- For every 10 ppb increase on ozone pollution in California, there was a 0.64% increase in mental health emergency department (ED) visits over the following 7 days. Mean concentrations of particles smaller than 2.5 microns were associated with a same day 0.42% increase in mental health ED visits. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0249675 9 comments science