Hordes of biodegradable beads such as these could protect corals from chemicals found in sunscreen
Researchers are working on designs to help sop up pollutants.
Microbeads have a pretty bad rap. The plastic ones we're used to hearing about look like tiny specks, but have added up to a lot of pollution in our lakes and oceans. These plastic microbeads have been banned from rinse-off toiletries like face wash in the United States, United Kingdom, and several other countries.
Yet microbeads don't have to be bad for the environment. Scientists are coming up with tiny beads made from materials naturally found in plants, algae, and shellfish. Some of these biodegradable microbeads could be used instead of plastic ones in personal care products. Others could absorb pollution, and even mop up a chemical in sunscreen that's deadly to corals from water along beaches and near reefs.
But just how bad are regular old microbeads? Traditional plastic ones are particles smaller than 0.2 inches long used to give texture and scouring power to exfoliating facial scrubs, body washes, toothpaste, makeup, deodorant, industrial cleaning products and more. They're commonly made from plastics like polyethylene—the same stuff as plastic bags—that don't break down in the environment. Many are tinier than a pinhead, allowing them to slip through filters at wastewater treatment plants after we wash them down the drain. In 2015, scientists estimated that the United States released enough of these beads into waterways daily to cover 300 tennis courts. The remaining 99 percent was captured in sewage sludge, which is often used as fertilizer—meaning that those microbeads could still wind up in our rivers and seas in runoff from storms and irrigation.
There, they are eaten by fish larvae and other tiny animals. Microbeads tend to absorb other pollutants that are harmful to people, raising concerns that they could build up in fish that feast on these smaller creatures and eventually be ingested by people.
Although many manufacturers have taken microbeads out of their cosmetics, there isn't always a great alternative, says Janet Scott, a chemist at the University of Bath in England. So she and her team set out to create biodegradable microbeads. Her beads are made of cellulose, the fibrous material that lends structure to plants.
At the time, Scott and her colleagues had been investigating using cellulose in circuit boards to make electronics more recyclable. “We…realized that we could easily shape [it] into small beads as well,” says Scott, who described the technique in the journal ACS Sustainable Chemistry & Engineering. To make the beads, she and her colleagues dissolve cellulose and force the solution through tiny pores in a glass membrane. They then add ethanol to help the droplets solidify.
Scott has been testing body washes laced with cellulose beads of different sizes. “They feel quite nice,” she says. By adding slightly larger beads, she can give the gels a bit of roughness, like you'd expect from an exfoliating scrub. “If they're very, very small it just feels smooth and creamy to touch,” Scott says. These beads could be a good substitute for the tiny microbeads that are used to give lotions and other cosmetics their soft, spreadable texture.
Scott and her team are investigating how the beads interact with the ingredients in the washes, creams, and other products they'd be used in. They're also testing them along with cellulose fibers to replace some of the ingredients used to make shampoos creamy. “If it's too thin and too runny, it just pours off your hand and you can't get it onto your head before it all runs down the drain,” Scott says. Currently, shampoos avert this fate by using detergents that unfortunately aren't biodegradable.
Ideally, the beads will break down once they reach wastewater treatment plants, which are filled with microbes that can degrade cellulose into simpler sugars. The cellulose itself would come from the raw plant pulp used by the paper industry.
“We're actually using less and less paper,” Scott says. “If you made lots of microbeads this way, they wouldn't have to cut down more trees and make more paper pulp; they would be able to sell some of the pulp that they're no longer able to sell to make paper.”
Scott also has another purpose in mind for the cellulose beads that has nothing to do with toiletries. Regular plastic microbeads are sometimes used to blast the paint off of airplanes before they are given a fresh coat. Microbeads are well suited to this job because they're spherical and softer than sand, making them less likely to damage the plane's metal body. The cellulose beads will likely be firm enough to scour paint off of planes too, Scott says, although she hasn't put them to the test yet.
Scott's microbeads are useful because of their texture—they can change the feel of cosmetics, scrub our faces clean of dead skin cells, and scour airplanes clean of paint. For other beads, it's all about absorbency. Scientists in Puerto Rico are developing biodegradable beads that will soak up an ingredient found in many sunscreens called oxybenzone.
This chemical blocks UV rays, but when it comes into contact with corals it damages their DNA and can leave them more vulnerable to bleaching. And it's dangerous at very low concentrations. Just a single drop of oxybenzone in a half dozen Olympic-size swimming pools worth of water can harm reefs.
The moment you step into the ocean, the oxybenzone you've slathered on your skin begins to seep into the waters around you. It doesn't take long for it to build up to dangerous levels, the researchers reported last summer at the American Chemical Society national meeting. They collected samples of water after one of the team put on sunscreen and took a swim near the beach. After just 10 minutes, the concentration of oxybenzone in the water they collected had reached 1.3 parts per million—around 13,000 times greater than the threshold that can damage reefs.
By 2020, over 1 billion people around the world will be visiting oceans for recreation and tourism, says Felix Román, an analytical environmental chemist at the University of Puerto Rico at Mayaguez and one of the researchers behind the experiment. “We're talking about lots of sunscreen that is going to be dumped into the ocean.”
The absorbent beads he and his team have created are a bit bigger than poppy seeds and made from materials derived from algae and chitin, which is found in the hard outer parts of the shells of lobsters and other crustaceans. Inside this gelatinous mix is a magnetic core made of iron oxide covered in a material called sodium oleate that makes the beads more absorbent.
“We can remove it using magnets or we can just have a net that we drag up and down the shore…after people have finished their day in the ocean,” Román says. One potential pitfall is that fish seem to like to snack on the beads, as Román and his team discovered while testing how long they would float in the ocean. So it might be best to contain the beads in a net or bag of some sort, much like tealeaves are sealed in a teabag.
The team found that the beads sink after about four hours. By drifting down to the seafloor, the beads could have a chance to collect sunscreen from the water right around the corals before they are retrieved, Román says.
He's also added these beads to water samples polluted with oxybenzone at a concentration of 30 parts per million. Within one hour, the beads had removed 95 percent of the contamination.
The team is planning to test the beads out by swimming in a saltwater pool and then seeing how long it takes the beads to sponge up the sunscreen left behind. They're also measuring precisely how absorbent the beads are, and hope to see how they compare with activated charcoal (which doctors sometimes use to soak up poisons people have swallowed before they can be absorbed from the gut).
These beads represent the first time that researchers have tried to protect coral reefs by removing oxybenzone from the water around them, Román says. So far, it seems like the beads can remove concentrations of oxybenzone 1,000 times higher than those that have been measured in the waters around coral reefs in the U.S. Virgin Islands.
It might also be possible to take advantage of the magnetic beads to clean up oil spills, says Victor Fernandez, another member of the team. They're testing similar beads to mop up arsenic and industrial dyes from wastewater treatment plants. In humans and other animals, some of these dyes can interfere with hormone levels or be turned into cancer-causing substances in the body. So Román says making sure dyes are completely removed from wastewater is important.
Any given clothes factory or paper mill will use a bunch of different dyes, so the scientists wanted to make sure the beads could absorb multiple dyes at once. They recently reported in the International Journal of Environmental Research that the beads can pull both a common blue and a red dye from water at the same time. Some of the dyes carry an electric charge, so the beads could be designed to have the opposite charge to attract the colorants even more powerfully.
In future, Román hopes to refine the beads that absorb sunscreen so they can be sold commercially to hotels and other organizations in charge of beaches. It's going to be awhile before they are reading to start saving corals, though. The same goes for Scott's cellulose microbeads. In the meantime, you can help by using sunscreens that don't contain oxybenzone if you're planning to spend time near coral reefs. You can also try to avoid cosmetics that contain plastic microbeads, since the bans typically don't extend to products meant to be left in place instead of washed off immediately, such as lipsticks or deodorants.