Polychlorinated biphenyls (PCBs) are an example of toxic substances because they consist of chlorine, carbon and hydrogen and emit harmful properties such as endocrine disruption, carcinogenic effects and bioaccumulation in living organisms and the environment/ecosystem. Toxins are chemicals produced naturally by living organisms that can pose a potential danger to the ecosystem, particularly its living populations. An example of a toxin is the venom produced by snakes and spiders. It is important to note that toxins and chemicals are not the same. NOT all chemicals are toxins, but all toxins are chemicals. Toxic substances are chemicals that enter the environment through anthropogenic activities. Toxic substances are often referred to as “man-made.” Herbicides are a good example of a toxic substance because they are harmful chemicals used to eliminate the presence of unwanted plant growth and introduced into the environment by humans, usually farmers and farm workers. Poisons are chemical substances that can have harmful effects on the biological system of their host upon exposure. Again, possible hosts include the environment, humans, plants, animals, and other biotic factors in the ecosystem. All chemicals could potentially be classified as poisons, as the term