Complex sentence: Gasoline used to include lead, which can cause damage to bodily functions and organs and sulfur was lowered over 90 percent in fuels because it doesn't allow a vehicle's catalytic converter to effectively clean up the exhaust.
Split into simpler sentences: Gasoline used to include lead, which can cause damage to bodily functions and organs. Sulfur was lowered over 90 percent in fuels because it doesn't allow a vehicle's catalytic converter to effectively clean up the exhaust.