I really dont know if its good or bad to use compost material from the city (lawn clippings,leaves,etc...)
BUT chemicals do break down &/or wash away, & some chemicals are harmless once dry. also remember all the chemiclas you intake from the air or produce you buy at the grocery store, or the fish you eat, or the toxins your body (skin) absorbs while swimming in certain waters or just being in contact with those chemicals (including your everyday products you use)
I kinda have a feeling city compost sites would be telling everyone not to use the stuff for edible produce (gardens) if there was an issue with toxins, but then again if there was a problem with toxins our sue happy lawyers would be all over the city for selling the stuff & that'd be closed down. so I think its safe.
chemicals can break down to be harmless &/or wash away, if they didnt your dog or cat would drop dead if it ever went in your lawn once you've used a weed control chemical. like I said chemicals can break down & be completely harmless once broken down, depending on what it is but you may only get sick & thats if you ate alot of whatever that had alot of the chemical on it.