Now they've been found in urban air in the United States, as well.

I could also prevent one more engine's contribution to our murky urban air.

This makes for a messy experiment when researchers try to expose animals to "urban air" in a laboratory.

Ozone is known to have the following health effects at concentrations common in urban air:

By far the most important factor is fine particulate matter pollution in urban air.

Deals with such issues as urban air, visibility, ozone, acid rain, and radiation.

There's a distinctly urban air about the place; not everyone looks as if they have to get home to relieve the baby sitter.

Recent atmospheric mercury contamination in outdoor urban air was measured at 0.01-0.02 g/m.

Thus some changes promoted by oil companies as a way to clean up urban air seem to have little net benefit, the study said.

During the winter months in particular, urban air obscures vision, and negatively impacts human health.