The special properties of the metal mercury have made it well-known for thousands of years, and it is not surprising that a Roman god and one of the planets around the sun have been named after it. Also there aren’t many metals that are in liquid form at room temperature.

It occurs naturally in rock form as cinnabar, a material that is deep red and the source of the colour vermilion. However, it’s best left undisturbed as the dust from this rock is very poisonous and mercury poisoning can be lethal for all animal life, including humans.

The saying ‘mad as a hatter’ results directly from the behaviour of hat-makers who used mercury to separate the fur from animal skins.

A small Japanese coastal town, Minamata, first found that its cats were walking backwards, and then dying, before thousands of the inhabitants became seriously ill and disabled. It wasn’t radioactive fall out from the Hiroshima bomb causing the problem, but 27 tonnes of mercury dumped into the sea by a petrochemical firm. Both the cats and the people had eaten mercury-saturated fish.

It’s just a pity that mercury is also rather useful, and, like many of the problems we make for ourselves, the difficulty comes when we try to get rid of it.

Not only is it used to recover gold, but it’s commonly found in thermometers, a variety of medicines, some mascaras, fluorescent lights, batteries and even the amalgam that dentists use for fillings. Much of this ends up in landfill, and there’s a significant level of mercury pumped into the atmosphere following cremation.

However, more than two-thirds of the mercury polluting the atmosphere and accumulating in the seas hasn’t been mined but is produced as a by-product of burning coal.

It had been absorbed by the original plant life that later was compressed into coal, and it’s released at power stations and wherever coal – and to a lesser extent, gas and oil – are burned.

Many countries have passed legislation to remove the mercury before it goes up the chimney and it’s collected by filtering through charcoal. However, there are real problems in storing the increasing quantities, and if these stockpiles caught fire, the mercury would be released.

The Americans reckon that if they could tighten-up on power station emissions they would save 11,000 premature deaths and more than 130,000 asthma attacks each year, but they are struggling to pass the Mercury and Air Toxic Standards Bill.

Unfortunately, a number of politicians hoping to be the Republican presidential candidate in November receive financial support from coal and gas industries, so they won’t support the legislation. The air we breathe deserves better than that.