Validation of the Models for Inhalation Workplace Exposure

Introduction
The aim of this work is to utilize of two first-tier non-measurement models: EASE and TRA-ECETOC-WORKER for assessment of inhalation exposures to different organic solvents for selected process categories and to compare of chosen real data with calculated exposures.

Methods
The exposure assessment is based on representative measured data and/or on EASE and TRA-ECETOC models calculations. Results of real data for four organic solvents: toluene, ethyl acetate, acetone and xylene in workplace atmosphere in Poland in working environment were available, so these measured data were used to revise the calculated concentrations. Statistical analysis was carried out using standardization to compare real and estimated data.

Results
The absolute values of the standardized differences between the measured value and the value from EASE assessment obtained from our calculations were within two standard deviations for toluene, ethyl acetate, acetone and xylene. The selected patterns well represent the conditions of use of the substances. For TRA ECETOC, some standardized difference values were higher than the determined range for three substances i.e. toluene, ethyl acetate and acetone. With xylene, 95% of the observations were within two standard deviations for both models. 

Discussion
EASE model well reflects exposure to selected organic solvents and is a sufficient representation of the way in which the substance is used. This assessment is transparent to user and easy to perform. EASE is a user-friendly computer program. TRA ECETOC model can be easily used to assess inhalation exposure at workplace, but selection of appropriate TRA process categories related to the uses identified is necessary to ensure successful exposure assessment. At present, it is clear that 25 scenarios do not suffice to represent all possible real situations.