The U.N. agency said the study broke new ground because it developed a "hit list" of environmental causes of disease that could best be tackled by a coordinated approach to reduce threats.
"The four main diseases influenced by poor environments are diarrhea, lower respiratory infections, various forms of unintentional injuries and malaria," the report said.
It recommended promoting better management of water resources including safer household storage, the use of cleaner fuels, better built housing and more careful use of poisons in the home and workplace.
Many road traffic injuries resulted largely from poor design of urban areas and transport systems, it said.
Chronic obstructive pulmonary disease, which leads to a gradual loss of lung function, often results from exposure to workplace dusts and fumes and other forms of indoor and outdoor air pollution, the report said.
"Preventing environmental risk could save as many as 4 million lives a year, mostly in developing countries," the report said.
"We call on ministries of health, environment and other partners to work together to ensure that these environmental and public health gains become a reality," said Dr. Maria Neira, director of WHO's Department for Public Health and Environment.
WHO said the report was based on systematic review of scientific literature as well as surveys of more than 100 experts worldwide.
Source: Associated Press