A Chinese man wears a mask to protect against pollution as he waits at a red light while commuting to work in heavy smog on December 8, 2015 in Beijing, China. The Beijing government issued a 'red alert' for the first time since new standards were introduced earlier this year as the city and many parts of northern China were shrouded in heavy pollution. Levels of PM 2.5, considered the most hazardous, crossed 400 units in Beijing, lower than last week, but still nearly 20 times the acceptable standard set by the World Health Organization. The governments of more than 190 countries are meeting in Paris to set targets on reducing carbon emissions in an attempt to forge a new global agreement on climate change. (Photo by Kevin Frayer/Getty Images)

A woman smokes marijuana during the annual 4/20 marijuana rally on Parliament Hill in Ottawa, Ontario, Canada, April 20, 2017. (Photo by Chris Wattie/Reuters)

A burning train wagon is seen after an explosion at Lac Megantic, Quebec, July 6, 2013. A large swath of Lac Megantic was destroyed Saturday after a train carrying crude oil derailed, sparking several explosions and forcing the evacuation of up to 1,000 people. (Photo by Mathieu Belanger/Reuters)

Isabel Schmalenbach, an environmental scientist with the Helgoland Biological Institute (Biologische Anstalt Helgoland), part of the Alfred Wegener Institute for Polar and Marine Research, holds a one-year old baby European lobster (Homarus gammarus) raised at the institute on August 3, 2013 on Helgoland Island, Germany. Later in the day Schmalenbach and her colleagues released a total of 415 one-year old lobsters into the North Sea as part of an effort to repopulate the lobster population around Helgoland (also called Heligoland). In the 19th century local fishermen caught up to 80,000 lobsters a year in the surrounding waters, combined with the heavy allied bombing of the island during and after World War II, as well as other environmental factors, decimated the lobster population. (Photo by Sean Gallup)

An mechanic in Brick Lane Bikes repairs a fixed wheel bike in their shop in Shoreditch on June 14, 2011 in London, England. The UK bike industry has seen a dramatic rise in the number of people building their own custom bikes or purchasing bespoke bikes. (Photo by Oli Scarff/Getty Images)

A woman carrying a basket of papayas while walking through a vegetable market in Bangkok, Thailand November 11, 2011. (Photo by Kerek Wongsa/Reuters)

An engineer (L) talks to a driver of a dump truck loaded with gold-bearing soil at the Vostochny opencast of the Olimpiada gold operation, owned by Polyus Gold International company, in Krasnoyarsk region, Eastern Siberia, Russia, June 30, 2015. Polyus Gold International is the largest gold producer in Russia and one of the top 10 gold miners globally by ounces produced, according to the official web site of the company. Olimpiada is Polyus Gold's largest operation. (Photo by Ilya Naymushin/Reuters)