It also means researchers can test a group of people simultaneously, under the same conditions. When particles get inside your lungs, a lining of epithelial cells tries to protect airways. In the last few years, scientists have discovered that these cells also act as triggers. They start a cascade of events that results in lung injury. The cells release compounds that start inflammation.
Bronchial passages end up tied into knots.
Peden, the asthma and allergy doctor, says one problem in studying fine particles is that they consist of a multitude of chemicals, unlike ozone for instance, which is a discrete gas. The ongoing debate centers on whether the offending particles are biological, like endotoxins, or metals like iron, zinc, and copper released by burning fuel oil or coal. The people at risk are people that for whatever reason have an increased sensitivity to air pollution. That's led to the notion of studying susceptible populations. There are many ways you can identify such a population.