The four main diseases influenced by poor environment worldwide are diarrhoea, lower respiratory tract infection, various forms of unintentional injuries and malaria, said a WHO statement.
The report, "Preventing Disease through Healthy Environments", underlined that over 40 percent of deaths from malaria and an estimated 94 percent of deaths from diarrhoeal diseases - two of the world's childhood killers - could be prevented through better environment management.
The UN health body suggested that all countries, especially the developing and underdeveloped courtiers, promote safe household water storage, use cleaner and safer fuel, increase safety of the built environment, use and manage toxic substances at home as well as work place more judiciously and improve water resource management among general public.
The report also estimated that more than 33 percent of diseases in children, under the age of five, were caused by environmental exposures.
"Preventing environmental risks could save as many as four million lives a year, mostly in developing countries," it said.
"We have always known that the environment influences health very profoundly, but these estimates are the best to date. 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," said acting WHO director-general Anders Nordström.
The report revealed that 2.6 million people died annually of cardiovascular problems, 1.7 million from diarrhoeal diseases and 1.5 million from lower respiratory tract infections.
It added that 1.4 million deaths occurred annually due to cancer, 1.3 million from chronic obstructive pulmonary disease, 470,000 from road traffic crashes and 400,000 from unintentional injuries.