The first paragraph of that second page reads:
"If econometric studies were all there were to the story of lead, you'd be justified in remaining skeptical no matter how good the statistics look. Even when researchers do their best—controlling for economic growth, welfare payments, race, income, education level, and everything else they can think of—it's always possible that something they haven't thought of is still lurking in the background. But there's another reason to take the lead hypothesis seriously, and it might be the most compelling one of all: Neurological research is demonstrating that lead's effects are even more appalling, more permanent, and appear at far lower levels than we ever thought."
And the rest of the second page goes into much more detail.
In other words, just saying "correlation doesn't imply causation" doesn't win you the thread. There is clear causation evidence at the neurological level.