| Formation of Strong Airway Irritants in Mixtures of Isoprene/Ozone and Isoprene/Ozone/Nitrogen Dioxide Cornelius K. Wilkins, Per A. Clausen, Peder Wolkoff, S. Thor Larsen, Maria Hammer, Kjeld Larsen, Vivi Hansen, and Gunnar D. Nielsen National Institute of Occupational Health, Copenhagen, Denmark Abstract
We evaluated the airway irritation of isoprene, isoprene/ozone, and isoprene/ozone/nitrogen dioxide mixtures using a mouse bioassay, from which we calculated sensory irritation, bronchial constriction, and pulmonary irritation. We observed significant sensory irritation (approximately 50% reduction of mean respiratory rate) by dynamically exposing the mice, over 30 min, to mixtures of isoprene and O3 or isoprene, O3, and NO2. The starting concentrations were approximately 4 ppm O3 and 500 ppm isoprene (+ approximately 4 ppm NO2) . The reaction mixtures after approximately 30 sec contained < 0.2 ppm O3. Addition of the effects of the residual reactants and the identified stable irritant products (formaldehyde, formic acid, acetic acid, methacrolein, and methylvinyl ketone) could explain only partially the observed sensory irritation. This suggests that one or more strong airway irritants were formed. It is thus possible that oxidation reactions of common unsaturated compounds may be relevant for indoor air quality. Key word: airway irritation, indoor air chemistry, isoprene, mouse irritation bioassay, nitrogen dioxide, ozone. Environ Health Perspect 109:937-941 (2001) . [Online 24 August 2001] http://ehpnet1.niehs.nih.gov/docs/2001/109p937-941wilkins/ abstract.html Address correspondence to C.K. Wilkins, National Institute of Occupational Health, Lersø Parkallé 105, DK-2100 Copenhagen Ø, Denmark. Telephone: +45 39 16 52 71. Fax: +45 39 16 52 01. E-mail: ckw@ami.dk This project was supported by the Center for Indoor Air Research (Award 99-11) . Received 12 December 2000 ; accepted 12 January 2001.
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