# Health Impact Assessment from Rice Straw Production in Cambodia
## 3 Results and Discussion
### Pollutants Emission Inventory  
We determined the total emissions of PM\({}_{2.5}\), both primary and secondary, in the 25 Cambodian provinces for three different categories: fertilizer usage, fuel combustion, and straw residue burning. The primary PM\({}_{2.5}\) was produced by the open burning of straw waste and fuel combustion during rice paddy production, and secondary formations were the result of fertilizer usage and open burning, which produced NH\({}_{3}\), NO\({}_{x}\), and SO\({}_{2}\) pollutants. We found that the annual amount of rice straw produced and subjected to burning in the field was approximately 8.24 million tons, while the amount of dry straw subjected to burning in the field was 675.1762 kg/ton of rice paddy. In addition, the average levels of air pollutants PM\({}_{2.5}\), NH\({}_{3}\), NO\({}_{x}\), and SO\({}_{2}\) emitted from fertilizer and fuel combustion were 0.02, 0.84, 0.69, and 0.22 kg/ton of rice paddy, respectively. These results are shown in Table 3, which is a graph of the estimated pollutant levels emitted by various sources: rice straw residues (RSOB), fertilizer, and fuel combustion, presented as tons. Provinces that produced more rice production produced higher quantities of pollutants as well. The total emissions of air pollutants in the whole process of \begin{table}
\begin{tabular}{c c c} \hline \hline
**Data Type** & **Data Used** & **Data Source** \\ \hline \multirow{4}{*}{Primary Data} & Whole process of Short-term rice production & Interview and Questionnaire (QN) \\  & Fertilizer usage for rice production & Interview and QN \\  & Diesel and Gasoline use for rice production & Interview and QN \\  & Farmers practice of rice straw Management & Interview and QN \\ \hline \multirow{2}{*}{Secondary Data} & Pollutants Emission Inventory & EMEP/EEA-guidebook-2019 \\  & Cambodia rice production 2021 & Ministry of Agriculture, Forestry, and Fisheries \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Sources of input data for analysis. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multicolumn{4}{c}{**Pollutants Emission Factor (kg/ton Rice)**} \\ \hline
**Pollutants** & **Prey Veng** & **Svy Rieng** & **Kampong Thom** & **Average** & **Emission Activities** \\ \hline PM\({}_{2.5}\) & 0.021 & 0.021 & 0.021 & 0.02 & Combustion \\ NH\({}_{3}\) & 1.25 & 0.62 & 0.65 & 0.84 & Fertilizer \\ NO\({}_{x}\) & 0.96 & 0.54 & 0.57 & 0.69 & Combustion \\ SO\({}_{2}\) & 0.22 & 0.22 & 0.22 & 0.22 & Combustion \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Pollutants emitted in rice production per data from the survey. rice straw production for PM\({}_{2,5}\), NH\({}_{3}\), NOx, and SO\({}_{2}\) were 37,414.53, 1713.23, 809.89, and 1935.43 tons, respectively. The emission factor of pollutants for particulate matter formation potential (PMFP) with respect to PM\({}_{2,5}\) from RSOB in Cambodia is shown in Table 11, and total pollutants emission is shown in Table 12. and total pollutants emission is shown in Table 12. Prey Veng was the top province where produced pollutants from rice production and followed by Battam Bang and Takeo province that have shown in Figure 3.  
The direct emission of PM\({}_{2.5}\) was caused by fuel combustion and the open burning of straw, accounting for 99.63% of the total generated from straw burning; the remaining 0.37% was generated by fuel combustion. We discovered that burning straw and applying fertilizer to the field caused the secondary PM\({}_{2.5}\) formation of NH\({}_{3}\). In this study, we also found another particulate matter formation (NO\({}_{\text{x}}\)), of which 24.10% was generated by fertilizer, 24.35% by fuel combustion, and 51.56% by straw burning. Both burning of straw and fuel combustion produce SO\({}_{2}\), which is the other important particulate matter pollutant. A total of 52.08% of SO\({}_{2}\) emissions was attributed to burning straw and 38.92% to combustion.