title: Lack of bronchoconstrictor response to sulfuric acid aerosols and fogs.
abstract: Sulfuric acid (H2SO4) is the most common acid air pollutant in the United States and is thought to have adverse respiratory effects. Sulfuric acid exists in polluted air as a dissolved solute in both small (haze) and large (fog) particles. Previous work in our laboratory has failed to demonstrate bronchoconstriction after near ambient, large-particle H2SO4 exposure in subjects with asthma. However, other investigators have found slight but significant changes in lung function following inhalation of small-particle or small-particle, low-relative-humidity (RH) H2SO4 aerosols, leading us to hypothesize that particle size and/or RH may be important variables in acid aerosol exposure. We initially studied the effects of resting inhalation of large-particle (volume median diameter, VMD, approximately equal to 6 microns) and small-particle (VMD approximately equal to 0.4 microns) aerosols with an H2SO4 concentration of 3 mg/m3 through a mouthpiece and found no effect on specific airway resistance (SRaw) or symptom scores. In a second mouthpiece study designed to compare high-RH (100%), large-particle (VMD approximately equal to 6 microns) and low-RH (less than 10%), small-particle (VMD approximately equal to 0.3 microns) aerosols with an H2SO4 concentration of 3 mg/m3, we again found no effect of either aerosol. We then examined the effects of small-particle aerosols inhaled in dry air during moderate exercise. Although breathing low-RH air during exercise provoked increases in SRaw in almost all subjects, this could not be attributed to H2SO4 since low-RH saline aerosol produced a similar result.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Lung Biology Center, San Francisco General Hospital, University of California 94143.
authors.forename: R
authors.initials: R
authors.lastname: Aris
authors.forename: D
authors.initials: D
authors.lastname: Christian
authors.forename: D
authors.initials: D
authors.lastname: Sheppard
authors.forename: J R
authors.initials: JR
authors.lastname: Balmes
mesh_terms: D000328:Adult; D000336:Aerosols; D000393:Air Pollutants / Q000009:adverse effects*; D000403:Airway Resistance / Q000187:drug effects; D016084:Bronchoconstriction / Q000187:drug effects*; D005260:Female; D005541:Forced Expiratory Volume / Q000187:drug effects; D006801:Humans; D006813:Humidity; D008297:Male; D010316:Particle Size; D013464:Sulfuric Acids / Q000008:administration & dosage / Q000009:adverse effects*; D014797:Vital Capacity / Q000187:drug effects
chemical_list: D000336:Aerosols; D000393:Air Pollutants; D013464:Sulfuric Acids; C033158:sulfuric acid