What can tenants do? 1. The most obvious answer (the one you don't want to hear) is QUIT SMOKING. (easier said than done)
2.
You could move. Remember that landlord can only make the change at the
end of the lease term. Tenant is free to accept the 'new' lease or
move.
3. Try to negotiate. If you are a good tenant (pay rent
on time, no disturbances), maybe your landlord will be willing to
'grandfather' you in under the old lease provisions. There's no
requirement that all leases be identical (as long as landlord is not
disfavoring a protected class.)
3. Ask for a smoking area on the grounds, away from the building that's somewhat protected from the elements...like a gazebo.