WHO - Global burden of disease due to indoor air pollution
In the year 2004, indoor air pollution from solid fuel use was responsible for almost 2 million annual deaths and 2.7% of the global burden of disease (in Disability-Adjusted Life Years or DALYs). This makes this risk factor the second biggest environmental contributor to ill health, behind unsafe water and sanitation.
Disease burden by level of development
The importance of indoor air pollution as a public health threat varies drastically according to the level of development: in low income countries, indoor air pollution is responsible for up to 4.0% of the burden of disease, while the same risk factor no longer features among the top 10 risk factors in industrialized countries.