(Photo: ... Smog in Beijing (April 23, 2012) | by Marc van der Chijs)
Do you want to live in a poisoned megacity on Planet Earth? Host
"...So Karen Cady-Pereira, a remote sensing scientist at Atmospheric and Environmental Research, an environmental consulting firm in Lexington, Massachusetts, decided to use a satellite to study air pollution above 18 of the world’s “megacities,” metropolitan areas with 10 million or more people. Since 2013, she and her team have measured levels of ammonia, formic acid, methanol, and ozone with an instrument called the Tropospheric Emission Spectrometer aboard NASA’s Aura satellite, which studies Earth’s atmosphere. Aura passes over each megacity every 16 days at approximately the same local time. That’s an important point, since air quality varies over the course of a day. Observations are also collected under the same atmospheric conditions, which means that data across cities can be accurately compared.
The team has found that Karachi, Pakistan, holds the world’s title for ozone. Of the nearly 300 measurements collected over 1 year, roughly a third exceeded what the researchers considered a “harmful” threshold for ozone, which can lead to smog. Ozone is high in other cities as well. But when it comes to ammonia, a gas that helps form airborne particles that can trigger lung disease, some cities stand out: Kolkata, India, exceeds the “harmful” threshold 47.1% of the time, Dhaka, Bangladesh, exceeds it 51.6% of the time, and Delhi exceeds it 73.5% of the time. Ammonia, which comes from livestock excrement and fertilizer, is more common in cities surrounded by lots of agricultural activity...."