Outdoor Environment and Pediatric Asthma: An Update on the Evidence from North America

Table 3

Association between pediatric asthma and aeroallergens and other exposures.

Source/year	Outdoor variables	Age group	Sample size	Region	Study design	Assessment method	Findings and limits
Asthma symptoms
Dellavalle et al., 2012	Tree, grass, weed, and all-type pollen	4–12 years	430	Northeast, US	Cross-sectional/adjusted for covariates	Questionnaire, daily diary, allergen-specific IgE panel for grass and ragweed; pollen and exposure	Weed pollen at low levels (6–9 grains/m3) was associated with shortness of breath, chest tightness, rescue medication use, wheeze, and persistent cough; grass pollen (≥2 grains/m3) was associated with wheeze, night symptoms, shortness of breath, and persistent cough. Limit: the study did not investigate the effect of tree pollen on sensitized children
Asthma-related symptoms and care utlization
Jariwala et al., 2011	Tree pollen, ragweed, mugwort	0–18 years; and adults	52 (weekly mean ED visits)	Northeast, US	Cross-sectional/adjusted for covariates	ED visit data (ICD-9-CM codes), hospitalization data, pollen count (particles per cubic meter)	ED visits highly correlated with tree pollen ( = 0.90, = 0.03) during Spring (March–May). No statistical association of pollen (i.e., ragweed, mugwort) during summer or fall. Limit: data limited to seven major hospitals in New York City, borough of the Bronx.
Asthma sensitivity tests
Sheehan et al., 2010	Trees (birch, oak, maple, elm), grass, ragweed mix,	0–21 years	1,394	Northeast, US	Cross-sectional/adjusted for covariates	Skin prick testing database	Grass and ragweed were least common sensitizers in younger children, with rates of 1.0% (0–2 years) and 2.8% (2–4 years) for grass and 1.0% (0–2 years) and 5.7% (2–4 years) for ragweed. The rates were higher among those aged 10–12 with rates of 28.8% for grass and 34.2% for ragweed. Trees were common outdoor exposure sensitizers in all age groups. Limit: given the retrospective not all patients received the same testing

NHANES: National Health and Nutrition Examination Survey. Note. (a) used modeling to estimate ambient pollen exposure.