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  • Over the years I've been making videos,

  • a lot of people have got in touch to tell me that in Warsaw, in Poland,

  • the tap water quality is tested and controlled by clams.

  • They said that the city constantly runs a sample of its tap water past some mollusks.

  • And those are filter feeders, so if there's a contaminant in the water, they will instinctively close.

  • Sensors attached to them will detect that and raise the alarm.

  • And I didn't believe it.

  • It seemed too weird to me.

  • And all the articles that I could find about it seemed dodgy, somehow.

  • They just set off red flags in the research parts of my brain.

  • There is a very arty Polish documentary about the system,

  • and a lot of sites repost that film's claims without even mentioning the source,

  • just as a "look at this funny thing off in Poland!"

  • It felt like it could be a misinterpreted or mistranslated joke,

  • or even a deliberate hoax by a filmmaker that got out of control,

  • and that the English speaking world was just believing it because it was quirky and harmless enough.

  • There have been plenty of fake things like that spread about in the past, accidentally or otherwise.

  • Or maybe the clam-sensors did exist, but it was a brief experiment that never went anywhere.

  • Well, I'm now here in Warsaw, on a famous building in the middle of the river,

  • with a Polish speaking team showing me around.

  • There is a lot of stuff we are not allowed to film here for security reasons.

  • Inside here is critical infrastructure.

  • Plus, it is far too noisy down there for me to talk,

  • but I'm happy to report that yes, the clams are real.

  • They actually do protect Warsaw,

  • but the story's a little more complicated than that.

  • Warsaw's water source is surface water, the water of the Vistula River.

  • If it turns out that there's ever a toxic substance in the water,

  • we must not allow that contaminated water to reach our residents.

  • So therefore, we would start a special procedure,

  • and our laboratories would carry out a number of tests,

  • to find out what is the cause of the water contamination.

  • And we would have about two days to do that.

  • The alarm has never sounded yet, but for water safety,

  • an early warning system is very important.

  • The important thing is: those clams aren't the only protection.

  • They're not even the main part.

  • This is still a modern water treatment system,

  • with 21st century sensors and detectors to keep everyone safe.

  • This is part of a defense in depth, one part of an early warning system,

  • one more alarm that can go off,

  • like an airport that uses explosive sniffing dogs but also electronic detectors.

  • These clams are caught from a very clean lake.

  • Then they got to our laboratory where they spend about two weeks acclimatizing.

  • At the same time, although it sound strange, they're also calibrated.

  • What angle of opening is 100% and what is zero?

  • It's very important that we're able to interpret the result later.

  • Eight individuals go to this aquarium.

  • And these clams are attached to pedestals to which there's also attached a probe,

  • receiving signals from the sensor that's mounted on the shell of each clam.

  • These sensors are fixed with a special glue, which is absolutely safe for animals.

  • Three months later, the clams are returned to their natural habitat.

  • We know that this is not a stressful situation for them.

  • We take care of our colleagues here!

  • How do we know if there's a problem, if something's happening to the water?

  • If, at the same time, six out of eight individuals close their shells for more than four minutes,

  • and at the same time, average closing percentage of all the shells falls below 25%.

  • We can see that most of these clams are very active now.

  • The average opening percentage, across all the clams, is 72%.

  • So, the water is safe.

  • The technical term for this is "biomonitoring,"

  • and it turns out from more research that this isn't the only place that does it.

  • There are other water companies in Poland that have similar setups,

  • plus one in Minnesota, USA, and probably more that I haven't found.

  • At which point I think I can say that: yes, the red flag in my head was wrong.

  • The clams in this building really do help protect Warsaw.

Over the years I've been making videos,

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