Nasal Mucosal Irritation By Microbial Volatile Organic Compounds (MVOCs): A Pilot Study

Rationale: Nasal symptoms can be associated with indoor mold overgrowth, even absent documented allergic sensitization.  An alternative pathogenic mechanism - mucous membrane irritation by microbial volatile organic compounds (MVOCs) - has been proposed.  We conducted a pilot human study of nasal irritation by two MVOCs: 1-octen-3-ol and 3-octanol, hypothesizing that the former would show greater irritant potency based upon the compounds’ relative irritant potencies in rodents.

Methods: Serial dilutions of the two test compounds were prepared in odorless mineral oil vehicle, with headspace vapor concentrations documented by gas chromatography.  Eight-step dilution series, with descending step concentration ratios of ~0.75, were prepared. A nasal lateralization protocol was utilized, effectively eliminating odor cueing.  Ten subjects (7 females), aged 23-69, were tested on four separate days, with each test compound presented twice in alternating / counterbalanced order.  Individual lateralization thresholds, taken as dilution step (reflecting % saturation vapor pressure), were averaged across subjects.

Results: Eight subjects were reliably able to lateralize stimuli for one or both test compounds.  Among the 16 trials completed by these 8 subjects for each compound, 1-octen-3-ol was successfully lateralized in 15/16, and 3-octanol in 11/16.  The mean dilution step at threshold was 3.13 for 1-octen-3-ol, and 2.58 for 3-octanol (step 0 = neat).

Conclusions:  When presented as brief (~ 4 sec.) stimuli, high concentrations of identified MVOCs can act as nasal mucous membrane irritants.  Both detectability and dilution step, although not differing significantly, exhibited trends consistent with animal experimental data.  Studies involving more protracted exposures with larger sample sizes may yield more realistic irritant threshold estimates.