What if figuring out if the air you're breathing is clean was as simple as taking a stroll in your garden? Scientists at the National Center for Atmospheric Research in Boulder, Colorado, have created what they call the 'Ozone Garden'. It's composed of plants that react visibly when ozone pollution gets high, warning you that the air you're breathing might be making you sick.
The photo above shows the leaf of a Tulip poplar, and you can see the dark spots that indicate high levels of ozone.
There are four types of plants in the Ozone Garden, with each having been selected for its sensitivity to ozone pollution: green shoots of milkweed, snap bean, potato and cutleaf coneflower. While the U.S. EPA has set ozone expure limits to 75 parts per billion, sensitive plants like those in the garden can show signs of damage from exposure as low as 40 parts per billion. "It's kind of like the canary in the coal mine," said Danica Lombardozzi, a postdoctoral researcher at NCAR and one of the garden's creators.
Of course the effect on the plants isn't instant, and a single day of pollution probably isn't enough to 'sound the alarm', so to speak. But over time, damage starts to become visible. It's the same for us; damage from air pollution is cumulative, so exposure through time matters too, not just exposure intensity.
Knowing is good, but cleaning up the air is the next logical step. Here are the best air-filtering plants according to NASA.
While NASA research has shown that air quality has been improving in most areas of the U.S., it doesn't mean that the exact spot where you live isn't polluted.
And on a global basis, urban air is getting so dirty that 7 out of 8 people who live in cities are breathing air that doesn't mean safe levels, according to the World Health Organization.
So it's not surprising that air pollution kills more people worldwide than AIDS and malaria combined, making it the biggest environmental health risk.
We can make things better by not burning so much fossil fuels, and making the vehicles and power plants that do burn them cleaner, but nature also provides us with tools, like the ozone garden. Trees are also great at cleaning the air; a study showed that tree leaves can capture 50%+ of particulate matter pollution.