Validation of a new method for structured subjective assessment of past concentrations

A new method has been developed to assess the level of exposure from airbor ne hazardous substances. The method provides subjective exposure assessment s using a structured approach, based on descriptive information about work activities and the work environment. Validation of the method has been carr ied out for 63 jobs involving five different agents: man-made mineral fibre s, asbestos, styrene, toluene and mixed respirable dust. In three cases, th ere were two occupational hygienists who completed the assessments and in t he remaining scenarios there was only one assessor. The subjective exposure assessments generally showed a statistically significant correlation with exposure measurements (correlation coefficient for the log-transformed data generally ranging from 0.31 to 0.93), The main exception to this pattern w as the styrene data set where there was a small difference between the high est and lowest measured exposure level and this resulted in a much poorer a ssociation between the estimated and measured values. The assessments were also positively biased, with the ratio of the geometric mean estimated leve l to the measured level typically ranging from 1.3 to 2.2. Possible causes of the bias are discussed along,vith strategies to minimise its effect. (C) 1999 British Occupational Hygiene Society. Published by Elsevier Science L td. All rights reserved.