Fire / Feu

Les cobayes de l’industrie chimique

Les fabriquants de pesticides ont recours depuis déjà bien longtemps aux animaux afin d’établir les normes selon lesquelles un produit peut être utilisé de façon sécuritaire. La réaction des animaux exposés à un produit détermine les effets que ce même produit provoquerait chez l’être humain. Pourtant, personne ne sait avec certitude que la réaction des animaux exposés à un produit chimique sera la même chez l’être humain.

Plusieurs études démontrent que les pesticides causent le cancer, menacent les systèmes aquatiques et sont nocifs dans l'ensemble. Bien qu'un grand nombre de personnes fassent encore confiance aux résultats des tests auxquels sont assujettis les animaux, la démarche doit être mise en question. Ne vaudrait-il pas mieux de dépenser de l’argent pour trouver de nouveaux produits au lieu de continuer à faire des expériences sur des animaux avec des produits déjà connus comme étant nocifs ?

Animal testing,
does it prove anything?

   Emily McMillan
   UNB Environmental Society
   January 1999


p.gif (360 bytes)esticides are used widely all over the world. Some see this practice as harmless, some see it as necessary, some see it as poisoning the landscape and the people who live on it. Are pesticides really dangerous? Many people would say no, pointing to the extensive testing done by the manufacturers of these chemicals as proof of their harmlessness. However, others see glaring problems with the testing process. One of the main problems is that the testing is only done on lab animals, not humans. No one knows for sure if the chemicals have the same effects on these lab animals as they would on humans. Are tests done on lab animals good enough to prove that any chemicals are safe for human use?

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Toxicity is defined as the inherent capacity of a substance to cause injury or death. It would seem anything toxic was a potential hazard; however, the pesticide manufacturing companies claim a substance can be toxic and not hazardous depending on the amount of exposure. Considering the lack of knowledge on safe exposure levels for humans, this claim is doubtful.

Most manufacturers of pesticides have certain tests that they perform on the chemical they are looking to sell. Results of tests on lab animals are used as a guide to how toxic the chemical would be to humans. New chemicals are tested on a variety of organisms - from rats to rabbits. A statistical value called the LD50 of the chemical is found through these tests. The LD50 is the amount of the pesticide that it takes to kill fifty percent of the test animals it is given to. This tells the acute toxicity of a chemical - meaning how poisonous it is on a short term basis and how intense its effects will be. In other words, will it kill you right away. The lower the LD50 value is, the more toxic the pesticide is since this means that less is needed to be fatal.

The LD50 is the value most often referred to by manufacturers when they talk about the safety of their product. However, the LD50 says nothing about chronic toxicity caused by long term exposure to small amounts. Some companies do test chronic toxicity; however, this is also done with test animals over their normal life span. Rats, which have a life span of two years, are commonly used. Would this type of test really show the effects of the eighty years or more of exposure to pesticides that most humans are subjected to?

Subacute toxicity is also looked at by the manufacturer. Subacute means that it is not fatal right away but that it may be harmful when the exposure time is longer. During these tests, it is determined what daily dosage is survivable, what level can be given daily with no effect and what are the effects if the substance is given above this level. Usually, six different levels are used, starting with fifty percent of the LD50. Daily observations are made and growth is monitored. Autopsies are also generally done on the test animals. These studies are normally done over 12 to 24 weeks.

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Labratory Mice

Rats are generally used for oral toxicity tests (how toxic the chemical is when ingested) and rabbits for dermal toxicity tests (how toxic the chemical is when applied to the skin). Rats are used for oral toxicity because they have a similar digestive system and similar metabolic responses as humans. In studying chronic toxicity, effects on reproduction are looked for as well as any evidence of carcinogenic (cancer causing) or teratological (birth defect causing) effects. Dermal toxicity is studied to determine the potential to cause skin irritation. Tests are done on rabbits’ skin, abraded skin, and eyes. For the abraded skin tests, the rabbit’s skin is rubbed with sandpaper until just before it bleeds and then the chemical is applied. Inhalation tests are also performed. It is questionable whether any of these tests are really useful to determine the effects of these chemicals on humans.

Testing determines toxicity as well as how much of the product is needed to control the pest targeted and what the exposure to humans would be if for example this amount was applied on someone’s lawn. If it is thought that humans will be exposed to more of the chemical than was found to be safe for test animals, then the product will not be approved for sale. This sounds good; however, many of these chemicals are used improperly by farmers and homeowners with too many applications in too short a time or not at the right time. This leads to higher levels of exposure to humans than the companies think there will be.

Critics of the testing process point out that the levels of toxicity determined are for an adult male of average size (70kg). This does not take into consideration females, children, and more sensitive people. These groups of people may be adversely affected by a much smaller exposure rate. Another criticism is that tests are only for exposures to pure active ingredients. In fact, pesticides are made up of both active ingredients and other substances called inerts. These inerts are not tested and they may be as toxic as the active ingredient. The pesticide may also contain more inerts than active ingredients, causing concern over the lack of testing of these chemicals.

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Precautionary statements on the label are intended to ensure the products are used safely and effectively. The active ingredients are listed on the label, however, the inerts are not. Due to laws protecting trade secrets, manufacturers are not required to list inerts on the labels of their products. However, it is generally admitted that although the inerts have no pesticidal action they may be irritating or toxic to humans.

The effects of pesticides on human health and the environment are not well understood and are very controversial. Many studies have shown that pesticides cause cancer, threaten aquatic systems and are generally harmful. Many people still trust in the testing process to ensure these products are safe. However, in my opinion, the testing processes are inadequate to show that these products are harmless to humans. Perhaps less money should be spent on testing chemicals and more put into finding alternatives to them.