Air pollution

FILE - In this file photo dated Saturday, Dec. 12, 2015, the sun sets behind smoke emitting from a coal powered power plant in the Bosnian town of Tuzla, 120 kms north of Sarajevo, Bosnia. In a report released Tuesday Junw 25, 2019, environment groups have called for urgent measures to combat air pollution in the central Bosnian town of Tuzla saying dust concentration far exceeds legal limits and causes premature deaths. (AP Photo/Amel Emric, FILE)

In this photo taken Sunday, June 23, 2019, a small crowd of local Republicans show their support of a Republican walkout outside the Oregon State Capitol in Salem, Ore. The gathering took place only a day after the Senate President ordered the statehouse to close over a "possible militia threat," the latest escalation in a Republican walkout over proposed climate policy that has put Democrats' top legislative priorities at risk. (AP Photo/Sarah Zimmerman)

FILE - This July 6, 2018, file photo shows boxes containing petitions in favor of a proposal to legalize casinos in Arkansas, delivered to the Arkansas secretary of state's office in Little Rock, Ark. Voters in several states dominated politically by Republicans have passed ballot initiatives in recent years to expand Medicaid, legalize marijuana, raise the minimum wage and reform the redistricting process. This has led several GOP legislatures and governors to begin cracking down on the initiative process in ways that will make it harder for the public to quality ballot measures. (AP Photo/Andrew Demillo, File)

A TV reporter interviews self-employed logger Bridger Hasbrouck, of Dallas, Ore., outside the Oregon State House in Salem, Ore., on Thursday, June 20, 2019, the day the Senate is scheduled to take up a bill that would create the nation's second cap-and-trade program to curb carbon emissions. Senate Republicans, however, pledged to walk out so there wouldn't be enough lawmakers present for a vote on House Bill 2020, which is extremely unpopular among loggers, truckers and many rural voters. (AP Photo/Gillian Flaccus)

A TV reporter interviews self-employed logger Bridger Hasbrouck, of Dallas, Ore., outside the Oregon State House in Salem, Ore., on Thursday, June 20, 2019, the day the Senate is scheduled to take up a bill that would create the nation's second cap-and-trade program to curb carbon emissions. Senate Republicans, however, pledged to walk out so there wouldn't be enough lawmakers present for a vote on House Bill 2020, which is extremely unpopular among loggers, truckers and many rural voters. (AP Photo/Gillian Flaccus)

FILE - In this July 27, 2018, file photo, the Dave Johnson coal-fired power plant is silhouetted against the morning sun in Glenrock, Wyo. The Trump administration announced on Wednesday, June 19, 2019, that it has rolled back a landmark Obama-era effort targeting coal-fired power plants and their climate-damaging pollution. (AP Photo/J. David Ake, File)

FILE - In this June 4, 2019, file photo, Kelsey Rose Juliana, of Eugene, Ore, speaks at a rally for a group of young people who filed an environmental lawsuit against the U.S. government in Portland, Ore. Oregon is on the precipice of becoming the second state after California to adopt a cap-and-trade program, a market-based approach to lowering the greenhouse gas emissions behind global warming. (AP Photo/Steve Dipaola, File)

In this photo taken on Thursday, June 13, 2019 sled dogs make their way in northwest Greenland with their paws in melted ice water. Diplomats and climate experts gathered Monday in Germany for U.N.-hosted talks on climate change amid growing public pressure for governments to act faster against global warming. Over the weekend, a picture taken by Danish climate researchers showing sled dogs on the ice in northwest Greenland with their paws in melted ice water was widely shared on social media. Greenland’s ice melting season normally runs from June to August but the Danish Meteorological Institute said this year's melting started on April 30, the second-earliest time on record going back to 1980. (Danmarks Meteorologiske Institut/Steffen M. Olsen via AP)

FILE - In this March 29, 2013, file photo, a worker helps monitor water pumping pressure and temperature, at an oil and natural gas extraction site, outside Rifle, on the Western Slope of Colorado. A Trump administration national security official has sought help from advisers to a think tank that disavows climate change to challenge widely accepted scientific findings on global warming, according to his emails. (AP Photo/Brennan Linsley, File)