More than 40,000 marathoners are preparing to compete on Sunday in the Indian capital New Delhi, where air pollution has reached dangerous levels. Images of the city this week show it blanketed in a thick yellow smog, some buildings barely visible through the haze. The air quality index, which ranks pollution on a scale of 0 to 500, reached 227 on Friday -- classed as "very unhealthy."
This score reflects the concentration of fine particle matter, known as PM2.5, per cubic meter. According to the World Health Organization, an acceptable air quality index score for humans to breathe regularly is 25.
Unsurprisingly, running in this environment can be dangerous. Microscopic pollutants like PM2.5, which are smaller than 2.5 micrometers in diameter, can enter deep into a person's lungs and bloodstream, increasing risk of respiratory problems, cancer, stroke and heart attack. Physical exercise can increase the amount of pollutants breathed in by up to five times.
This score reflects the concentration of fine particle matter, known as PM2.5, per cubic meter. According to the World Health Organization, an acceptable air quality index score for humans to breathe regularly is 25.
Unsurprisingly, running in this environment can be dangerous. Microscopic pollutants like PM2.5, which are smaller than 2.5 micrometers in diameter, can enter deep into a person's lungs and bloodstream, increasing risk of respiratory problems, cancer, stroke and heart attack. Physical exercise can increase the amount of pollutants breathed in by up to five times.
