When talking about toxicity, the easiest way to divide chemicals is by the organ or system they damage. These target organs or systems are often referred to in safety data sheets and toxicology books. The commonest are: the lungs, the skin, the gut, the liver, the kidneys, the nervous system, the blood, the cardiovascular system, the immune system, and the reproductive system. There are even chemicals which can affect h
earing.Chemicals causing liver damage are sometimes called 'hepatotoxins', those which damage the kidneys 'renal toxins', and those harming the nervous system 'neurotoxins'. Chemicals that cause cancer, although they may affect either one or several organs, are lumped together and described as 'carcinogens'. Those that cause birth defects are called 'teratogens'.
"A toxin is generally understood to be a substance that is harmful to biological systems, but within this simple concept lies a great deal of variability. A substance that is harmful at a high dose may be innocuous or even essential at a lower dose. A toxin may damage a specific body system, or it may exert a general effect on an organism. A substance that is toxic to one species may not be toxic to another because of different metabolic pathways or protective mechanisms. And the biologic damage may be temporary, permanent over the organism's lifetime, or expressed over subsequent generations" (H. Frumkin in Levy and Wegman).created by *nazirah bt mohd izani*
