Patient: Marcus
Marcus is a 6-year-old male, who is accompanied by his mother. He presents with a worsening cough, wheezing, and shortness of breath. He has a history of asthma that was previously well controlled on his inhaler therapy.
You recall that the AQI is 145. What do you do for Marcus?
Please think about this case as you work through the module. We will be coming back to Marcus’s story later.
Understanding the Air Quality Index (AQI)
The Air Quality Index (AQI) is a standardized 0–500 scale used by the EPA to translate pollutant concentrations into a single number that communicates health risk to the public.
It tracks six pollutants—ground-level ozone, PM2.5, PM10, carbon monoxide, sulfur dioxide, and nitrogen dioxide—and reports the worst one on any given day. A higher number means dirtier air and greater health concern.
Think of it like a vital sign for outdoor air: As SpOâ‚‚ (oxygen saturation) below 95% flags hypoxia. AQI above 100 flags a population-level exposure risk that warrants clinical attention.
Unhealthy for sensitive groups
At orange, air quality is acceptable for most healthy adults, but people with respiratory or cardiovascular disease, children, the elderly, and active outdoor workers are at real risk of symptom exacerbation.
Two pollutants to remember
PM2.5 and Ozone. Together these two pollutants account for the vast majority of AQI alerts that affect your patients. When AQI is elevated, one of these two is almost always the culprit.
Global air quality context
Key statistics
- In 2021, air pollution contributed to 8.1 million deaths globally (about 1 in 8 deaths).
- Air pollution is described as the second leading risk factor for early death worldwide (behind high blood pressure). It outranks tobacco use as a leading cause of death and disability.
- Globally, nearly all people breathe air exceeding the World Health Organization guideline limits (99% is widely cited by WHO).
- The World Bank estimates that $8.1 trillion is spent in annual global economic costs (accounting for healthcare, lost productivity, and premature deaths).
These numbers represent a worsening trend, not improvement. While tobacco deaths are declining due to cessation programs, air pollution deaths are rising due to industrialization, climate change, and population growth in high-pollution areas.
Global data shows a worsening crisis
- PM2.5 concentrations have increased in many regions despite regulations in high-income countries.
- Strong correlation between temperature increases and air quality degradation (climate change amplification).
- Low- and middle-income countries face disproportionate and worsening burden.