There’s an Air Quality Alert in effect for today and another one for tomorrow. So far, 18 alerts have been called this year; that's the same number declared last year.Air pollution causes irritation in the lungs, and the immune system reacts to it. But when someone has breathing problems and is exposed to natural allergens in the air AND pollution, the effects are intensified.Dr. Gerald Lee is a professor of allergy and immunology at the University of Louisville. He’s done research on the effect of diesel exhaust particles and dust mites on asthmatic mice.“When I had an asthmatic mouse and I gave diesel to that mouse, their asthma severity, their antibodies against the house dust mite, all these things were enhanced in the presence of that pollutant,” he said.So pollution can affect those with other allergies or asthma first. But Lee says the answer to the city’s growing number of Air Quality Alert days isn’t necessarily to stay inside.“I don’t think it’s going to make a difference for the kinds of central issues we’re talking about, which is how pollution plays a huge role in enhancing our responses to these things that are usually benign,” he said.To improve air quality, Lee says Louisville ultimately will have to reduce some of its biggest sources of pollution, from the highways to the power plants.Tomorrow is the first alert day this year that’s predicted to have such high ozone levels that it’s dangerous for everyone.