[Spooky23]

Not really. It's just a widespread area that rolls up to zipcodes, etc.

My mom was in public health research -- there's a ton of cancer clusters tied to industry and other factors which don't get recognized because of the methology for defining place and jurisdictional boundaries. In rural areas you have population issues because environmental impacts can be localized due to low population density.

One example at I can't find a free article online for was a 20-30 mile long county highway that was paved with oiled gravel in the 1960s and 70s. Incidence of lung cancer in non-smokers was higher than smokers in the general population, and with smokers significantly higher. Reason? A local industry donated waste oil from industrial processes to the county highway departments. They were laden with PCBs, dioxins and other goodies, delivered to your home in the form of road dust. Another was a plant that processed depleted uranium for munitions, that elevated kidney and bladder cancers in a narrow range across a few jurisdictions. The contractor settled claims there.

Around Houston, I'd expect what I experienced as a child downwind of the former Greenpoint garbage incinerator and Newtown creek refineries in NYC ... more childhood asthma, higher incidence of cancers of lung/mouth from long tenured residents, etc. Lots of nasty stuff is emitted in refining and chemical operations.