I an American student from the East San Francisco Bay Area and I now attend college in San Diego. This summer, I have the opportunity to spend the entire month of July studying abroad in Seoul. I have read online that the air quality is poorest during the spring and summer months in Seoul. I don't have asthma or any other respiratory problems but I feel like I am more susceptible to chemicals and such as I feel their effects quite quickly. Do you think that I would have problems with the air quality is Seoul during July? Any long term effects?
Seoul actually has pretty good air quality for a large metropolitan area in a valley. In general, you shouldn't worry about air pollution there aside from specific local events or occurrences - standing in central Gangnam in rush hour isn't recommended but I guess you wouldn't stand in Manhattan rush hour traffic either. There are occasionally issues with winds from China bringing the pollution from there (well documented phenomenon that periodically affects Korea and Japan when winds from the Gobi push the air in China east) but this is something they warn in advance on TV and other media.
Bear in mind that Seoul as a city does a lot more than California does for pollution control - cars are predominantly higher standard gasoline-based, buses run on natural gas and mass transit is ubiquitous and powered predominantly by nuclear and hydro as opposed to coal like China.
It may be humid and hot - which cause different problems potentially - but hard to tell how this will affect you until you get there. Nothing to worry about if you're coming from California frankly.
No one here can tell you if it's safe for you or not.
What can be done is to highlight published facts on air quality, in Seoul, for the middle of the year.
I was able to find air quality index data (a snapshot) for Seoul taken in June, 2015.
The measurements ranged between the measurement bands of "moderate" and "unhealthy for sensitive groups".
This means, according to the CA Index that S Korea uses (scroll about two thirds of the way down for the colorful table), that
at best for the sample four day period:
Air quality is acceptable; however, for some pollutants there may be a moderate health concern for a very small number of people who are unusually sensitive to air pollution. ...Active children and adults, and people with respiratory disease, such as asthma, should limit prolonged outdoor exertion.
And at worst:
Members of sensitive groups may experience health effects. The general public is not likely to be affected.
Given the air quality is virtually identical in July and August (trending to worse), it seems reasonable to infer that during this time of year unusually sensitive individuals, as well as those who have diagnosed medical complaints such as asthma, need to exercise caution on some days.
You and your medical professional need to work out if this means you.