Project at a Glance

Title: Effects of hydroxmethanesulfonate on airway function in subjects with asthma

Principal Investigator / Author(s): Sheppard, Dean

Contractor: UC San Francisco

Contract Number: A733-063

Research Program Area: Health & Exposure

Topic Areas: Acid Deposition, Health Effects of Air Pollution


The organic ion, hydroxymethanesulfonate (HMSA), has been measured in micromolar concentrations in acid fogs in Southern California. HMSA is formed in the atmosphere by the combination of bisulfite (HS03-) and formaldehyde (CH20). HMSA is a stable adduct in fogs with a pH range of 3-5, but it is likely to dissociate at pH 6.6, the Ph of the fluid lining human airways. The dissociation of inhaled HMSA under the conditions present in the airway lumen should theoretically generate sulfur dioxide and CH20, both of which have bronchoconstrictor potential. Thus, we hypothesized that hydroxymethanesulfonic acid may have a specific bronchoconstrictor effect independent of its strength as an acid. In order to determine whether HMSA has such a specific bronchoconstrictor effect, we studied a total of 19 subjects with mild to moderate asthma, following two separate protocols. Because of the lack of precedent for exposing human subjects to HMSA, the initial study involved inhalation during rest of sequentially increasing concentrations for a short duration (3 minutes) via a mouthpiece system. After no significant bronchoconstrictor effect of HMSA was demonstrated under the conditions of this pilot study, we then performed an experiment in an exposure chamber in which freely breathing and intermittently exercising subjects inhaled simulated fogs containing HMSA, at a concentration (1000 ÁM) higher than what has been measured in the atmosphere, for one hour. The results of the exposure chamber study again indicated no significant bronchoconstrictor effect for HMSA. Thus, we conclude that individuals with asthma are not likely to develop clinically significant bronchoconstriction when exposed to fogs containing HMSA in the ambient range.

For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753

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