バイオ燃料利用増加のためのィンドネシァにおけるオイルパーム栽培およびィンドにおけるサトウキビ栽培による農薬の環境リスクについて

摘要

バイオ燃料の利用によるインドネシアのオイルパームおよびィンドのサトウキビの栽培拡大政策に起因する農薬施用量の増加による環境リスクの比較·評価を行うために，面積当たり施用量等に基づきボックスモデル(MuSEM)により現状および将来(2020年)の環境濃度および摂取量の予測を21農薬について行った。その結果，主要な生産州の平均で現状または将来にパラコート，ワルフアリン等10種で，暴露量の耐容一日摂取量比が1を超える可能性が予測された。また，将来の暴露量は，栽培面積の拡大に応じて増加すると予測された。このため今後，これらの農薬について優先的に環境中分解性の精査やモニタリングよる詳細なリスク評価を行うことが重要である。%Using an environmental fate model, environmental risks caused by increased use of agricultural chemicals to cultivate biofuel crops, namely oil palm in Indonesia and sugarcane in India, were assessed by estimating current (Indonesia in 2005, India in 2008) and future (2020) environmental concentrations and exposures of each chemical in major producing states. A MuSEM (Multimedia Simplebox-systems Environmental Model), was used for the assessment based on data such as estimated application amount per unit area of chemicals, cropping area, and physical and chemical properties of agricultural chemicals. Twenty-one agricultural chemicals were studied and average exposures of 10 chemicals including paraquat and warfarin were estimated to exceed respective Tolerable Daily Intake (TDI) levels in some cases. In particular, estimated exposures of propenofos and defenolconazole in Indonesia, which are assumed to be non-degradable in the environment, were more than 10 times TDI levels. It was also estimated that in 2020 the average exposure would increase up to three to four times for five chemicals such as paraquat in five states in Indonesia and one and a half times for four chemicals in four states in India if the cropping areas continued expanding in accordance with the governments' current policies. Estimations were made and compared using the ChemCAN model for some Indonesian cases. Estimated concentrations and distribution among environmental media as estimated by ChemCAN were similar to those of the MuSEM. Sensitivity analysis of glyphosate and paraquat showed that concentrations in soil decreased by 40% if half of the application amount was put into air and water. In both countries, it is necessary to scrutinize assessment of these 10 chemicals based on detailed data such as input amount of agricultural chemicals, degradability of the chemicals in the environment and other means of environmental monitoring.