In a UK study, a causal relationship has been established between air pollution and cognitive decline / dementia. The primary cause is a decline in blood flow to the brain.
Cognitive decline, dementia and air pollution
COMEAP reviewed nearly 70 studies in human populations (epidemiological studies) which looked at possible links between air pollution and a decline in mental ability and dementia in older people. They also considered studies which investigated how air pollution might affect the brain.
From this review, it can be concluded that it is likely that air pollution does contribute to these effects. The most likely way this occurs is through effects on the circulation. It is known that air pollutants, particularly small particles, can affect the heart and blood vessels, including to the brain.
WORST CITIES FOR OZONE POLLUTION
#1: Los Angeles-Long Beach, CA
#2: Bakersfield, CA
#3: Visalia, CA
#4: Fresno-Madera-Hanford, CA
#5: Phoenix-Mesa, AZ
#6: San Diego-Chula Vista-Carlsbad, CA
#7: Denver-Aurora, CO
#8: Houston-The Woodlands, TX
#9: Sacramento-Roseville, CA
#10: Salt Lake City-Provo-Orem, UT
#11: Las Vegas-Henderson, NV
#12: El Paso-Las Cruces, TX-NM
#13: San Jose-San Francisco-Oakland, CA
#14: New York-Newark, NY-NJ-CT-PA
#15: El Centro, CA
#16: Chicago-Naperville, IL-IN-WI
#16: Dallas-Fort Worth, TX-OK
#18: Fort Collins, CO
#19: San Luis Obispo-Paso Robles, CA
#20: Chico, CA
#21: Reno-Carson City-Fernley, NV
#22: Albuquerque-Santa Fe-Las Vegas, NM
#23: Redding-Red Bluff, CA
#24: Detroit-Warren-Ann Arbor, MI
#25: San Antonio-New Braunfels-Pearsall, TX
WORST CITIES FOR PARTICLE POLLUTION
#1: Bakersfield, CA
#2: Fresno-Madera-Hanford, CA
#2: Visalia, CA
#4: San Jose-San Francisco-Oakland, CA
#5: Los Angeles-Long Beach, CA
#6: Medford-Grants Pass, OR
#7: Fairbanks, AK
#8: Phoenix-Mesa, AZ
#9: Chico, CA
#10: El Centro, CA
#11: Sacramento-Roseville, CA
#12: Cincinnati-Wilmington-Maysville, OH-KY-IN
#13: Indianapolis-Carmel-Muncie, IN
#14: Pittsburgh-New Castle-Weirton, PA-OH-WV
#15: Bend-Prineville, OR
#16: Detroit-Warren-Ann Arbor, MI
#16: Redding-Red Bluff, CA
#18: McAllen-Edinburg, TX
#18: Philadelphia-Reading-Camden, PA-NJ-DE-MD
#18: Eugene-Springfield, OR
#21: Yakima, WA
#22: Chicago-Naperville, IL-IN-WI
#22: Houston-The Woodlands, TX
#24: St. Louis-St. Charles-Farmington, MO-IL
#25: Augusta-Richmond County, GA-SC
#25: Shreveport-Bossier City-Minden, LA