Air pollution

Lawmakers convene at the Oregon Senate after the minority Republicans ended a walkout they had begun on June 20 over a carbon-emissions bill they said would harm their rural constituents, at the Oregon Senate in Salem, Ore., Saturday, June 29, 2019. Nine of the 12 minority Republicans returned after Senate President Peter Courtney said the majority Democrats lacked the votes to pass the legislation aimed at countering climate change. ( AP Photo/Andrew Selsky)

Democratic presidential candidate former vice president Joe Biden, speaks during the Democratic primary debate hosted by NBC News at the Adrienne Arsht Center for the Performing Arts, Thursday, June 27, 2019, in Miami. (AP Photo/Wilfredo Lee)

A man stands as convoy of trucks and tractors circle the Oregon state Capitol on Thursday, June 27, 2019 in Salem, Ore. Protesters are supporting the eleven Republican senators who walked out over a week ago to avoid a vote on climate legislation. (Michaela Roman/Statesman-Journal via AP)

Protesters flood the steps of the Oregon State Capitol Tuesday, June 25, 2019, to push back against a Republican walkout over a climate change bill that has entered its sixth day in Salem, Ore. The president of the Oregon Senate said Tuesday there weren't enough votes in his majority Democratic caucus to approve a landmark climate bill that has sparked a walkout by Republicans and left other key issues such as the state budget in limbo. (AP Photo/Sarah Zimmerman)

FILE - In this Thursday, June 20, 2019, file photo, a TV reporter interviews self-employed logger Bridger Hasbrouck, of Dallas, Ore., outside the Oregon State House in Salem, Ore. The stark divide in Oregon between the state's liberal, urban population centers and its conservative and economically depressed rural areas makes it fertile ground for the partisan crisis currently unfolding there. Rural voters worry the cap-and-trade bill would be the end for logging and trucking. "It's going to ruin so many lives, it's going to put so many people out of work," said Bridger Hasbrouck, a self-employed logger from Dallas, Ore. (AP Photo/Gillian Flaccus, File)

A man enjoys the sunrise on the Drachenberg over Berlin, Germany, Wednesday, June 26, 2019. Temperatures of up to 38 degrees are expected in the German capital. (Kay Nietfeld/dpa via AP)

Children cool off in the fountain of the Trocadero, in Paris, Tuesday, June 25, 2019. More than half of France, including around Paris, was placed on an orange alert for intense heat Monday _ the second-highest level on the scale _ as very hot temperatures were predicted across continental Europe this week. (AP Photo/Thibault Camus)

Protesters flood the steps of the Oregon State Capitol Tuesday, June 25, 2019, to push back against a Republican walkout over a climate change bill that has entered its sixth day in Salem, Ore. The president of the Oregon Senate said Tuesday there weren't enough votes in his majority Democratic caucus to approve a landmark climate bill that has sparked a walkout by Republicans and left other key issues such as the state budget in limbo. (AP Photo/Sarah Zimmerman)

FILE- In this Sept. 30, 2015 file photo, Louis Fernandez walks along a flooded street in Miami Beach, Fla. The street flooding was in part caused by high tides due to the lunar cycle, according to the National Weather Service. When Democratic presidential candidates meet in Miami for their first debate it'll be in what you could call the country's Ground Zero for any climate-related sea level rise. (AP Photo/Lynne Sladky, File)