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　　Recent research has claimed that an excess of positive ions in the air can have an ill effect onpeoples physical or psychological health. What are positive ions? Well, the air is full of ions, electrically charged particles, and generally there is a rough balance between the positive and the negative charged. But sometimes this balance becomes disturbed and a larger proportion of positive ionsare found. This happens naturally before thunderstorm, earthquakes when winds such as theMistral, Hamsin or Sharav are blowing in certain countries. Or it can be caused by a build-up of static electricity indoors from carpets or clothing made of man-made fibres, or from TV sets,duplicators or computer display screens.

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　　When a large number of positive ions are present in the air many people experience unpleasant effects such as headaches, fatigue, irritability, and some particularly sensitive people suffer nausea or even mental disturbance. Animals are also affected, particularly before earthquakes, snakes have been observed to come out of hibernation, rats to flee from their burrows, dogs howl and cats jump about unaccountably. This has led the US GeographicalSurvey to fund a network of volunteers to watch animals in an effort to foresee suchdisasters before they hit vulnerable areas such as California.

　　Conversely, when large numbers of negative ions are present, then people have a feeling ofwell-being. Natural conditions that produce these large amounts are near the sea, close to water falls or fountains, or in any place where water is sprayed, or forms a spray. This probablyaccounts for the beneficial effect of a holiday by the sea, or in the mountains with tumblingstreams or waterfalls.

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