Details
49 CFR Part 40 regulations related to Toilet Blueing state:
Secure all sources of water and other substances that could be used for adulteration and substitution (eg. water faucets, soap dispensers and place bluing agent in all toilets - secure toilets to prevent access)
Plumbers use True Blue for testing customers toilets. Municipalities have the home owner test their own toilets for water conservation.
True Blue can be used to detect leaking flapper of ball valves.
True Blue is placed in the toilet tank and if the valve is defective the bowl will turn blue.
This is not a WHMIS controlled product.