I pulled the information below from City-data.com (Summary of publicly available information to report about every interesting fact about any city in the US).  I was somewhat skeptical about data referenced in other posts so I did some quick research on my own.  Most importantly, the ambient pollutant trends below show positive reductions in most (in bold) since 1990, while the remaining ambient pollutants hold fairly steady.  Cleveland is not exactly the poisonous pot of sludge typically referenced in other blogs.  It appears to be a city heading in the right direction.  Hey I am 100% glass half full guy.  I see the best in almost everything, and respect others opinions as they view the glass half empty.  This city will turn around, business and industry will return, job growth will continue to climb, and the tax revenue, covetted by the career polititions, will return and provided a solid base to strenthen our infrastructure.  C'mon Cleveland!!!Time to get positive.

Cuyahoga County has a predicted average indoor radon screening level between 2 and 4 pCi/L (pico curies per liter) - Moderate Potential

Air pollution trends in Cleveland

Pollutant: Carbon Monoxide 2nd Max at 3 sites: 2.4 ppm in 2005 (it was 4.5 ppm in 2000, 5.3 ppm in 1990).
Pollutant: Ozone 4th Max at 5 sites: 0.086 ppm in 2005 (it was 0.078 ppm in 2000, 0.085 ppm in 1990).
Pollutant: Ozone 2nd Max at 5 sites: 0.106 ppm in 2005 (it was 0.101 ppm in 2000, 0.108 ppm in 1990).
Pollutant: Particulate Matter (PM10) Weighted Annual Mean at 7 sites: 29.7 µ/m3 in 2005 (it was 30.9 µ/m3 in 2000, 33.4 µ/m3 in 1990).
Pollutant: Particulate Matter (PM2.5) Weighted Annual Mean at 7 sites: 18.0 µ/m3 in 2005 (it was 17.6 µ/m3 in 2000).
Pollutant: Lead: 0.03 µ/m3 in 2005 (it was 0.03 µ/m3 in 2000, 0.10 µ/m3 in 1990).
Pollutant: Sulfur Oxides Annual Mean at 5 sites: 0.0061 ppm in 2005 (it was 0.0057 ppm in 2000, 0.0112 ppm in 1990).

Read more: http://www.city-data.com/city/Cleveland-Ohio.html#ixzz12O3xtH9r