The sum of the "point cancer risk" from local carcinogenic emissions, including chloroprene, is about 800x the national average.

Sorry, but I still don't see it. One of your links is to an EPA web site where the number "826" does not appear, and the other is to a local Fox News affiliate (not the most reliable source for environmental reporting IMHO) talking about "total cancer risk", whatever the hell that might mean.

Even if we take this 826 number at face value (and I don't see that number anywhere on the EPA page) then for that to be 800 times higher than the national average, then the national average would have to be 1 in a million -- over what time period? Annually? Life time? This whole discussion is a hopeless mess. But again, I can't think of any interpretation under which one in a million is a reasonable measure of anything. There are only 300 million people in the U.S. One in a million means there are 300 people who are affected. Three times that many people are diagnosed with cancer every day in the U.S.