What do ammonium nitrate and iodine have in common? Both substances are of immense service to humankind, and the history of their discovery is closely linked to that of the production of explosives.
A chemical found in products as diverse as fireworks and food packaging, perchlorate can interfere with thyroid function as well as foetal brain development.
New research into iodine tablets suggests the case for giving them to all pregnant women is compelling.
A study linking water fluoridation to hypothyroidism has been criticized by researchers for poor design and overstating its findings.