TOXICOLOGICAL AND ENVIRONMENTAL ASPECTS RELATED TO THE USE OF PESTICIDES ON TOMATOES
The handling of any agricultural pesticide exposes the user to the irritating effects of the formulated product on the skin, lungs, eyes, nose and throat. The intensity of these effects naturally depends upon inherent toxicity to the active ingredient in the formulation as well as upon the type of formulation and its active ingredient and adjuvant contents. The effects may be noticed during the the preparation of the spary or during the application of the diluted product. The product is naturally much more toxic during the first operation when it is being handled in a concentrated form. Any of those effects will be aggravated if the product is applied on a windy day and if care is not taken to spray it in the same direction as the wind is blowing.
The type of active ingredient influences the degree of toxicity and this is demostrated by two products producing differing effects: parathion which causes serious intoxication even when only a few drops touch the skin and dicofol which would require a great quantity to produce this effect. As regards the type of formulation, oily solutions and emulsifiable concentrates are known to be more toxic to the skin than an aqueous solution since the former penetrate much more quickly. As far as the active ingredient content is concerned, it has been observed the higher its percentage in a commercial brand, the greater is the degree of the brand's toxicity and this may mean that products having the same active ingredient will be classified into two different toxicological groups depending upon the percentage of active ingredient in them. Lastly, as regards the adjuvants, these may on occasions increase the acute toxicity of the product or the possibility of its causing irritation, as is the case for instance with solvents and diluting agents in an emulsifiable concentrate.
In Portugal, each pesticide is appraised by the Pesticide Toxicology Commission before being put on the market. If it is considered to be toxicologically favourable, the Commission will indicate which toxicological group the product comes under and the precautions to be observed in its use depending upon the toxicological data submitted.
The classification system used by the Commission takes into account the product's acute oral and dermal toxicity as well as the degree of intoxication which would result from inhalation of the pesticide. In Portugal the products are classified into four toxicological groups numbered in descending order of acute toxicity from I to IV. The products in the first three groups are labeled with the corresponding symbol showing the product's degree of toxicity. In addition, the Commission specifies the precautions which have to be observed from the moment of purchase of the product up to the time the crop is harvested. The precautions include instructions on how to prepare, use and apply the product and these, if properly observed, will reduce the toxicological effects arising from the use of pexticides.
In Portugal fifty active ingredients are approved for use on tomato crops. Provisional Sales Licence have been granted to their formulations; nine of them fall into Group I, six into Group II, thirty eight into Group III and only one into Group IV. The sum total adds up to over 50 because some of the active ingredients are sold in different types of formulations or in similar formulations but with a different active ingredient content and consequently show varying degrees of acute toxicity. Such products may therefore be classified into both Groups I and II or II and III.
Annex T contains two examples of the type of precautions which are specified by the Pesticide Toxicology Commision for some type of formulation based on two active ingredients used on tomato crops in Portugal, one belonging to Group I and teh other to Group III. Greater care is recommended in the use of pesticides in Group I than those in Group III.