The upper airway response to pollen is enhanced by exposure to combustion particulates: a pilot human experimental challenge study.

Abstract

Although human experimental studies have shown that gaseous pollutants enhance the inflammatory response to allergens, human data on whether combustion particulates enhance the inflammatory response to allergen are limited. Therefore, we conducted a human experimental study to investigate whether combustion particulates enhance the inflammatory response to aeroallergens. "Enhancement" refers to a greater-than-additive response when combustion particulates are delivered with allergen, compared with the responses when particulates and allergen are delivered alone. Eight subjects, five atopic and three nonatopic, participated in three randomized exposurechallenge sessions at least 2 weeks apart (i.e., clean air followed by allergen, particles followed by no allergen, or particles followed by allergen). Each session consisted of nasal exposure to combustion particles (target concentration of 1.0 mg/m 3 ) or clean air for 1 hr, followed 3 hr later by challenge with whole pollen grains or placebo. Nasal lavage was performed immediately before particle or clean air exposure, immediately after exposure, and 4, 18 and 42 hr after pollen challenge. Cell counts, differentials, and measurement of cytokines were performed on each nasal lavage. In atopic but not in nonatopic subjects, when allergen was preceded by particulates, there was a significant enhancement immediately after pollen challenge in nasal lavage leukocytes and neutrophils (29.7 × 10 3 cells/mL and 25.4 × 10 3 cells/mL, respectively). This represents a 143% and 130% enhancement, respectively. The enhanced response for interleukin-4 was 3.23 pg/mL (p = 0.06), a 395% enhancement. In atopic subjects there was evidence of an enhanced response when particulates, as compared to clean air, preceded the allergen challenge.

<p>Air Pollution and Allergic Rhinitis: Role in Symptom Exacerbation and Strategies for Management</p>

“…41 Other forms of air pollutant exposure include oil fly ash, a particulate produced from coal combustion. Hauser et al (2003) found increased nasal lavage leukocytes, neutrophils, and IL-4 in AR subjects coexposed to an allergen and residual oil fly ash. 42 Coexposure with allergen and atmospheric levels of ozone resulted in elevated nasal lavage neutrophils, eosinophils, and mononuclear cells.…”

Mitochondrial Dysfunction Increases Allergic Airway Inflammation

“…Previous studies on human subjects have reported that nasal exposure to ozone (64) or particulate matter air pollution (65) followed by challenge with allergen significantly enhanced the allergic responses. Similarly, repeated pollen exposure amplified and sustained allergic symptoms (66).…”

Pollen Loads and Allergic Rhinitis in Darwin, Australia: A Potential Health Outcome of the Grass-Fire Cycle

“…A potent and largely overlooked factor is the rapid transformation of natural vegetation via a grass-fire cycle. The ongoing broadscale use of fires in tropical regions (van der Werf et al, 2006;Turner et al, 2007) produces severe recurrent episodes of particulate air pollution, which can further potentiate the clinical response to allergen exposure (Hauser et al, 2003;Saxon and Diaz-Sanchez, 2005). It might also be possible that tropical grasses with the C4 photosynthetic pathway are more allergenic than temperate grasses, explaining the strong association we observed with very low concentrations of grass pollen.…”