Water, air, and soil pollution causes 40 per cent of deaths across the world, according to a survey conducted by Cornell researchers.
Such environmental degradation, coupled with the rise in the world population, are major causes behind the rapid increase in human diseases that the World Health Organization has recently reported, says David Pimentel, Cornell professor of ecology and agricultural sciences.
He says that the two factors contribute to the malnourishment and disease susceptibility of 3.7 billion people.
Pimentel and a team of Cornell graduate students came to these conclusions after examining data from more than 120 published papers on the effects of population growth, malnutrition and various kinds of environmental degradation on human diseases.
"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, whose report on the study has been published online in the journal Human Ecology.
He says that 57 per cent of the world population of about 6.5 billion is malnourished, compared with 20 per cent of a world population of 2.5 billion in 1950.
The researchers says that malnutrition not only causes the death of 6 million children every year, but also makes millions of people much more susceptible to various killer diseases like respiratory infections, malaria, and a host of other life-threatening diseases.
Pimentel says that 1.2 billion people lack clean water, and waterborne infections account for 80 per cent of all infectious diseases. He said that increased water pollution creates breading grounds for malaria-carrying mosquitoes, claiming 1.2 million to 2.7 million lives a year.
The study says that air pollution from smoke and various chemicals kills about 3 million people a year, and unsanitary living conditions account for more than 5 million deaths each year, of which more than half are children.
Pimentel says that soil is contaminated by many chemicals and pathogens, which are passed on to humans through direct contact or via food and water. Increased soil erosion worldwide not only results in more soil being blown, but also in the spreading of disease microbes and various toxins, he adds.
Drug-resistance of microbes and the influence of global warming and biological diversity on parasite evolution have further raised the risk of tuberculosis and influenza, says the researcher. New threats, such as West Nile virus and Lyme disease, have also developed, he adds.
"A growing number of people lack basic needs, like pure water and ample food. They become more susceptible to diseases driven by malnourishment, and air, water and soil pollutants," Pimentel says.
"Relying on increasing diseases and malnutrition to limit human numbers in the world diminishes the quality of life for all humans and is a high-risk policy," he concludes.