Competing in the world's most grueling race to circumnavigate the globe was already the biggest challenge of Kojiro Shiraishi's sailing career.
But for the 53-year-old skipper, who this month became the first Asian sailor even to complete the Vandee Globe event, sailing through some of the most remote waters on Earth was the perfect opportunity for achieving another goal -- helping fight the increasing scourge of marine plastic pollution.
The four-time around-the-world solo sailor sacrificed some of his already limited hours of sleep at sea to deploy special equipment from his boat to help answer a key mystery -- just where the vast quantity of plastic waste, including microplastics, is lurking across the expanse of the world's seas.
Plastic items such as bottles and shopping bags are one of the most common types of trash from human activities on land to find their way into the oceans. Tiny bits of broken-down plastics, meanwhile, have accumulated in the world's waters in the form of microplastics, defined as less than 5 millimeters in diameter.
While public awareness of plastic pollution has grown over the years due to shocking images of marine life such as whales, turtles and fish as well as birds that have suffered or died as the result of swallowing indigestible plastic waste, mapping the spread of the debris, estimated to total as much as 45 million tons, has proved tough.
Shiraishi realized he had a unique chance to do his bit to help.
"I felt an urge to play my part toward unraveling the problem as one of the lucky few who have a chance to sail through remote waters such as the Arctic Ocean," said Shiraishi, who on Feb. 11 finished 16th in the field of 33 in the latest edition of the race, held every four years with boats setting off from France.
Over the 94 days and 21 hours he was at sea, a specially designed device capable of capturing plastics as small as a fraction of a millimeter, attached to a seawater filter for making drinking water, continued to capture dated samples aboard the 18-meter long DMG Mori Global One sailboat.
The data collected from around the world is "extremely valuable," said Katsunori Fujikura, an official at the Japan Agency for Marine-Earth Science and Technology.
Fujikura, who jumped on the chance to take up Shiraishi on his offer of help and prepared the equipment he took with him, will conduct a detailed analysis of the microplastics, which form when plastic items begin to be broken down by sunlight and are almost invisible on the water's surface.
Marine plastics threaten not only the health of marine life but humans, too, since they accumulate in predators like bigger fish that can often end up on dinner tables.
Fujikura said science has located only 1 percent of marine plastic waste, making it vital to establish effective methods to gather samples. He believes much of the so-called "missing plastics" is floating deep under the surface of the seas or stranded between currents.
Requesting similar cooperation to that provided by Shiraishi from commercial ships like cargo transporters could be one answer, said Fujikura, who is director of JAMSTEC's Marine Biodiversity and Environmental Assessment Research Center. He also noted that the marine adventurer's offer of help had provided him with an opportunity to look into developing suitable devices.
When Shiraishi was asked why he decided to wage a two-front battle when already facing his biggest sailing challenge, he recounted his increasingly frequent encounters with waste floating in remote seas, ranging from fishing nets to freight containers.
But it was his experience of seeing the cleanup of Tokyo Bay -- a body of water facing Japan's capital as well as other major cities such as Yokohama -- that helped make him feel the problem could be solved.
Growing up in the town of Kamakura on the southwest side of the bay, Shiraishi observed since he was a teenager the efforts by residents and local authorities to improve the waters, which were once full of chemical ooze and sludge from industrial waste.
The bay's waters are now once more a rich fishing ground whose catch can fetch high prices as ingredients for sushi and other dishes in and outside Tokyo.
Shiraishi said he and his team will continue to commit to the issue in partnership with JAMSTEC. "I'll be glad my humble effort can be of any help toward preserving, or better, improving the environment I owe so much to," he said.