The relationship between the maximum and the mean dust concentration in a colliery – results from routine sampling in British pits in 1971

Results from routine gravimetric dust sampling during nine months in 1971 are examined in order to study the continuing validity of one of the assumptions made when research data were used to estimate risks of developing pneumoconiosis given implementation of the 8 mg/m dust standard.The average results from production faces are consistent with the assumption made previously. On 89/2 of the occasions when the 8 mg/m3 standard was achieved at all faces in a particular month, the colliery mean concentration did not exceed 8/1.32 = 6.1 mg/m3 .A similar analysis is made of results from sampling in coal drivages and bord and pillar working. On average, the ratio between the highest coal drivage concentration and the mean of all coal drivage concentrations in that colliery and during the month concerned was 1.35 – a result identical with that found during an earlier study of data from 1969 and 1970.