A study of nitrous fumes in coalmines in relation to effects on health. Final report on CEC Contract 6253-44/8/019

It is often suggested that nitrous fumes from explosives and diesel locomotives, either alone or in combination with dust, may have harmful effects on the health of mine workers. This report reviews the evidence for this contention and finds that there is little information available concerning the magnitude of the exposure or the effects of prolonged exposure to low levels. Other factors which need to be considered are the relative effects of the constituent gases -nitric oxide and nitrogen dioxide (complicated by the slow oxidation of nitric oxide to nitrogen dioxide) – of peak or shift-average concentrations, and whether adsorbed gases affect the biological response to dust particles.Existing sampling techniques for nitrous fumes are also reviewed but none is considered to be suitable for the determination of full-shift exposures in mines. It was necessary, therefore, as a first stage of a longer term study into the effects of these gases on the health of mine workers, to develop a sampling technique for this purpose. A sampling attachment,* based on the use of the specific absorber for nitrogen dioxide first described by LEVAGGI, SIU and FELDSTEIN (1973), was designed for inclusion in the MRE gravimetric dust sampler. This procedure enabled shift-average concentrations of both oxides of nitrogen to be measured simultaneously with the respirable dust concentrations during routine dust sampling. Laboratory and field tests are reported which confirm the operational reliability and performance of the method; in particular, othermine gases are shown not to affect the performance to any significant extent. The method can be used to measure shift average nitrogen dioxide and nitric oxide concentrations between 0. 05 and 25ppm.Preliminary investigations of the exposure of various underground occupations to oxides of nitrogen have been started at the collieries included in the National Coal Board’s Pneumoconiosis Field Research (JACOBSEN,RAE, WALTON and ROGAN, 1971). Initial results indicate that the nitrous fume concentrations are generally low but some differences between collieries and occupations occur. Shift-average concentrations seldom exceed 2ppm for nitric oxide or 0. 2ppm for nitrogen dioxide. The highest mean concentrations (7. 1ppm for nitric oxide and 2. 1ppm for nitrogen dioxide) were observed for diesel locomotive drivers at a colliery where diesel transport is widely used.The sampling attachment is protected by patent; application number 06126/76 It is proposed that future measurements of nitrous fume should be used to establish the pattern of exposure for the different occupations and mining conditions at the Pneumoconiosis Field Research collieries. The results would be analysed in conjunction with past medical and environmental records to assess the evidence for any effect of nitrous fume exposure on health. Future work should also include some measurements of both peak exposures and the biological effects of adsorbed gases on dusts; it was only possible to include some preliminary work on these subjects during this contract.