There are plenty of reasons. The lead in the water supply is just one of many.So it’s the water ?
If you go dig deeper into the subject you'll find out that their government would fill their communities up with drugs and then started the drug wars. They are only 13% of the population but make up 13-15% of drug arrests, 50% of the drug convictions and 40% of the prison population despite the fact that they use drugs at the same rate as crackers. All the fathers are locked up in a prison. There are many cases in which a cop that has to fill his quota planted drugs on innocent black people forcing them to lose a decade of their lives in prison. They can't get a job after they finish their decade-long sentence because drug crimes (non-violent crimes) gives them a felony so they're not allowed to work anywhere and they are forced to do an illegal activity to live.
This is a system, not people that lack brain capacity like some people on this site think it is. You should do some reading on this subject. I've only covered less than 10% of the discrimination that AAs have to go through in America.