Asthma is only one of many possible heath impacts. It was associated with others, just not Asthma.

When compared to actors from the non-"smoke" productions, actors from two or more of the four productions utilizing theatrical "smoke" reported experiencing a significantly greater prevalence of nasal symptoms (sneezing, runny or stuffy nose), respiratory symptoms (cough, wheeze, breathlessness, chest tightness), and mucous membrane symptoms (sore throat, hoarseness, dry throat, itchy/burning eyes, dry eyes) during their performances for the week prior to the survey.

The final line is: The quantity and frequency of use of the various fogs during a performance should be minimized.

PS: A method of action was suggested to be the breakdown of glycol due to high temperature.