Bromine Bromine is a very corrosive oxidising liquid whose vapour attacks the eyes and lungs with painful effects. Bromides salts should be treated as toxic. Excessive bromide intake leads to depression and of weight loss. Iodine Elemental iodine, I2, is toxic, and its vapour irritates the eyes and lungs. The maximum allowable concentration in air when working with iodine is just 1 mg m-3.
All iodides are toxic if taken in excess.
Astantine Astatine does not occur does not occur to any significant extent in the biosphere and so normally never presents a risk. Astatine is studied in a few nuclear research laboratories where its high radioactivity requires special handling techniques and precautions. From a chemical point of view one, can speculate that its toxicity would mimic that of iodine. The chloride ion is the principle anion found in the fluid which bathes our body cells. Lead in petrol, however, is presently being phased out in many countries.