Đang chuẩn bị liên kết để tải về tài liệu:
Pesticide profiles : Toxicity, environmental impact and fate - Chapter 5

Organophosphates 5.1 Lớp cái nhìn tổng quan và bối cảnh mô tả chung Organophosphates là thuốc trừ sâu được sử dụng phổ biến nhất. Họ cũng sử dụng như thuốc diệt cỏ và thuốc diệt nấm. Mặc dù phát triển trong những năm đầu thế kỷ 19, nó đã không được cho đến khi 1932 rằng những tác động của các hợp chất này trên các loài côn trùng đã được phát hiện (1). Organophosphates (OPS) được đặc trưng bởi một nguyên tử phốt pho trung ương và các chuỗi bên rất nhiều. Hầu hết các OPS được sử dụng như thuốc. | chapter five Organophosphates 5.1 Class overview and general description Background Organophosphates are the most commonly used insecticides. They are also employed as herbicides and fungicides. Although developed in the early 19th century it was not until 1932 that the effects of these compounds on insects were discovered 1 . Organophosphates OPs are characterized by a central phosphorus atom and numerous side chains. Most of the OPs used as insecticides are dimethoxy and diethoxy compounds. These broad groups of pesticides contain the well-known insecticides malathion and diazinon. The generalized structure of the organophosphate compounds is shown in Figure 5.1 2 . Figure 5.1 Generic organophosphate structure. One feature of the OPs that has led to their wide usage in agriculture and in the home is that they are much less persistent in the environment than the organochlo-rines such as DDT. The compounds in the latter group were the pesticides of choice before the development of the OPs. The OPs are considerably more acutely toxic to vertebrates than the organochlorines 3 . The OPs are being replaced in some applications by the carbamate insecticides which have lower toxicities to humans and wildlife. The commonly used OPs are listed in Table 5.1. Organophosphate usage Organophosphate insecticides can be effective whether they are ingested by the pest or are absorbed through the cuticle skin of the insect. However some of the OPs are specifically formulated as stomach poisons or as contact poisons. The OPs are used against a wide array of insects and mites. OPs are used extensively on cotton corn wheat and a variety of other agricultural crops. They are also used for domestic pest control. Some of the OPs such as dichlorvos DDVP are administered orally to livestock to control internal parasites like the bot larva. Several others are used externally on livestock to control parasites on the animal s skin. 2000 CRC Press LLC Table 5.1 Organophosphates Acephate .