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California is poised to issue the world’s first guidelines for microplastics in drinking water despite no data on how plentiful they are in the state, no scientific agreement on how to test water for them and little research on their health risks.
The pieces of plastic — smaller than an ant, some so tiny they can be seen only with a microscope — have contaminated wildlife and human bodies through their food, air and water.
Under a 2018 state law, California must require four years of testing for microplastics in drinking water, and the state must consider guidelines to help water providers and consumers determine what levels may be safe to drink.
Now the state Water Resources Control Board is blazing a trail to issue a preliminary health-based threshold and testing methods by July 1.
The state’s aim is to take a precautionary approach, moving to tackle potential threats posed by microplastics.
But there are big obstacles to such early action: Research into the consequences of ingesting tiny plastic fragments is still in its infancy. No one knows how widespread microplastics in California’s drinking water really are. There isn’t even a standardized method to test for them. And no one knows what dose may be “safe” to consume, since the human health effects are largely unknown.
California’s water regulators are pushing to close those gaps. “To be honest, if the legislature hadn’t given us such an aggressive deadline, with rather high goals, this might not happen this year,” said Scott Coffin, a research scientist with the State Water Resources Control Board. “It really is accelerating the field quite a bit.”
Theresa Slifko, chemistry unit manager at the Metropolitan Water District of Southern California, which provides imported water to 19 million Californians, warns that monitoring drinking water for microplastics is going to be “very complicated and time consuming, and that’s why it’s expensive.”
Developing a health guideline for microplastics is “a tough one,” said Razmik Manoukian, the Los Angeles Department of Water and Power’s director of water quality.“But there’s a lot of studies worldwide done on plastic exposures … so it could be they can come out with a preliminary number.”
Researchers applaud California’s efforts to move forward, even though they caution that drinking water is not thought to be the biggest source of microplastics people consume. People probably absorb more simply by breathing.
“We now know that we live in a soup of plastic that is getting ever denser. And we don’t seem to be changing our ways. And the contaminants, they live longer than we do, meaning that the soup will get thicker,” said Rolf Halden, director of the Biodesign Center for Environmental Health Engineering at Arizona State University.
“So is it too early to do something? No, it is actually a bit late.”
Awash in microplastics
Microplastics have contaminated the environment and the bodies of animals around the world: Ice cores in the Arctic, invertebrates in Antarctica, humpback whales in the North Sea, seals and seabirds in the Southern Ocean, fish and shellfish on six continents and even human placentas.
California banned microbeads in toiletries like facial scrubs and toothpaste five years ago. But sources of tiny plastic are still ubiquitous: Synthetic clothing sheds microplastics in wash cycles that discharge into sewers, fragments rub off car tires and ever-increasing plastic waste crumbles into tiny particles. All of these particles can wind up in waterways that provide drinking water, such as the massive, 444-mile long California Aqueduct.
Trillions of microplastic particles are floating on the surface of the world’s oceans, weighing at least 100,000 tons. And that doesn’t include the unknown quantities in freshwater rivers and lakes, or the particles that have sunk into the oceans, washed ashore or been consumed by marine life.
While from pole to pole there’s been widespread study of the environment to figure out where microplastics have wound up, there’s been less research into their possible effects on people.
No government has developed a health-based threshold for microplastics in drinking water, according to the water board’s Scott Coffin.
The health threshold won’t be an enforceable standard at this point; it’s unlikely to carry the weight of regulation. Instead, it will probably be a preliminary guideline to help water providers and consumers assess the levels in their water, and it is likely to change with more research, Coffin said.
“It will be the world’s first health-based guidance value of any sort for microplastics formally recommended by a working group or government agency,” he said. “This will carry a lot of authority, even if it is just a preliminary guidance level.”
California’s efforts took off when a constituent reached out to state Sen. Anthony Portantino, a Democrat from the La Cañada Flintridge area, warning that plastic fibers in drinking water may contain toxic chemicals.
Despite opposition from the Metropolitan Water District and other water providers, the Legislature passed Portantino’s bill in 2018 calling for standardized testing methods and four years of monitoring statewide. The law also urged the water board to consider recommending a health threshold by July 1 2021. Another law instructs the state’s Ocean Protection Council to develop a strategy for addressing microplastics in oceans.
The goal of the drinking water guideline is to help Californians understand the levels of microplastics detected in their water when the agencies start making the testing data public, which could happen as soon as next year.
“The question from the public (is), ‘Well, what does that (level) mean?’ It’s never a satisfactory answer to say, ‘Geez, I don’t know,’” said Mic Stewart, water quality section manager of the Metropolitan Water District. “We’ll need to look to the state for guidance on that.”
Now, an international team of researchers assembled by the water board and the Southern California Coastal Water Research Project, a public agency that has been studying waterway health since 1969, are scouring scientific literature for hints about the toxicity of microplastics.
Researchers have fed microplastics to rodents and reported changes to their immune systems and heart tissue. Mice that ate microplastics had lower sperm counts, and ones fed very high doses produced more abnormal sperm. Microplastics, which have turned up human stool, can pass through the intestinal lining of rats and cause gut inflammation in mice.
The challenge is extrapolating the findings in lab animals to potential effects in people.
The World Health Organization concluded in 2019 that there was too little evidence to understand the toxicity of microplastics, and “no reliable information suggests it is a concern through drinking-water exposure.”
Water providers who opposed California’s microplastics bill also said at the time that it was premature to set a guideline. “Without studying the effect exposure to microplastics has on the human body, there is no way to determine the impact of the varying levels of microplastics found in drinking water,” the California Municipal Utilities Association wrote in 2018.
But environmental health researchers in Europe pushed back against what they called this “‘no risk’ soundbite.” Two scientists wrote in the journal Environment International that “logic does not allow the current knowledge gap… to steer the bias towards a belief that ‘microplastics are safe.’”
“We can say with pretty high confidence that eating plastic and breathing in plastic is not beneficial,” said Susanne Brander, an environmental toxicologist at Oregon State University who is working with Coffin’s team.
“We’re pretty sure this is a problem. It’s just a matter of having enough data to say how much is too much.”
Since the World Health Organization’s report, the number of toxicity studies about microplastics has roughly doubled, Coffin said in a recent hearing.
“We’ll actually be able to say with some level of certainty whether or not this is an immediate issue for people’s health, or if it’s an issue that will arise down the road,” he said.
It’s the opposite approach to how drinking water is usually regulated. In most cases, state or federal water regulators know how much of a contaminant is in the water, and research has already linked it to health effects in humans.
Bart Koelmans, a professor of aquatic ecology and water quality at Wageningen University in the Netherlands, said that California’s approach is warranted as an early risk assessment of an emerging contaminant.
“It is not that people do this (assessment) when it can be done. It is done when an answer is needed,” said Koelmans, who has participated in California’s assessment of the health effects. “That makes us then take a more precautionary approach, to stay on the safe side.”
The hunt for microplastics
Even as the state works to develop drinking water limits on microplastics, state officials know nothing about how plentiful they are in California’s water supply because testing has not started yet.
“We have been studying these things since 1959. And we still don’t have a standard method,” Coffin said.
Until just a few years ago, many scientists peered through a microscope and sorted the particles by hand, Coffin said. “You squeeze the particle with tweezers, and you kind of have a guess if it’s plastic or not,” he said. “Very crude, honestly.”
Now some labs stain the particles to make them easier to spot. They shine an infrared beam or laser at a particle and look for telltale wavelengths of light that it absorbs or bounces back to confirm it is plastic. Another way is to vaporize the sample and analyze the gases.
The state assembled an international assortment of laboratories working to streamline these techniques and figure out which are the most cost-effective for testing drinking water, sediment, ocean water and fish tissue. They expect to reveal by July what tests water providers must use.
The Southern California Coastal Water Research Project is leading the effort, sending jars of water spiked with microplastics and other materials to more than two dozen labs to see if they can distinguish microplastics from other contaminants and accurately count particles.
“The sample sets that were put together for us were very interesting,” said Slifko of the Metropolitan Water District, which is one of the labs. “They had rabbit hair in them. There was also cellulose fibers from toilet paper. There was a lot of different red herrings in there.”
Slifko’s researchers filtered the water and then peered at the particles through microscopes. They picked out pieces of plastic with forceps, then put them on a petri dish lined with sticky tape to count them.
“Each of those samples took at least 120 hours per sample,” Slifko said. “In drinking water, it’s essentially looking for a pin in a haystack.”
Another potential obstacle: contamination from plastic in the lab or researchers’ clothing, said Steve Weisberg, the Southern California water research project’s executive director.
“We actually have a lock on my laboratory. I do not have a key, and I run the place. Why? because I wear these polyester shirts! You’re not allowed in the lab with a polyester shirt,” Weisberg said.
Stopping the flow
Some experts question whether focusing on drinking water is enough. Bottled water, for instance, may be a bigger source of microplastics than tap water.
“That health threat will not be addressed by just removing microplastics from drinking water, sadly,” said Arizona State University’s Halden.
Ultimately, experts say, the solution will be to reduce the flow of plastics into the environment.
When your house is flooding, “the first thing is you have to stop the pipe,” Halden said. “We have to stop the pipes that are flooding our environment, our food, our water, everything with these types of materials.”
Treatment plants tend to catch larger plastic particles. But sewage treatment plants can still release billions of tiny particles every year into waterways. They also can make their way back into the environment through sewage sludge applied to crops.
California lawmakers are looking for ways to stop the flow of plastics with a package of bills announced last week. Some would require new washing machines to be equipped with filters. But these bills may face an uphill battle. Last year, lawmakers after a fiery discussion rejected a pair of bills aimed at restricting single-use plastic packaging and food products. Another that would have required filters in state laundry facilities died.
Testing water and setting a guideline is the first step.
“I’m excited to see California’s influence on other states,” said Oregon State’s Brander. “It’s nice to see them taking the lead, and potentially setting a really good precedent going forward.”
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