# Chemical Substance Exposure of Some Cleaning Workers in Korea: Focusing on Inhalation Exposure
## 3 Results
### Analysis of 5-Year Work Environment Measurement Data for Korean Cleaning Workers (2016-2020)
#### 3.1.4 Comparison of Measurement Values across Industries  
Sodium hydroxide and phosphoric acid were measured across all industries, and 2-butoxyethanol, isopropyl alcohol, potassium hydroxide, hydrogen peroxide, and hydrochloric acid were measured in both building cleaning and restaurant industries. For substances measured at least seven times in both industries (i.e., sodium hydroxide and potassium hydroxide), comparisons were made between the industries, and between each individual industry and the overall measurements. For sodium hydroxide, significant differences in measurement values were found between the building cleaning and restaurant industries, and between the building cleaning industry and the overall data (\(p<0.001\)). However, no significant difference was observed between the restaurant industry and overall data (\(p=0.237\)). Similarly, for potassium hydroxide, significant differences were found between the building cleaning and restaurant industries (\(p=0.002\)), and between the building cleaning industry and the overall data (\(p=0.003\)), but not between the restaurant industry and the overall data (\(p=0.316\)). For sodium hydroxide, there were 132 restaurant samples and 52 building samples. For potassium hydroxide, there were 33 restaurant samples and 18 building samples. Because the restaurant samples make up 2/3 of the total samples, the \"all industries\" category is highly influenced by the restaurant results, which limits the evaluation of all industries. The comparison results are shown in Figure 1.  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Classification**} & \multirow{2}{*}{**Substance**} & \multirow{2}{*}{**No. of Measurements**} & \multirow{2}{*}{**Unit**} & \multirow{2}{*}{**OEL**} & \multicolumn{4}{c}{**Representative Value**} \\ \cline{5-10}  & & & & & * **AM** & \(\dagger\) **SD** & \(\ddagger\) **GM** & \(\lx@sectionsign\)**GSD** \\ \hline Acid and & & & & & & & & \\ \(\ddagger\)Alkali & Sodium hydroxide & 2 & mg/m\({}^{3}\) & C2 & 0.073 & 0.015 & 0.313 & 1.234 \\ \hline \hline \end{tabular}  
* AM: Arithmetic mean.
* OEL: Occupational exposure limit. \(\ddagger\) SD: Standard deviation. \(\ddagger\) GM: Geometric mean. \(\lx@sectionsign\) GSD: Geometric standard deviation.  
\end{table}
Table 4: Number of measurements and measurement values for each harmful factor to be measured in the education industry.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Classification**} & \multirow{2}{*}{**Substance**} & \multirow{2}{*}{**No. of Measurements**} & \multirow{2}{*}{**Unit**} & \multirow{2}{*}{**OEL**} & \multicolumn{4}{c}{**Representative Value**} \\ \cline{5-10}  & & & & * **AM** & & \(\ddagger\)**SM** & \(\ddagger\)**GM** & \(\lx@sectionsign\)**GSD** \\ \hline \multirow{3}{*}{Acid and  Alkali} & Sodium h-droxide & 132 & mg/m\({}^{3}\) & C2 & 0.095 & 0.110 & 0.236 & 2.510 \\  & Potassium hydroxide & 33 & mg/m\({}^{3}\) & C2 & 0.041 & 0.054 & 0.151 & 2.729 \\ \cline{1-1}  & Hydrogen peroxide & 2 & ppm & 1 & 0.014 & 0.000 & 0.157 & 1.010 \\ \cline{1-1}  & Hydrochloric acid & 6 & ppm & 1 & 0.008 & 0.016 & 0.060 & 3.391 \\ \hline \hline \end{tabular}  
* AM: Arithmetic mean.
* OEL: Occupational exposure limit. \(\ddagger\) SD: Standard deviation. \(\ddagger\) GM: Geometric mean. \(\lx@sectionsign\) GSD: Geometric standard deviation.  
\end{table}
Table 3: Number of measurements and measurement values for each harmful factor to be measured in the restaurant industry.