农药菌核净在登记作物（水稻、油菜、番茄）上的残留行为、在加工过程中的转移规律及膳食摄入风险评估

Pesticide residues are one of the important factors affecting the quality and safety of food. Dimethachlon [N-(3,5-dichlorophenyl)-succinimide, is a dicarboximide fungicide with certain kidney damage. For the sake of human health, dimethachlon is a banned pesticide in the United States and Europe. Due to being effective against various plant pathogenic fungi, such as Sclerotinia stem rot, Sclerotinia blight, gray gray mould on crops, dimethachlon has been registered for use on rice, rape and tomato in China. At present, no country or organization has defined the maximum residue levels (MRLs) of dimethachlon on vegetable crops. .The dimethachlon was applied to the rice, rape and tomato with a relatively large dose (600-1500 g a.i./ha), and the numbers of application for prevention were 2-3 times, and the residues in the primary agricultural products were large, during the cultivation and processing, dimethachlon may produce highly toxic metabolites. So, it is essential to clear the transfer rule of dimethachlon and its metabolites in plant-processing, which is helpful to find the key procedure to control the pesticide residue, and to reduce the risk of dietary intake. This study intends to identify the metabolites of dimethachlon in the planting of rice, rape and tomato by field trial and food processing step, quantitatively examine the parent compound and metabolites in the raw agricultural commodities and processing products, and track the target compound to obtain the processing factor (PF). It is possible to clarify the transfer law of dimethachlon from field to food. On the basis of processing factor (PF) and residues in the crops, dietary risk assessments were conducted with the Chinese dietary structure. The research will provide scientific data and method to evaluate the risk of dimethachlon from application in the registered crops comprehensively, and provide theoretical and technical basis for defining proper residue limited values on rice, rape and tomato.

菌核净在美欧属禁用农药，而在中国已在水稻、油菜、番茄上登记使用，目前，国际国内都未制定菌核净在食品中的最大残留限量标准值（MRLs）。菌核净在作物上施用剂量较大，防治施用次数2-3次，残留量较大，在种植过程和加工过程中还可能产生高毒代谢物，明确菌核净及其代谢物在种植-加工-食用过程的转移规律，对于科学计算膳食摄入风险具有重要意义。本研究拟设计菌核净在登记作物上的田间喷药试验和不同农产品的加工试验，鉴定菌核净在作物种植过程中和加工步骤中的代谢物种类，推测代谢机理，定量考察母体化合物菌核净和主要代谢物在初级农产品和加工食品中的残留量，获得加工因子（PF），阐明菌核净从田间到食用过程中的转移规律；在建立初级农产品残留量和加工因子的基础上根据中国膳食结构进行菌核净膳食风险评估。本项目的完成将为全面科学地评价菌核净的膳食风险提供科学数据和方法，为制定有科学依据的菌核净残留限量提供理论和技术基础。

筛查并确定了菌核净在土壤中主要产生4-((3,5-二氯苯基)氨基)-4-氧代丁酸（DCBAA）、3,5-二氯苯胺（3,5-DCA）、琥珀酸和粘康酸四种代谢物；在番茄、水稻等作物中主要代谢为DCBAA和3,5-DCA。开展了DCBAA和3,5-DCA两种主要代谢物对土壤中四种酶活性的影响，初步评价了代谢物对土壤的毒性。分别建立了菌核净及四种代谢物在土壤、菌核净及两种代谢物在水稻基质（包括水稻植株、稻壳和糙米）、番茄基质（包括番茄植株和番茄）、油菜基质（包括油菜籽、油菜籽壳和籽油）中准确灵敏的残留检测方法，方法的定量限均小于0.05 mg/kg。.菌核净在三种土壤中降解迅速，半衰期小于1 d，降解过程中DCBAA和3,5- DCA残留量最大可达母体浓度的22.5% ~ 35.2%。在灭菌土壤中，30 d时菌核净在三种土壤中的降解率均小于31%，降解非常缓慢，三种灭菌土壤中代谢产物DCBAA和3,5- DCA的产生率均低于母体的16%，且土壤中不产生粘康酸或琥珀酸。按推荐剂量高剂量施药2次，0-21 d在水稻稻谷中菌核净总残留量（菌核净、DCBAA和3,5- DCA之和，以菌核净计）为0.54-36.43 mg/kg；菌核净在水稻稻谷、植株上的半衰期为2.96-6.24 d。0-14 d番茄果中菌核净总残留量为0.05-7.29 mg/kg；菌核净在番茄果、番茄植株上的半衰期为1.67-2.73 d。0-14 d油菜籽中菌核净总残留量为0.106-6.35 mg/kg，在菜籽壳中菌核净总残留量为4.35-112.8 mg/kg；菌核净在油菜籽、油菜籽壳上的半衰期为0.70-5.21 d。.番茄经过清洗加工系数为0.06-0.08，说明菌核净的清除率为92%以上，番茄经过捣碎加热翻炒成酱加工系数为1.25-1.56，菌核净浓度增大。稻谷加工成糙米或稻谷加工成精米或精米煮成米饭，加工因子为0.03-0.15，各加工程序菌核净的清除率为85%以上。菜籽经过80℃烘12 h，加工系数为0.78-0.84，残留量减少约22%；烘烤后的油菜籽压榨成菜籽油，菌核净加工系数为0.38-1.04。结合我国农药登记情况和我国居民的人均膳食结构，普通人群菌核净的国家估算每日摄入量是0.076 mg，占日允许摄入量的93.31%，结果表明对一般人群健康不会产生不可接受的风险。