Almost a quarter of global disease is caused by avoidable environmental factors, with a toll of 13 million lives a year, the World Health Organisation said in a new report on June 16.
Such hazards, which include polluted water, unsafe fuel, rickety buildings and dangerous traffic, are to blame for one-third of deaths in developing countries, said the WHO.
Preventing environmental risk could save as many as four million lives a year, mostly in developing countries, said the UN health agency.
The WHO said that its study was the most comprehensive and systematic yet undertaken on how preventable environmental hazards contribute to a wide range of diseases and injuries. "We have always known that the environment influences health very profoundly, but these estimates are the best to date," said Dr Anders Nordstrom, acting head of the WHO.
"This will help us to demonstrate that wise investment to create a supportive environment can be a successful strategy in improving health and achieving development that is sustainable."
Over 40 percent of deaths from malaria and an estimated 94 percent of deaths from diarrhoeal diseases, two of the world's biggest childhood killers, could be prevented through better environmental management, according to the WHO.
Besides diarrhoea and malaria, the two other main health problems influenced by a poor environment are lower respiratory infections and various forms of accidental injuries.
Pointing to potential measures to reduce the burden, the WHO cited safer household water storage and better hygienic measures, as well as better overall management of water resources.
Also crucial, it said, are the use of cleaner and safer fuels, increased safety of the built environment and more judicious use and management of toxic substances in the home and workplace.
The report said that one way or another, the environment significantly affects more than 80 percent of a host of other major diseases, including cancer and heart conditions.