Analysis of short-term influences of ambient aeroallergens on pediatric asthma hospital visits

doi:10.1016/j.scitotenv.2006.06.019

Science of The Total Environment

Volume 370, Issues 2–3, 1 November 2006, Pages 330-336

https://doi.org/10.1016/j.scitotenv.2006.06.019 Get rights and content

Abstract

The objective of our study was to investigate the association between daily pediatric asthma hospital visits and daily concentrations of aeroallergens and their specific species. Records of daily asthma visits in Cincinnati area were retrieved from Cincinnati Children's Hospital Medical Center and aeroallergen sampling was performed by the Button Inhalable Sampler. The Poisson generalized linear model was carried out in which the log of the number of asthma hospital visits was related to aeroallergen level, treated as a continuous variable with adjustment for seasonal time trend, day of the week, ozone and PM_2.5 concentrations, temperature and humidity. The aeroallergens having a significant impact on asthma hospital visits were ragweed, oak/maple and Pinaceae pollen. Their relative risks on asthma hospital visits with respect to a 100 counts/m³ increase in concentration were in the range of 1.23 to 1.54. The effects in causing the asthma exacerbation were delayed by 3 or 5 days.

Introduction

Approximately 20.3 million people in the United States have asthma, 4500 of whom die annually from the disease. Asthma is now one of the most commonly reported diseases of childhood. An estimated 8.7% of children under age 18 have asthma.

It is usually accepted that about 60% of asthmatics are atopic and it has been known for some time that the aeroallergens, such as pollen and fungal spores, can affect the prevalence and/or severity of asthma. They could act to induce, or augment directly, airway inflammation and hyperresponsiveness, and some of them may have the ability to facilitate allergic sensitization or to enhance the severity of allergic reactions. The skin-prick test and intradermal test using extracts of pollen and/or fungal spore allergens can determine atopic characteristics. Blood tests such as the raido-allergosorbent test (RAST) and multiple allergosorbent chemiluminescent assay (MAST_CLA) can also indicate allergy to pollen and fungal spore allergens (Agata et al., 1993, Kam and Hsieh, 1994). Although the associations have been evidenced in studies in a clinical setting, few studies were conducted to investigate the impact of ambient aeroallergens on the burden of illness in the population and the findings of those studies were not in agreement. Some studies found significant association between daily fungal spore concentration and asthma hospital visits (Rosas and McCartney, 1998, Dales et al., 2000), while others found significant association of the daily pollen concentration, but insignificant association of daily fungal spore concentration, with the number of hospital asthma visits (Lierl and Hornung, 2003). The inconsistencies may have been related to the sampling methods employed in measuring the aeroallergens. The Rotorod and Hirst-Burkard samplers were used in these studies, and they are not the optimal sampling methods for measuring airborne pollen and fungal spores as their sampling efficiency are lower for the particles less than 10 μm and 2.5 μm, respectively (Frenz, 1999, Aizenberg et al., 2000). In the mean time, in order to obtain a better understanding of the association between aeroallergen and asthma, research is needed on the influence of individual aeroallergen species.

The goal of the present study was to examine the relationship of daily number of hospital visits for treatment of acute pediatric asthma attacks and daily concentrations of total outdoor pollen and fungal spores in the air of the greater Cincinnati area. Individual allergenic species were also investigated. Included species were pollen grains of ragweed, grass, oak/maple, Pinaceae and fungal spores of Alternaria, Aspergillus/Penicillium and Cladosporium. The Button Inhalable Aerosol Sampler (SKC, Inc., Eighty Four, PA) was used to monitor the aeroallergens. This sampler is known to be efficient for the sampling of outdoor aeroallergens and especially for small size particles (< 5 μm) (Adhikari et al., 2003).

Section snippets

Hospital asthma visits

Cincinnati Children's Hospital Medical Center (CCHMC) is the major pediatric hospital serving the Greater Cincinnati Metropolitan area. An “asthma visit” was defined as either an emergency room visit or an outpatient clinic visit for the diagnosis of asthma. Daily records of CCHMC asthma visits from April through October 2002 were retrieved by means of a hospital computer search for all visits with ICD9 codes 493–493.91. The age range of the subjects was 1–18 years. If a child had more than one

Results

As shown in Table 1, there were 1254 children between the ages of 1 and 17.9 years in this analysis. Sixty-eight percent of the subjects were age 5 or over. Table 2 provides the descriptive statistics of monthly means (standard deviations) for aeroallergen concentrations, temperature, humidity, ozone, PM_2.5 and asthma hospital visits for the months of April through October 2002. Daily asthma hospital visits were highest in the months of May, September and October and lowest in July and August.

Discussion

The impact of total concentrations of airborne pollen and fungal spore on pediatric asthma hospital visits was investigated as well as the effects of their seven individual allergenic species. Significant predictors for asthma visits were found for the concentrations of oak/maple pollen, Pinaceae pollen and ragweed pollen. Various patterns of delayed effects were also observed among these different types of aeroallergens. The associations found do not necessarily reflect a cause and effect

Acknowledgement

This work was supported by National Institute of Environmental Health Science Grant No. R01 Es 11170.

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Analysis of short-term influences of ambient aeroallergens on pediatric asthma hospital visits

Abstract

Introduction

Section snippets

Hospital asthma visits

Results

Discussion

Acknowledgement

Atmos Environ

Environ Pollut

Atmos. Environ.

Ann Allergy Asthma & Immun

Ann Allergy Asthma & Immun

J Allergy Clin Immunol

Comparison of the MAST chemiluminescent assay system with RASAT and skin tests in allergic children

Ann Allergy

Performance of Air-O-Cell, Burkard, and Button Samplers for total enumeration of airborne spores

AIHAJ