Grantee Research Project Results
2012 Progress Report: Projecting Pollen Allergens and Their Health Implications in a Changing World
EPA Grant Number: R834358Title: Projecting Pollen Allergens and Their Health Implications in a Changing World
Investigators: Flagan, Richard , Lamb, Brian , Gilliland, Frank D. , VanReken, Timothy M. , Guenther, Alex , Chung, Sandra
Current Investigators: Flagan, Richard , Gilliland, Frank D. , VanReken, Timothy M. , Guenther, Alex , Lamb, Brian , Chung, Sandra
Institution: California Institute of Technology , National Center for Atmospheric Research , University of California - Los Angeles , Washington State University
EPA Project Officer: Chung, Serena
Project Period: October 1, 2009 through September 30, 2012 (Extended to September 30, 2013)
Project Period Covered by this Report: October 1, 2011 through September 30,2012
Project Amount: $900,000
RFA: Climate Change and Allergic Airway Disease (2008) RFA Text | Recipients Lists
Research Category: Climate Change , Human Health
Objective:
The overall goal of this project is to improve our understanding of linkages among global change, pollen occurrence, and respiratory health impacts through a combination of focused experimental studies, modeling, and statistical analysis that will ultimately lead to the integration of pollen allergen and population health outcome models into an existing air quality modeling framework. These models will be used to estimate the impacts that these contaminants may have on allergic airway disease.
Efforts to assess the dose response relationship were leveraged by linking the pollen measurements made under this project with ongoing health outcome studies undertaken by the USC group as part of the Southern California Children's Health Study, thereby providing data on pollen concentrations during the period of health evaluations at schools in a number of southern California communities. These data have been augmented in the health study period for the southern California area with models developed by the NCAR group to provide high spatial resolution estimates of vegetation and pollen potential, and pollen emission and air quality modeling by the WSU group. These studies are largely complete for select pollens during the health evaluation period, and demonstrate that the model works well for the southern California area.
Progress Summary:
A pollen model has been developed to simulate the timing and production of wind- dispersed allergenic pollen by terrestrial, temperate vegetation. The Simulator of the Timing and Magnitude of Pollen Season (STaMPS) model is driven by meteorological conditions and is designed to be sensitive to climate shifts, as well as flexible with regards to the vegetation species and plant functional types (trees, grasses, etc.) represented and the climate zones simulated. The initial focus for the model is the simulation of the pollen emission potential by important allergenic tree and grass species that typically flower between March-June in Southern California (S. CA), which is characterized by moderate Mediterranean and oceanic climate zones as well as regions of arid desert and arid steppe. Vegetation cover and species composition data are obtained from numerous datasets, and a database of allergenic vegetation species, their pollen production potential and relative allergenicities has been developed.
For the selected allergenic species and spring-early summer simulation period, temperature is the main driver controlling the timing of pollen release while precipitation (and temperature, for some species) controls the magnitude of pollen produced. These effects were parameterized in a model that provides species-specific pollen potential maps for each day of the simulation period, which are then used by a pollen dispersal model to simulate ambient pollen concentrations. The STaMPS model was used to quantify the possible impact of climate change on pollen season under the IPCC SRES A1B scenario as simulated by the ECHAM5 global climate model. Current (1995-2004) and future (2045-2054) meteorological conditions downscaled using the Weather Research and Forecasting (WRF) model were used to drive STaMPS and generate estimates of the relative magnitude and timing of pollen season for important allergenic tree and grass species blooming during March-June in a larger domain covering all of CA and Nevada. Differences in the simulated timing and magnitude of pollen season for the selected allergenic species under current and future climate scenarios are presented and suggest that across all of the species, pollen season starts an average of 5-6 days earlier under predicted future climatic conditions compared to present simulations (with future average annual temperatures being ~1°C warmer than current temperatures). Differences in the amount of pollen produced under the two scenarios vary by species and is affected by the selected simulation period (01 March-30 June).
Figure 1. (a) Domain coverage of 12-km California (D1) and 4-km Southern California (D2) with terrain height and (b) the location of pollen sampling sites (red) and the AWS sites (blue).
A regional-scale pollen emission and transport modeling framework was developed by integrating the estimated daily pollen pool that can then be emitted into the atmosphere by wind from STaMPS with models of pollen entrainment, and treating the allergenic pollens as non-reactive tracers within the WRF/CMAQ air-quality modeling system. The hourly pollen emission flux was parameterized in terms of 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 over southern California 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 allergic sensitization data at nine sites. Two nesting domains with horizontal resolutions of 12 km and 4 km, illustrated in Fig. 1, 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. Pollen allergen also enters the atmosphere as respirable fragments. Efforts to measure those fragments directly were confounded by the large numbers of samples that must be analyzed to obtain results that are statistically significant, and the associated high costs of immunoassay kits. Studies of respirable antigen have, therefore, focused on laboratory studies. Because of the paucity of quantitative data on pollen rupture, WSU modified its scope to include laboratory studies of relative humidity driven rupture for several key pollen species. Experimental methods have been developed for wheat, taking advantage of extensive agricultural research resources at WSU. The experiments on wheat have been completed. The WSU group has now begun applying the methods developed on wheat to the study of pollen fragment production by other grasses.
The Caltech team has assembled a substantial library of pollen samples for the Pasadena area in addition to the geographically distributed data gathered during the health evaluation studies. The Pasadena data have been fully analyzed by traditional manual pollen identification and counting methods. In addition, under separate funding, Caltech has developed an automated pollen counting system based upon computer vision methods. The same slides that have been counted manually have been evaluated by the computerized system. Manuscripts on the method and its validation against established techniques are being prepared that will acknowledge partial support by EPA. Over the coming year, the pollen samples will be analyzed in concert with the pollen potential and emission parameterizations to probe the role of meteorological influences at a resolution that has not been possible heretofore, including diurnal variations in pollen release. The study period has included years with significant variation in annual precipitation, temperature, and unusual meteorological events that have led to dramatic changes in pollen concentrations.
Future Activities:
The USC team has identified additional genera with potential health impacts in addition to the vegetative genera already included in the pollen potential and dispersion models. Under the no-cost extension, the STaMPS parameterizations will be extended to provide additional pollen data for use in the health impact studies. Future work in this project by the WSU and NCAR groups will demonstrate the pollen potential model for future climate scenarios during the coming year and will expand the pollen release and dispersion simulations to provide data on additional species that are needed in the dose response studies for the southern California region, and for national estimation of changes in exposure. The future studies will be conducted on a coarser (12 km) grid than the local studies described above and will, therefore, focus on the pollen potential since we have decided that estimations of pollen concentrations would not be scientifically justified given the lower spatial resolution.
WSU will conduct further laboratory investigations into the pollen rupture potential of grasses. Having established their methodology using readily available wheat specimens, they have moved on to other grass pollens more relevant for AAD: ryegrass and timothy grass. The WSU group has specimens of these other grasses in the greenhouses currently for experiments that will be conducted in late winter through early summer, with data analysis to follow in early fall. These new pollen rupture experiments are designed to provide the basis of future parameterization suitable for inclusion in the pollen potential model.
Over the coming year, the pollen samples will be analyzed in concert with the pollen potential parameterizations to probe the role of meteorological influences at a resolution that has not been possible heretofore, including diurnal variations in pollen release. The study period has included years with significant variation in annual precipitation, temperature, and unusual meteorological events that have led to dramatic changes in pollen concentrations.
Journal Articles on this Report : 2 Displayed | Download in RIS Format
Other project views: | All 13 publications | 2 publications in selected types | All 2 journal articles |
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Duhl TR, Zhang R, Guenther A, Chung SH, Salam MT, House JM, Flagan RC, Avol EL, Gilliland FD, Lamb BK, VanReken TM, Zhang Y, Salathe E. The Simulator of the Timing and Magnitude of Pollen Season (STaMPS) model: a pollen production model for regional emission and transport modeling. Geoscientific Model Development Discussions 2013;6(2):2325-2368. |
R834358 (2012) R834358 (Final) |
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Zhang R, Duhl T, Salam MT, House JM, Flagan RC, Avol EL, Gilliland FD, Guenther A, Chung SH, Lamb BK, VanReken TM. Development of a regional-scale pollen emission and transport modeling framework for investigating the impact of climate change on allergic airway disease. Biogeosciences Discussions 2013;10(3):3977-4023. |
R834358 (2012) R834358 (Final) |
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Supplemental Keywords:
pollen; pollen potential; respirable allergen; pollen fragmentation; respiratory health; asthma; climate change; vegetation distribution;, RFA, Health, Air, climate change, Air Pollution Effects, Risk Assessments, Atmosphere, environmental monitoring, pollen, allergic airway disease, respiratory illnessRelevant Websites:
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.