The aquaducts revolutionized life in Ancient Rome, but due to being sealed in places with lead, they caused toxicity in the water. The extent and impact of the toxicity is up for debate, but what else could they have used?
The lengths of the aqueducts were not coated with lead. The length of an aqueduct would be nearly entirely stone and concrete. Lead would only really be used in piping, mostly to domestic houses from larger holding tanks in the city proper. The substitute that the Roman's could have used, and did use, are terracotta pipes.
Lead poisoning in the Roman's water supply is greatly exaggerated, as the lead pipes would quickly be coated with calcium / lime deposited, and the fresh water flowing through them wouldn't ever come in contact with the lead. (If anybody has ever walked across the top of the Pont du Garde can attest, it is really incredible the amount of calcium / lime that can accumulate on the channel walls of an aqueduct.)