The study estimates that most of the 339,000 deaths each year between 1997 and 2006 came from these two regions.
Fay Johnston, a researcher at the University of Tasmania, Australia who led the study, said she was surprised the figures were so high given the intermittent nature of smoke exposure.
She was speaking at the American Association for the Advancement of Science's annual meeting in Vancouver, Canada last week (18 February), the same day as her study was published in Environmental Health Perspectives.
Using data on fire emissions, mortality rates, population density and weather conditions, the team assessed how small particles in wildfire smoke affect health.
They included fires from agricultural burning, grass fire, peat fire, and tropical deforestation, using a variety of data from global datasets and satellites.
"We have known for a long time that fires release gases and particulate matter with adverse effects on health, but nobody has been able to quantify this for landscape fires until now," said Guido van der Werf, an earth scientist at the VU University Amsterdam, in the Netherlands, who was not involved in the study.
He told SciDev.Net the predictions still underestimate the number of deaths, as they do not include an assessment of the impact of ozone and nitrogen, which are also produced in fires.
Rising temperatures caused by climate change could lead to more wildfires and even greater health impacts, the study says.
The study concludes that reducing landscape fires would save lives and also help preserve biodiversity and mitigate climate change, since fires emit gases and particles that also contribute to climate change.
But van der Werf said it may not be easy to reduce the number of fires.
"Most of the fires in the tropics are man-made. Humans use fire as a tool to manage the landscape," he said, adding that it is one of the few options to do so available to people who do not have access to machinery and fertilisers.
Savannah fires are beneficial for nutrient recycling and to prevent trees invading the landscape, he said, and fires are used to clear land for agriculture or other uses.
Dieter Schwela, a researcher at the University of York, in the United Kingdom, said: "This research is significant because it draws attention to a scarcely recognised problem".
He added that more needs to done to reduce exposure to landscape fire smoke, especially in Africa, where there are no initiatives to address the problem.
Current practices, such as the burning of agricultural residues after harvest in Sub-Saharan Africa and the burning of forests in South-East Asia need to change, Schwela told SciDev.Net.
For this to happen, more research on the actual exposure on regional and local level is needed, added Schwela.
Environmental Health Perspectives doi:10.1289/ehp.1104422 (2012)