Foreigners polluting US

As if US pollution isn't bad enough, it turns out they're importing the stuff:

Mercury from China, dust from Africa, smog from Mexico — all of it drifts freely across U.S. borders and contaminates the air millions of Americans breathe, according to recent research from Harvard University, the University of Washington and many other institutions where scientists are studying air pollution. There are no boundaries in the sky to stop such pollution, no Border Patrol agents to capture it.

Quick, somebody call the UN. Hah.