I don't understand what the big deal about bleach is????? I am a chemist and I can tell you that "exposure to bleach" is not harmful unless you drink it or breathe too much of the vapors from the liquid. Walking on a sidewalk that has been cleaned with it will not hurt your child!!! The smell of bleach in the air is not harmful in any way. It requires direct skin contact or prolonged exposure to concentrated vapors to do any damage. The bleach is sodium hypochlorite mixed with water. Sodium hypochlorite is basically table salt with added oxygen. The added oxygen is the cleaning/ disinfecting agent in bleach. It is not more of a "harmful chemical" than lemon juice and is just as natural.The difference in the two really lies in the amount of water present. Concentrated lemon juice is just as caustic as bleach, and bleach is one of the safest cleaning agents out there that will actually disnifect. You can't get much more natural than salt and oxygen. I just don't get the "let's not expose our child to any chemicals" thing. It is completely impossible because everything, our own bodies included are completely made up of chemicals. Water is a chemical. Every chemical has some sort of naturally occuring source. You cannot just create something form nothing.
Uh, sorry, you might be a chemist, but you're not taking into account lung issues, allergies etc. I'd be in Emerg within about 10 minutes of that kind of exposure....and 10% solution at MOST is all that's needed for any project, and in close quarters, it's common courtesy to inform/check with your neighbours first. And repeated exposure is one of the leading causes of allergic reactions to it. It's quite sensible to protect a baby from it.
Let it go. I think he's just being a good neighbor by keeping things clean. I seriously wouldn't give a second thought to using it outside. Inside a building in a common area...yes.
My mum used it on everything from the porch to scrubbing our window screens with it in the spring. 