Environment

President Donald Trump and Robert O'Brien, just named as the new national security adviser, board Air Force One at Los Angeles International Airport, Wednesday, Sept. 18, 2019, in Los Angeles. (AP Photo/Evan Vucci)

This Feb. 14, 2019, photo released by Caltrans District 3 shows a 7-mile back up on the South bound Interstate 5, as it reopens to traffic in Maxwell in Colusa County, Calif. The Trump administration is poised revoke California’s authority to set auto mileage standards, asserting that only the federal government has the power to regulate greenhouse gas emissions and fuel economy. (Caltrans District 3 via AP)

This Feb. 14, 2019, photo released by Caltrans District 3 shows a 7-mile back up on the South bound Interstate 5, as it reopens to traffic in Maxwell in Colusa County, Calif. The Trump administration is poised revoke California’s authority to set auto mileage standards, asserting that only the federal government has the power to regulate greenhouse gas emissions and fuel economy. (Caltrans District 3 via AP)

Democratic presidential candidate and South Bend, Indiana, Mayor Pete Buttigieg speaks Tuesday, Sept. 17, 2019, as organizer Alicia Garza, right, looks on during an event with Supermajority in Columbia, S.C. (AP Photo/Meg Kinnard)

FILE - In this July 8, 2019, file photo President Donald Trump listens as then-Secretary of the Interior David Bernhardt speaks during an event on the environment in the East Room of the White House in Washington. In less than three years, Trump has named more former lobbyists to Cabinet-level posts than his most recent predecessors did in eight, putting a substantial amount of oversight in the hands of people with ties to the industries they’re regulating. (AP Photo/Evan Vucci, File)

FILE - In this Aug. 7, 2018 file photo, a doctor performs an ultrasound scan on a pregnant woman at a hospital in Chicago. A new study released Tuesday, Sept. 17, 2019, suggests when a pregnant woman breathes in air pollution, it can travel beyond her lungs to the placenta that guards her fetus. During pregnancy, particle pollution is linked to premature births and low birth weight, but scientists don’t understand why. (AP Photo/Teresa Crawford, File)

Backhoes dig a pit to bury culled pigs at a farm in Paju, South Korea, Tuesday, Sept. 17, 2019. South Korea is culling thousands of pigs after confirming African swine fever at a farm near its border with North Korea, which had an outbreak in May. (AP Photo/Ahn Young-joon)

In this photo released by Indonesian Presidential Secretariat, Indonesian President Joko Widodo inspects a burnt forest in Pelalawan, Riau province, Indonesia, Tuesday, Sept. 17, 2019. Widodo traveled to the area hardest hit by forest fires, as neighboring countries urged his government to do more to tackle the blazes that have spread a thick, noxious haze around Southeast Asia. (Laily Rachev, Indonesian Presidential Secretariat via AP)

President Donald Trump arrives to speak at a campaign rally at the Santa Ana Star Center, Monday, Sept. 16, 2019, in Rio Rancho, N.M. (AP Photo/Evan Vucci)