A German bunker full of blood and urine has the best record of how chemicals contaminate us

Some 400,000 specimens from German citizens, collected over four decades and stored in an old military bunker, trace the rise—and sometimes the fall—of chemical pollutants in an industrial country.

By Florian Sturm
Published 28 Sept 2022, 16:45 BST
At the German Environmental Specimen Bank, Dominik Lermen stands among cryo-storage tanks that hold thousands of vials of blood and urine. A scientist at the Fraunhofer Institute for Biomedical Engineering, Lerman leads the team that collects samples every year from students and stores them here on behalf of the German Environment Agency.
Photograph by Esther Horvath, National Geographic

Fifteen minutes southeast of this university town, residential streets give way to farm fields, and the road winds and narrows. Next to a large wood, behind a tall chain-link fence, lie five old military bunkers—low swells in the landscape, their curved roofs covered with grass.

Dominik Lermen heads toward one and takes a bunch of keys out of his pocket. The clattering is swallowed by birds chirping and wind whooshing through the trees. Finally, he finds the right key, and I follow him through the plain green door—into the world’s best archive of how humans have been contaminated by chemical pollutants.

“In here,” Lermen says, “we’ve got about 400,000 samples from more than 17,000 people. Mostly whole blood, urine, and plasma.”

We’re standing in a huge, windowless, dimly lit room, with bare concrete walls around six feet thick. White pillars prop up the curving roof. It’s cold—a little over 10ºC—but not nearly as cold as it is inside the 42 stainless steel cryo-vats that fill the room in neat rows. Each is about six feet tall, two feet across, and connected to metal pipes that run the length of the building.

This is the human-sample archive of the German Environmental Specimen Bank (ESB), an effort by the federal environment ministry “to systematically monitor and analyse human exposure to chemicals like lead, mercury, plasticisers and others,” Lermen says. More than four decades old, it’s the best and longest record of its kind.

The specimen bank is housed in a bunker that once served as a medical depot for the German army, outside the western city of Münster.
Photograph by Esther Horvath, National Geographic

Every year Lermen and his colleagues from the Fraunhofer Institute for Biomedical Engineering collect and analyse samples of blood and urine from volunteers from the four corners of Germany, then store the samples here for future research. The project has two goals: to reveal which substances have already accumulated in large and potentially dangerous quantities in German bodies, and to verify whether bans and regulations of some of those substances have actually worked.

Regulation clearly can work: Blood levels of lead and mercury have plummeted in recent decades in Germany, as they have in other industrialised countries. At the same time, the proliferation of synthetic organic compounds such as PFAS (aka “forever chemicals”) has created disquieting new threats that make the work done in this obscure facility all the more urgent.

Lermen, 44, bald with a full beard and a pleasantly sonorous voice, puts on a face shield, climbs up a mobile stairway, and lifts the lid off one of the tall cryo-storage vats. White fog gushes from the opening and dissipates as it sinks to the concrete floor.

“All of these tanks are filled with about 160 litres of liquid nitrogen,” Lermen says. “Only at these extreme temperatures can we ensure the longevity of our archive.”

Inside the tanks, liquid nitrogen keeps the samples in a deep freeze below -256ºF. The vials are stored in racks that sit in the cloud of gaseous nitrogen above the liquid.
Photograph by Esther Horvath, National Geographic

His hands and forearms protected by special gloves, Lermen reaches into the tank and lifts a rack full of vials from the nitrogen cloud that sits above the liquid nitrogen lake. The temperature in the cloud is below -160°C, or -256°F. After a few moments, he lowers the rack back into the container and closes the lid.

“When we take the samples out of the tank, the vials experience a rapid change of temperature of about 170°,” he says. “Of course, we want to keep this to a minimum.” If you’re trying to preserve a record for eternity, every second counts.

'Students are our early warning'

Though scientists at the University of Münster began hatching plans for the ESB in the 1970s, it was officially launched in 1985. The first samples were collected from people near Münster, in western Germany, but after West and East Germany were reunited in 1990, the annual sampling program was expanded to Greifswald in the north, Halle in the east, and Ulm in the south. The idea was to get a truly national picture of chemical contamination.

The ESB also collects environmental samples—bird eggs, plants, fish, mussels, deer, earthworms, and soil— from 14 different locations, including cities, nature reserves, and farms. But only human samples are stored in the Münster bunker, a former army medical depot. The archive moved here from the university in 2012. The thick walls, strong enough to withstand a bomb or a plane crash, also shield the samples from cosmic radiation that might otherwise degrade them over the very long term.

The samples in the bunker are taken not from Germans of all ages, but only from students between 20 and 29 years of age—in part to exclude people who might have high occupational exposure to chemicals.

Till Weber, a scientist at the German Environment Agency, manages the specimen bank. It began operating in 1985 and maintains the world's most consistent record—and one of the longest—of humans' changing chemical burden.
Photograph by Esther Horvath, National Geographic

“We deliberately sample students” as indicators of the threat faced by the population at large, says Marike Kolossa-Gehring, lead scientist and project manager of the ESB at the German Environment Agency in Berlin.

“Students are not exposed to certain substances due to their job. And assuming that exposure to persistent substances tends to increase as well as accumulate with age, if we found high levels of substances already in young students, we would know that we must pay close attention to these substances in particular.

“In a sense, students are our early warning system.”

New blood for the bunker

Anjuli Weber, a 21-year-old medical student at the University of Ulm, is one recent recruit to this system. After hearing about the biobank from a campus-wide e-mail, she “was curious to learn more about it—as well as about the state of my body,” she says. Participants eventually receive a few of their test results.

One morning in May, Weber reports to the Fraunhofer Institute’s large mobile lab, which has pulled into a parking lot on the outskirts of Ulm for three days of testing. Before she goes inside, a staff member reviews details of Weber’s medical history and living situation, including her eating habits and use of medication and cosmetics. A dentist checks her teeth for amalgam fillings, which contain mercury and other metals.

Inside the truck, Weber encounters a state-of-the-art medical facility, with a shielded biosafety 2 lab for six workers, a mobile cryo-tank for storing samples, and a back office. She hands over a large, brown plastic bottle containing her urine from the past 24 hours. A technician immediately starts analysing it.

Then another technician draws about 180 millilitres of Weber’s blood—around six times more than you might surrender in an ordinary medical test, but much less than the pint you give up when you donate. Within 45 minutes, the blood has been analysed for routine parameters and divided into 16 whole blood and 24 plasma aliquots. Registered and bar-coded, they are placed in the liquid-nitrogen container, to be delivered to one of the bigger cryo-tanks in the bunker near Münster.

Some 400,000 samples are stored in the bunker outside Münster, and new ones are added every year from four sampling locations around Germany.
Photograph by Esther Horvath, National Geographic

From there they’ll travel to external labs to be analysed for toxic chemicals—through an uninterrupted cold chain that keeps the samples deeply frozen, thus limiting the risk that they’ll be altered.

There are about two dozen environmental specimen banks worldwide; the oldest, in Stockholm, dates to the 1960s. What makes the German ESB unique are the quality and consistency of its data. Whereas some ESBs work opportunistically—when a dead otter or whale washes up on shore, its tissues go into the bank too—the German archive follows a strict protocol and standard procedures. The same mobile lab travels to all four sampling sites around Germany every year.

“We have been using the same standardised sampling and storage methods for over three decades. That makes our data truly comparable and allows us to make confident analyses and predictions,” says Kolossa-Gehring.

Good news and bad

Back in the bunker, another environment agency scientist named Till Weber (no relation to Anjuli Weber) tells me that researchers from many countries have studied the German data. The results have been both uplifting and worrying.

One study shows that mercury levels in blood and urine fell by 57 percent and 86 percent respectively between 1995 and 2018. “One of the reasons for this continuous decline is the decreasing use of amalgam in dentistry and probably the awareness of mercury exposure from fish and seafood,” Weber says.

A cryo-workbench in the bunker allows the samples to be checked and analyzed without interrupting the cold chain—which is essential for preserving them as a long-term record.
Photograph by Esther Horvath, National Geographic

Lead has followed a similar trend. Data derived from 3,851 young adults in Münster shows that the average blood lead level decreased by about 87 percent between 1981 and 2019. The main reason: Germany’s ban on leaded gasoline took effect in 1988, and so car exhaust no longer pollutes the air with lead.

“No manufacturer deliberately puts harmful substances onto the market,” Weber believes. “But sometimes only with time do we learn about the true toxicity of certain chemicals. That’s what makes bio-monitoring like ours so important for the entire society.”

Even though certain testing is mandatory before using new substances in commercial products, data about long-term health effects is scarce for most of them. The number of synthetic chemicals is growing so fast it’s almost impossible to keep track of their individual effects, let alone their combined ones.

The European Union probably has the strongest chemical regulations. In April, the European Commission published a “restriction roadmap”: Up to 12,000 substances linked to hormonal disruption, cancer, obesity, or diabetes could be banned, officials said. It would be the “largest ever ban of toxic chemicals” to date, according to the European Environmental Bureau (EEB), a network of citizens’ groups, and it could come as a harsh blow to the petrochemical industry.

One main target: PFAS, dubbed “forever chemicals” because they take hundreds of years to naturally degrade. Food-packaging and flame retardants, waterproof clothing and outdoor gear, umbrellas and non-stick pans—all use toxic PFAS-substances.

Traces of these and other substances such as phthalates, which are used as solvents and as plasticisers, have been found in literally every sample since the ESB began looking for them, Lermen and Weber say. The chemicals are omnipresent and it is impossible to reliably trace their source. That is why regulating their use is extremely important.

Europe has banned or regulated individual phthalates, identified as endocrine disruptors that might interfere with reproduction, since 1999. Manufacturers have responded by changing the formula of banned substances ever so slightly to invent new, unregulated chemicals with similar features. Studies derived from the German ESB show that the overall exposure to phthalates has increased.

“This clearly indicates that the number of substitute chemicals keeps rising—and we don’t know a lot about their effects yet,” Kolossa-Gehring says.

It’s important for people to know as much as possible about the chemicals they’re exposed to, Till Weber says before closing the green door of the bunker for the day.

“We don’t want to scare anybody or tell them to not use any plastic in their life anymore. But all of us need to build an awareness of what’s around us, and, eventually, also inside our bodies.”


Esther Horvath is a Germany-based photographer who documents polar regions. Follow her on Instagram. Freelance journalist Florian Sturm is also based in Germany.


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