Tám chương tiếp theo sẽ được dành cho việc nghiên cứu độc học sinh thái của các nhóm các hợp chất đã gây ra mối lo ngại trên tài khoản thật hay cảm nhận tác động môi trường của họ và đã được nghiên cứu trong phòng thí nghiệm và trong lĩnh vực. Đây là những chủ yếu là hợp chất được sản xuất bởi con người. Tuy nhiên, một vài trong số họ, ví dụ, methyl thủy ngân, asen methyl, và polycyclic aromatic hydrocarbons (PAHs), cũng xuất hiện tự nhiên. Trong trường hợp thứ hai này, có thể có. | Part 2 Major Organic Pollutants The next eight chapters will be devoted to the ecotoxicology of groups of compounds that have caused concern on account of their real or perceived environmental effects and have been studied both in the laboratory and in the field. These are predominantly compounds produced by humans. However a few of them for example methyl mercury methyl arsenic and polycyclic aromatic hydrocarbons PAHs are also naturally occurring. In this latter case there can be difficulty in distinguishing between human and natural sources of harmful chemicals. The compounds featured in Part 2 have been arranged into groups according to their chemical structures. In many cases members of the same group show the same principal mechanism of toxic action. The chlorinated cyclodienes act upon gamma aminobutyric acid GABA receptors the organophosphorous and carbamate insecticides are anticholinesterases the pyrethroids act upon sodium channels the anticoagulant rodenticides are vitamin K antagonists and some of the PAHs are genotoxic. From an ecotoxicological point of view there are advantages when groups of compounds can be identified that share the same mechanism of action. Here it becomes possible to relate the toxicity of a mixture of similar compounds to a single event for example acetylcholinesterase inhibition or vitamin K antagonism and so biomarker assays can be developed which monitor the effects of combinations of chemicals see Chapter 13 . Unfortunately processes are not always so simple. The members of groups such as polychlorinated biphenyls PCBs and PAHs for example do not all operate through the same principal mechanism of action. Also some individual pollutants such as p p -DDT or tributyl tin work through more than one mode of action. Thus it is often not possible to measure the combined effects of members of one group of pollutants with a single mechanistic biomarker assay. The situation 2009 by Taylor Francis Group LLC 100 Organic Pollutants An .
