Bison along the Bitterroot Valley's Eastside Highway north of Stevensville, Montana, are covered in snow following a blizzard on November 23, 2010. (Photo by Perry Backus/The Missoulian)

Sorana Cirstea of Romania hits the ball against Jie Zheng if China during the Sony Ericsson Open at Crandon Park Tennis Center on March 22, 2011 in Key Biscayne, Florida.

In this handout from the Food and Drug Administration (FDA), a new FDA warning label for a cigarette packs is seen. The FDA released nine new warning labels that will be required for cigarette packs in the U.S. (Photo by FDA via Getty Images)

Waxahachie firefighters battle a massive fire at the Magnablend chemical processing plant on October 3, 2011 in Waxahachie, Texas. The burning chemical plant is not far from several residential areas and Wedgeworth Elementary School. (Photo by Tom Pennington/Getty Images)

Actor and former California Governor Arnold Schwarzenegger (R) and his son Patrick Schwarzenegger (L) attend “Arnold Classic Europe” 2011 Party at “Jardines Cecilio Rodriguez” on October 7, 2011 in Madrid, Spain. (Photo by Carlos Alvarez/Getty Images)

Indian boy Hassan Malik works in a leather shoe factory at Topsia in Calcutta, eastern India, 19 November 2013. The leather industry occupies an important place in the Indian economy. It is an employment intensive sector with a vast potential for growth and exports but also a pollution intensive industry that relies on cheap labor. One of the major production centers for leather and leather products is located in Calcutta, West Bengal. Hundreds of tanneries are operated in the city’s Tiljala, Topsia and Tangra districts. They are mostly run by local families living and working under poor conditions. (Photo by Piyal Adhikary/EPA)

A worker manually changes the direction of the bonde, the typical tram line in Santa Teresa neighborhood, using a rope in Rio de Janeiro, Brazil, September 9, 2015. The Santa Teresa bonde, called “Bondinho” in Portuguese, is running with passengers as a part of a test period, after the service was suspended in 2011 following an accident that killed six people, according to residents. (Photo by Pilar Olivares/Reuters)

A sofa floats in the polluted waters of Jacarepagua Lagoon, during a press tour in Rio de Janeiro, March 9, 2015. A press tour was organised by biologist Mario Moscatelli, to call attention to pollution on the waters of the lagoons which surround the Rio 2016 Olympic Park. (Photo by Ricardo Moraes/Reuters)