Air quality issues exist in the inland parts of the LA area, but in general the local air quality is of most concern during the summer months, when students are least likely to be on campus.
For the 2016 calendar year (full 2017 data not yet posted), there were only four days in which the Claremont air quality was rated as “unhealthy”. All four days were in June, July, or August.
There were 30 days in 2016 when local air quality was rated as “unhealthy for sensitive groups”. Again, most of these days (23 of 30) were in June, July, or August.
So in the non-summer months of 2016, which is more or less when students were on campus, there were only 7 of about 273 days with air quality that was “unhealthy”, and then only to “sensitive groups”. In other words, most people probably didn’t notice any problems even on those days.
https://www.homefacts.com/airquality/California/Los-Angeles-County/Claremont.html