Question

Many organic compounds are man-made chemicals not found in nature. Examples of such chemicals are halogenated organic compounds, organophosphorus compounds and polymers. Such chemicals are often used as herbicides, pesticides and nerve toxins, and often persist in the environment. Styrene made into Styrofoam, for example, is very stable and doesn’t break down when disposed of in landfills. Why do you suppose such man-made chemicals are toxic to plant and animal life and persist in the environment?

Answer 1

Man-made Chemicals are toxic to plant and animal life and also persist in environment because of two reasons -

1. biomagnification and

2. bioaccumulation

Bioaccumulation is the condition where the Chemicals are accumulated in the environment. This is because the complex organic chemicals or pesticides are not degraded into simpler molecules in the environment and therefore persist into the soil and water. Degradation of compounds occur by action of microbes mainly.

Biomagnification is the condition is which the complex molecules enter food chain and reach human body. These molecules are present in soil and water because they accumulate in environment. These are then taken up by plants. Human beings and herbivores animals eat plants and these molecules then enter the organisms at second trophic level (herbivores). These herbivore animals are then eaten up by carnivores and other humab beings. In this way these molecules enter food chain and increase in concentration till they reach top consumers.

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