A study of 60 million Americans 65 years old and older (the entire Medicare population) found that long-term exposure to airborne fine particulate matter (PM2.5) and ozone at concentrations below current national standards increases the risk of premature death ("all cause mortality") even when the levels are below current national standards. This effect was most pronounced among racial minorities and people with low income. The national standards are called National Ambient Air Quality Standards (NAAQS), and they are established by the U.S. Environmental Protection Agency (EPA).
Note that PM2.5 refers to fine particles in the air smaller than 2.5 micrometers - these are truly small particles. It is thought that these tiny particles contribute to the development of potentially fatal diseases various ways - by causing chronic inflammation, and also because they slip past the body's defenses and can be absorbed deep into the lungs and bloodstream. They are not sneezed or coughed out the way larger natural particles (like airborne soil and sand) are removed from the body's airways.
These study results are a strong argument in support of the view that our air needs to be protected and standards need to be strengthened - not loosened. Earlier posts on this topic have found links between air pollution (especially fine particulate matter smaller than 2.5 micrometers) and cognitive decline and dementia in older women, strokes, high blood pressure, an increase in death (especially cardiovascular disease), etc. From Medical Xpress:
A new study of 60 million Americans—about 97% of people age 65 and older in the United States—shows that long-term exposure to airborne fine particulate matter (PM2.5) and ozone increases the risk of premature death, even when that exposure is at levels below the National Ambient Air Quality Standards (NAAQS) currently established by the U.S. Environmental Protection Agency.