Home
登录
注册
听力练习
听力练习
/
Video
/
SciShow
/
How Laundry Detergent Caused an Environmental Disaster
How Laundry Detergent Caused an Environmental Disaster
选择学习模式:
查看字幕
选词
重写单词
Highlight:
3000 Oxford Words
4000 IELTS Words
5000 Oxford Words
3000 Common Words
1000 TOEIC Words
5000 TOEFL Words
字幕 (281)
0:00
When you turn on the faucet in your kitchen or bathroom,
0:02
you probably expect clean water to come out.
0:04
If it does, you can thank regulations like the Clean Water Act.
0:07
This US law was introduced in 1972
0:10
to curtail water pollution across the States.
0:13
And we desperately needed it.
0:14
Lakes were filling with toxic green slime,
0:17
people were drowning in polluted sludge,
0:20
and rivers were literally catching on fire.
0:22
If that wasn’t gross enough,
0:24
this polluted water was even invading homes.
0:28
Tap water was coming out… bubbly.
0:30
The cause of all this pollution was the last thing you’d expect to
0:34
make things dirtier: Laundry detergent that was way too good at its job.
0:41
[♪INTRO]
0:43
In the 1940s, laundry machines were spreading
0:45
to households across the United States.
0:47
The appliances promised to free up hours, or even days,
0:51
that people used to spend scrubbing clothes by hand.
0:55
And that is so worth it, in my opinion.
0:57
I mean, I have a washing machine
0:59
and I still think laundry takes too long.
1:01
But for all the time they saved, those early washing machines
1:03
weren’t quite as dirt-busting as good old-fashioned hand washing.
1:07
For one thing, the washing machines just didn’t scrub hard enough.
1:10
And soap needs to get to the dirt in order to work.
1:13
Each soap molecule has a hydrophilic end that binds well to water
1:17
and a hydrophobic end that avoids water at all costs.
1:20
The hydrophobic end, however, does stick well to grease
1:24
and dirt and all the gross stuff we want to wash out of our clothes.
1:27
So the hydrophobic ends encapsulate the dirt and grime,
1:31
leaving the hydrophilic ends sticking out.
1:33
Then, when you rinse your clothes, the hydrophilic ends of
1:36
the soap blob stick to the rinse water and carry the dirt away.
1:39
For the deepest clean, the soap needs
1:41
to get all up in the fibers, and also get back out again.
1:46
And washing machines of the 1940s didn’t have the mechanical
1:49
power to do that as well as a human with a washboard.
1:52
The second problem was hard water.
1:54
Hard water contains lots of calcium and magnesium ions.
1:58
It’s common in areas that rely on groundwater,
2:00
ike the Midwest and Rocky Mountains.
2:02
As water moves through dirt and rock, it dissolves calcium
2:06
and magnesium, carrying them into the water supply.
2:09
Hard water makes it hard to do your laundry because soap
2:12
reacts with those ions and forms a solid called soap scum.
2:16
Scum is stubborn to get rid of, as cleaning
2:18
commercials are constantly reminding me.
2:21
Because once scum forms, it sticks to your hands, shower,
2:25
washing machine, even itself.
2:27
If soap molecules get scummy,
2:28
then they can’t stick to the dirt anymore.
2:30
So harder water typically means soap is
2:33
less effective than it is in soft water.
2:35
Despite these problems, washing
2:37
machines were still a huge time saver.
2:39
And cleaning companies saw big dollar signs ahead if
2:42
their scientists could find some consumer-friendly solutions.
2:45
One company, Proctor and Gamble, was perfect for tackling this new
2:49
soap problem, because they were already a giant in the soap industry.
2:52
One of P&G’s founders, James Gamble,
2:55
even got his start as a soap maker.
2:57
They were based in Cincinnati, a city nicknamed
2:59
“Porkopolis” for, you guessed it, its booming pork industry.
3:03
Like centuries of craftspeople before them, P&G used animal fats,
3:07
byproducts of the meat industry, to make soap.
3:10
When P&G researchers turned their attention
3:12
to laundry, they switched to using synthetic detergents
3:15
rather than soaps made from animal products.
3:17
Soaps and detergents clean dirt in similar ways,
3:20
and all soaps are detergents, but not all detergents are soaps.
3:24
A lot of people use the terms interchangeably, regardless.
3:27
But because they’re designer chemicals,
3:29
synthetic detergents are usually really great at their jobs.
3:33
The scientists also found that adding certain builder
3:35
chemicals made the detergents more effective.
3:38
Builders help by reacting with the calcium
3:40
and magnesium ions in hard water.
3:43
They lock those ions away, leaving the
3:45
rest of the detergent free to do its job.
3:46
Builders also make it easier for the soap-y molecules to get deep into
3:51
your clothes fibers and stick to the stubborn dirt embedded there.
3:54
With builder in the detergent mix, machine-washed
3:57
clothes got just as clean as hand-washed clothes!
4:00
Clean, as in the dirt molecules got scooped up.
4:03
But when the hard water minerals reacted with the builder, it left
4:06
a bunch of tiny solids that didn’t rinse away with the soap blobs.
4:10
Meaning clothes came out of the machine all stiff and crunchy.
4:13
Not ideal for your comfy couch sweatpants.
4:15
So P&G chemists spent nearly a decade trying to figure
4:19
out how to get machine-washed clothes both clean and soft.
4:23
Cutting down on the amount of builder helped a bit, but not enough.
4:26
Until one day, a scientist tried flipping
4:29
the ratio of builder to cleaning agent.
4:31
Like, using way more builder than you would
4:34
ever need to lock up the hard water ions.
4:36
For whatever reason, that did the trick.
4:39
No one could figure out why it worked so well,
4:41
but clothes were coming out of the wash clean and soft.
4:44
In the end, P&G chemists landed on a formula that
4:47
used three times as much builder as cleaning agent.
4:50
The best builder they found was sodium tripolyphosphate,
4:54
and the cleaning agents they settled on
4:56
were branched alkylbenzene sulfonates.
4:58
We’ll come back to those.
4:59
This formula ultimately became the first
5:01
fully synthetic laundry detergent: Tide.
5:03
Within a few years, Tide and other synthetic
5:06
detergents had found their foothold:
5:08
consumers were buying a billion pounds of the stuff every year.
5:11
It wasn’t just because it kept people’s clothes clean and soft.
5:14
Part of Tide’s success came from an
5:16
innovative new advertising strategy.
5:18
P&G bought airtime on radio and TV.
5:21
Not just for ad spots, but for entire entertainment programs
5:24
written specifically for their target audience: housewives.
5:28
I know, I know, it was the 1950s, after all.
5:31
Sandwiched between those programs were detergent commercials.
5:34
And these long-running serials came to be known as “soap operas.”
5:37
But for all the time these new detergents saved on household chores,
5:41
people soon started noticing a little problem.
5:44
The detergent bubbles were just too dang bubbly.
5:47
Now, people wanted the bubbles. They liked seeing the bubbles.
5:51
The bubbles convinced consumers that their soaps were
5:53
working when they did the dishes or cleaned their clothes.
5:56
You might even feel this way when you
5:58
wash your pans or shampoo your hair!
6:00
Bubbles form from soapy water because the surfactant
6:03
in detergent pushes its way between water molecules.
6:06
The hydrophilic ends of the molecule stick to the water,
6:09
while the hydrophobic ends line up on
6:12
the air-facing sides of the bubble.
6:14
It’s like the opposite of those dirt blobs,
6:16
and the result is a wafer thin layer of water
6:20
suspended between two layers of soap.
6:22
But tons of bubbles are actually a sign of excess
6:25
soap molecules that aren’t sticking to dirt—
6:28
if your detergent is doing its job, extra lather doesn’t
6:31
mean a better clean, it just means wasted detergent.
6:35
Regardless, P&G leveraged their audience’s desire for suds,
6:39
bragging that Tide produced “oceans of suds.”
6:42
And oh boy, did it make suds.
6:44
But those suds had to go somewhere.
6:46
And all that detergent-filled water was going straight down the drain.
6:50
Household water waste is usually shuttled
6:52
through a sewage treatment plant,
6:53
and one of the water treatment steps
6:55
involves using bacteria to break down pollutants.
6:58
But unlike regular soaps, which were
7:00
traditionally made from natural fat sources,
7:03
synthetic detergents were made with designer
7:06
surfactant chemicals that microbes couldn’t easily digest.
7:09
So the detergent molecules never broke down,
7:12
resulting in obscenely persistent “oceans of suds”.
7:16
Up until the 1960s, the most common cleaning agents in detergent
7:20
were those branched alkylbenzene sulfonates we mentioned before.
7:23
That’s a lot of syllables, but the problematic
7:25
part of these molecules is that they’re branched.
7:28
The branching makes it hard for the bacteria’s
7:30
enzymes to get in there and digest the molecule.
7:33
So the surfactants survive the water treatment process,
7:36
and are free to keep making havoc-wreaking bubbles.
7:39
Don’t laugh at the bubbles! This was really really serious!
7:42
Those bubbles coalesced into giant mats
7:44
and blobs, clogging rivers and lakes.
7:48
Some of those blobs were so big that
7:50
people mistook them for icebergs.
7:51
It got so bad that bubbles even made
7:53
their way into household water taps.
7:56
In the 1960s, some people were doing their dishes
7:59
with water straight from the faucet, no extra soap needed.
8:04
Which saves a couple seconds on chores, I guess,
8:07
but is also terrible for, you know, drinking.
8:10
Eventually, researchers came up with a new detergent formula
8:13
that bacteria could break down. AKA biodegradable.
8:17
They replaced the branched surfactants with linear molecules
8:20
that weren’t so hard for bacteria to chow down on.
8:23
And the linear surfactants are the ones
8:25
that are still used in detergents today.
8:27
The new formula still made a bunch of bubbles,
8:29
which kept consumers happy.
8:31
But water treatment microbes could
8:33
finally break down the detergent molecules.
8:35
Bye bye, bubble bergs!
8:36
So the water problems ended there,
8:38
and we all lived happily ever after…right?
8:41
Wrong.
8:41
Because the surfactant wasn’t the only detergent
8:44
ingredient that was ending up in waterways.
8:46
Remember sodium tripolyphosphate?
8:48
The builder that made up three quarters of P&G’s detergent formula?
8:52
Well, it turns out that dumping a bunch of that in the waterways
8:56
was triggering another disaster entirely: massive blooms of algae.
9:01
Every living thing needs phosphorus.
9:03
You might remember a little thing called adenosine triphosphate,
9:07
or ATP, from biology class.
9:09
It stores and transfers energy in all
9:11
our cells and powers our bodies.
9:12
Yeah, that thing.
9:13
Well, turns out algae thrive with easy access to phosphorus.
9:17
Like the phosphorus in sodium tripolyphosphate.
9:20
Thanks to warm water and an all-you-can-eat nutritional buffet,
9:24
algae populations began to bloom out of control.
9:27
It filled lakes and rivers with slimy green sludge.
9:30
And the blooms weren’t just a cosmetic nightmare.
9:32
When the algae died and sank to the bottom of a lake or river,
9:36
their corpses became fuel for bacteria.
9:39
As they decompose stuff, bacteria consume oxygen.
9:42
And when they started eating all that algae,
9:44
the bacteria used so much oxygen that it created oxygen-depleted
9:49
“dead zones” that choked out other aquatic wildlife, like fish.
9:53
This was particularly bad in Lake Erie.
9:56
In the 1960s, some people declared the lake completely dead
10:00
because the oxygen-deprived dead zones were so extensive.
10:04
If you have an older edition of The Lorax by Dr. Seuss,
10:07
you might find a reference to Lake Erie there.
10:09
It was rhymed with “smeary.”
10:11
Not great press for Cleveland.
10:13
And here’s what really gets my goat:
10:14
By the time everyone started worrying about the algae blooms,
10:17
phosphorus wasn’t even that useful in detergent anymore…
10:20
Its job was, basically, to be a water softener.
10:24
But by the late 60s, a lot of American
10:27
households no longer had hard water.
10:29
So for many consumers, that overabundance of
10:32
sodium tripolyphosphate wasn’t actually doing much.
10:36
Besides feeding algae. And there were other,
10:39
phosphate-free chemicals that could do the same job.
10:41
Still, many detergent manufacturers,
10:43
including P&G, pushed back against efforts to curb their pollution.
10:48
They insisted they weren’t the only ones
10:50
responsible for polluting the waterways.
10:52
Technically, that was true.
10:54
Human waste in sewage was also a major
10:56
source of fuel for these algae blooms.
10:58
But the bubbles certainly weren’t lying!
11:01
While some businesses fought against phosphate bans,
11:04
others leaned into the environmental angle.
11:07
Purex, one of Tide’s competitors, ran an ad in 1970 that called
11:11
out the harmful effects phosphates had on the environment.
11:14
And Purex didn’t come to play.
11:16
They named names and listed the amounts of
11:18
phosphates in each of their competitors’ products.
11:20
That marketing tactic, combined with community activism
11:23
and the first Earth Day celebration in 1970, led to a growing list
11:27
of city- and statewide bans on phosphate detergents.
11:31
Phosphates were eventually removed from detergent entirely.
11:34
And the Clean Water Act of 1972 also came around
11:37
to help curb pollution and regulate water quality.
11:40
With these new protections, waterways
11:42
across the US began to improve.
11:44
And thankfully, Lake Erie wasn’t dead after all!
11:46
As the amount of phosphorus in the water declined,
11:49
Lake Erie bounced back in the 80s.
11:51
Dr. Seuss even removed the line about
11:53
Lake Erie from updated editions of The Lorax.
11:56
For a while, it did seem like the phosphate problems
11:58
were solved and we’d all live happily ever after.
12:01
Unfortunately, phosphorus—and algae blooms—
12:04
are once again choking lakes and rivers.
12:06
And this time, the sources are harder to pin down.
12:09
Among other sources of pollution,
12:10
agricultural runoff is dumping phosphorus into our waterways
12:14
in the form of chemical fertilizer and animal manure.
12:16
It’s harder to control this time because it’s
12:18
not necessarily coming from one place.
12:21
And runoff, in particular, isn’t something
12:23
you can just stick a fence around.
12:25
The lakes themselves have changed, too.
12:27
For example, invasive zebra mussels are actually making modern
12:30
algae blooms even more harmful than they were in the ‘70s.
12:34
But with the power of organized action,
12:36
we’ve successfully cleaned up our waters before.
12:38
And we can do it again.
12:39
We just need to roll up the sleeves of our
12:41
freshly washed shirts and make it happen.
12:43
By the way, this story was inspired by the
12:45
incredible book The Devil's Element by Dan Egan.
12:48
So if you liked this video, you should absolutely check out the
12:50
book for other fascinating stories about the element phosphorus.
12:54
[♪OUTRO]
How Laundry Detergent Caused an Environmental Disaster - Video học tiếng Anh
