Much of the plastic we use ends up in the oceans and landfills as pollution, but there's a much less obvious form of pollution heading to the seas.

Those comfy, often-controversial yoga pants and other stretchy athletic wear and comfort clothes also are contributing to marine pollution. Clothes made out of synthetic fabrics can contain microplastic fibers — tiny shreds of plastic, according to the National Oceanic and Atmospheric Administration's Marine Debris Program. These fibers are discarded little by little each time the clothes are washed. A 2001 study found that on average more than 1,900 fibers can be shed by a synthetic clothing garment during just one trip through the washing machine. The fibers are flushed into wastewater systems and eventually make their way out into the ocean.

"This suggests that a large proportion of microplastic fibers found in the marine environment may be derived from sewage as a consequence of washing of clothes," the researchers wrote. "As the human population grows and people use more synthetic textiles, contamination of habitats and animals by microplastic is likely to increase."

Testing the waters

For the NOAA-funded Florida Microplastic Awareness Project (FMAP), citizen scientists collect coastal water samples, filter them and analyze them to check for microplastics. In the first year, 89 percent of the samples collected contained at least one piece of plastic, and 82 percent of the plastics found were microfibers.

University of Florida researcher Maia McGuire runs the project. She told the Associated Press that when she first started to study the types of plastic in Florida's water, she thought she would discover primarily microbeads, the tiny plastic specks found in personal care products like toothpaste and body wash that were banned by the U.S. government in 2015. Instead she found microfibers, like the kind found in fleece-type jackets, workout clothes or anything that has nylon or polyester on the tag.

Studies have shown the fibers can end up in the stomachs of marine animals, including some that wind up as seafood. The research has prompted some environmentalists to consider targeting microfibers (and washing machine manufacturers) as the new microbeads in an effort to lower the amount of plastic pollution in the oceans.

"It would be really great if the washing machine companies would get on board and come up with a filter to trap these microfibers," Caitlin Wessel, regional coordinator for NOAA's Marine Debris Program, told the AP. "I think there's a big push right now — nobody really disagrees that marine debris is an issue that needs to be addressed."

In the meantime, what can you do? Check your tags. Where possible, buy clothes with all-natural, non-synthetic materials. After all, cotton yoga pants can be comfy, too.

Mary Jo DiLonardo writes about everything from health to parenting — and anything that helps explain why her dog does what he does.