LUNG-CANCER AMONG IRON-ORE MINERS IN EAST SLOVAKIA - A CASE-CONTROL STUDY

The biological effects of ionising radiation (BEIR IV) report included a summary of risks of lung cancer in cohorts of miners exposed to radon daughters,(1) and concluded that ''without exception, these studies indicate an excess probability of death due to lung cancer...'' Iron ore mines have been in operation at Roznava and Nizna Slana in east Slovakia throughout this century. The mines, which are 10 km apart, are major employers in the area. Data on radiation exposures and dust concentrations are available for the period 1980-89. Local authorities found average levels of ct radiation from radon and its daughters to be 0.13 WL (working levels) in the Roznava mine and 0.091 WL in the Nizna Slana mine. Average concentrations of total dust in the two mines are similar (Roznava 2.6 mg.m(-3), Ninza Slana 2.4 mg.m(-3)). During drilling operations, dust concentrations are about 15 mg.m(-3). Principal components of ores from the two mines are similar (oxides of iron, manganese, magnesium, calcium, phosphorus, and arsenic together with silica, sulphur, and carbon). Diesel machinery was introduced into the Nizna Slana mine in 1973; Roznava still uses electrically powered machinery. Evidence of occupational lung cancers arising from employment in these mines has been reported before.(23) A case-control study has now been carried out to quantify the likely risks associated with employment in each mine.