Other than tobacco smoke, nothing is absolutely surely connected to bladder cancer
(except for some relatively rare things.) However, firefighters and beauticians do seem to have a higher than usual chance of bladder cancer. I think that the case for customers who use hair dyes has not been confirmed.
That being said, just as with most other cancers, it is probably not possible to assign blame to one specific event or agent. Along the way, something went off track in the tissue, and with the millions of biological events going on in the body all the time this is not a surprise. Here is a summary from the National Cancer Institute
www.cancer.gov/about-cancer/causes-prevention/risk/myths/hair-dyes-fact-sheet
Wishing you the best of luck....
Sara Anne