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PART 3 Further issues and future prospects © 2001 C. H. Walker CHAPTER 13 The ecotoxicological effects of herbicides 13.1 Introduction Chapters 5–12 deal with groups of pollutants that have been studied in some depth and detail, largely because they have appreciable – sometimes very high – mammalian toxicity and are perceived as human health hazards. Some of them are markedly persistent and undergo biomagnification with passage along food chains. As has been explained, individual compounds, or mixtures of related compounds, have sometimes been shown to cause adverse ecological effects. Although it was necessary to take such pollutants as examples, it is important now to consider the more. | PART 3 Further issues and future prospects 2001 C. H. Walker CHAPTER 13 The ecotoxicological effects of herbicides 13.1 Introduction Chapters 5 12 deal with groups of pollutants that have been studied in some depth and detail largely because they have appreciable sometimes very high mammalian toxicity and are perceived as human health hazards. Some of them are markedly persistent and undergo biomagnification with passage along food chains. As has been explained individual compounds or mixtures of related compounds have sometimes been shown to cause adverse ecological effects. Although it was necessary to take such pollutants as examples it is important now to consider the more complex situation in which organisms are exposed to mixtures of compounds differing in their chemistry and or mode of action. The present chapter is the first of the final part of the text in which the emphasis moves on from the detailed descriptions of particular types of pollutants given in the foregoing chapters to address some wider issues. Apart from the question of the complexity of pollution in the real world certain other issues arise directly from the findings of ecotoxicological studies on individual pollutants reported in the earlier text. Herbicides constitute a large and diverse class of pesticides that with a few exceptions have very low mammalian toxicity and have received relatively little attention as environmental pollutants. Paraquat and other bipyridyl herbicides have appreciable mammalian toxicity and will be discussed in Chapter 14. Dinoseb and 2001 C. H. Walker 226 Further issues and future prospects related dinitrophenols which act as uncouplers of oxidative phosphorylation in mitochondria are general biocides that are little used today because of their hazardous nature. They will be mentioned briefly in section 14.2. Herbicides are in general readily biodegradable by vertebrates and are not known to undergo substantial biomagnification in food chains. Their principal
