Exposure Group Determination In The Solvent Spraying Industries Using Simple Survey Methods (time Study, Work Sampling, Hygiene, Risk Assessment).

Abstract

Employees who have the highest exposure to solvents can be identified prior to personal exposure sampling using an exposure group determination method based on simple survey techniques. Workers can be placed into the proper exposure groups either (i) by means of exposure rankings, or (ii) by means of predicted exposures, so that subsequent personal exposure surveys can be economically conducted. For subjects engaged in the same hazardous tasks exposures can be accurately predicted, without personal exposure sampling, using work measurement methods (time study or work sampling) to survey subject activities. During pilot studies a prospective method to establish exposure groups was proposed. The method calculated each subject's exposure using (i) the time spent by the subject in the performance of hazardous tasks, (ii) rate of ventilation through the subject's breathing zone, and (iii) the percent of solvent (by weight) used by the subject. A final survey of glue sprayers was conducted to test the method's accuracy by simultaneously measuring these parameters and then evaluating the agreement between subjects' observed and predicted exposures to five target solvents (acetone, methyl ethyl ketone, 1,1,1 trichloroethane, n-hexane, and toluene). The final survey showed that the rate of ventilation was not a determinant of exposure (but the presence or absence of proper ventilation controls did influence the ability of the model to accurately predict exposures). That is, exposures to one solvent (1,1,1 trichloroethane) did not vary with the predictor variable because of significant background concentrations caused by improper ventilation controls. Subject exposures to the other four solvents were accurately predicted using the model derived in this study. For subjects using acetone and toluene, r('2) between predicted and observed exposures ranged from 0.53 to 0.76 ((alpha) = 0.0022 to 0.0001). For subjects using methyl ethyl ketone and hexane, observed and predicted exposures also were correlated; r('2) ranged from 0.37 to 0.99 ((alpha) = 0.2745 to 0.0000). The wide range of r('2) and (alpha) for methyl ethyl ketone and hexane were a result of small sample size for those solvents. Using the exposure group determination model, simple survey methods such as time study can be used to create accurate exposure groups.