Farmer weed crop International Institute of Tropical Agriculture/Flickr

Comment de bonnes substances deviennent dangereuses

PALO ALTO – Depuis le développement de la science de la toxicologie au XVIème siècle, son principe directeur est que « la dose fait le poison ». Cette règle s'applique aux médicaments utilisés par les patients dans le monde plusieurs milliards de fois par jour. D'un point de vue thérapeutique, la bonne dose d'aspirine peut être un don du ciel, mais une consommation excessive peut être mortelle. Ce principe s'applique même aux aliments : de grandes quantités de noix de muscade ou de réglisse sont réputées pour leur toxicité.

Le risque d'une substance dépend principalement de deux facteurs : sa capacité inhérente de nuisance et l'exposition d'une personne à cette substance. C'est une idée simple, mais même certains professionnels dignes de foi semblent incapables de la saisir, comme en témoigne la décision prise par le Centre International de Recherche sur le Cancer (CIRC), une branche de l'Organisation Mondiale de la Santé, qui a classé l'herbicide 2,4-D à l'usage le plus répandu, comme étant « probablement cancérigène pour l'être humain. »

Dans le domaine des herbicides, le CIRC ne semble pas vraiment en veine. L'organisation a dernièrement classé le glyphosate, un autre herbicide populaire, comme « probablement » cancérigène, une conclusion contradictoire avec celles des organismes de réglementation partout dans le monde.

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