Car after car passed through the Pearl City police station Saturday, with motorists handing over potentially dangerous expired, unused and unwanted prescription and illegal drugs — no questions asked.

The steady stream of traffic was part of the Drug Enforcement Administration’s National Prescription Drug Take Back Day, which provided an opportunity for local participants to assist various branches of law enforcement in preventing drug addiction, deaths from overdose and environmental harm, especially to Hawaii’s coastal waters.

At least 12 collection sites, including locations on Oahu, Maui, Kauai and Hawaii island, were open from 10 a.m. to 2 p.m. While the day’s take hasn’t been computed, overall the DEA has collected 8.1 million pounds or more than 4,050 tons of pills during its previous 13 events nationwide.

DEA launched the program after the Environmental Protection Agency and the Food and Drug Administration advised the public that flushing medicines down the toilet or throwing them in the trash was hazardous to human health and the environment.

Angela Kaiwikuamoohoihou, who was collecting drugs on behalf of the state Attorney General’s Office, said the state supports the endeavor because it sees the data “that shows prescription abuse and misuse is adversely affecting Hawaii.”

Kaiwikuamoohoihou said prescription drug deaths are now the No. 2 cause of fatalities in Hawaii, behind falls. She said accidental ingestion of prescription drugs is also the main reason children up to age 5 visit Hawaii emergency rooms.

“It’s better to be on top of your old medications and dispose of them properly. If you flush it down the toilet, it can clog pipes or get into the sewers. If you throw it away, people may find it dumpster diving. Or if it ends up in the landfill, it can get into the environment, too,” she said.

Kaiwikuamoohoihou said drugs collected as part of the event are taken to HPOWER, where they are destroyed and converted into energy.

Watson Okubo, former supervisor of the monitoring and analysis section of the Clean Water Branch, dropped off a large bag of unused prescriptions and said he hoped others would follow suit. Based on his experiences in monitoring water quality, he said “everybody should participate in the program.”

“We don’t normally talk about the drugs that are in our water and in our environment,” Okubo said. “They don’t smell bad, they don’t look bad like brown water or sewage spills, but they go right through the wastewater treatment process. The more drugs we can keep out of toilet bowls, cesspools and landfills, the better for Hawaii.”

Okubo said there already are signs that drugs have leached into Hawaii’s environment and caused damage.

“We don’t see the diversity of limu, and fish like nehu, aku, manini and mullet aren’t as plentiful as they once were,” he said. “When I retired, I thought I’d spend time diving. My friends tell me, ‘What you gon’ dive for? No more fish.’”