# Occupational Inhalation Health Risk Assessment of TCE Exposure in the Korean Manufacturing Industry
## 2 Materials and Methods  
Figure 1 presents a diagram of methods. In total, 7046 TCE measurements were obtained from WEMP data. The industry classified the measured values using the Korean Standard Industrial Classification (KSIC 10 th) [39]. Only industries with more than 30 measured values were chosen as research subjects to assume a log-normal distribution [40; 41]. Excluding STEL measurements, this study used 6311 measurements in total. Of the 6311 classified data points for the 20 industries, 2923 measured values were 0. To avoid statistical underestimation, a measurement value of 0 was corrected to the detection limit/2 when calculating the mean (AM) and standard deviation (SD) [42]. The detection limit of TCE  
was determined by referring to the technical guidelines of the Korea Occupational Safety and Health Agency (KOSHA) to measure and analyze the work environment for TCE [43]. The risk assessment of TCE was conducted according to the Korea Occupational Safety and Health Agency's Hazard and Risk Assessment Guidelines for Chemical Substances (KOSHA GUIDE W-6-2021) [44] based on the Environmental Protection Agency (EPA) model and the Occupational Safety and Health Research Institute's (OSHRI) Hazard and Risk Assessment Research Report on Hazardous Chemical Substances [45]. Because inhalation is workers' primary mode of TCE exposure, this study conducted carcinogenic and non-carcinogenic assessments for inhalation. For the Point of Departure (POD), the No Observed Adverse Effect Level (NOAEL) and Inhalation Unit Risk (IUR) values were obtained from the Environmental Protection Agency Integrated Risk Information System (EPA IRIS). In 1999, EPA applied the concept of nonlinear extrapolation to liver cancer caused by TCE [46]. According to an EPA report, using nonlinear extrapolation, the risk assessment method depends on the procedure used. If an RfD or RfC was calculated, the hazard can be expressed as a hazard quotient (HQ) [47; 48]. The IUR was converted to reference concentrations in workplaces of carcinogenicity (RfCworkcarcinogen) based on a risk level of \(10^{-4}\)[45; 49]. The IUR is the risk that a 70 kg adult would be exposed to 24 h a day for 70 years, and conversion is required to apply it to workplace risk assessment. Equation (1) is the process of converting IUR to the workplace risk value, and Equation (3) is the process of converting Rfcworkcarcinogen, which is the concentration at risk level \(10^{-4}\), which is the permitted concentration in the workplace [45; 49]:  
\[\text{IURworkplace}=\text{IUR}\div\text{CF} \tag{1}\]  
\[\text{CF}=\text{AsRV}/\text{KwRV}\times\text{AEF}/\text{KwEF}\times\text{AED}/ \text{KwED}\times\text{ABW}/\text{KwBW} \tag{2}\]  
Here, AsRV is the American standard Respiratory Volume, KwRV is the Korean worker Respiratory Volume, AEF is the American Exposure Frequency (days/year), and KwEF is the American and Korean worker Exposure Frequencies (days/year). AED is the American Exposure Duration (years), and KwED is the Korean worker Exposure Duration (years). ABW is the American body weight (kg), and KwBW is the Korean worker body weight (kg) [45; 49]. \[\text{RfCworkcarcinogen}=1/(\text{IURworkplace}\text{ (risk/ppm)})\times 10^{-4}\text{ (risk)} \tag{3}\]  
Figure 1: Diagram of research methods. The RfCwork for carcinogenicity and non-carcinogenicity applied appropriate coefficients to Korean workers, and correction coefficients were applied based on a KOSHA research report [45]. \[\text{HQ}=\text{EC}\ (\text{ppm})\div\text{RfCwork}_{\text{non-carcinogen}}\ (\text{ppm}) \tag{4}\]  
\[\text{HQ}\text{carcinogen}=\text{EC}\ (\text{ppm})\div\text{RfCwork}_{\text{carcinogen}}\ (\text{ppm}) \tag{5}\]  
Here, the exposure concentration (EC), the concentration of TCE, is a value recorded in the WEMP by measuring TCE in personal samples from all Korean workplaces that handle TCE and analyzing them using gas chromatography [43]. The hazard quotient (HQ) was used to determine the non-carcinogenic and carcinogenic risks to workers.