What Is Toxicity?

Pictures- (Upper Left)A View Of The Forest, (Upper Right) This Will Someday Break Down and Fertilize the Earth, (Left) Professor Rosane Holds Some Compost. This Stuff is Our Future.

_____On our trip to Inwood Park, we stopped and listened to a lecture by a pile of compost. We talked about how the compost would break down and be nutrients for the earth. Dead organisms also break down and make nutrients for the earth. Yet, i was surprised to learn that a human being was to be allowed to decompose, that it would be considered toxic waste. But what exactly is toxicity? What makes a substance toxic?
_____Toxicity has nothing to do with the substance itself, but with the amount of the substance. Certain amounts of medications to a human can be considered harmful or beneficial to a human, but the same amounts given to a smaller animal could be deadly. A certain substance may not be harmful to a human, yet increase the intake of the substance and it may have a negative effect on that person. Plants produce a certain amount of chemicals and substances that are beneficial to them, yet given back more of that chemical then needed, the plant may die. Nitrogen can be good for soil, yet increase the amount and it can become harmful.
_____Things such as pollution also contribute to toxicity. When oils and radioactive wastes are not disposed of in proper containers , they can damage the earth. Tragedies such as the the one at Chernobyl make the areas contaminated toxic, because of the excessive amounts of the radioactive waste.
_____In that case, nothing is really toxic, but certain amounts, harmful. If after a human dies and would be considered toxic how is this so? Humans consume so much food that raise the levels of certain substances in a given body. Broken down, the human body along with all these substances would do more harm then good to the earth. Humans consume many processed foods and chemicals such as caffeine. Some consume some substances such as alcohol. These in excessive amounts could be harmful to the earth. So, if we rid ourselves from these substances, would we still be considered toxic waste?