About 40 percent of deaths worldwide are caused by water, air and soil pollution, concludes a Cornell researcher. Such environmental degradation, coupled with the growth in world population, are major causes behind the rapid increase in human diseases, which the World Health Organization has recently reported. Both factors contribute to the malnourishment and disease susceptibility of 3.7 billion people, he says.

David Pimentel, Cornell professor of ecology and agricultural sciences, and a team of Cornell graduate students examined data from more than 120 published papers on the effects of population growth, malnutrition and various kinds of environmental degradation on human diseases. Their report is published in the online version of the journal Human Ecology (available at http://www.springerlink.com/content/101592/, to be published in the December print issue).

"We have serious environmental resource problems of water, land and energy, and these are now coming to bear on food production, malnutrition and the incidence of diseases," said Pimentel.

Of the world population of about 6.5 billion, 57 percent is malnourished, compared with 20 percent of a world population of 2.5 billion in 1950, said Pimentel. Malnutrition is not only the direct cause of 6 million children's deaths each year but also makes millions of people much more susceptible to such killers as acute respiratory infections, malaria and a host of other life-threatening diseases, according to the research.

Among the study's other main points:

• Nearly half the world's people are crowded into urban areas, often without adequate sanitation, and are exposed to epidemics of such diseases as measles and flu.

• With 1.2 billion people lacking clean water, waterborne infections account for 80 percent of all infectious diseases. Increased water pollution creates breeding grounds for malaria-carrying m
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