TEXAS: a Tool for EXposure ASsessment-Statistical models for estimating occupational exposure to chemical agents

Measurements of occupational exposure to chemical agents are performed by sampling and analyzing workplace atmospheres. In France, this is done by the industrial hygienists of the prevention network of the Social Security Service, who collect and then enter the data in the COLCHIC database. More than 900000 measurements performed in French companies over the past 25 years have been collected. Using this amount of data is major challenge for obtaining knowledge and predicting occupational exposures. This study presents the way in which statistical models are built and used on the basis of almost 19000 recent measurements of 26 frequent chemical substances. For a given substance, the models use 13 exposure determinants as inputs, such as the task performed, the occupation of the operator or the type of process employed. The models permit to estimate two parameters: the geometric mean and geometric standard deviation. These parameters are used to build an exposure profile. By combining them with the limit value, an exposure index is estimated using a Bayesian network. A decision rule based on the interpretation of this probability is proposed to qualify the predicted situation as 'well-controlled situation', 'controlled situation', and 'poorly controlled situation'. On the basis of this decision rule, 62% of predictions are true for all substances confounded, an average of 36% of predictions are approximate and only 2% of them are wrong. The result of this study led to the development of a pragmatic software tool named TEXAS, tool for exposure assessment, which enables industrial hygienists to obtain a rapid estimation of the level of exposure control as a function of simple determinants of work situations.