Data: EPA AirNow, FEMA National Risk Index Last verified: 2026-05-03

What is AQI?

The Air Quality Index (AQI) is a standardized scale from 0 to 500 that measures air pollution levels. 0-50 is "Good," 51-100 is "Moderate," 101-150 is "Unhealthy for Sensitive Groups," and above 150 is "Unhealthy" for everyone. AQI tracks five major pollutants: ground-level ozone, particulate matter (PM2.5 and PM10), carbon monoxide, sulfur dioxide, and nitrogen dioxide. Markham's average AQI of 62 falls in the "Moderate" range.

Air Quality by ZIP Code in Markham

AQI varies across Markham's 1 ZIP codes based on proximity to pollution sources and local geography.

ZIP Code	AQI	Category	Wildfire	Mold
60428	62	Moderate	16	65	View report →

Air Quality Overview

Markham, Illinois has moderate air quality with an average AQI of 62. Air quality is acceptable, though some pollutants may be a concern for a small number of people who are unusually sensitive to air pollution. The dominant pollutant is PM2.5.

The Air Quality Index (AQI) is an EPA-standardized scale from 0 to 500. Values below 50 are "Good," 51-100 "Moderate," 101-150 "Unhealthy for Sensitive Groups," 151-200 "Unhealthy," 201-300 "Very Unhealthy," and above 300 "Hazardous."

Dominant Pollutant: PM2.5

PM2.5 (fine particulate matter) consists of particles smaller than 2.5 micrometers — about 30 times thinner than a human hair. These particles can penetrate deep into the lungs and enter the bloodstream.

Health effects of PM2.5 exposure:

• Short-term: coughing, shortness of breath, aggravated asthma
• Long-term: reduced lung function, cardiovascular disease, premature death
• Most vulnerable: children, elderly, people with heart or lung disease

Common sources in urban areas: vehicle exhaust, construction dust, industrial emissions, wildfire smoke, residential wood burning.

Air Quality by ZIP Code in Markham

AQI varies across Markham's 1 ZIP codes based on proximity to pollution sources, traffic patterns, and local geography:

Wildfire Smoke Risk

Markham has an elevated wildfire smoke risk with an average smoke risk score of 16 (scale 0-100). There have been 1 fires recorded within 100 km of city ZIP codes.

Metric	Value
Avg. smoke risk score	16
Max smoke risk score	16
Fires within 100 km	1
High-risk ZIP codes	0

Wildfire smoke contains PM2.5, carbon monoxide, and volatile organic compounds. Even short-term exposure can trigger asthma attacks and respiratory distress.

Indoor Mold Risk

Markham has an average mold risk score of 65 out of 100, with 1 ZIP codes in the high-risk category.

Factor	Value
Mold risk score	65/100
Average humidity	68% RH
High-risk ZIPs	1
Peak season	summer high

Mold risk is influenced by humidity levels, housing age (older homes have more moisture issues), flood history, and water infrastructure quality. Indoor humidity above 60% creates favorable conditions for mold growth.

Signs of mold problems: musty odors, visible growth on walls or ceilings, worsening allergies indoors, condensation on windows. Professional mold testing ($300-$600) can identify hidden issues.

Health Recommendations

With moderate air quality (AQI 62), most people can be active outdoors. Sensitive groups should take precautions:

• Sensitive groups (asthma, COPD, heart disease): consider reducing prolonged outdoor exertion
• Keep windows closed on high-pollution days
• Use a HEPA air purifier in main living areas
• Check AirNow.gov before outdoor exercise

Markham vs. Nearby Illinois Cities

How Markham's air quality compares to nearby cities:

ZIP Codes in Markham

Markham covers 1 ZIP code. Air quality can vary by neighborhood based on proximity to highways, industrial areas, and green spaces. Check your specific ZIP code for localized data.

Data Sources

• Air quality: EPA AirNow — real-time and historical AQI data
• Wildfire risk: FEMA National Risk Index
• Mold risk: Derived from EPA, FEMA, Census ACS (humidity, housing age, flood history)
• Monthly AQI: EPA Air Quality Statistics

Updated daily.