As the science of detecting microplastics matures, so too does consensus about their ubiquity. Everywhere researchers have looked to find them, there they’ve been: In human brains and lungs; in breast milk and semen; in alpine snow and deep-sea sediment; in corn plants and beer.

And that, say researchers, is the rub: Scientists are not just finding them in our livers, arteries and ovaries. They are also everywhere else: in research laboratories, pipettes, refrigerators, solvents, bottles, goggles and the very lab coats investigators are wearing to find them.

So how do we know if those particles seen under the lens of a microscope are inherent in the sample, or contamination from plastic fibers floating in the air? Or from tiny particles that sloughed off from the inside of a bottle of solvent?

Microplastics scientists are keenly aware of the problem and urgently studying it, because the credibility of the research is on the line.

Their research suddenly skyrocketed in importance with the federal government’s announcement Thursday that it will begin actively investigating the wayward, potentially toxic particles in people and drinking water.

“We cannot regulate what we don’t understand,” Robert F. Kennedy Jr., secretary of Health and Human Services, said at a news conference.

Nicolas Leeper, head of vascular medicine at Stanford University, said he is “absolutely” concerned that “at least some part of what has been reported [in the scientific literature] may be spurious or artifactual.”

For instance, a 2024 headline-stealing study showed a relationship between microplastics found in the arterial plaque of patients undergoing heart surgery, and a higher risk of heart attack and stroke. Several medical researchers, including Leeper, questioned the findings. They argued the authors hadn’t accounted for the introduction of microplastics during surgery.

Like most scientists in this new relatively new field, Leeper didn’t set out to study tiny, broken bits of plastic. But that study caught his attention.

“I take care of people that have atherosclerosis,” he said in an interview. “We’ve known for a while that genetics only explains about half of our lifetime risk.”

He now wonders if microplastics could be that X factor he’s been looking for, and is investigating the issue in his laboratory. But he’s aware the particles are everywhere.

“Think about it: Every time we work with a human bio specimen, we’re wearing plastic gloves and using plastic needles and plastic petri dishes,” he said.

Leeper is pretty sure microplastics can lead to ill health. He just wants his — and everyone’s — research to be beyond reproach.

“Given the potential public health impact of these ubiquitous … products, it is essential we know exactly what we are dealing with, how to quantify it, and how to be certain we aren’t chasing a signal that may be driven, in part, by contamination artifact,” he said.

It’s not a new concern. In fact, it’s a relatively old one.

Claire Gwinnett, a forensic scientist at the University of Staffordshire, in England, said she’s been fretting about microplastic contamination in her research for decades.

She’s spent most of her career inspecting dead bodies for signs of foul play. Her work requires painstaking quality control. When examining a cadaver for DNA, fibers or other chemicals and materials that could help identify a murderer, or information about a struggle, she needs complete confidence that the evidence she gathered came from the body, or perpetrator, and not from her own body, clothing or equipment.

“My entire career has been based around these teeny, tiny particulates you can’t see with the naked eye, but that I’m trying to confidently convince the courts were present on that victim in that crime scene, and not due to procedural contamination,” Gwinnett said.

About 10 years ago, she read a headline saying that researchers had found microplastic contamination in samples of deep ocean sediment — more than two miles below the surface.

“And the question for me was: Is that real? Were they actually using methods that would confidently allow them to say they actually found these microplastics at these depths, and that it wasn’t procedural contamination?”

She started working with environmental scientists at her university and then across the world to get them to start thinking like a forensic scientist: How can you reduce plastic in your lab or account for microplastics that are there? Are they using plastic when they could be using glass or metal? What are they wearing in the lab? Are they creating “blanks” — faux samples that go through the same preparation, in the same places, with the same researchers, using the same chemicals and materials — to account for microplastic background “noise”?

It was around this same time that Susanne Brander, director of scientific advancement efforts for the Pew Charitable Trust’s safer chemicals project, said she and other environmental scientists started asking similar questions, and establishing protocols to address contamination.

By the late 2010s, she and colleagues started replacing plastic with glass and metal, used HEPA filtration, and instituted special cleaning procedures for their equipment.

But, as often happens in science, knowledge in one research discipline doesn’t necessarily bleed into another.

There’s a silo effect, Brander said. So when people who study human health started asking questions about microplastics, they didn’t necessarily look to the water, fish and forensic folks for advice.

She doesn’t fault them for not reading her papers; “it’s a different research space,” she said. But it meant some of the early work on microplastics and human health didn’t use the quality controls that forensic and environmental scientists had adopted.

“Some of us have even talked about bringing these two research fields together, she said. “Maybe we should reconvene and talk about how we’ve already kind of done this.”

The human work is drawing a lot more scrutiny than the earlier work ever did.

It’s one thing to find microplastics in plants, snow and other animals. When we see it in our brains, placentas, testicles and blood — that’s different.

And as the federal government jumps into the fray, looking not only for the particles but also the potential effects on human health, the risk to the multibillion-dollar chemical and fossil fuel companies that manufacture and distribute these products grows.

So could scrutiny on the way we live: from food packaging, carpet manufacturing and water filtration, to medical supplies, car tires and clothing.

Plastic never goes away; it just breaks down into smaller and smaller pieces. According to the United Nations Environmental Programme, the world has produced more than 9.2 billion tons of plastic since 1950, with half of that amount produced in the last 13 years alone.

Matthew Campen, professor of pharmaceutical research at the University of New Mexico, has done some of the most well-known microplastic research on human tissue. He found it in placentas, livers, kidneys, lungs and brains.

He said the issue of contamination is real, but wonders if it’s over-hyped.

Campen was at the panel Thursday with Kennedy and Lee Zeldin, the administrator of the U.S. Environmental Protection Agency, as they announced their intention to make microplastics a research priority.

Although his work has also been challenged, he said that’s to be expected: The whole field of microplastic research is new, and there will be kinks that get ironed out as it matures.

“We knew that cigarettes caused cancer in the 1930s and the surgeon general didn’t say anything about it until 1966,” he said. “Ultimately, I think we’re going to move pretty fast. We’re going to invest in science in the coming years, and over the next five years, we’ll have much more confidence as to how this is getting into our bodies and what it could be doing.”

An Australian company has launched a rare earths mining project just outside Joshua Tree National Park in critical desert tortoise habitat, an area the company’s director refers to as an “emerging heavy rare earth district.”

The company, Dateline Resources Ltd., says that historical sampling of the area in the Pinto Mountains south of Twentynine Palms found enrichment in elements key to powering electric vehicles, wind turbines and defense systems.

The United States depends heavily on China for its supply of these critical minerals, a major national security vulnerability the Trump administration has sought to address through a series of regulatory changes and financial incentives aimed at shoring up domestic production.

The project is in its early stages, and it’s unclear whether further testing will confirm the presence of rare earth elements across a broad enough area to warrant extracting them. The site is roughly 100 miles southwest of the nation’s only fully functional rare earths mine — Mountain Pass operated by MP Materials, in which the U.S. Department of Defense holds a 15% stake.

It’s also steps from Joshua Tree National Park, one of the nation’s most beloved desert getaways where about 3 million people visit annually. The 1,200-square-mile park and the public lands that surround it are home to sensitive plants and wildlife that environmentalists say would be harmed by a major mining project that could deplete water supplies, draw traffic and generate toxic waste.

“This is truly one of the most iconic landscapes in America,” said Chance Wilcox, California desert program manager for the National Parks Conservation Assn., as he stood atop a rocky slope within the project footprint on Friday.

Beside him, a wooden stake marked the corner of a mining claim. About 100 feet away, a metal post denoted the park’s boundary. In the valley below sat the fee booth for the east entrance.

If mining were to go ahead here, visitors would likely be able to see the activity while driving into the park, Wilcox pointed out. “It just emphasizes this company’s blatant disregard for our nation’s crown jewels,” he said.

Dateline did not return messages seeking comment on the project. The company also operates the Colosseum Mine in the nearby Mojave National Preserve, which the Trump administration has touted as pivotal to its efforts to develop a homegrown critical minerals supply chain.

Dateline first announced the venture — the Music Valley heavy rare earths project — late last month, saying it had acquired 57 claims totaling 1,140 acres and had also invested $1 million in Fermi Critical Minerals Inc., an American company that holds uranium and rare-earths projects in multiple western states. Dateline later broadened the footprint by staking an additional 969 claims covering 19,380 acres, a subsequent release states.

Twentynine Palms Highway looking west runs through downtown on Friday in Twentynine Palms, Calif.

(Gary Coronado / For The Times)

The company now holds claims over a roughly 32-square-mile area, the vast majority within the Bureau of Land Management’s jurisdiction.

U.S. Geological Survey geologists first identified rare earth mineralization in the Music Valley area in 1954, with sampling reporting enrichment in dysprosium, terbium, yttrium and ytterbium, Dateline Resources said in a press release. The company is now training modern exploration techniques on outcroppings of a 1.8-billion-year-old type of metamorphic rock called Pinto gneiss.

While rare earths will be the primary focus, exploration will also assess the potential for gold mining — the area is dotted with old, small-scale adits and shafts.

The project is located in what’s known as an area of critical environmental concern. The U.S. Fish and Wildlife Service has deemed the sweeping landscape to be crucial to the survival of the Mojave desert tortoise, which is endangered in California thanks to a stew of threats including development, disease, raven predation and climate change.

The land abutting the Pinto Mountains Wilderness is also home to badgers, bighorn sheep and Mojave fringe-toed lizards. Massive yuccas and barrel cacti stud its steep slopes.

A chuckwalla lizard suns itself on a rock in the Pinto Mountains.

(Gary Coronado/For The Times)

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On Friday, desert iguanas and whiptails scampered across an access road, portions of which wind through the national park. A chuckwalla sunned itself on a boulder. Nearby, a desert tortoise had emerged from its burrow to munch on some grass — a rare sight that elicited a whoop of joy from Wilcox. “This is a really special place,” he said.

If the area proves to be a valuable source of heavy rare earth elements, it would be significant as the U.S. has none, said Daniel O’Connor, co-founder and chief executive of Rare Earth Exchanges, a website that covers the global rare earths market. Mountain Pass primarily produces light rare earth elements, which are typically more abundant.

“Our entire war machinery — missiles, radar, fighter jets — all need these heavy rare earths,” O’Connor said.

Still, he said, even if the U.S. were to start producing heavy rare earths, the country would likely remain reliant on China to process them — a complex, multi-stage undertaking that involves chemically separating the elements from ore. Companies controlled by the Chinese treasury currently separate and refine an estimated 90% of the world’s supply of rare earth elements, and about 90% of the specialized magnets they are used to create are also manufactured in China, he said.

A mural illustrating miners in the Dirty Sock Camp is painted on a wall in downtown Twentynine Palms, Calif.

(Gary Coronado / For The Times)

O’Connor described the Music Valley project as early-stage and speculative, pointing to a mining tradition dating back to the Wild West in which prospectors tout samples that show heavy concentrations of minerals in a bid to loosen investors’ wallets. There’s no way to know how widespread or systematic those concentrations are without technical reports disclosing a project’s mineral contents and quality, he said. Dateline does not yet appear to have released any such report, which are industry standard, he said.

Rare earths mining typically involves pulling out ore with jackhammers or dynamite and grinding it down before chemically treating it — processes that consume a lot of energy, generate toxic waste and can unleash radiation that’s often present in the ore, he said.

“It’s hard to think of a worse place for a massive industrial project than sensitive desert tortoise habitat on the very edge of Joshua Tree National Park,” wrote Brendan Cummings, conservation director for the Center for Biological Diversity, in an email.

A buildout of the claims could end public access to the area and permanently scar the landscape, drawing traffic and light pollution and harming springs and groundwater stores, he said. Given those potential impacts, he is skeptical that the developers could lawfully be granted the necessary federal, state, and local approvals to proceed.

Conservationists also point to Dateline’s history operating the Colosseum Mine as a source of concern, saying the company flouted National Park Service rules and damaged the surrounding landscape.

“They don’t respect public lands, national parks or the law, so there’s every reason to be deeply concerned about this proposal,” said Rep. Jared Huffman (D-San Rafael), the ranking member on the House natural resource committee who said the project “has red flags waving in every way.”

“We do need domestic and critical minerals sourced from friendly countries and responsible actors,” he added, “but it doesn’t mean we need them everywhere or at any cost.”