A good portion of the United States (1/3) is under a weather advisory for severe heat and high UV Index.  Under these conditions, the particulate matter aka air pollution hovers around us - it does not dissipate.  The Weather Channel advises that everyone limit exposure during these 100+ degree days with UVIs of 10.  As the scale only goes to 10, I think it is much higher in relative terms.
   Air Quality which is impacted by the weather, is tracked by the government.  There are metropolitan centers that can provide you with local data.  The national website is here.  Today's map includes a lot of orange and red.  In fact, my town is colored red and my entire state is orange.  I am happy to see that where my family lives in the Northeast and Florida, it is merely yellow (which of course is not good  - green is good - ONLY green is good, but yellow is less bad than orange or red). 
   If you click on the link that I embedded above, you can find your own state and check the air quality.  This morning my area was in code orange and the radio announcers were warning that it was unsafe for sensitive groups to be outside.  I take issue with the USG days vs the UNH (unhealthy) for two reasons.  One is that the cut off between orange and red is arbitrary - 150 is orange and 151 is red.  But more importantly, there is no safe level of air pollution.  There is a level where harm begins to be seen.  One may see harmful effects, like difficulty breathing, sooner in people who are compromised (asthma, young, old) but that does NOT mean that the air is safe for someone who doesn't immediately show symptoms.
   Toxic air is toxic for anyone that breathes it. No one has immunity to pollution.  We may be at different levels of risk or susceptibility for the immediate effects, but the particulates damage the tiny air sacs in everyone's lungs and the pollutants (chemicals in the air) get in our blood stream raising the risk for heart attack.  Reminds me of when people say that they are allergic to tobacco smoke.  EVERYONE is allergic to tobacco smoke... it is poison.
   If you click on this link and scroll down a little, you can see the numbers that make up the air quality categories.