Each subject completed a standardized respiratory questionnaire, underwent direct medical history, and had a physical examination (all performed by S.M.B.). The subject’s medical records were examined for completeness, breadth of information, validity of lung function tests, diagnosis of asthma, criteria establishing “allergic” or atopic status, assessment of exposure considered causative of the asthmatic condition; and, survey of analytical, toxicologic, and environmental data of the exposure, including its duration, nature, and intensity. The clinical, exposure, and toxicologic information for each subject was examined independently by two physicians experienced in occupational medicine (J.G., K.J.).
Exposure event was a specific workplace or environmental exposure to an irritant and/or sensitizing agent believed to be responsible for asthma. The exposure information was reviewed by an industrial hygienist (Y.H.) and the toxicologic details were assessed by a toxicologist (I.R.).
Time to onset was the span of time of continued or repeated exposure before the patient first developed asthma symptoms.
Allergic or atopic status (allergy/atopy) was established by one or more of the following criteria: at least one positive radioallergosorbent test (RAST) to a battery of common aeroal-lergens for southeastern United States (by Smith-Kline Laboratories; Alternaria, Bermuda grass, cat dander, Cladosponum hebarum, common ragweed, Dermatophagoides farinae, dog dander, June grass, oak, rough pigweed); and/or at least two positive skin prick and/or intradermal (>2+) skin tests to a battery of common aeroallergens; and/or total serum IgE concentration of ^250 U/mL in the absence of other known causes of elevated IgE; and/or reported personal history of an allergic disorder (ie, allergic rhinitis, conjunctivitis, hay fever, or asthma); and/or reported presence of an allergic disorder (ie, allergic rhinitis, conjunctivitis, hay fever, or asthma) in a close family member (parents, sibling, child).