To preserve the health of the citizens of the city, it is necessary that the streets, alleys, parkways and public places be sprayed with chemicals to kill flies, mosquitoes and other insects in preserving public health. The water department of the city is authorized to commence the spraying of the streets, alleys and parkways with a chemical of sufficient strength to kill flies, mosquitoes and other insects for the preservation of the public health. (2000 Code § 8-601)