Estimates of present and future asthma emergency department visits associated with exposure to oak, birch, and grass pollen in the United States

Pollen is an important environmental cause of allergic asthma episodes. Few prior studies have assessed potential climate change impacts on future oak pollen exposure and associated health impacts. Here we present work that uses pollen monitor data and epidemiologic functions to report new estimates of the current and projected future health burden of oak, birch, and grass pollen across the contiguous US. Our results suggest that tree pollen in the spring currently accounts for between 25,000 and 50,000 pollen-related asthma emergency department (ED) visits annually (95% C.I.: 14,000 to 100,000), roughly 2/3 of which occur among people under age 18. Grass pollen in the summer season currently accounts for less than 10,000 cases annually (95% C.I.: 4,000 to 16,000). Compared to a baseline in which asthma ED visits grow over time only due to population increases, projections of future temperature and precipitation show an increase in ED visits of 14% in 2090 for a higher greenhouse gas emissions scenario, but only 8% for a moderate emissions scenario. Grass pollen, which is more sensitive to changes in climatic conditions, is projected to become a primary contributor to ED visits in the future, with the largest effects in the Northeast, Midwest, and Southern Great Plains regions. More complete assessment of the current and future health burden of pollen is limited by of the availability of data on pollen types (e.g, ragweed), other health effects (e.g. other respiratory disease), and economic consequences (e.g., medication costs) - each of these limitations are the subject of active ongoing research efforts to more completely understand the full health and economic burden of pollen in the US, and the role of forecast climatic change in exacerbating that burden.