室內木炭燃燒產生空氣污染物之研究

Abstract

為瞭解燒烤店飲食方式產生之空氣污染物對人體健康之危害，本研究選擇10種市售常見木炭，置於管狀高溫爐內燃燒，模擬燒烤店於高溫中再加炭燃燒之形式，並以不同溫度與不同空氣供應量，測試其燃燒後污染物排放差異，再配合氣膠監測儀、多氣體分析儀及DNPH化學吸收，分析木炭燃燒產生之HC、CO、CO2、NOx、PM10、PM2.5及羰基化合物之濃度。由前述測量結果估算排放因子與排放速率，將之與木炭基本成分進行相關性比較，並經由情境模擬轉換為室內濃度進行健康風險評估，供燒烤店木炭使用選擇參考。 實驗結果顯示，當空氣供應量控制在10 LPM，燃燒溫度由450 ℃提升至550 ℃，於悶燒階段內PM10與PM2.5受燃燒溫度影響（P value < 0.05），並隨燃燒溫度提高排放量有上升趨勢。當溫度控制於500 ℃，改變空氣供應量（由10 LPM提升至20 LPM），則是HC與CO於焚燒階段受空氣供應量影響（P value < 0.05），並隨空氣供應量增加排放量有上升趨勢。控制空氣供應量在20LPM、燃燒溫度500℃進行木炭種類燃燒實驗，CO及CO2排放因子範圍分別落於77 ~ 300 g kg-1與776 ~ 1225 g kg-1。各木炭中備長炭（B1）為PM2.5、PM10排放因子最低之木炭，平均值（含1倍標準差）依序為20 ± 4 mg kg-1、36 ± 2 mg kg-1；炭精（I1S）為羰基化合物排放量最少者，僅偵測到甲醛及乙醛，其排放因子分別為6.1 ± 0.4 mg kg-1、1.3 ± 0.3 mg kg-1。環保球炭（C2S）為燃燒時污染物排放量最高者，其HC、PM2.5、PM10、甲醛、乙醛5項污染物排放因子均為各木炭之首，分別為11209 ± 1276 mg kg-1、16542 ± 2040 mg kg-1、20109 ± 2301 mg kg-1、519.9 ± 200.8 mg kg-1、769.5 ± 31.6 mg kg-1，其中，PM2.5、PM10、甲醛、乙醛等4項，更遠大於排放量次高之木炭5 ~ 10倍，即使該木炭適用於戶外烤肉，其大量污染物排放對人體健康危害仍不容忽視。 針對燒烤店工作人員之健康風險評估顯示，吸入途徑之非致癌風險，以懸浮微粒所造成的健康危害最大，各木炭PM2.5危害商數（HQ）皆大於1；估算甲醛及乙醛的吸入性致癌風險，環保球炭（C2S）、紅木炭（I2）、豆炭（I3S）、環保炭（T1S）及相思木炭（T2）等5種木炭對人體致癌風險已超過容許範圍（10-4），不適合於室內使用；無煙煤木炭（C1S）、環保竹炭（C3S）、炭精（I1S）、龍眼木炭（T3）、備長炭（B1）仍在可接受範圍（10-4 ~ 10-6之間），使用上應儘量縮短暴露於此環境的時間。然而考量無煙煤木炭（C1S）與環保竹炭（C3S）可供熱值較低，且灰分量偏高，僅推薦炭精（I1S）、龍眼木炭（T3）及備長炭（B1）等3種木炭予燒烤店選擇。以20歲體重70公斤的青年為例，演算消費者的甲醛及乙醛吸入性致癌風險評估，得知平均每年最多可至使用炭精（I1S）燒烤店用餐44次、使用備長炭（B1）或龍眼木炭（T3）燒烤店用餐16次，仍在可接受罹癌風險（10-6）內。反之，若燒烤店使用環保球炭（C2S）為燃料，即使每年僅用餐一次仍會超過可接受罹癌風險度（10-6）。

In order to understand the human health hazard resulted from air pollutants produced in BBQ restaurants, 10 commonly available charcoals in Taiwan were selected for combustion experiments in a tube furnace under several temperature and airflow conditions. The properties of the gases released from charcoal combustions including PM10, PM2.5, HC, CO, CO2, NOx and carbonyl compounds were measured by aerosol monitor, multi-gas analyzer and DNPH-HPLC chemical absorption. In addition, Health risks assessments for employees and consumers in BBQ restaurants were also conducted as well. The results showed that PM10 and PM2.5 were affected by the combustion temperature in the smoldering stage when combustion temperature increased from 450 ℃ to 550 ℃ with the airflow at 10 LPM. Their emission rates are proportional to temperatures. As the temperature is controlled at 500 ℃ but the airflow was changed from 10 LPM to 20 LPM, the emission rate of HC and CO were affected in the flaming stage. To make batter comparisons on experimental results, the combustion conditions of 20 LPM and 500 ℃ for 10 charcoal samples were selected. The emission factors of CO and CO2 ranged from 77 to 300 g kg-1 and from 776 to 1225 g kg-1, respectively, without difference among charcoals. Binchōtan (abbreviated as B1) causes the lowest PM2.5 and PM10 emission; the emission factors were 20 ± 4 mg kg-1 and 36 ± 2 mg kg-1, respectively. Sawdust briquette charcoal (coded as I1S) resulted in the lowest emission of carbonyl compounds, only formaldehyde and acetaldehyde analyzed, whose emission factors were 6.1 ± 0.4 mg kg-1 and 1.3 ± 0.3 mg kg-1, respectively. The highest pollutants emission was released from eco-friendly charcoal (coded as C2S) with the emission factors of 11209 ± 1276 mg kg-1 for HC, 16542 ± 2040 mg kg-1 for PM2.5, 20109 ± 2301 mg kg-1 for PM10, 519.9 ± 200.8 mg kg-1 for formaldehyde, and 769.5 ± 31.6 mg kg-1 for acetaldehyde. For the staff of BBQ restaurants, PM2.5 is the most hazardous pollutants according to the non-cancer risk calculated. The cancer risk assessments via inhalation of formaldehyde and acetaldehyde suggested that 5 charcoals exceed the acceptable range (>10-4) and are not suitable for indoor use. They are charcoal briquettes (C2S), mangrove charcoal (coded as I2), charcoal briquettes (coded as I3S), eco-friendly charcoal (coded as T1S), and acacia charcoal (coded as T2). Other charcoals, including eco-friendly charcoal (coded as C1S), charcoal briquettes (coded as C3S), sawdust briquette charcoal (I1S), longan charcoal (coded as T3), and binchōtan (B1), are within the acceptable range (between 10-4 to 10-6). On the other hand, due to the insufficient heating value and high ash content in eco-friendly charcoal (C1S) and charcoal briquettes (C3S), only sawdust briquette charcoal (I1S), longan charcoal (T3), binchōtan (B1) are recommended to be used in BBQ restaurants. The health risk assessments for 20-year-old consumers of BBQ restaurants demonstrated that the annual visiting limit, taking the acceptable cancer risk (10-6) as the criterion, for a 70-kg youth is 44 times/yr if sawdust briquette charcoal (I1S) is used in a BBQ restaurant; 16 times/yr for those using binchōtan (B1) or longan charcoal (T3). Unfortunately, even if a person only visit the BBQ restaurants using charcoal briquettes (C2S) as fuel once a year, the acceptable cancer risk (10-6) will be exceeded.