halogen bleach systems for example incorporation of a dye would be a valuable activity signal for the consumer halogen donating compounds containing nanoparticles delivered to the toilet tank would dissolve more rapidly due to their small size and release sufficient quantities of halogen to sanitize the toilet bowl with each flush over approximately a thirty day period delivery of efficacious amounts of active to achieve sanitization has typically been an insurmountable hurdle for automatic toilet bowl cleaners due to the large volume of water than must be treated over time the quantity of available active halogen donating compound should fall within the range of 35 to 70 weight percent in the toilet bowl cleaner for effective efficacy useful halogen donating compounds include halohydantoins such as 1 3 dichloro 5 5 dimethylhydantoin 1 3 dichloro 5 ethyl 5 methylhydantoin and 1 bromo 3 3 chloro 5 5 dimethylhydantoin calcium hypochlorite and similar compounds commercially available compositions containing these hydantoins include dantochlor u00ae rw and 8273 dantoin u00ae 8 2 5 available from lonza inc fair lawn n j the particles of this invention contain a discrete phase of a halogen donating compound as described above having a surface modifier adsorbed on the surface thereof useful surface modifiers are believed to include those which.