Concentration of diesel exhaust particulates and gases in coalmines where diesel locomotives and free-steer vehicles are used. Phase I

A number of studies have suggested that diesel exhaust emissions, particularly the soot, may be carcinogenic. Diesel-powered equipment has been used in British collieries for many years but there is little published data on the extent of miners’ exposure to soot emissions. This is in large part due to the difficulty in assessing these exposures in the coalmine environment.This report describes the first phase of a joint British Coal ECSC research contract on diesel exhaust emissions in coalmines. The aim of the project is to evaluate the evidence on possible human cancer risks in relation to exposure to diesel emissions and to define and implement the lines of research most likely to be helpful in informing decisions on control measures necessary in coalmining. In the first stage the work has included:1) measurement of the chemical characteristics of paniculate diesel emissionsfrom engines designed for coalmine use and comparison of these withconventional engines;2) an evaluation of the evidence for carcinogencity of diesel emissions in man;3) an evaluation of available exposure-response information in man, animals andmutagenicity tests; and4) a review of the above information and identified areas for future research,including phase II of the present study.Analyses of paniculate emissions from a standard based coalmine diesel engine indicated that without the conditioner box the exhaust particulates contained similar amounts of polyaromatic hydrocarbons as normal, general purpose, surface engines. The exhaust conditioner box substantially reduced the amounts of these chemicals associated with the particulates emitted from the exhausts.The detailed literature review on evidence for carcinogenicity of diesel exhaust emissions covered both animal studies and human epidemiological research. There have been a number of studies in which tumours have been detected following inhalation of diesel exhaust by rodents. These normally occurred late in the animals’ lives and were typical of tumours which arise after the lungs’ dust clearance mechanism has been impaired by excessive dust exposure. Questions remain regarding the mechanism of the development of these and the effects of coalmine dust exposure on the response to diesel exhaust emissions exposure. Many epidemiological studies of cancer mortality and exposure to diesel exhaust emissions have been undertaken. Individual studies can be criticised on the basis of inadequate exposure assessments and poor information, if any, on smoking habit. Nevertheless, taken as a whole, the evidence, particularly from studies of American railroad workers, suggests that there is an association between lung cancer risk and occupational exposure to diesel exhaust emissions. A scientifically sound mortality study can be undertaken in the British coal industry to identify whether historically there is an excess of lung cancer associated with exposure to diesel exhaust emissions. A proposal for this has been approved by the ECSC under the ECSC Medical Programme.Studies attempting to quantify exposure response relationships for exposure to diesel exhaust emission and lung cancer have been reviewed. Considerable progress has been made but, in our view, the insufficient data are available for these risk assessments to be of great value to the policy maker. In relation to the British Coal industry in particular, the application of even a perfect model would be impossible as precise exposure information is not yet available.A programme of research for the second phase of the project has been drawn up. Its aims are:1. To determine whether diesel exhaust particulates are likely to be present in coalmine air as individual particles or agglomerated with larger coalmine dust particles. If they are agglomerated, size selective samplers based on microorifice impactors will not be capable of separating the fine diesel exhaust particulates from respirable coalmine dust and further work with these samplers would be inappropriate in coalmines.2. To assess the value of simple analytical procedures for estimating concentrations of diesel exhaust particulates in coalmines.3. To examine the effects of various fuel types, additives, catalysts and filters on diesel exhaust particulates composition.4. To use existing information on modelling of diesel exhaust exposures in coalmines to assess the likely concentrations of diesel exhaust emissions to which coalmines may have been exposed in the past.The work will include determining whether diesel exhaust particulates are present in coalmines as free particles or agglomerated with larger mineral dust particles using electron microscopy, analysis for polyaromatic hydrocarbons and related chemicals in engine exhausts and reviewing factors which influence miners’ exposures to diesel exhaust fumes. This work will be undertaken within the overall aim of assisting the development of methods of assessing and controlling exposures to diesel exhausts in coalmines. “”