Abstract
ABSTRACTA surrogate approach was deployed for assessing long-term exposures of multiple chemicals at 8 selected working areas of 3 manufacturing processes located at a clean room of a thin film transistor liquid crystal display (TFT-LCD) industry. For each selected area, 6 to 12 portable photoionization detector (PID) were placed uniformly in its workplace to measure its total VOCs concentrations (CT-VOCs) for 6 randomly selected workshifts. Simultaneously, one canister was placed beside one of these portable PIDs, and the collected air sample was analyzed for individual concentration (CVOCi) of 107 VOCs. Predictive models were established by relating the CT-VOCs to CVOCi of each individual compound via simple regression analysis. The established predictive models were employed to construct a year-long CVOCi databank based on the measured year-long CT-VOC for each selected area using the same portable PID. The ethanol (381 ppb–2,480 ppb), acetone (123 ppb–624 ppb) and propylene glycol monomethyl ether acetate 29 (PGMEA; 14.4 ppb–2,241 ppb) dominated in all selected areas, and all measured CVOCi were much lower than their permissible exposure limits. Predictive models obtained from simple linear regression analyses were found with an R2 > 0.453 indicating that CT-VOCs were adequate for predicting CVOCi. The predicted year-long CVOCi reveals that long-term total multiple chemical exposures of all selected areas fall to the range 0.10%–20% of the permissible exposure level. Using the CT-VOCs as a surrogate for the routine checking purpose, the present study yielded allowable CT-VOCs fall to the ranges of 49.1 ppm–577 ppm. Considering the approach used in the present study requires less cost and manpower, it would be applicable to similar industries for conducting long-term multiple chemical exposure assessments in the future.
Highlights
IntroductionFor high-tech industries, many studies have shown their exposure concentrations of an individual compound (such as ethanol, acetone, butyl acetate, isopropyl alcohol (IPA), and propylene glycol monomethyl ether acetate (PGMEA)) could be much lower than that of traditional industry, and lower than their time-weighted-average permissible exposure concentrations (PEL-TWAs) (Zappe, 1995; Chuah et al, 2000; Wu et al, 2004; Chang et al, 2010a; Park et al, 2011; Cheng et al, 2016; Chou et al, 2016; Guerra et al, 2017)
There are at least sixteen Volatile Organic Compounds (VOCs) detected from the studied areas which might belong to unknown byproducts or unreleased raw materials used in the manufacturing processes
The above results further confirm that the exposure scenarios of workers in the clean room of the thin film transistor liquid crystal display (TFT-liquid crystal display (LCD)) industry are very complicated, which is consistent with the conclusion made by one previous study (Park et al, 2011)
Summary
For high-tech industries, many studies have shown their exposure concentrations of an individual compound (such as ethanol, acetone, butyl acetate, isopropyl alcohol (IPA), and propylene glycol monomethyl ether acetate (PGMEA)) could be much lower than that of traditional industry, and lower than their time-weighted-average permissible exposure concentrations (PEL-TWAs) (Zappe, 1995; Chuah et al, 2000; Wu et al, 2004; Chang et al, 2010a; Park et al, 2011; Cheng et al, 2016; Chou et al, 2016; Guerra et al, 2017). Considering the exposure concentration of a chemical might be varied greatly over time in the high-tech industry, conducting long-term exposure assessment has become a crucial issue, especially for those chemicals with chronic health effects. It is true that some current available sampling methods can be used to collect multiple chemicals in one sample and do the analysis simultaneously (e.g., the NIOSH method 2549; using thermal desorption tube/gas chromatography, mass spectrometry for analyses (NIOSH, 1996)). These methods might be not widely adopted in the field because of the constraints of the cost associated with chemical analyses. Developing approaches which require less manpower and lower cost has become an important issue in the industrial hygiene field
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