One of the more infuriating stories that have come out of the disaster in Flint is the number of other US cities who also have elevated lead levels in their water. This is due to the use of lead pipes for water supplies, which cities installed left and right as populations grew in the 19th century. But lead was used in other products like paint and gasoline. But by the 1920s the evidence that lead was harmful was more than clear. Yet the lead industry went on the offensive, threatening lawsuits against anyone who dared say lead was harmful.
It wasn’t until the 1970s the lead paint was finally banned. Lead pipes in new construction hung on until the 1980s. Lead in gasoline began being phased out in 1979 but was still present until January of 1996 (it remains in aviation gasoline and other specialty fuels). But old lead water pipes continue to serve many cities and there simply isn’t enough money to replace them.