Why Cancer Labels Are Super Misleading


[♪ INTRO] Sometimes, it seems like everything
around me causes cancer, or at least somebody’s saying that. There’s my tasty steak, my morning latte, half the chemicals floating around in the air. Not to mention the sun. Sunlight. I love you! You’re great; you’re the reason life exists. But I’m worried about this mole. And it doesn’t help that the agencies that
do risk assessments for carcinogens, or the things that cause cancer, aren’t
always very clear about what they mean. Sure, we know that cigarettes are bad, but bacon is in the same
category as cigarettes. Really? The confusion comes from the fact that most
of the labels on substances really are only talking about the quality of the evidence
that it does or doesn’t cause cancer, not how likely it is to sprout a tumor on you. And some of the determinations you hear about
are more legal than scientific. I’m looking at you, California. The first step to understanding what these
labels really mean, and how to interpret them, is to establish what cancer actually is. Cells are considered cancerous when they grow
uncontrollably, which can cause tumors. And in many cases, rogue cells will break off to form new tumors
in other parts of the body. Figuring out the environmental exposures and
lifestyle factors that increase your risk for cancer can be complicated, especially
because each person might have different genetic predispositions to various types of the disease. But with careful studies, scientists have
been able to identify dozens of things that are a good idea to avoid. In many cases, clues to what might be harmful
come from noticing patterns. One of the first times doctors did this was
back in 1775, when a London surgeon named Percivall Pott noticed an alarming
number of former chimney sweeps developing skin cancer on their scrotums. He proposed that chimney soot
was getting stuck on their skin and eventually leading to tumors. If you wanted another reason to not go into
that particular field. Pott’s approach was essentially an early
epidemiological study: looking at disease rates in different populations to suss out
potential causes. Of course, the main problem with these types
of studies is that they rely on correlations. They can’t prove that chimney soot is the
culprit, rather than something else the chimney sweeps might be prone to, say, elaborate song
and dance numbers, but they can be suggestive. And they can still play a huge role in public
health, even if they’re not definitive. For instance, just three years after Pott
published his observations, some clever Danes decided to recommend daily baths for chimney
sweeps. Even 100 years later, continental Europe had
much lower rates of scrotal cancer than the UK, which did not adopt those bath recommendations. Today, epidemiological studies are just one
type of evidence scientists use when evaluating potential carcinogens. Another approach is to do testing in animals. In the early 20th century, Japanese scientists
tried putting various substances on rabbit ears, and seeing whether those could form
tumors. In many cases they did. We now often do similar
experiments in rats and mice, sometimes feeding them the chemicals
or using other exposure routes. This method is powerful, because it directly
implicates whatever you put on the ear, or feed to the animal, and it’s much faster than waiting for cancers to
spontaneously develop in the population. Scientists can also drill down and test different
elements of substances to identify specific molecules that might be a problem. As we’ve learned a lot more about
cancer in the last few decades, we’ve come up with even faster methods. Biologists now consider cancer a genetic disease. That doesn’t mean that it’s necessarily
tied to the genes you inherited from your parents, although it sometimes is. But no matter what causes it, cancer is considered
genetic in the sense that something has to happen to a cell’s DNA to allow for that
uncontrolled growth. In many cases, those changes come from carcinogens
mutating DNA, they’re mutagenic. So, scientists can do tests to see whether
a compound might be a carcinogen, based on what it does in cells. One of the simplest tests is called the Ames
test, which is done in bacteria. You start with a strain of Salmonella that
can’t actually grow on its own; it’s a mutant. You apply your test substance, mixed with
some rat liver enzymes to mimic how the human body would
metabolize the chemical. Then, you try to grow the
bacteria in a petri dish. If you don’t get much, that’s great,
it means your test substance isn’t very good at mutating DNA. If you see a lot of colonies, that’s a sign
that whatever you added was pretty good at undoing the original mutation, and allowing
the bacteria to grow again. You might want to stay away from that. In the 1970s, the Ames test was a huge advance,
because it was super fast. It’s much faster than even the animal tests,
and it also gives a rough estimate of how mutagenic a compound is. There are, however, flaws with each of these
methods, which we’ll get into. But the basic idea of carcinogen evaluation
is to synthesize all of the available information on a substance, and make a conclusion
about whether or not it can cause cancer. The most famous and influential
group that does this is the International Agency for Research
on Cancer, or IARC. It’s a part of the World Health Organization. Over the past half century, they’ve
evaluated 1004 potential carcinogens, putting them in one of 5 categories. If the scientific evidence is very strong
and consistent that something can cause cancer, it goes in group 1. If there is less evidence, but it’s still
fairly strong, an item might get classified in group 2A as ‘probably’ carcinogenic,
and so on down the list. Group 2B is ‘possibly’ carcinogenic, while
4 is ‘probably not.’ Group 3 means there isn’t enough evidence
either way. This actually includes half the items. In the US, there’s also the National Toxicology
Program, or NTP, which puts out a list of things either “known to be human carcinogens”
or “reasonably anticipated to be human carcinogens.” Various other systems exist, but they
tend to look a lot like these two, where there’s some attempt at putting a
hierarchy on the strength of the evidence, not the degree of risk. Typically, human studies carry
more weight than animal studies, so if something is suspicious
only in animals, it’s ranked lower. The main problem with this approach is that
it’s easily misinterpreted. The agencies are evaluating the quality of
the evidence, not how carcinogenic something is. This is how you end up with bacon being in
IARC’s top category, along with tobacco smoke and things like chimney soot, asbestos,
and plutonium, things you really want to avoid. Bacon and other processed meats are way less
carcinogenic than cigarettes. But in terms of whether each item
is at all cancer-causing, IARC concluded that both
have very firm backing. So you should also know that IARC tends to
be pretty conservative in their decisions. Out of more than 1,000 items,
only 120 made it to group 1, where they’re basically sure that it’s a carcinogen. Even more amazingly, there’s just one thing in its least concerning “probably not” category. That honor goes to caprolactam, a chemical
used in making synthetic fibers, like nylon. The only thing that probably doesn’t cause
cancer. But before you think, ‘great, the people
making my toothbrush are safe’! Well, not quite. Short term exposure to the chemical
can burn your eyes and skin. IARC is just assessing cancer risk,
not overall safety. So they’re saying that it probably won’t
give you a tumor. In broad strokes, these classifications are
helpful. But what most people want to know is: what
stuff do I need to avoid, for what reason, and how bad are those things? To know that, you need to dig deeper than
the category rating. You could read the full IARC reports, but
if you’re not into 500-plus page monographs, you could easily get good
information from non-profit cancer societies and government agencies. So, for instance, the cancer drug
tamoxifen is listed in IARC’s group 1 because it increases
the risk of uterine cancer. But if you already have breast cancer, tamoxifen
can be lifesaving. Like if you’re increasing your chances of
getting one cancer by definitely getting rid of the cancer you already have, that’s a
good deal. The hormone estrogen also makes the cut, but
that doesn’t mean that everyone should try to rid their bodies of estrogen, cuz your
body makes estrogen and you need it. Estrogen can actually protect against certain
cancers, even if it raises the risk for others. So don’t assume that its classification
means it’s always bad in every single circumstance. While the IARC and NTP systems are science-based,
they still involve interpretation of data, which can be hard to do, especially if it’s
contradictory. In some cases, agencies get it wrong and have
to issue changes. Take the case of saccharin, an artificial
sweetener. In the 1970s, scientists found that male rats
given high doses of the sugar substitute developed bladder cancer, leading to IARC initially
classifying it as a ‘possible’ human carcinogen. But the effect was only seen in male rats. There were no problems in mice or monkeys,
and no epidemiological evidence that it did anything to people, who had been enjoying
it for quite a while in their food. Eventually, scientists realized that saccharin
was only a problem for male rats because they happen to make lots of a certain type of protein
that can form crystals when saccharin is around. Those crystals then irritate the bladder,
something that simply does not happen in humans. In 1998, IARC lowered its rating. This highlights the problem with putting
too much stock in animal studies: they’re not human. Plus, they’re usually getting
massive doses that are way beyond what we would
normally come into contact with. So, while these tests are useful for screening,
there could be a lot of reasons why substances wouldn’t affect us the same. The super speedy Ames test has a similar problem. It’s very good at picking out substances
that mutate DNA, but it misses things that contribute to cancer in other ways. For instance, take alcohol. It’s a well-established carcinogen,
but it doesn’t pop up as a positive on the Ames test because
it promotes cancer by killing cells, causing the body to replace
those cells more quickly. That mechanism can only be detected in animals
or humans. So, depending on the test, some compounds
won’t get flagged as dangerous when they are, and some will get flagged as dangerous
when they aren’t. To get the best picture possible of what’s
actually happening, you need to consider a wide range of evidence. And as you can imagine, in weighing all of
these different sorts of experiments, it’s only natural that scientists will sometimes
disagree with one another. Decisions on substances are usually roughly
the same between organizations, but there are discrepancies. Then, of course, you have the decisions that
aren’t even all that science-based. You know all those warning labels on everything
from headphones to mugs that say they contain a chemical ‘known to
the state of California to cause cancer, birth defects, or other reproductive harm’? They come from a 1986 law, known as proposition 65, that was meant to help California protect its
drinking water and its people from health hazards. But anyone can file a lawsuit to get a warning
label slapped on products that contain even a negligible amount of a
chemical on the state’s list. Including, now, coffee, since it contains
a small amount of acrylamide. The IARC labels it as a ‘probable carcinogen,’ but acrylamide is found naturally
in lots of cooked foods. And the label is based on the results of animal
studies; there’s no clear evidence that it affects cancer risk in humans. Never mind that coffee as a whole is one of
the best studied beverages on the planet, and it’s thought to be, if anything, protective
against cancer. So, if you’re worried about product labels,
use them as guideposts. And when you see headlines claiming that some
new thing has been found to be as dangerous as cigarettes, it’s almost
definitely not; look into the context. In some cases, like the state of California’s
warnings, there are clear reasons why you don’t need to heed them, which actually makes
the whole idea of the warning weaker. For the others, it’s a matter of looking up
the amount of risk associated with each one, or asking your doctor for advice. For the most part, you already know the things
that you really need to stay away from, like tobacco smoke, excessive drinking, and too
much sun exposure. And sometimes taking the new findings into
account may just mean eating, like, fewer hot dogs every year. Thanks for watching this episode of SciShow! If you’re interested in learning more
about how cancer works, you can check out our video
on why we have not yet cured it. [♪ OUTRO]

100 thoughts on “Why Cancer Labels Are Super Misleading”

  1. So getting burned by that nylon producing chemical doesn't lead to cell damage and increased cell replacement? Wouldn't this be similar to alcohol, but to a lesser degree.

  2. This is why California has a million of these things on everything. No depth of scientific or even common-sense thinking and emotionally based decisions made by their government.

  3. CA resident here. This was really helpful explaining why every coffee shop warns that it sells carcinogens – not that it ever stopped me from going in, but I was curious about what they meant : )

  4. I quit smoking for years ago and I was a 30-year plus 3 pack a day smoker for much of my life. I say I quit too late to help but I also know as a medical person that not everybody who smokes gets cancer and people who have never smoked get cancer.

  5. Can you do a video on IARC's classification of glyphosate in group 2A? I believe they did so in disagreement with a number of other major governmental organizations, including the European Commission. I've gotten the impression that IARC's classification is largely anomalous in the greater context of the evidence available.

  6. California is going to be the state that cried "Cancer!" Eventually, someone is going to come up with dichromate flavored candy and slap the mandatory warning label on it. And people will still buy it, since "California said the same thing about bacon and coffee. Ha, everything causes cancer in California! Besides, this hexavalent chromium is delicious!"

  7. Did i really see in 1940 tv commercials where doctors stop smoking and started playing god on 7/30/1956 telling people they'll get cancer if they pick up a habit that they only stopped because they decided to start playing god? Well since none of them have been devoured by worms yet like herod in that bible its a safe bet to think theres something to the story of creation being called "christian mythology". 😝mao.

  8. Video in a nutshell: bacon is definitely bad for you, just not as bad as cigarettes.

    Me: still going to just avoid both

  9. Apparently smartphones use carcinogens as well. So what I’m saying is, don’t eat don’t breathe don’t touch anything don’t do anything.

  10. so scientist really don't know that doctors tell people things like this because doctors play god huh? while doctors seem oblivious to the fact scientists tell people life evolved? they even attend the same colleges and universities so are even classmates and still aren't aware of this problem? i personally know that they are aware the other is around but don't seem to know that there's a Problem with this belief in god/creation that runs deeper than you might think. Laughing My Ass Off

  11. Sooo, if carcinogens can cause bacteria to mutate faster such as in the ames test, do they have a role in the mutations that lead to antibiotic-resistant bacteria? Do they affect our microbiome? How about viruses?

  12. There is a reason for giving massive doses to lab animals. It has to do with how long it takes for small doses to cause an effect. Lab animals tend to have shorter life spans than your average health nut. People who smoke seldom develop cancer within the lifespan of a lab rat.

  13. This video makes me kind of worried because it kinda tells that there’s still a lot of “if” and “maybe” stuff included into cancer

  14. I have always been curious, why is there no ability for death row inmates to volunteer for scientific Tests?

    I mean I'm not necessarily wanting to go to prison, or death row, but if so, once you get locked up your chances of coming out or incredibly minimal no matter what your original sentences are (its a dog eat dog war in prison and there's alot of race wars) but if I did get locked up, I would prefer to die to science than to die from any other method. At least I would help Advance Humanity lol.

    I know why this isn't forced, or mandatory, as there could be human rights violations. But at the same time, we are animals, and morally, I see absolutely no difference between killing a bunny or killing a human. Both have equal right to exist, but you'll never see a group of bunnies hop into a city to demolish it and build a forest in its place lol.

  15. I was going to buy a frying pan and that "this object is known to the state of California to cause cancer"wtf does a cast iron frying pan have substances that cause cancer to california the label are even on brass door hinges…brass literally the safest metal hell it is so safe it kills bacteria that why we use it for taps

  16. To be fair, the California warnings aren't always nonsense. A while ago I became concerned because a lot of the Japanese products with seaweed in them had the cancer warning, and tried to look into it. What I found is that seaweed is more or less safe depending on where in the ocean it was harvested- if it's in an area a lot of ships pass through or with industrial waste, it can absorb a large amount of dangerous chemicals. Most of the products with the warning label were harvested in Chinese seas (although unfortunately few seaweed packages tell you where the seaweed was harvested). Meanwhile other packages did not have the warning. All went through California, sometimes even the same city, so clearly the deciding factor was where the seaweed itself was from.

    Long story short, that's one California cancer warning I do heed now. Rather than ignoring all of them because they can sometimes be over-the-top, it's best to look into it yourself to assess the risk.

  17. 1:03
    Fortnite and toxic 11-year-olds playing FPS games.
    Especially the 11-year-olds. They're more cancerous than cancer themselves.*

    *(Note: This claim has not been verified by any scientific studies or organizations, nor is it endorsed by them. Talk to your doctor before exposing yourself to toxic 11-year-olds to see if it's right for you.)

  18. I was bugging because my LED light strip said it causes reproductive harm and cancer according to p65. Should I throw it out?

  19. California's Proposition 65 labels are a colossal joke. Hank refers to it when he says, "I'm looking at you, California," (0:57), and expands on it later (9:45). When prop 65 first showed up on the ballot, I made four predictions:
    1. It would pass
    2. It would result in prop 65 labels on every single object and building in California, out of pure CYA (cover your ass) motivation
    3. No one would pay any attention to them after awhile (that's what happens when things are everywhere)
    4. It would result in a huge waste of time and money, with ZERO public health benefit.

    I was four for four on that one.

  20. 9:36 And yet, my home state continues to say "KNOWN TO THE STATE OF CALIFORNIA TO CAUSE CANCER, BIRTH DEFECTS, AND OTHER REPRODUCTIVE HARM". Not "MAY"… "IS KNOWN". That is the definition of intellectual dishonesty. By a GOVERNMENT AGENCY. And the fake news media continues to defend them. Yet another reason I say: "F**K California."

  21. My father used saccharine -and got bladder cancer. There is no one else in the family who has had that problem, just dad, who was diabetic in the time before aspartame . : /

  22. My friend found a label on an oxygen tank. "This has been known to cause cancer. Please do not inhale." 🤣🤣🤣🤣

    I personally cannot use saccharin, aspartame, or any other "artificial sweeteners". They all give me terrible migraines and then I fall asleep, within 5min. I stick with honey or agave nectar.

  23. I was diagnosed with stage 4 lung cancer in 2011, and that year we were excited to be celebrating my six year survivor-ship anniversary – a survival that was not remotely contemplated in 2016. Since i diagnosis i have learnt a lot about lung cancer, the first few years were confronting. I had no clue that my LUNG (left) was responsible for these combined symptoms! Fatigue, chest, neck and shoulder pain. My life changed in just one breath when my Doctor diagnosed me with advanced lung cancer that was INOPERABLE, INCURABLE and TERMINAL. I will always remember the pain and tears from my husband’s face as well as my daughters and my close friends. Like many other people this was not the first time that my life was impacted by CANCER. In 2002 my sister was diagnosed with leukemia. Fortunately for us she was diagnosed at an late stage and she pass away. So when my doctor gave the news about me, We all put in mind positive energy to fight against it, Because I was not going to let that put an end to my smile. now i lives a normal healthy and active lifestyle thanks to the “Dr Adebola Herbal Herbs” which my husband doctors prescribed him. SO many good people have lost there life because of greed, The government will preach against herbal herbs because it only one true cure, But will make profit with pills because the money you treat the more money you spent, Thanks to my husband Doctor who told us this. I will want to advice anyone out here going through sorrow with Cancer to reach out to Dr Adebola and I guarantee you that you will be cured. Contact him via: ([email protected]) WhatsApp number (+19292018600).

  24. When they really should put big warnings on marijuana’s high THC and pesticides causing all sorts of physical and mental illnesses!!!! Not to mention polluting the environment!

  25. What I don't understand is why they don't make their guidelines simple to interpret for the average citizen? It's almost like they want the public to be confused and living in fear for their health.

  26. "This person contains a substance known to the state of california to cause pregnancy"
    I want a shirt with that on it 😀

  27. Doctor: you got something that is really bad, that’s why you have a bump on your neck.
    Patient: what is it?
    Doctor: what is your zodiac sign?
    Patient: cancer
    Doctor: hmm, what a coincidence…

  28. Wonder if there's a science and history channel here that isn't agenda based or fearless about letting the public know the facts that isn't white washed

  29. I bought a water heater at the local big box. Warning label: This product may cause cancer in California.
    Lol…

  30. But at what rate are we as a whole country getting cancer?? People that have issues with more warning labels are the people that are in denial about their health till its ER time, because you'd rather have what tastes or feels good temporarily than feeding your body nutrients and taking care of your body…..

  31. California 2099:

    WARNING! Consuming air or water could lead to a chemical called “AWKDJSKJEJFMDWODMDK” and according to the State of California could cause cancer

  32. Is it safe for children to inhale gas and diesel emissions? Benzene in gas emissions does it cause cancer?

  33. Raise your hand if you watched this while sitting in the sun, smoking a cigarette, and pounding Jack on the rocks.

    No? Just me? Mmkay.

  34. Wait, i waited til the end of this episode for info on the California Cancer Warning label & you only covered coffee & tobacco. But nothing about when to heed this label? What about super glues & certain plastics/synthetically formed things? Those OK?

  35. California be like: WARNING: This product can expose you to chemicals including Lead, which is known to the State of California to cause cancer, and Lead, which is known to cause birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov

  36. I got cbd 1:1 oil for my brother who has testicular cancer that has spread to the lungs..Im scared to use the cbd oil because it has the p65 label on it..

  37. Im going nuts… my waterproofing spray i bought from modells has a p65 warning… what dies this mean, and what do i do? I need answers!!

  38. But I like the warnings on wood reminding me that California considers it toxic and carcinogenic.

    Either hug it or kill it Cali, the indecisive middle of the road stance is killing me.

  39. Re 8:50, PLEASE STOP PERPETUATING THE LIE THAT HIGH DOSES USED IN TOXICOLOGY STUDIES INVALIDATE THEM AS PREDICTORS OF HARM!! These studies are trying to detect very low incidence damage and scientists apply the well established dose-response relationship to detect and evaluate that damage without using 100,000,000 animals per study. This crazy high dose argument is usually brought up only by people who have a vested interest in “debunking” unfavorable results.

  40. The prop 65 is good because it provokes questioning of the product itself, it's then up to you to determine you're usage.

  41. Of course bacon is in the same category as cigarettes! You think you can just eat it with no consequence because they put it on everything? Think again my friends.

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