Airborne pollen concentrations and daily respiratory disease mortality

Background: Ambient air pollution from anthropogenic sources is a main cause of mortality from respiratory disease worldwide, but little is known about the role of pollen. Objective: To test a priori hypothesis that exposure to allergenic pollen from trees and grass increases the risk of death from respiratory diseases. Methods: We conducted a time-series analysis of the relations between daily levels of allergenic pollen and mortality from respiratory causes in the Helsinki Metropolitan Area, Finland, 1994-2014. The study population provided by the Statistics Finland comprised 153 378 deaths, 9 742 (6.4%) from respiratory causes. Daily (average) pollen counts for alder, birch, mugwort, and grass were from the Helsinki University Hospital monitoring stations and air quality data from the Helsinki Region Environmental Services Authority. The main outcome was daily respiratory mortality. Results: The average number of daily deaths was 20.0 (SD 4.78) for all causes, and 1.3 (SD1.25) for respiratory diseases. In quasi-Poisson regression analysis adjusting for long-term trends, ambient temperature, and main air pollutants, abundant daily concentrations of alder increased significantly the risk of death from respiratory diseases, with an 11.9% increase (95% CI 7.8-16.1) for previous day abundant level and 9.1% (3.2-15.3) for 0-4 days’ cumulative exposure. No associations were seen for other pollen. Conclusions: Our results provide new evidence of relation between daily levels of alder pollen and respiratory mortality. These findings identify an important global public health impact and the results support development of population-based prevention through alarm systems and personalised medical advice at the clinics.