Do you live with air pollution? I recommend a hepa filter for your home. You can't protect yourself outdoors, but it's easy to keep home air clean.
Living in areas of high air pollution can lead to decreased cognitive function in older adults, according to new research ...
"As a result of age-related declines in health and functioning, older adults are particularly vulnerable to the hazards of exposure to unhealthy air," Ailshire said. "Air pollution has been linked to increased cardiovascular and respiratory problems, and even premature death, in older populations, and there is emerging evidence that exposure to particulate air pollution may have adverse effects on brain health and functioning as well."
... fine air particulate matter -- composed of particles that are 2.5 micrometers in diameter and smaller, thought to be sufficiently small that if inhaled they can deposit deep in the lung and possibly the brain -- may be an important environmental risk factor for reduced cognitive function. [emphasis mine]