We have to be bold. We have to provide leadership. Now it's true that we disagree on this. The governor said that he doesn't think this problem is necessarily caused by people. He's for letting the oil companies into the Arctic National Wildlife Refuge. Houston has just become the smoggiest city in the country.
Houston has air polution
Smog refers to air pollution, so this statement is definitely correct. The system may not have understood the concept of pollution. 
( z1 pollute :ARG1 ( z2 city :name ( z3 name :op "Houston" ) ) :mod ( z4 air ) )