Journeys from the Centre of the Earth by Iain Stewart

Author:Iain Stewart
Language: eng
Format: epub
ISBN: 9781448149421
Publisher: Random House

The problem is that just as different types of rocks are unevenly spread around regions like the Mediterranean, so trace elements are not uniformly distributed either. In other words, geology gives different regions different health effects, and possibly different diseases. For example, it is globally recognised that low concentrations of iodine are found in soils at high elevations and in limestone terrains, both characteristics common in the Mediterranean. Medical studies show that iodine is an essential nutrient and a human being normally contains 15–20 grams of it, mostly in the thyroid gland. Deficiency in iodine can lead to serious enlargement of the thyroid gland – the endemic disease goitre – an affliction already recognised in parts of Greece and Egypt where iodine levels in drinking water are abnormally low.

While too little iodine in drinking water is a problem, too much fluorine in it is equally bad. Fluorine is an essential element and our principal source for it is water where the natural content is less than 1 part per million. A deficiency in it leads to increased tooth decay, especially in children, and so in many places it is regularly added to our water. It is also believed that taking small daily amounts of a few parts per million of fluorine over a lifetime could help to stave off osteoporosis. However, in some areas, groundwaters derived from rocks, volcanic gases and mineral springs with high fluorine levels can lead to very high fluorine levels in drinking water. High natural concentrations of fluorine have been found to lead to over-abundant deposition of the calcium phosphate which builds our bones. Too much fluorine in our bodies can be lethal. Fortunately with fluorine the difference between a beneficial dose (1 mg/litre) and a deadly one is very large. With current amounts added to drinking water you’d need to drink about 4,000 litres (1,000 gallons) of water within a day or so (fluorine doesn’t accumulate in the body) to have a lethal dose.

The picture gets complicated because the harmful effects of some geological materials are seriously overplayed. Asbestos is probably the most feared natural mineral in recent decades, and yet there is little real public understanding of this extraordinary substance. The term describes types of fibrous minerals that occur naturally in rocks formed from ancient ocean crust; in the Mediterranean, asbestos-bearing rocks have been mined in northern Italy, northern Greece, central Turkey, Cyprus and Corsica. The remarkable property of asbestos is the ability of its fibres to resist heat. The fire-retardant properties of asbestos were known as long as 5,000 years ago. It was the ancient Greeks, in awe of the stone that could be woven but not consumed by fire, who gave it its name ‘asvestos’, meaning inextinguishable. Throughout ancient history, it was renowned as a substance of almost magical properties.

There are six types of asbestos mineral and today they are all officially labelled as harmful. When materials that contain any kind of asbestos are disturbed or damaged, the fibres can separate and become airborne.

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