Một vật gây hại, theo nghĩa rộng, là bất kỳ sinh vật - thực vật, động vật, hoặc vi sinh vật - có nghĩa là phá hoại hay phiền hà, hoặc sống mà nó là không mong muốn. Thuốc trừ sâu liên quan đến bất kỳ hóa chất nhằm mục đích phòng ngừa, ngăn chặn, tiêu diệt, hoặc làm giảm khả năng của dịch hại đối với cạnh tranh với các sinh vật mong muốn, chẳng hạn như cây trồng, động vật, hoặc con người. Thuốc trừ sâu có thể được phân loại theo những cách khác nhau, chẳng hạn. | CHAPTER 13 Pesticides and Related Materials INTRODUCTION A pest broadly defined is any organism plant animal or microorganism that is destructive or troublesome or living where it is unwanted. Pesticide refers to any chemical intended to prevent deter destroy or otherwise impair the ability of pests to compete with desired organisms such as crops animals or humans. Pesticides can be classified in various ways such as by their target chemical nature physical state and mode of action. Classification based on the target is perhaps the most widely known as the following examples indicate insecticides herbicides fungicides and rodenticides Table . In this chapter we will consider the chemistry characteristics and health effects of several representative groups of pesticides and herbicides. We will then discuss several halogenated hydrocarbons that have become of much concern to us in recent years including PCBs and dioxins. INSECTICIDES Insecticides are those compounds that are effective against insects. Many insecticides have been developed and used to control various species of insects. While most insecticides are applied as sprays others are applied as dusts aerosols fumigants and baits. The majority of insecticides used today are synthetic organic chemicals and most of them are nerve poisons. They act by inhibiting the organism s enzymes or interacting with other target sites vital to the proper functioning of the insect s nervous system. Other insecticides act by blocking essential processes such as respiration. Although there are many synthetic organic insecticides in this chapter we will focus on three main groups chlorinated hydrocarbons organophosphorus compounds and carbamates. 187 2001 by CRC Press LLC 188 ENVIRONMENTAL TOXICOLOGY Table Classification of Pesticides Method of Classification Examples By target Insecticides herbicides fungicides rodenticides algicides nematocides By chemical nature Natural organic compounds inorganic .
