Abstract
A copious amount of chemical substances can be found within our modern living environments. The Chemical Abstracting Service (CAS) in the United States has already created a register to track them, which currently exceeds 140 million different ones. The toxicity of each chemical substance is evaluated through a general toxicity test. In this paper, the 50 % lethal dose (LD50) and the no-observed adverse effect level (NOAEL) are compared in order to evaluate the level of toxicity. Humans are exposed to these environmental pollutants via a number of different routes. Subsequently, many chemical substances are detoxified through means such as absorption, distribution and the metabolism process. However, some environmental pollutants result in metabolic activation by cytochrome P450 ; its active metabolites convert into highly toxic substances. This paper provides an outline of the toxicity test and cytochrome P450. Moreover, a few examples of metabolic activation are given and the importance of the toxic evaluation of the chemical substances and their metabolites is asserted.
