Testing pesticides

There are a number of national and international bodies that approve new pesticides within their areas of responsibility. These include Codex Alimen-tarius, the European Union, and the US Food and Drug Administration (USFDA). Currently, within the European Union, registration of pesticides is being harmonized under Directive 91/414 EEC. Annexe 1 of this directive will identify all active ingredients permitted in pesticides. As yet this annexe is incomplete and member states are still acting under their national laws.

Within the UK pesticide registration is carried out under the Control of Pesticide Regulations 1986 and is the responsibility of the Ministry of Agriculture, Fisheries, and Food who are advised by the Advisory Committee on Pesticides.

In the USA a new Food Quality Protection Act of 1996 replaced both the Food, Drug, and Cosmetic Act and the Insecticide, Fungicide, and Rodenticide Act to provide a comprehensive regulatory scheme for pesticides.

In order to gain approval for use, pesticides are subjected to an extensive testing program including toxicity tests on mammals, plants, insects, fungi, birds, bees, fish, earthworms, and other soil organisms. The toxicity studies include effects of pesticides on fetuses and infant animals. There are also environmental tests which include laboratory tests on the breakdown and movement of the chemical in plants, soil, water, air, mammals, birds, and fish. These latter tests determine the rate of decay in the various species. Laboratory tests are followed by prolonged field trials to determine the fate of the chemical and its breakdown products in the environment and to estimate how the pesticide is concentrated up the food chain. On average it takes about 10 years to develop a new pesticide at a cost of about £50 million. The complete dossier of results has to be submitted to the approval body who determine whether the tests have been sufficiently rigorous to allow an acceptable daily intake (ADI) of the pesticide to be set. The ADI is defined as the amount of a pesticide that can be taken in each day throughout a person's life with the practical certainty, on the basis of all known facts, that no harm will result. This is determined on the basis of the highest level at which the pesticide has no observable effect in animal tests. This is then reduced by a factor of 10 in case humans are more sensitive than the animals used in the tests, and by a further factor of 10 to allow for cases where some humans may be more sensitive than others. In some cases, where the data show unusual effects, the safety factor can be increased from 100 to 500 or 1000. In practice the amount of pesticides to which the population is exposed is far below this level.

Table 1 includes the ADI for a number of the more common pesticides. There is no evidence that there are any cases where the combined effects of two pesticides are greater than the sum of their individual effects, in other words there is no evidence of synergy in toxicology between the different pesticides. Once maximum residue limits (MRL see below) for foodstuffs have been set on the basis of good agricultural practice, a total dietary intake is determined by considering all commodities in which the pesticide is likely to be used, and assuming the upper range of consumption, all foodstuffs at the MRL and no losses during transport, storage or food preparation. This figure is then compared with the ADI. For all permitted pesticides in the UK the figure is below the ADI.

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