| 摘要: | 蔬菜在種植過程中會累積大量的硝酸鹽，尤其是葉菜類蔬菜。由於植物葉子需要氮才能進行光合作用，使得大量的硝酸鹽累積在葉和莖組織中，根部亦會有少量累積。另一方面，由於蔬菜具有許多健康上的益處，因此為人類飲食不可或缺的一部分，也因此蔬菜被廣泛認為是人體攝取硝酸鹽的重要來源，而飲食中的硝酸鹽與高鐵血紅蛋白血症和胃癌等致命疾病的風險增加有關。因此，本研究調查了臺灣普遍種植及最常被食用的八種不同蔬菜的硝酸鹽含量，比較有機和慣行農法栽培蔬菜的硝酸鹽濃度，以探討不同耕作方式對硝酸鹽的累積濃度的影響；此外，本研究亦基於毒理學，計算台灣地區成年男性和女性，因攝食蔬菜而暴露於硝酸鹽之風險。研究中採用美國環境保護署（US EPA）發布之人體健康風險評估準則，評估臺灣居民的致癌及非致癌風險。為考量參數之不確定性，將參數以機率分布表示，並使用 Oracle Crystal Ball軟體執行蒙地卡羅模擬法。 研究結果顯示，有機蔬菜硝酸鹽濃度的幾何平均值和幾何標準偏差值分別為996.02 mg/kg和4.37，慣行蔬菜則為2497.97 mg/kg和1.91(慣行蔬菜之樣品數為 192、有機蔬菜之樣本數為 38)。在非致癌風險部分，研究結果顯示男性和女性於攝食慣行栽培蔬菜時，危害商數 HQ之平均值分別為 0.23 和 0.28；若攝食有機蔬菜，則男性及女性之HQ值分別為0.30及0.36，代表不論攝食慣行或有機蔬菜，非致癌風險為可接受的。若保守考量最壞的情境，亦即考慮風險值之97.5 百分位數，男性攝食慣行栽培蔬菜所產生之 HQ值 和標的致癌風險 TR值分別為0.82和1.31 x 10-5，相較之下，女性之HQ及TR值則分別為 1.08 和 1.73 x 10-5。由前述結果可知，在食用慣行種植的葉菜時，女性因硝酸鹽所造成之風險比男性高。若考量攝食有機蔬菜，則男性之 HQ 和 TR之 97.5 百分位數值，分別為 1.77 和 2.83 x 10-5，而女性的 HQ 和 TR 值，則分別為 2.23 和 3.56 x 10-5。因此，當食用有機種植葉菜時，基於保守觀點，亦有一定的非致癌及致癌風險。此外，研究結果亦顯示在攝食葉菜類而暴露於硝酸鹽所產生的健康風險，女性比男性高。 本研究之結果，可作為臺灣制定蔬菜硝酸鹽含量標準之法規的參考依據之一。然而，在未來的研究中，建議對更多種類的葉菜類，乃至其他類型的蔬菜進行研究，另在討論不同類型蔬菜種類時，各類別的樣本數應盡量相同為佳。
Vegetables can accumulate an enormous amount of nitrate during cultivation, especially leafy vegetables. Plant leaves require the presence of nitrogen in order to photosynthesize. As a result, a large amount of nitrate could build in the leaf and stem tissues, followed by the roots. Vegetables, on the other hand, are strongly suggested to be included in a human's diet due to their widely acknowledged health benefits. For this reason, vegetables are widely considered to be the most important source of nitrate intake. Today, dietary nitrate has been linked to an increased risk of fatal conditions such methemoglobinemia and gastric cancer. Thus, this research investigated the nitrate content of eight different vegetables that are widely grown and consumed in Taiwan. The goal of this study is to examine the nitrate concentrations of vegetables cultivated organically and conventionally, as well as to determine the impact of various farming practices on nitrate accumulation and concentration. This study calculated and compared the toxicological risk to people, mostly adult males and females, linked with the consumption of several vegetables containing varying levels of nitrate. The US Environmental Protection Agency's (US EPA) human health risk assessment paradigm was used to assess the non-carcinogenic and carcinogenic risk of Taiwan residents. Due to their large uncertainty and variability, the parameters were considered as distribution and the risk was calculated by Monte Carlo simulation using the Oracle Crystal Ball software. The results showed that the geometric mean and geometric standard of nitrate concentrations of vegetables grown organically were 996.02 mg/kg and 4.37, respectively, ¬¬¬ and 2497.97 mg/kg and 1.91 for conventional one (192 samples for conventional grown vegetables and 38 samples for organic grown vegetables). For non-carcinogenic risk, the mean value of the hazard quotient (HQ) of consuming conventional vegetables for male and female was 0.23 and 0.28, respectively. For the consumption of organic vegetables, the mean HQ for male and female was 0.30 and 0.36, respectively. This result indicated that the “average” non-carcinogenic risk for both groups can be considered “acceptable”. However, in the worst-case scenario, the 97.5%-tile values of HQ and target cancer risk (TR) of nitrate in males by consuming vegetables under conventional practice was respectively 0.82 and 1.31 x 10-5, whereas the HQ and TR value for females was 1.08 and 1.73 x 10-5, respectively. Therefore, it can be concluded that with the consumption of conventionally grown leafy vegetables, the female population is more prone to risk than the male population. As for the results on organic practice, the 97.5%-tile value of HQ and TR for males is 1.77 and 2.83 x 10-5, respectively, while the female has a value of 2.23 and 3.56 x 10-5, respectively. Thus, from a conservative viewpoint, consumption of organically cultivated leafy vegetables used in this study might put the target populations at risk. Furthermore, based on the results, it could be clearly seen that females are more likely to be exposed to risk than males due to the consumption of leafy vegetables. The results of the present study can be applied while setting the local regulation standard for nitrate in Taiwan. However, experiments with more kinds of leafy vegetables and other types of vegetables are suggested in future research. It is as well a suggestion to use the same numbers of samples for future experiment. |
