Information relating the allergic/atopic status to the different types of irritant-induced asthma for 54 cases of irritant-induced asthma showed that 25 of 38 (66%) subjects with new-onset irritant-induced asthma possessed an allergic/atopy predisposition. Of the remaining 16 who suffered an exacerbation of preexisting asthma that was in remission, 12 of 16 (75%) were positive for allergy/atopy (Fig 1).
There was an increased odds ratios (±95% confidence limits) for “allergic/atopy” presence of 7.3 (2.5 to 22.2) (p<0.001) for the irritant-induced asthma group as a whole. The odds ratio for “allergic/atopy” was 15.9 (2.0 to 339.67) for irritant-induced asthma occurring in the preexisting asthma in remission group (p<0.001). The odds ratio was 1.92 (0.73 to 5.09) for new-onset irritant-induced asthma (p=0.14). A lower odds ratio was observed for both the allergic occupational asthma (0.06 [0.0 to 0.47]) (p<0.001) and not occupational/environmental exposure asthma groups (0.40 [0.12 to 1.10]) (p=0.07). The finding of allergic/atopy, by itself, was not a reliable predictor of asthma occurrence: sensitivity was 66% and the specificity was 29%; the positive predictive value was 68% and the negative predictive value was 28% (p was not significant).
There were 65 exposure events: 54 persons were exposed to irritants and 11 persons were exposed to sensitizers. There was a multiplicity of exposures for irritant-induced asthma; S02 and pesticide spraying in four circumstances each; chlorine gas and ammonia/bleach/caustic soda in three cases each; solvent vapors/mist and paint vapors/spray in two persons each; there were also other exposures as noted in Table 2. Occupational asthma was caused by diisocyanates in five cases, acrylates in four cases, and flour exposure (“baker’s asthma”) in the two remaining subjects (Table 2).
Time to Onset
Table 3 summarizes this information (duration of exposure before asthma symptoms began) for all 54 irritant-induced asthma cases. For 29 (54%) subjects, the onset of asthma was sudden or immediate (<24 h). In contrast, for 25 subjects (46%), asthma evolved from irritant exposures that were repeated and continued for >24 h (not so sudden).
Among the 29 subjects with sudden-onset irritant-induced asthma (<24 h), two subcategories were recognized: the first consisted of 23 (79%) subjects with documented RADS. The second group included six (21%) persons with apparent RADS who had suffered a recurrence of preexisting asthmatic state exacerbated by the irritant exposures.
Figure 1. Schematic representation of the numbers of subjects assigned to various irritant-induced asthma groups. The two classifications of new-onset and preexisting asthma were further subcategorized into sudden (<24 h) and not-so-sudden onset (>24 h) irritant-induced asthma. The numbers of atopic and nonatopic subjects identified for the two subcategories are shown. A significant prevalence of atopy/allergy is noted for the not-so-sudden group (p<0.01).
Table 2—Exposure Events
|Pesticide sprayingCement sealantMixed solvent vapors and mist|
Household bleach vapors
Sulfur dioxide gas
Titanium tetrachloride mist
Volatile organic vapors from poor indoor air quality
Muriatic acid spill
Burned freon fumes
Fire retardant aerosol
Caustic soda aerosol
|Diphenylmethane diisocyanate Hexamethylene diisocyanate Toluene diisocyanate Flour dustAcry 1 ate s- in ethacrylate and cyanoacrylate ester|
Table 3—Duration of Exposure Before Asthma Onset Among Subjects With Irritant-Induced Asthma
|Asthma Category||<24 h||1-7d||1-4wk||1-4mo|