Warning bells from nature. Proving a clear link between a chemical and health damage can be tricky in the best of times. At what dose does the chemical become poisonous? One drop, or two? What if the harmful effect of the chemical lies dormant for a while and only shows up 10 or 20 years later? To complicate the picture further, a healthy 70kg adult might not suffer any damage from a chemical dose which is highly toxic in a developing foetus or new-born baby. Durban Mercury, South Africa.