Cook, Illinois vs Los Angeles, California Air Quality

Side-by-Side Analysis

Cook, Illinois outperforms Los Angeles, California on overall air quality with a Grade D (49/100) versus D (36/100). Cook, Illinois's 5-year median AQI of 57 sits in the "Moderate" range, while Los Angeles, California averages 75 ("Moderate") — a 18-point gap that shows up consistently in year-over-year readings, not just in a single year.

The two cities are moving in opposite directions: Cook, Illinois is stable (-0.1 AQI/yr) while Los Angeles, California is improving (-0.9 AQI/yr). Over time, today's ranking may flip if these trends hold.

What's in the Air

Both cities share the same dominant pollutant: Fine Particulate Matter (PM2.5). These cities' dominant issue is fine particulate matter — typically driven by combustion (vehicles, wildfire smoke, industry, residential wood burning). PM2.5 is the air pollutant most strongly linked to long-term cardiovascular and respiratory disease because the particles penetrate the bloodstream.

Health Implications

Over a 5-year window, Cook, Illinois averages roughly 18 unhealthy air days per year (AQI above 100, where sensitive groups should limit outdoor exertion) versus 100 for Los Angeles, California. That 82-day gap matters most for residents with asthma, COPD, heart disease, or pregnancy — and for outdoor workers, who accumulate the most cumulative exposure. The city with fewer unhealthy days offers a meaningfully different baseline risk picture for sensitive populations. For long-term residents, the cleaner-air city is associated with measurably better outcomes on respiratory disease, cardiovascular events, and life expectancy — Harvard cohort research consistently finds 0.5 to 1.0 years of additional life expectancy for each 10-µg/m³ reduction in long-term PM2.5 exposure.