Air pollution from wildfires and human health vulnerability in Alaskan communities under climate change

Alaskan wildfires are becoming more frequent and severe, but very little is known regarding exposure to wildfire smoke, a risk factor for respiratory and cardiovascular illnesses. We estimated long-term, present-day and future exposure to wildfire-related fine particulate matter (PM_2.5) across Alaska for the general population and subpopulations to assess vulnerability using observed data for the present day (1997-2010), modelled estimates for the present day (1997-2001), and modelled estimates for the future (2047-2051). First, we assessed wildfire-PM_2.5 exposure by estimating monthly-average wildfire-specific PM_2.5 levels across 1997-2010 for 158 Alaskan census tracts, using atmospheric transport modelling based on observed area-burned data. Second, we estimated changes in future (2047-2051) wildfire-PM_2.5 exposure compared to the present-day (1997-2001) by estimating the monthly-average wildfire-specific PM_2.5 levels for 29 boroughs/census areas (county-equivalent areas), under the Intergovernmental Panel on Climate Change (IPCC) A1B scenario from an ensemble of 13 climate models. Subpopulation risks for present and future exposure levels were estimated by summing area-weighted exposure levels utilizing the 2000 Census and State of Alaska's population projections. We assessed vulnerability by several subpopulation characteristics (e.g. race/ethnicity, urbanicity). Wildfire-PM_2.5 exposure levels during 1997-2010 were highest in interior Alaska during July. Among subpopulations, average summer (June-August) exposure levels for urban dwellers and African-American/Blacks were highest at 9.1 μg m^-3 and 10 μg m^-3, respectively. Estimated wildfire-PM_2.5 varied by Native American tribe, ranging from average summer levels of 2.4 μg m^-3 to 13 μg m^-3 for Tlingit-Haida and Alaskan Athabascan tribes, respectively. Estimates indicate that by the mid-21st century, under climate change, almost all of Alaska could be exposed to increases of 100% or more in levels of wildfire-specific PM_2.5 levels. Exposure to wildfire-PM_2.5 likely presents a substantial public health burden in the present day for Alaska communities, with different impacts by subpopulation. Under climate change, wildfire smoke could pose an even greater public health risks for most Alaskans.