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Ebook Pesticide toxicology and international regulation: Part 2

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Part 2 book “Pesticide toxicology and international regulation” has contents: Toxicology of herbicides, microbial pesticides, biocides, variability of residues in unprocessed food items and its impact on consumer risk assessment, occupational aspects of pesticide toxicity in humans, treatment of pesticide poisoning, and other contents. | Pesticide Toxicology and International Regulation. Edited by Timothy C. Marrs and Bryan Ballantyne Copyright 2004 John Wiley & Sons, Ltd.TISBN: 0-471-49644-8 7 Toxicology of Herbicides Timothy C. Marrs Herbicides Herbicides are substances that kill plants. They have variable degrees of specificity. Some, for example paraquat, kill all green plants, whereas others, for example the phenoxy compounds, are specific for certain groups of plants. A chemical classification is given in Table 7.1. These compounds, particularly the non-selective examples, are less likely to appear in food than insecticides and fungicides as they are less likely to be used on crops, but exposure of operators can occur as with other pesticides. Inorganic herbicides Substances such as common salt (sodium chloride) have been used as herbicides for many years. Indeed, the Romans are reputed to have sterilized the soil of Carthage with salt after the Romans’ victory in the third Punic war in 146 BC. The disadvantage with such herbicides, from the agricultural point of view, is that they are non-selective. Nevertheless, sodium chlorate continues to be used as a herbicide and when ingested in man it produces vomiting and abdominal pain, diarrhoea, methaemoglobinaemia, and intravascular haemolysis (Helliwell and Nunn, 1979; Proudfoot, 1996). Sodium chlorate is an oxidizing agent and poses a fire hazard (Pesticide Manual, 1991). Bipyridylium herbicides This group of pesticides contains two well-known non-selective herbicidal compounds, namely paraquat and diquat (Figure 7.1). In experimental animals and in humans, the mechanism of toxic action of both compounds is very similar at the The views expressed in this chapter are those of the author and do not necessarily reflect the views of any UK Government Department or Agency. 306 TOXICOLOGY OF HERBICIDES Table 7.1 Main groups of herbicidesa Group Examples Inorganic Bipyridylium Organic acid Sodium chlorate Parquat .