Data about trash collected by more than 6,500 volunteers at San Diego County beach cleanups in 2016 revealed that 80 percent of all trash contained plastic.
Cigarettes containing plastic foam filters were one of the most common types of trash found in the sand, according to the San Diego Coastkeeper and Surfrider Foundation in the San Diego County Chapter.
Thirty-two percent of all trash removed consisted of cigarette butts.
The plastic foam filters are full of toxins, creating an alarming pollution threat to San Diego's waters, said officials from the organizations.
Officials say the cigarettes leach a number of toxins such as arsenic, formaldehyde and heavy metals that could be particularly harmful to San Diego's marine ecosystems.
"Much of the trash we find on the beach is first littered miles away from the coast. It reaches the beach when wind and rain blow trash into our canyons, creeks and storm drains," says Kristin Kuhn, San Diego Coastkeeper Programs Director, in a statement.
"Small, lightweight plastics are particularly dangerous because they move easily to the coast, are hard to remove and look like food to aquatic and marine life," said Director Kuhn.
La Jolla Shores wins the title of cleanest beach in San Diego County in 2016.
Volunteers picked up nearly 188,000 pieces of trash last year alone, through the two organizations in San Diego. As they collected litter, they tracked the amount, type and weight of the trash.
The purpose was to allow for end-of-year analysis, according to the organizations.
The beach volunteers also picked up more than 4,300 plastic bags during 2016. This shows a continuing trend of slight decreases in the number of bags found at the beaches each year.