Chemicals are all around us, whether man-made or naturally occurring. A common misconception is that all man-made chemicals are harmful, and all things natural are good for us.
In fact, many naturally-occurring chemicals can be just as harmful to human health, if not more so.
Everyday fruit and vegetables such as pears, potatoes and courgettes contain natural chemicals that are toxic to humans. But the critical issue is the dose, or amount present, which is usually well below harmful levels.