risen considerably in the black gold miners in the last forty years: this cancer is also common in the PGM workers. All sites of cancer and buccal cancer are each diagnosed at similar ages in the PGM group as in the gold industry men. Conclusion. These major contrasts of cancer between two extractive industries in South Africa are suggestive of occupational or environmental differences. No obvious carcinogenic risk has been suggested to exist in either industry, and specific enquiry is warranted to explain the low overall cancer incidence among the PGM's largely Tswana workforce.