My name isXXXXX am a licensed attorney and registered nurse. I am very happy to try and answer your question today. I am genuinely sorry for your circumstances and hope things soon look much brighter for you.
You were absolutely lawfully entitled to a workplace free from unlawful discrimination, including that based upon your asthma. Accordingly, I'm pleased to say there is something you can do, namely by sharing your concerns with the U.S. Equal Employment Opportunity Commission. You can certainly could file a complaint, technically called a charge, entirely free of charge. You have six months from the last incident in which to file. Everything you need is provided here for free:
Filing A Charge
This is an exclusive procedure, meaning it's the only way to properly pursue your complaint rather than starting out by filing a lawsuit and so forth. I would urge you to also exhaust your union grievance procedure, despite what you were told to the contrary.
I really do hope things soon look brighter for you, and please know that you deserve to be treated in a lawful manner. If you have a follow-up question or need clarification, please just say the word by using "reply" to reach me. I will be sure to check back for any further word from you when I am again working online in this forum.
I truly hope all works out for you and that the information I have provided proves useful. Thanks so much for using this service!
Ben, J.D., R.N.