University of Puget Sound chemist Dan Burgard keeps a freezer full of archived samples from two wastewater treatment plants in western Washington in case he needs to rerun the samples or analyze a specific drug he didn't test for the first time. Dan Burgard hide caption
Melodie Beckham (left), here with her daughter, Laura, had metastatic lung cancer and chose to stop taking medical marijuana after it failed to relieve her symptoms. She died a few weeks after this photo was taken. Melissa Bailey/Kaiser Health News hide caption
Researchers looked at states with medical marijuana dispensaries and those that allow home cultivation. Evelyn Hockstein/The Washington Post/Getty Images hide caption
Scientists are finding that, just as with secondhand smoke from tobacco, inhaling secondhand smoke from marijuana can make it harder for arteries to expand to allow a healthy flow of blood. Maren Caruso/Getty Images hide caption
Seattle City Attorney Pete Holmes (left) looks as Mayor Jenny Durkan (right) announces on Thursday the city's intention to vacate misdemeanor marijuana possession convictions. Elaine Thompson/AP hide caption
Marijuana plants are grown for medicinal purposes in a clandestine greenhouse in Mexico City in 2015. Mexico legalized medical marijuana in 2017, but recreational pot remains largely illegal. Yuri Cortez/AFP/Getty Images hide caption
When Jenna Sauter's youngest son, Axel, tested positive for THC — marijuana's active ingredient — after he was born, she got a home visit from local social services. Sauter says she and her friends don't smoke near their children. Sarah Varney/Kaiser Health News hide caption
One 8.5-oz. serving of THC-laced beverage (left) alongside three ounces of dried marijuana (right). Miles Bryan/Wyoming Public Media hide caption
Sheriff's deputies in York County, Neb., arrested an elderly California couple who had approximately 60 pounds of marijuana in their vehicle. York County Sheriff's Department hide caption
Teens' use of vape devices is increasing, and they're not always aware if nicotine is in the mix. Jane Khomi/Getty Images hide caption
Chalfonte LeNee Queen of San Diego grappled with violent vomiting episodes for 17 years until she found out her illness was related to her marijuana use. Pauline Bartolone/California Healthline hide caption
Kids who saw an ad for legal marijuana were more likely to report smoking it one year later, according to a Rand Corp. report. Tomas Rodriguez/Getty Images hide caption
In every group the researchers studied, the more marijuana people smoked the more sex they reported having. Katarina Sundelin/PhotoAlto/Getty Images hide caption
