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 rad on 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 Sl ovakia throughout this century. The mines, which are 10 km apart, are major employers in the area. Data on radiation exposures and dust conc entrations are available for the period 1980-89. Local authorities fou nd 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 drill ing operations, dust concentrations are about 15 mg.m(-3). Principal c omponents of ores from the two mines are similar (oxides of iron, mang anese, magnesium, calcium, phosphorus, and arsenic together with silic a, sulphur, and carbon). Diesel machinery was introduced into the Nizn a Slana mine in 1973; Roznava still uses electrically powered machiner y. Evidence of occupational lung cancers arising from employment in th ese mines has been reported before.(23) A case-control study has now b een carried out to quantify the likely risks associated with employmen t in each mine.