Tens of thousands of small blue and white pieces of plastic have littered the length of Kailua Beach, but one expert says it’s likely not from the Japanese tsunami.

The pieces are spread thin, but are extensive.

Chris Woolaway of the “Get the Drift and Bag It” campaign says the debris could be from household items or fishing floats.

It could also be from the Great Pacific Garbage Patch, a notorious vortex of flotsam about halfway between Hawaii and California, she said.

But it takes years for debris to break down into pieces as small as those found on Kailua Beach, she said, so they are not likely from the March 2011 Japanese tsunami.

Marine plastic is a chronic problem for Hawaii and elsewhere, said Woolaway, Hawaii coordinator for the International Coastal Cleanup initiative.

Deborah Ward, spokeswoman for the state Department of Land and Natural Resources, said it may be impossible to identify the source of the Kailua Beach plastic. 

“There is a lot of marine debris in our waters that is locally generated or may come from other sources in the Pacific,” she said by email Saturday.