A couple weeks ago I loaded a good amount of urbanite into my car (broken up concrete sidewalk) from a site and brought the pieces to my backyard with the intention of building and herb spiral.
Today I broke up the pieces into smaller and more brick like ones with a sledgehammer, and it created a massive amount of dust. I was working on a concrete surface that used to be a small basketball court so I was just able to sweep up the debris, but I'm sure a good amount of dust and debris landed on the grass nearby. Having only a small space to garden, I was really intending to use that land as part of my Permaculture design. It is zone 1 space so I would like to grow low level herbs and some greens.
Should I worry about the sprinkling of dust that got on the grass? I'm not sure if there's anything dangerous enough in concrete dust that would prevent me from either A. sheet mulching over the grass or B. tearing up the grass and composting it to grow some spinach, lettuce or beans.
PS. I also have the same concern for non-lead paint chips on the side of my house; if they find their way into the soil, is it going to end up in the food you grow there?
I'm a bit less paranoid than most here, but I think both are fine. As a matter of fact, I've floated the idea of using concrete as a source of agricultural lime on this site a couple of different times.
Sidewalks are generally poured from very traditional recipes; ones old enough to be demolished probably have fewer exceptions to that rule. I'd rather eat a tablespoon of the stuff, than breathe a pinch of it.
I'd recommend sending soil samples off for testing if you haven't already done so, partly to ascertain any pH or nutrient issues, but partly to assess previous heavy metals contamination.
Similarly, I'm of the opinion that dry paint is benign unless lead, cadmium, etc. are part of the formula. Hazardous waste treatment facilities mostly handle paint by letting it dry (although they do take measures to dispose of any solvents that are released in that process).
"the qualities of these bacteria, like the heat of the sun, electricity, or the qualities of metals, are part of the storehouse of knowledge of all men. They are manifestations of the laws of nature, free to all men and reserved exclusively to none." SCOTUS, Funk Bros. Seed Co. v. Kale Inoculant Co.