DOCTOR REPLY NEEDED PLEASE - If someone has severe COPD, can repeated short term exposure to mildew...?

DOCTOR REPLY NEEDED PLEASE - If a woman is 62 and has severe COPD, can repeated short term exposure (a minute at a time maybe) to mildew from a wet towel in the bathtub over a 9 day period make her sick enough to kill her? Our mother had COPD and numerous other problems and my brother won't accept that she died and my is trying to blame it on everything than what the coroner said (that her heart just gave out, doing the toxicology and she may have had a stroke). He is hung up on the idea that a stupid towel he left in the bathroom for several days is what did her in. Please answer so he will stop questioning. Thankyou very much, I really appreciate this. He wanted me to come online and ask a doctor so I agreed, in hopes that he would stop talking about it, and stop blaming myself, my father and himself when I feel thatno one can be blamed, we did the best we could for her and it was her time. I believe it was her time....THANKYOU FOR YOUR HELP -Maryanne