Wednesday, June 30, 2010

Chemical, Toxicity and Risk

Life is not risk-free. We all take many risks everyday, often without even thinking about it. We may decide to ride a motorbike rather than a "microlet", even though possibility to get accident on a motorbike is greater than that on a microlet. Some people decide to smoke cigarettes, even though they know that smoking has killed many people. Many people like eating "cilok" even though they might know that cilok contains sauce colored with red coloring agent usually used to color textile, and potentially dangereous monosodium glutamate (MSG) as flavor enhancer. Many reports indicate that our food often contains pesticides and dangerous additive. Newspapers often report that our lands is polluted by toxic waste dumps and some medicines are unsafe. How bad are the risks from chemicals, and how are the risks evaluated ?

it is important to realize that everything, including our body, is made of chemicals. There is no chemical free food, cosmetic, cleanser, or anything else. In addition, there is no meaningful difference between "natural" substance and "synthetic" one. A chemical is a chemical, whether it is natural or synthetic. Many naturally occurding substances such as strychnine and morphine are very toxic, and many synthetic substances such as polyethylene and glass are harmless.

Risk evaluation of chemicals is carried out by exposing test animals, usually mice, to a chemical and then monitored for signs of harm. To reduce the time and the expense required for testing. the amount of chemicals administered is hundred or thousand of times larger than those people might normally encounter. The acute chemical toxicity observed in animal tests is reported as an LD50 value, the amount of a chemical per kilogram of body weight that is a lethal dose for 50% of the animal tests.

The risk of human exposure to a given chemical is still not easy to assess even though the LD50 value of it has been obtained in test animals. All chemicals are toxic to some organisms to some extent, and the difference between medicine and toxin is often a matter of quantity. Vitamin A, for example, is necessary for vision, yet it might cause cancer at high doses. Arsenic trioxide is very poisonous. However, recent research has shown that it to be effective at inducing remissions is some types of leukemia.


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