The last time I read the equity "study" I largely took issue in it's conclusions as it admits that other factors (the mere running of the show, humidity of the space,
etc) were at
play, yet it ALSO decides on an arbitrary value of 25mg/m3.
If the study were were actually committed to finding the truth, the conclusion would be that more research is required in order to eliminate external factors, instead of jumping to set a guideline. From the
AEA study:
"The epidemiologic methodology does not allow us to conclude that a given individual’s symptoms were directly caused by exposure to these theatrical effects."
Correlation coefficients were weak, shows with highest reported vocal issues were also shows rated as "most demanding" vocally.
Take from that what you will, but every study I've seen has been wishy washy, or otherwise not found any adverse health effects from propylene glycol or mineral oil
haze.
So that brings us back to the question, does anyone know what 25mg/m3 looks like?