1. There are two flasks, labelled A and B A tastes like water and will not immediately harm you if you drink it. However, if you drink more than a litre of it, you have a 1 in 4 chance, in five years’ time, of developing a terrible liver disease that will kill you. B tastes ghastly. If you drink one mouthful it will kill you painlessly in 5 minutes. Which is more dangerous? Why?

2. Things to think about You probably think that B was the most dangerous as it would definitely kill you. However, the source would be rapidly identified and nobody else would die. Flask A could go on killing people for many years as it would be very difficult to find the cause 5 years later. This is the problem with medical research. Many people claim that mobile phones can cause illness. Proving this link (one way or the other) is extremely difficult.

3. Lesson 8 Mobile Phones and Health

6. How Safe? - Activity