No spraying for mosquitoes is not dangerous as long as nobody is outside while the spraying for the mosquitoes is being done.
When the city has someone come out to spray for mosquitoes they usually do so early in the morning or in the evening when people are asleep.
But if they do spray for mosquitoes during the day when people are out they should warn people to stay in their homes until the mosquito spraying is done.
In order for the mosquito spraying to be dangerous to a persons health the person would have to inhale the mosquito spray directly.
So if you're in your house or at least not right near the mosquito spraying then you should be just fine.
The mosquito spraying effective at killing mosquitoes if done correctly and at the right times.
Mosquitoes should be sprayed when they are active and not when they are non active.