Green Chemistry

It is not only important to select chemicals and processes that reduce waste, but the hazards of those chemicals and processes are equally important. Process safety is covered in the pollution prevention and accident prevention principles. This principle of Green Chemistry addresses the hazards of chemicals, especially when it concerns the choice of chemicals for a reaction in a lab or manufacturing plant. For every reaction, there are a multitude of possible reactants, auxiliary substances, apparatus and protective equipment we can choose from. Chemicals are generally chosen for performance over greenness. Highly efficient reactions that are complete in a short time are beneficial from a cost, waste and energy perspective. What Green Chemistry tells us is that the hazards of the substances we use should also be considered.

Chemical hazards range in severity. There are physical hazards such as flammability or the potential to explode. There are toxicological hazards, ranging from skin irritation to poison effects to chronic (long term) damage to organs. Biological samples can have health hazards, and radioactive samples can cause cancer and other negative effects. Some chemicals are ecotoxic (toxic to species in the environment) or damage the ozone layer. The risk a chemical poses is down to its inherent hazards and the likelihood of exposure. A cancer-causing substance that is used in a sealed environment with no exposure to people could be considered less of a risk than a process involving skin irritating substances without protective measures (e.g. gloves). 

There is never a definitive answer to the least hazardous chemical synthesis. A combination of efforts are required and there is always a balance between efficiency, risk, and cost, resulting in several acceptable solutions.