Science

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)

FILE - In this March 12, 2010 file photo Mercedes Grand Prix driver Michael Schumacher of Germany is pictured in the pits during the first practice session at the Formula One Bahrain International Circuit in Sakhir, Bahrain. A Paris newspaper says seven-time Formula One world champion Michael Schumacher is being treated with a cutting-edge stem-cell therapy in one of the French capital's hospitals. (AP Photo/Ben Curtis, File)

This Saturday, Sept. 7, 2019 photo shows items in a vending machine in New York. Americans are addicted to snacks, and food experts are paying closer attention to what that might mean for health and obesity. (AP Photo/Patrick Sison)

A row of hearts, each with the name of a victim, adorn a growing memorial to those who died aboard the dive boat Conception, seen early Friday morning, Sept. 6, 2019 at the harbor in Santa Barbara, Calif. The Sept. 2 fire took the lives of 34 people on the ship off Santa Cruz Island off the Southern California coast near Santa Barbara (AP Photo/Stefanie Dazio)

File - In this Sept. 14, 2017, file photo, salmon circle just below the surface inside a lock where they joined boats heading from salt water Shilshole Bay into fresh water Salmon Bay at the Ballard Locks in Seattle. Federal scientists say they're monitoring a new ocean heat wave off the West Coast. Researchers with the National Oceanic and Atmospheric Administration said Thursday, Sept. 5, 2019, the expanse of unusually warm water stretches from Alaska to California, and it resembles a similar heatwave that disrupted marine life five years ago. It remains to be seen whether this heat wave will linger or dissipate more quickly than the last one. (AP Photo/Elaine Thompson, File)

FBI investigators unload equipment to begin examining evidence obtained from the wreckage of the dive boat Conception on Wednesday, Sept. 4, 2019, in Santa Barbara, Calif. A fire raged through the boat carrying recreational scuba divers anchored near an island off the Southern California Coast on Monday, Sept. 2, leaving multiple people dead. (AP Photo/Christian Monterrosa)

A memorial for the victims of the Conception vessel is seen outside of the Sea Landing at Santa Barbara Harbor in Santa Barbara, Calif., Tuesday, Sept. 3, 2019. Officials say no one likely escaped the flames that tore through a boat packed with scuba divers and the search for survivors has been called off. (AP Photo/Christian Monterrosa)

Divers with the San Luis Obispo County Sheriff's Dive Team prepare to search for a second day for missing people following a dive boat fire off Southern California's coast that killed dozens sleeping below deck, in Santa Barbara, Calif., Tuesday, Sept. 3, 2019. (AP Photo by Christian Monterrosa )

This GOES-16, GeoColor satellite image taken Tuesday, Sept. 3, 2019, at 17:10 UTC and provided by National Oceanic and Atmospheric Administration (NOAA), shows Hurricane Dorian moving off the east coast of Florida in the Atlantic Ocean. (NOAA via AP)

FILE - In this Aug. 15, 2019, file photo, marijuana grows at an indoor cannabis farm in Gardena, Calif. Federal health officials are issuing a national warning against marijuana use by adolescents and pregnant women, as more states legalize some forms of the drug's use. (AP Photo/Richard Vogel, File)