The list of synthetic chemicals manufactured and used is very long, and it is vital that potential effects on human health are understood. Each substance must be assessed for risk.
When assessing the safety of a chemical, three questions need to be asked:
· How much exposure can people tolerate?
· What are the effects of being exposed?
· Will the effects wear off, or are changes permanent?
The hazard presented by a chemical is a combination of these three
factors, which we can call potency, severity and reversibility. As an
example, a small amount of lemon juice splashed in the eye produces
a painful sensation - the juice has a high potency. Thankfully the actual
tissue damage is minimal, and a few drops of saline tears are enough
to reverse the effects. The same cannot be said for concentrated sulphuric
The numbers game