Effects of Ambient Pollen Concentrations on Frequency and Severity of Asthma Symptoms Among Asthmatic Children

Abstract

Background Previous studies on the associations between ambient pollen exposures and daily respiratory symptoms have produced inconsistent results. We investigated these relationships in a cohort of asthmatic children, using pollen exposure models to estimate individual ambient exposures. Methods Daily symptoms of wheeze, night symptoms, shortness of breath, chest tightness, persistent cough and rescue medication use were recorded in a cohort of 430 children age 4-12 years with asthma in Connecticut, Massachusetts and New York. Daily ambient exposures to tree, grass, weed and all-type pollen were estimated using mixed effects models. We stratified analyses by asthma maintenance medication and sensitization to grass or weed pollens. Separate logistic regression analysis using generalized estimating equations were performed for each symptom outcome and pollen type. We adjusted analyses for maximum daily temperature, maximum 8-hr average ozone, fine particles (PM2.5), season and antibiotic use. Results Associations were observed among children sensitized to specific pollens; these associations varied by use of asthma maintenance medication. Exposures to even relatively low levels of weed pollen (6-9 grains/m3) were associated with increased shortness of breath, chest tightness, rescue medication use, wheeze, and persistent cough, compared with lower exposure among sensitized children taking maintenance medication. Grass pollen exposures ≥2 grains/m3 were associated with wheeze, night symptoms, shortness of breath and persistent cough compared with lower exposure among sensitized children who did not take maintenance medication. Conclusion Even low-level pollen exposure was associated with daily asthmatic symptoms.

Variation of the group 5 grass pollen allergen content of airborne pollen in relation to geographic location and time in season

“…This could explain why even low levels of 2 to 9 pollen grains/m 3 can result in allergic symptoms. 42 Also, at high humidity, more allergen was detected in the fraction of air containing smaller particles that can penetrate deeper into the lungs 43 (Fig 5; ie, depending on humidity, a part of the allergen could penetrate deeper into the airways, approximately double at 100% relative humidity [rainy days] vs dry days with 30% relative humidity; P < .001). As a consequence, pollen concentration predicted allergen exposure but only with an r 2 correlation of 0.497 (P < .001, see Fig E2).…”

Nature and Health

“…Trees, grasses, and other plants release pollens, which can aggravate allergies and asthma in susceptible people (18,27). The culprits vary with geography but include ragweed, grasses (e.g., Timothy, Bermuda, bluegrass), and trees such as catalpa and walnut.…”

Effects of Airborne Birch Pollen Levels on Clinical Symptoms of Seasonal Allergic Rhinoconjunctivitis

“…However, the development of rigorous methods which take into account nonlinear relationships between variables for time series analyses in air pollution studies provides a useful approach for examining the contribution of aeroallergens [19,20]. Although recent panel grass studies have assessed the effect of pollen and respiratory health using these methods [21,22], no such studies are available in the case of birch pollen. …”