Abstract
Abstract. Exposure to bioaerosol allergens such as pollen can cause exacerbations of allergenic airway disease (AAD) in sensitive populations, and thus cause serious public health problems. Assessing these health impacts by linking the airborne pollen levels, concentrations of respirable allergenic material, and human allergenic response under current and future climate conditions is a key step toward developing preventive and adaptive actions. To that end, a regional-scale pollen emission and transport modeling framework was developed that treats allergenic pollens as non-reactive tracers within the coupled Weather Research and Forecasting Community Multiscale Air Quality (WRF/CMAQ) modeling system. The Simulator of the Timing and Magnitude of Pollen Season (STaMPS) model was used to generate a daily pollen pool that can then be emitted into the atmosphere by wind. The STaMPS is driven by species-specific meteorological (temperature and/or precipitation) threshold conditions and is designed to be flexible with respect to its representation of vegetation species and plant functional types (PFTs). The hourly pollen emission flux was parameterized by considering the pollen pool, friction velocity, and wind threshold values. The dry deposition velocity of each species of pollen was estimated based on pollen grain size and density. An evaluation of the pollen modeling framework was conducted for southern California (USA) for the period from March to June 2010. This period coincided with observations by the University of Southern California's Children's Health Study (CHS), which included O3, PM2.5, and pollen count, as well as measurements of exhaled nitric oxide in study participants. Two nesting domains with horizontal resolutions of 12 and 4 km were constructed, and six representative allergenic pollen genera were included: birch tree, walnut tree, mulberry tree, olive tree, oak tree, and brome grasses. Under the current parameterization scheme, the modeling framework tends to underestimate walnut and peak oak pollen concentrations, and tends to overestimate grass pollen concentrations. The model shows reasonable agreement with observed birch, olive, and mulberry tree pollen concentrations. Sensitivity studies suggest that the estimation of the pollen pool is a major source of uncertainty for simulated pollen concentrations. Achieving agreement between emission modeling and observed pattern of pollen releases is the key for successful pollen concentration simulations.
Highlights
Exposure to respirable allergenic materials from ruptured pollen grains can stimulate the production of antibodies in the human body and trigger allergic airway diseases (AAD), Published by Copernicus Publications on behalf of the European Geosciences Union.R
Pa = εsp · αP,TP · γ where εsp is the pollen pool size, which was directly derived from the literature values or the associated average values for the plant functional types (PFTs) to which a given species belongs; αP, T P is a coefficient with values between 0 and 1 that modifies the pool size according to either precipitation or both temperature and precipitation; and γ is the total area occupied by the species in a grid cell
Meteorological variables predicted by Weather Research and Forecasting Model (WRF) and processed through Meteorology–Chemistry Interface Processor (MCIP) are used by the MEGAN and Community Multiscale Air Quality (CMAQ) models to model the pollen potential, emissions, and regional dispersion
Summary
Exposure to respirable allergenic materials from ruptured pollen grains can stimulate the production of antibodies in the human body and trigger allergic airway diseases (AAD), Published by Copernicus Publications on behalf of the European Geosciences Union.R. Exposure to respirable allergenic materials from ruptured pollen grains can stimulate the production of antibodies in the human body and trigger allergic airway diseases (AAD), Published by Copernicus Publications on behalf of the European Geosciences Union. AAD is a serious public health concern worldwide with the most prevalent impacts among children and adolescents (Nathan et al, 1997; WHO 2003; Miguel et al, 2006; Taylor et al, 2007). Building a quantitative model to link airborne pollen levels, concentrations of respirable allergenic material, and human allergenic response under current and future climate conditions is needed to assess the health impacts on AAD and develop corresponding preventive actions (Hugg and RantioLehtimäki, 2007; Efstathiou et al, 2011). Simulating the spatiotemporal variation of pollen occurrence is the central task toward this goal
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