# U.S. Cities Have the Worst Air Quality in the World How to stay safe from wildfire smoke - **Source:** [Scientific American Content: Global](https://brifing.si/source/4f066134-e06d-4415-87ef-305e3dc2aba6) - **Published:** 2026-07-17 - **Topic:** [Business](https://brifing.si/c/business) - **Original article:** - **On Brifing:** https://brifing.si/s/8e31bfac-74e1-4d30-bcee-a09b40b6aa1d ## Air Pollution Crisis Wildfires in Canada are sending dense smoke to the Midwest and Atlantic coast of the U.S. Cities like Chicago, Detroit, and Washington, D.C., rank among the worst in air quality globally. ## Health Impacts Wildfire smoke may be 10 times more dangerous than other air pollutants. A 2021 study linked this smoke to increased respiratory illnesses. ## Death Rates Between 2006 and 2020, wildfire smoke caused over 24,000 deaths annually in the U.S. Research shows there is no safe exposure threshold. ## Ozone and Smog Wildfire smoke reacts with sunlight and urban pollutants to produce ozone, which contributes to smog formation and increases mortality rates. ## Mental Health Effects Wildfire smoke can elevate stress and depression rates. Children are particularly vulnerable to its adverse effects. ## Protection Measures The EPA recommends keeping doors and windows closed and using air filters indoors. Wearing N95 masks and avoiding outdoor exercise are also crucial precautions. ## Sources covering this story - https://www.scientificamerican.com/article/u-s-cities-have-the-worst-air-quality-in-the-world-right-now-heres-how-to-stay-safe/ — --- _Summary written by Brifing from the original reporting. Copyright in the original article belongs to its publisher; read the full piece at the link above._