字幕列表 影片播放 列印英文字幕 Hi, this is Kate from MinuteEarth. Lead is poisonous and it can leach into water, so you probably wouldn't gulp from a cup made of lead. Yet today, hundreds of millions of us worldwide get our water from plumbing that contains lead. Seriously, humans? How did we get here? We've actually had a complicated relationship with lead for a long time. Scholars first recognized its dangers in ancient times, yet for the next 2000 years, we relied mainly on lead to transport our water. After all, lead is plentiful, and since it has a low melting point, it's easy to extract. It's a super-soft metal, so it can easily be formed into pipe-y shapes, and it can last for centuries - far longer than other plumbing contenders. Lead is such an ideal water-transporter that the word “plumbing” literally came from the Latin word for lead. And while people have known for a long time that lead could make us sick, it was tricky to nail down how big a risk it actually was. It can take years to see the effects of lead on our bodies, and even then, its symptoms can be mistaken for lots of other maladies. But what really *led* to confusion was that in some places, lead pipes didn't seem to make people sick. Generally, lead can leach right out of a pipe and into the water rushing through it, poisoning people one refreshing drink at a time. But in places where water has lots of dissolved minerals, a hard, scaly crust builds up inside pipes, which separates the water from the lead, keeping most of it out of our cups. By 1900, we had figured out these quirks and fully understood the dangers lead pipes posed, but two thousand years of plumbing had given lead some serious inertia. By then more than 70 percent of large US cities used lead water lines. Pipefitters and plumbers still preferred plumbum for their plumbing work. And in some places, the powerful lead industry worked hard to keep promoting lead pipes for decades. All in all, it took many countries until the late 20th century - or longer - to ban the installation of new lead pipes. But there were still lots of lead pipes already out there, and replacing them would be incredibly costly and difficult. But we could put to work one of the things that had initially confused us about lead pipes; we started adding dissolved minerals to water that didn't naturally contain them, artificially forming that protective crust that makes lead pipes safe...well, safe-ER. Occasionally, disaster happens - like when a drought in England caused the protective barrier in a town's pipes to crumble, poisoning hundreds of people when water started flowing again; or when officials in Flint, Michigan neglected to add minerals to the town's water, exposing tens of thousands of households to lead. It's time to get over the cost and effort of removing and replacing all that plumbum, so that safe plumbing is no longer just a pipe dream. In the US, instead of replacing lead pipes, the Environmental Protection Agency has tried to monitor and limit lead levels in drinking water. But here's the thing: their flawed testing method systematically misses high lead levels in water. What's more, the lead limit the EPA has adopted isn't actually based on what's best for human health in the first place. These not-so-minor details mean that tens of millions of Americans are currently at risk of lead poisoning. For more information about what's actually going on here, you can check out Buried Lead; the result of a collaboration by APM Reports and The Water Main, the sponsor of this video and an initiative of American Public Media that's working to build public will for clean, affordable, accessible water. You can read the story at apmreports.org/water. Thanks to the Water Main for helping us make this video, and for trying to make sure the water we're drinking is plentiful and safe.