I bought my first set of film processing chemicals (Rodinal, Photoflo, Kodak Stop and Fix) in 25 years this past weekend. I have not mixed or opened anything yet, but I have already felt some twitchiness in my asthmatic lungs from one of the still-sealed packages. Not sure which it is that's doing it.
For people with respiratory issues, it doesn't take much to make you symptomatic (even a strong perfume with certain scents on my wife can do it; I try to give her ones that don't bother me as Valentines Day gifts to avoid problems; she never complains; go figure).
If Al said he chain smoked in his darkroom, I believe him. Maybe he enjoyed it, but I can't imagine it did much for his health.