00:00Today, we're talking about one of the most dangerous good things humanity ever used.
00:04Leed. It might be the first metal humans ever recognized and used.
00:08Its melting point is low, it's soft, easy to shape, easy to mine, easy to work with.
00:13The ancient Romans used lead to build their aqueducts.
00:16Ancient Chinese used lead powder as a whitening cosmetic.
00:20For thousands of years, lead was a cheap, everyday material.
00:23But when did humans learn lead was toxic? Much earlier than most people assume.
00:28In the late 19th century, Australian doctors had already systematically documented cases of severe lead poisoning,
00:34and had clearly linked children's health damage to lead exposure.
00:37So if we knew lead was toxic in the 19th century, why did lead use grow even bigger in the
00:4120th?
00:42Because in 1921, something appeared that made lead seem irreplaceable.
00:46At the time, car engines had a common technical problem, engine knocking.
00:50The fuel-air mixture ignited prematurely, before the designed ignition timing, and it damaged the engine badly.
00:56An American chemist, Thomas Midgley, and his team at General Motors discovered that adding a compound called tetraethyl lead to
01:02gasoline could effectively suppress this problem.
01:05Leaded gasoline made engines run smoother.
01:07But tetraethyl lead was far more toxic than plain metallic lead.
01:11It was volatile, easily absorbed through skin or by breathing its fumes, and could poison you quickly.
01:16So how did something so obviously poisonous get sold to the whole world?
01:20The first thing the companies did was give this additive a brand new name.
01:23They called it ethyl.
01:25In their marketing, they never once mentioned the word lead.
01:28Because it genuinely solved the knocking problem, leaded gasoline spread fast.
01:32By the 1960s, leaded gasoline made up about 98% of all gasoline sold in America.
01:37At the same time, lead pipes and lead-based paint were being used on a massive scale in construction.
01:43In 1928, the American Lead Industry Association was formally founded, becoming the core organizer of the industry's interests.
01:50And as more and more medical evidence pointed to the dangers of lead, how did the industry fight back?
01:54With a complete, organized strategy.
01:57They funded academic research that favored their cause, paying researchers to conclude that lead occurs naturally in the human body
02:03and is completely harmless.
02:04When independent doctors published papers showing that lead poisoning caused children's intellectual disabilities,
02:09the association threatened to sue, and even tried to buy them off with money.
02:13They shifted the blame from the product to the user, claiming children got poisoned because their parents weren't careful enough.
02:19They placed their own representatives inside standard-setting bodies, influencing safety limits and label content for lead products.
02:25For decades, this playbook effectively delayed regulation of lead products around the world.
02:30So who finally broke that control?
02:32It wasn't one single person.
02:34But there was one very important man.
02:37Claire Patterson, a geochemist at Caltech.
02:39By analyzing polar ice cores and deep-sea sediments, he reached a striking conclusion,
02:44modern human bodies contain more than a hundred times more lead than people who lived before the Industrial Revolution.
02:49He concluded that atmospheric lead pollution was far more serious than anyone admitted.
02:53Despite industry pressure and academic attacks, Patterson did not give in.
02:57He publicly criticized the industry-funded research that claimed lead was harmless.
03:02And his work became a key factor driving the phase-out of leaded gasoline in the 1970s.
03:07Then, through a decade of calls from academia, environmental groups, and the media,
03:11the anti-lead movement pushed leaded gasoline toward its end.
03:14But the story didn't end there.
03:16Lead has a very unique property.
03:18Inside the human body, it gets stored in the bones, and its half-life is decades.
03:23Even after a person stops being exposed, the lead stored in their bones gradually releases back into the bloodstream, for
03:28years.
03:29Inside a pregnant woman's body, it can re-enter circulation during pregnancy and harm the developing fetus.
03:35And the World Health Organization states that there is no safe level of lead exposure.
03:39From the arrival of leaded gasoline in 1921, to the year the last country in the world finally banned it,
03:442021, that's exactly 100 years.
03:47And yet, according to model studies from UNICEF, even though leaded gasoline has been phased out,
03:52many children around the world still have blood lead levels above what public health experts consider concerning.
03:5720 years after the phase-out, lead levels in the dust of many cities remain far too high.
04:01The lead we poured into the air, the soil, and our own bodies, is still with us.
04:06It stays in our bones, in our environment, and in generations yet to come.
04:10And that is the real reason this dangerous metal is so hard to leave behind.
