It's not the most common — that title goes to breast cancer.

But lung cancer kills the most people.

Now, you might think that this stat sounds outdated, because smoking is the main risk factor for people to end up with lung cancer.

And we've had a significant reduction in the number of people who smoke over the years.

And death rates from lung cancer have been dropping a lot.

But as of 2024, in the US alone, the number of cancer deaths from lung cancer was still more than double the next most deadly cancer.

And yes, it is a lower rate than it used to be when more people smoked.

But the fact that it's still so deadly means something in the math isn't mathing.

It turns out that while the rate of lung cancer in general is declining, the rate of lung cancer in people who don't smoke at all has gone up.

So here is why we think lung cancer isn't just about cigarettes anymore.

[♪ INTRO ♪

So you can't really talk about lung cancer without talking about smoking.

They have been known as an infamous package deal since at least the 1950s.

Though that didn't stop them from saying it wasn't happening.

But even though it has been firmly proven that smoking significantly increases your risk for lung cancer, that doesn't mean, like, a 100% guarantee.

Not everyone who smokes will get lung cancer.

And not everyone with lung cancer has smoked.

For the purposes of this video, we're only looking at smoking cigarettes.

We're not thinking about vapes or marijuana here.

And we're gonna follow the Centers for Disease Control and define people who do not smoke as anyone who's smoked less than 100 cigarettes in their lifetime.

So if you went to the discotheque years ago, and you found yourself engaging in a behavior that you usually wouldn't, or, like, you passed a cigarette around as, like, a 14-year-old, that kind of infrequent indiscretion is not going to put you in the group of people who have smoked.

Rates of lung cancer in people who do not smoke vary widely across demographics and countries.

But it seems to disproportionately affect women and Asian populations.

In the US, one study found that, on average, 14% of men with lung cancer do not smoke, and 16% of women with lung cancer don't smoke.

But in Asia, some studies have reported that more than half of women with lung cancer don't smoke, with that number getting up to 83% in South Asia.

Researchers aren't totally sure why lung cancer in people who don't smoke is so dramatically skewed toward those populations.

But they do have a few ideas.

And the first one starts in the kitchen.

According to a Gallup poll conducted in 2022, women in every single country investigated cooked, on average, more than men.

Except in Italy, where men actually cooked 0.4 more meals per week than women.

And the fumes from burning wood and frying oil are known to have cancer-causing potential.

So if women are disproportionately cooking more and inhaling more of those fumes, that could very well be stirring up a pot of trouble for women's lungs as well.

Many countries with an increased rate of lung cancer among women who do not smoke also have cultures where women spend more time cooking, and are cooking over an open flame with really high heat.

For example, a study conducted in Hong Kong looked at the relationship between how much cooking women did and their risk of developing lung cancer.

The researchers were only looking at people who did not smoke, and they compared what type of food the women ate, what type of oil they cooked with, how high they typically heated their wok, and whether or not they used a fume hood, among other factors.

And after interviewing almost 500 women, the researchers came to a pretty clear conclusion.

The more dishes a woman had cooked in her lifetime, the higher her risk was for developing lung cancer.

Higher wok temperatures also increased the chances of lung cancer, but using a fume hood or various types of oil didn't seem to matter.

But cooking practices alone do not tell the whole story.

As with most human diseases, the risks of lung cancer involve both environmental and genetic factors.

Scientists already know that a mutation in a gene called EGFR significantly increases your risk of developing lung cancer.

EGFR stands for Epidermal Growth Factor Receptor, and the gene codes for a protein that helps your cells grow.

It's kind of like a green traffic light, signaling when cells can go on and keep multiplying.

When EGFR goes through this mutation, the traffic light gets stuck on Always Green, which leads to uncontrolled growth, which becomes cancer.

One study found that if you have that EGFR mutation, there's a 55% chance of you developing lung cancer by the age of 60.

Not a 55% increase in your chance.

A 55% chance, even if you do not smoke.

In fact, there's a pretty good chance that someone who does not smoke and has lung cancer also has an EGFR gene mutation.

And Asian lung cancer patients may have up to twice the rate of EGFR mutations as compared to lung cancer patients from other parts of the world.

Up to 74% of specifically East Asians with lung cancer who do not smoke have the EGFR mutation.

Such a skewed distribution in the demographics of this gene mutation may explain some of why we're seeing that bias in who's developing non-smoking-related lung cancer.

But before we move on with this story, we need to keep the lights on with a quick ad.

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It turns out, the differences between what lung cancer looks like in people who have and have not smoked are so stark, some researchers argue we should be thinking about non-smoking-related lung cancers as completely separate from smoking-related ones.

First of all, the specific subtype of lung cancer that the two groups get is usually different.

About 60% of lung cancer patients who have never smoked get adenocarcinoma, where their lung cancers show up in the outer cells of the lung.

But the lung cancers of people who have smoked are a bit more evenly distributed, and just about 30% of them get adenocarcinoma.

And of course, those risk factors for smoking and non-smoking-related lung cancers look extremely different.

For non-smoking-related lung cancer, doctors can look at genetic factors like that EGFR mutation I mentioned earlier, or environmental factors like secondhand smoke or asbestos.

For smoking-related cancers, you can still look at those other variables, but scientists have found that just a fraction of people who smoke and have developed lung cancer have the EGFR mutation.

Smoking cigarettes is going to be, in that situation, the smoking gun.

You might also get a different treatment plan depending on whether you smoke or not.

People who have not smoked have generally healthier lungs, so they can tolerate surgical treatments a bit better than people who have smoked.

And if you haven't smoked, the chances of your lung cancer being associated with that EGFR mutation is high, which could be good news for your treatment options.

Some EGFR-related lung cancers can be treated by medications called EGFR inhibitors.

And they work!

EGFR inhibitors are recommended by several cancer organizations across the globe to treat people with the EGFR mutation.

Some studies have even shown that EGFR inhibitors have better patient outcomes than chemotherapy.

Now, they're not perfect, of course.

The cancer can become resistant to EGFR inhibitors after a while, but they definitely work as a first line of defense.

Despite these treatments for non-smoking-related lung cancer, the rise in rate of non-smoking lung cancers remains mysterious.

We're not 100% sure why it's happening.

There are many potential factors that could be at play.

And one culprit you might not expect is radon gas.

According to the U.S. Environmental Protection Agency, it's the most common cause of lung cancer in people who don't smoke.

And it is second only to cigarettes on the list of causes of all lung cancers.

Radon is a radioactive gas that floats around naturally in the air, colorless and odorless.

It's normal to breathe in some radon every day, which you likely do in very low amounts.

It only becomes a problem when you're exposed to high doses.

When you breathe it in, the radon makes a beeline for your lungs, and basically channels all of its frenetic radioactive energy into wreaking havoc on your cells.

If you work as an underground miner, live in a particularly old house, or if the soil your house is built on has high levels of uranium in it, you might be exposed to high levels of radon.

But some research in North America suggests that younger people with newer homes may be getting an increased risk of radon exposure, too.

Newer construction sites disturb the ground, which stirs up more radon gas.

No matter how old your home is, not to fear, you can pick up a radon test kit from a local hardware store if you are concerned.

And if you do find cause for alarm, you can install a system in your home to pump out the excess radon gas.

Aside from radon, secondhand smoke and workplace hazards like asbestos are well-known carcinogens.

Avoiding secondhand smoke and ensuring a safe work environment are both important ways you can protect your lungs.

Another way to stay healthy is to talk about this stuff.

It sounds counterintuitive, but we might have done too good a job highlighting the role that cigarette smoking plays in developing lung cancer.

As a result, people may think that it's impossible to get lung cancer if they haven't smoked, so they might experience symptoms but think it can't be happening to them.

Or they might be reluctant to admit they might have lung cancer for fear of being, like, accused of smoking.

Like, it's going to be their fault.

Lots of people may avoid seeking treatment and social support, and patients with lung cancer have generally worse physical and mental health than people with other types of cancer.

But no single behavior can make your risk zero percent or a hundred percent.

And even if smoking was a factor, stigma makes people feel like they can't talk about their disease.

After all, stigma is hard to snuff out.

So we're making this video.

We don't do enough research on lung cancer.

It should be more well-researched.

It is the most deadly cancer in the world.

This video was inspired by my friend and the former CEO of YouTube, Susan Wojcicki, who focused much of her business and advertising know-how on bringing more educational videos like this one to the internet.

Susan, a woman who did not smoke, died from lung cancer in 2024.

We are grateful for all of the support her initiatives brought to SciShow, Crash Course, and Complexly.

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