Les cobayes de lindustrie chimique
Les fabriquants de pesticides ont recours depuis déjà bien longtemps aux
animaux afin détablir 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 lêtre humain. Pourtant, personne ne sait
avec certitude que la réaction des animaux exposés à un produit chimique sera la même
chez lêtre 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
largent pour trouver de nouveaux produits au lieu de continuer à faire des
expériences sur des animaux avec des produits déjà connus comme étant nocifs ?
does it prove anything?
UNB Environmental Society
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?
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
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.
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 rabbits 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 someones 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.
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.