LONDON (NYTIMES) - The River Thames, the tidal artery that squiggles through central London, holds up a mirror to life on dry land: scraggly remains of fir trees float by after Christmas; in the first days of a fresh year, bobbing Champagne bottles hint at recent revelry.

Ms Lara Maiklem, author of "Mudlark: In Search of London's Past Along the River Thames", scours the shoreline for items such as coins, tokens, buckles and potsherds, some dating to the period of Roman rule.

Loosed from pockets or heaped as infill, these are the flotsam of centuries lived on London's streets.

"I find stuff because humans are litterbugs," Ms Maiklem said. "We've always been chucking things into the river."

But lately, Ms Maiklem is encountering a type of garbage she had not seen there before: the remnants of Covid 19-era personal protective equipment (or PPE), particularly masks and plastic gloves bloated with sand and resting in the rubbly silt.

Ms Maiklem once counted around 20 gloves while canvassing 100 yards (91m) of shoreline. She was not surprised; if anything, she had feared the shore would be even more inundated with pieces that had flown from pockets or trash cans or swirled into the Victorian sewers.

Happily, Ms Maiklem said, the carpet of Covid-inspired rubbish at the edge of the Thames was not nearly as plush as it is elsewhere.

PPE litter is fouling landscapes across the globe. Dirtied masks and gloves tumbleweed across city parks, streets and shores in Lima, Peru; Toronto; Hong Kong and beyond.

Researchers in Nanjing, China, and La Jolla, California, recently calculated that 193 countries have generated more than 8 million tonnes of pandemic-related plastic waste, and the advocacy group OceansAsia estimated that as many as 1.5 billion face masks could wind up in the marine environment in a single year.

Since January, volunteers with the Ocean Conservancy's International Coastal Cleanup have plucked 109,507 pieces of PPE from the world's watery margins.

Now, across the litter-strewn planet, scientists, officials, companies and environmentalists are attempting to tally and repurpose PPE - and limit the rubbish in the first place.

Marine scientist Todd Clardy sometimes counts the PPE he sees on the 10-minute walk from his apartment in Koreatown in Los Angeles to the metro station. One day this month, he said, he spotted "24 discarded masks, two rubber gloves and loads of hand sanitation towelettes".

Sometimes, he sees them atop grates that read: "No Dumping, Drains to Ocean."

Dr Clardy suspects that some masks simply slip from wrists. "Once it falls on the ground, people probably look at it like, 'Huh, I'm not wearing that again'."

Breezes likely free some from rubbish bins, too. "The bins are always full," Dr Clardy added. "So even if you wanted to put it on top, it would fly away."

His accounts are not part of a formal project, but there are several such undertakings underway.

In the Netherlands, Leiden University biologist Liselotte Rambonnet and Naturalis Biodiversity Centre biologist Auke-Florian Hiemstra keep a running count of masks and gloves littering streets and canals. They track animals' interactions with the castoff gear.

Among their documented examples are an unfortunate perch trapped in the thumb of a phlegmy-looking latex glove, and birds weaving PPE into nesting materials, risking entanglement.

"Nowadays, it would be difficult to find a coot nest in the canals of Amsterdam without a face mask," Ms Rambonnet and Mr Hiemstra wrote in an e-mail.

The researchers maintain a global website, Covidlitter.com, where anyone can report animal and PPE incidents. Dispatches include sightings of a brown fur seal tangled in a face mask in Namibia; a mask-snarled puffin found dead on an Irish beach; and a sea turtle in Australia with a mask in its stomach.

Back home, the researchers, who also lead canal cleanups in Leiden, worry that PPE waste will increase now that the Dutch government has reinstated mask requirements.

"Every weekend we encounter face masks - new ones and old, discoloured ones," Ms Rambonnet and Mr Hiemstra wrote. "Some are barely recognisable, and blend in with autumn leaves."

Cleanup efforts are also underway in London, where staff members and volunteers with the environmental group Thames21 count and collect rubbish from the river's banks. In September, the group closely surveyed more than 1km of shoreline and found PPE at 70 per cent of their study sites - and notably clustered along a portion of the Isle of Dogs, where 30 pieces pocked a 100m stretch.

"I don't remember seeing any face masks until the pandemic; they weren't on our radar," said Ms Debbie Leach, the group's chief executive, who has been involved since 2005.

Ms Leach's team sends the PPE to incinerators or landfills, but small bits are still left behind because the rubbish "releases plastics into the water that can't be retrieved", she said.

Researchers in Canada recently estimated that a single surgical-style mask on a sandy shoreline could unleash more than 16 million microplastics, far too small to collect and haul away.

Roaming sandy swaths along Chile's coast, Dr Martin Thiel, a marine biologist at the Universidad Católica del Norte in Coquimbo, saw plenty of signs asking visitors to mask up - but few instructions about ditching used coverings. To his frustration, masks were scattered, swollen with sand and water and tangled in algae.

"They act a little like Velcro," he said. "They very quickly accumulate stuff."

But a few beaches, including one in Coquimbo, had rubbish bins designated specifically for PPE. Unlike oil-drum-style alternatives nearby, some had triangular tops with tiny, circular openings that would deter rummaging and prevent wind from tousling the garbage.

In a paper published in Science of the Total Environment this year, Dr Thiel and 11 collaborators recommended that communities install more purpose-built receptacles, as well as signs reminding people to consider the landscape and their neighbours - human and otherwise.

"We think there is more to the story than, 'just protect yourself'," said Dr Thiel, the paper's lead author.

In South Africa, shoppers grabbed fistfuls of wet wipes as they entered stores, draping the cloths over shopping cart handles while roaming aisles, said Ms Annette Devenish, marketing manager at Sani-touch, a brand that supplies many national Shoprite Group supermarkets with wipes for customer use. Sani-touch found that usage soared 500 per cent early on and has fallen, but still hovers above pre-pandemic figures.

Environmentalists often rail on wet wipes, many of which snarl sewer systems when they are flushed down drains and degrade into microplastics that drift through food webs.

Ms Devenish said that manufacturers ought to focus on making them recyclable or compostable, and Sani-touch had launched a project to give used wipes a second life. Customers can drop off wipes before leaving the store, and recycling companies will turn the polypropylene wipes into plastic pallets for use in Sani-touch's manufacturing facilities.

Fashioned from many materials, including metal and elastic, single-use masks can be harder to recycle, Ms Devenish said, but she hopes that they can be stuffed into plastic bottles to become "ecobricks" - low-cost building blocks of benches, tables, trash bins and more.

Preventing PPE from polluting urban environments will be a boon to the spaces where residents have sought solace.

"In stressful times, people seek out these places, but they've been pretty bad about taking rubbish and trash away with them," said Ms Leach of Thames21.

"Masks blow hither and thither," she said, and finally come to rest when they hit a patch of water, grass or sidewalk, where they, too, often remain.