Perhaps some tumors occur when disease or environmental exposure disregulates the genetics of cells and alters their identity.

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As a royalty owner, the company receives between 0.5% to 5% of the value of all precious metals produced by the mines on which it has invested, without any exposure to rising costs or environmental liabilities.

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Evidence of oxidative stress can appear under other conditions, including exposure to certain environmental pollutants or infections in the urinary genital tract.

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Smoking bans could have an effect on reducing heart attacks or heart disease generally by one of two major routes: either by inducing current smokers to quit or by reducing the exposure of non-smokers to environmental tobacco smoke (ETS).

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That is called epigenetics and is controlled by environmental factors such a temperature, solar radiation exposure or food or lack of food.

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"Currently, we have identified no infectious agent common to all of the cases, " the statement said, adding that no evidence exists that the cases were caused by exposure to chemical or biological weapons, SARS or environmental toxins.

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"These increases could be caused by increasing exposure to environmental risk factors such as peanuts and other foods or latex, to an increased susceptibility in the population to these allergens or a combination of these factors, " they wrote.

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