Complex sentence: Residents complained about the taste, smell, and appearance of the water for 18 months before a Flint physician found highly elevated blood lead levels in the children of Flint while the Michigan Department of Environmental Quality insisted the water was safe to drink.
Split into simpler sentences: Residents complained about the taste, smell, and appearance of the water for 18 months before a Flint physician found highly elevated blood lead levels in the children of Flint. During that time period, the Michigan Department of Environmental Quality had insisted the water was safe to drink.