Wikipedia said:
For any two correlated events, A and B, the following relationships are possible:
A causes B; (direct causation)
B causes A; (reverse causation)
A and B are consequences of a common cause, but do not cause each other;
A causes B and B causes A (bidirectional or cyclic causation);
A causes C which causes B (indirect causation);
There is no connection between A and B; the correlation is a coincidence.
So, if lead doesn't cause crime, what are the other options?
Crime causes lead?
A factor they forgot to look at causes both lead and crime. Hmm. Cars cause crime?
If crime and lead cause each other in a vicious circle, that still counts as lead causing crime.
If for some C, lead causes C which causes crime, that still counts as lead causing crime.
It's all a coincidence?
But, in all fairness, Wikipedia is not to be trusted -- they left out one of the most common and important possible relationships between two correlated observables:
Quantum entanglement.