Dean Hewish recommends adding sodium hypochlorite to ethidium bromide
solutions. However, reference to Sambrook Fritch and Maniatis
(Molecular Cloning, a lab manual) turned up the following:
"Treatment of dilute solutions of ethidium bromide with hypochlorite
is not recommended as a method of decontamination. Such treatment
.... converts the dye into a compound that is mutagenic ....
Quillardet P and Hofnung M Trends Genetics 4:89 (1988).
Draw your own conclusions,
Nigel Blackhall
University of Nottingham.