As much as 24 per cent of global disease is caused by environmental exposures which can be averted. Well-targeted interventions can prevent much of this environmental risk, the World Health Organization (WHO) demonstrates in a report. The report further estimates that more than 33 per cent of disease in children under the age of 5 is caused by environmental exposures. Preventing environmental risk could save as many as four million lives a year in children alone, mostly in developing countries.

The report, Preventing disease through healthy environments - towards an estimate of the environmental burden of disease, is the most comprehensive and systematic study yet undertaken on how preventable environmental hazards contribute to a wide range of diseases and injuries. By focusing on the environmental causes of disease, and how various diseases are influenced by environmental factors, the analysis breaks new ground in understanding the interactions between environment and health. The estimate reflects how much death, illness and disability could be realistically avoided every year as a result of better environmental management.

"The report issued today is a major contribution to ongoing efforts to better define the links between environment and health," said Dr Anders Nordström, Acting WHO Director-General. "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."

The report estimates that more than 13 million deaths annually are due to preventable environmental causes. Nearly one third of death and disease in the least developed regions is due to environmental causes. Over 40 per cent of deaths from malaria and an estimated 94 per cent of deaths from diarrhoeal diseases, two of the world's biggest childhood killers, could be prevented through better environmental management.

The four main diseases influenced by poor environments are diarrhoea, lower respiratory infections, various forms of unintentional injuries, and malaria. Measures which could be taken now to reduce this environmental disease burden include the promotion of safe household water storage and better hygienic measures; the use of cleaner and safer fuels; increased safety of the built environment, more judicious use and management of toxic substances in the home and workplace; better water resource management.

"For the first time, this new report shows how specific diseases and injuries are influenced by environmental risks and by how much," said Dr Maria Neira, Director of WHO's Department for Public Health and Environment. "It also shows very clearly the gains that would accrue both to public health and to the general environment by a series of straightforward, coordinated investments. 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."

This research, which involved systematic review of literature as well as surveys of over 100 experts worldwide, identifies specific diseases impacted by certain well-known environmental hazards -- and by how much. "It brings together the best evidence available today on environmental links to health in 85 categories of disease and injury. Since the research focuses strictly on environmental hazards that are amenable to change, we can also see where preventive health measures combined with better environmental management and cleanup can have the biggest impact. In effect, we now have a 'hit list' for problems we need to tackle most urgently in terms of health and the environment," noted Dr Neira.

Diseases with the largest total annual health burden from environmental factors, in terms of death, illness and disability or Disability Adjusted Life Years (DALYs) are:

Diarrhoea (58 million DALYS per year; 94 per cent of the diarrhoeal burden of disease) largely from unsafe water, sanitation and hygiene

Lower respiratory infections (37 million DALYs per year; 41 per cent of all cases globally) largely from air pollution, indoor and outdoor.

Unintentional injuries other than road traffic injuries (21 million DALYs per year; 44 per cent of all cases globally), classification which includes a wide range of industrial and workplace accidents.

Malaria (19 million DALYs per year; 42 per cent of all cases globally), largely as a result of poor water resource, housing and land use management which fails to curb vector populations effectively.

Road traffic injuries (15 million DALYS per year; 40 per cent of all cases globally), largely as a result of poor urban design or poor environmental design of transport systems.

Chronic Obstructive Pulmonary disease (COPD) -- a slowly progressing disease characterized by a gradual loss of lung function. (COPD, 12 million DALYs per year; 42 per cent of all cases globally) largely as a result of exposures to workplace dusts and fumes and other forms of indoor and outdoor air pollution.

Perinatal conditions (11 million DALYS per year; 11 per cent of all cases globally).

Most of the same environmentally-triggered diseases also rank as the biggest killers outright -- although they rank somewhat differently in order of lethality. Diseases with the largest absolute number of deaths annually from modifiable environmental factors (these are all parts of the environment amenable to change using available technologies, policies, preventive and public health measure). These diseases include:

2.6 million deaths annually from cardiovascular diseases
1.7 million deaths annually from diarrhoeal diseases
1.5 million deaths annually from lower respiratory infections
1.4 million deaths annually from cancers
1.3 million deaths annually from chronic obstructive Pulmonary disease
470,000 deaths annually from road traffic crashes
400,000 deaths annually from unintentional injuries

The report shows that one way or another, the environment significantly affects more than 80% of these major diseases. Moreover, it looks to quantify only those environmental hazards that are modifiable - that is, those that are readily amenable to change through policies or technologies that already exist. The report also spells out us how much environment-related disease is preventable.

By acting assertively and setting priorities for measures aimed at curbing the most serious killers, millions of unnecessary deaths can be prevented every year. Working with sectors such as energy, transport, agriculture and industry to ameliorate the root environmental causes of ill health is crucial.