always something new to worry about
Decades of concern over air quality in Southern California has reduced the number of smog alert days in Los Angeles. But current research in Los Angeles is showing an increase in ultrafine particles in the air as cars become more efficient at filtering out the larger particles using catalytic converters. In the past, ultrafine particles attached themselves to the larger particles in car tailpipes. Now, with fewer large particles to attach to, the ultrafine particles stay in the air longer, increasing the risk of inhalation. They go deeper into the respiratory system, penetrating lung tissue and entering the bloodstream.