Using Bayesian Decision Analysis Technology to Assess Exposure and Health-Risk from Oil Mist and Polycyclic Aromatic Hydrocarbons (PAHs) in a Fastener Manufacturing Industry

Abstract

Collecting multiple and long-term samples is necessary for properly describing the exposure profile of a similar exposure group (SEG) but only few industries are affordable because of the cost and manpower An integrated approach was developed in this study to assess workers’ exposures to oil mist and polycyclic aromatic hydrocarbons (PAHs) (including inhalatory and dermal) arising from processes using metalworking fluids (MWFs) in a fastening industry This study includes three parts In the first study measured oil mist concentrations (Cm n = 11) were randomly collected on eleven days during one year (served as the likelihood distribution in Bayesian decision analysis (BDA) and daily fastener production rates (Pr n = 250) were used as a surrogate for predicting the yearlong oil mist exposure concentrations (Cp) (served as the prior distribution in BDA) The resultant BDA posterior distributions were used for assessing the long-term oil mist exposures to threading workers in a fastener manufacturing industry The feasibility of the proposed methodology was finally examined by reference to the effect caused by the sample size of the Cm In the second study one previously developed model in first study and one new model were adopted for predicting oil mist exposure concentrations emitted from MWFs and PAHs contained in MWFs by using the fastener Pr and cumulative fastener production rate (CPr) as predictors respectively By applying the annual Pr and CPr records to the above two models long-term workplace inhalatory PAH exposure concentrations were predicted In addition true exposure data was also collected from the field The predicted and measured concentrations respectively served as the prior and likelihood distributions in the BDA and the resultant posterior distributions were used to determine the long-term exposure and health-risks posed on workers The third part study was to develop an integrated approach for conducting long-term health-risk assessments on dermal PAHs for fastener manufacturing industry workers The approach involves first the development of a predictive model based on the surrogate method for predicting long-term oil mist and dermal PAHs concentrations in the workplace Then the predicted long-term oil mist and dermal PAHs concentrations and limited field measured dermal PAHs concentrations were served as the prior and likelihood distribution in the BDA respectively Finally the resultant posterior distributions were used to assess the long-term dermal PAHs health-risk posed on fastener manufacturing industry workers The results obtained from the first study show that threading workers experienced more severe thoracic and respirable oil mist exposures than the exposures to the inhalable fraction Using Pr as a surrogate was adequate to explain ~92% variations of Cm By combining Cp and Cm our results suggest that the adopted BDA technique was beneficial for predicting workers’ long-term exposures By judging the consistency of the resultant posterior exposure ratings this study suggests that the proposed methodology could be feasible even the sample size of Cm was set as low as 3 The results obtained from the second part show that long-term exposures to inhalatory PAHs would result in a 3 1% 96 7% and 73 4% chance of exceeding the OEL-TWA (0 2 mg/m3) action level (0 1 mg/m3) and 50 times of acceptable health risk (10?3) respectively The result from the third part show that the dermal PAH exposure levels was 5 88×106 ng/day and the top five exposed surface areas were lower arm hand upper arm neck and head/front The estimated probability of excess lifetime skin cancer risk was lower than that of lung cancer risk but both were higher than the significant risk level (10-3) defined by the US Supreme Court in 1980 The installation of a local exhaust ventilation system at the threading machine should be considered as the first priority measurement because both lung and skin cancer risks can be reduced simultaneously If the personal protection equipment would be adopted in the future both respiratory protection equipment and protective clothing should be used simultaneously

Date of Award	2015 Jan 12
Original language	English
Supervisor	Perng-Jy Tsai (Supervisor)