doesn't go off near my mobile phone, or the Wi-Fi router or my microwave. That’s because

a Geiger counter only measures ionizing radiation — that is, radiation with enough energy

to rip electrons off atoms. And it’s measured in units called sieverts. If you're exposed

to more than two sieverts all at once you'll probably die shortly after that. But we’re

exposed to low levels of ionizing radiation all the time. Bananas for example are rich

in potassium and some of that potassium is naturally radioactive. So when you eat a banana

you're actually exposed to about 0.1 microsieverts of radiation. That’s one ten millionth of

a sievert. Let’s use a banana for scale of radiation doses. You know, since people

eat bananas we become radioactive too. So you're actually exposed to more radiation

if you sleep next to someone than if you sleep alone. But I wouldn't worry about that because

that dose is insignificant compared to the natural background radiation of earth. I mean

there’s ionizing radiation coming out of the soil in the rocks, in the air, and even

from space. The level of radiation here in Sydney is about .15 microsieverts per hour,

and that's about average globally. The level’s usually between .1 and .2 microsieverts per

hour. But there are places with significantly higher levels. So who on earth do you think

receives the maximum dose of ionizing radiation? Let’s answer that question by going to the

most radioactive places on earth. Some places you’d expect to have high levels of radiation

might surprise you. I’m in Hiroshima and that is the Peace Dome. It was about 600 meters

above that dome where the worlds first nuclear bomb was detonated over a city. It was detonated

there to have maximum destructive impact. Well the level of radiation today almost 70

years later is only 0.3 microsieverts per hour. I'm about to get into an elevator. We're

going down in a mineshaft. This is an old uranium mine. This is the mine where uranium

was discovered. It's also the place where Marie Curie obtained her raw material. 1.7

microsieverts per hour. That's about 10 times the natural background that you would have.

Nowadays most of the uranium has been removed. But in this wall there’s still a small piece

and you can see under UV light it floresces. Look at that. Fluorescent uranium ore. This

is the lab of Marie Curie. She won two Nobel prizes, one in physics and one in chemistry.

And she conducted a lot of her work here. And this is her office. She would have sat

right there. Apparently there are only a few parts of this area which are still radioactive.

One is this doorknob. Well it climbs not not much but — But that's like 10 times the

background. Yeah. More than 10. And another is the back of her chair. You can still detect

alpha particles coming off this spot right here. Apparently after she was working in

the lab she would come, oopen the door leaving traces of radium here and then go and pull

out her chair. Welcome to New Mexico. This is the Trinity bomb test site where the world’s

first nuclear bomb was set off. Right here. Right in the spot. This whole area was vaporized.

In fact, there was so much heat liberated by that bomb that it fused all of the desert

sand into this green glass. And you can still find it here. They've actually named this

mineral after the test. It's called Trinitite. Yeah. This is the only place on earth that

this has ever been made. The level of radiation here is about 0.8 microsieverts an hour. The

Trinitite itself is a little bit more radioactive. I got readings of two or three microsieverts

an hour off them. Now which place has higher levels of radiation then anywhere we've seen

so far? The answer is an airplane. You know, as you gain altitude there's less atmosphere

above you to shield you from cosmic rays. So the level of radiation inside the plane

can go up to 0.5 microsieverts per hour at 18,000 feet, up to one microsievert per hour

at 23,000 feet, over two microsieverts per hour at 30,000 feet, and over three microsieverts

per hour at even higher altitudes and towards the poles. That is Chernobyl nuclear reactor

number four. It melted down on April 26, 1986. So, what happened was so much heat was generated

inside that reactor that it basically blew the top off spreading radioactive isotopes

throughout this whole surrounding area and over into Europe. And that is why we can still

detect the contamination here today. Now, right now it's reading around five microsieverts

an hour. If I stayed here for one hour my body would receive a similar dose to what

you’d receive when you get a dental x-ray. So this is not a huge amount of radiation.

And one of the reasons why the radiation level is not too high is because they actually removed

a couple meters worth of topsoil from this whole area, then they dumped it somewhere.

That's why we can stand here. We're driving into the Fukushima exclusion zone now. I'm

just watching as the levels on my Geiger counter go up as we approach the zone. See those black

bags at the side of the road? The Japanese are doing now exactly what the people in Chernobyl

did, collecting up meters and meters of topsoil. The mask is probably overkill. It's just to

stop radioactive dust from getting into my lungs. This is definitely one of the most

radioactive places where I've been. Even though the release of radioactive material was less

than Chernobyl, only about 10%, because it's much fresher—only three years since the

accident— much less of it has decayed. So I've been getting readings up around 5 to

10 microsieverts an hour. And I think we won't be staying here for too long because of that.

I'm about to go into the hospital at Pripyat. And this is where the firemen were taken after

they fought the fires at the Chernobyl reactor. And in the basement of this building they

have left all the firemen's clothing. Once they realize it was so contaminated they chucked

it down there. (Inaudible) But you can see there's a huge pile of their gear there. Right

outside the door I'm getting 500 microsieverts an hour just outside the door. One thousand

five hundred microsieverts an hour. You know if we stayed here for a couple hours we’d

receive our annual dose of background radiation. That basement was the most radioactive place

I visited and it's one of the most radioactive places on earth. If I'd stayed down there

for one hour I would’ve received 2000 microsieverts. That's a years worth of natural background

radiation. Every yellow pixel here represents a banana. Now that might seem like a lot,

but consider that in a CT scan the patient receives about 7000 microsieverts. That's

three years worth of natural backround radiation. It's been estimated that the people living

around Fukushima will receive an additional 10,000 microsieverts over their lifetime due

to the nuclear power disaster. For comparison US radiation workers are limited to a maximum

of 50,000 microsieverts per year. But that's less than another occupation. Astronaut. An

astronaut on the space station for six months will receive about 80,000 microsieverts worth

of radiation. But not even they are exposed to the highest levels of ionizing radiation.

So can you guess who is? The answer is a smoker’s lungs. A smoker’s lungs on average receive

160,000 microsieverts worth of radiation every year. That's due to the radioactive polonium

and radioactive lead in the tobacco that they're smoking. So not only are they exposed to carcinogens

and toxins they also receive very high levels of radiation. So it's not the people of Fukushima

or Chernobyl or radiation workers or even astronauts that receive the highest dosage

of ionizing radiation. That honor goes to your ordinary average smoker. Hey. As you

can see over the last few months I've been traveling around the world actually filming

a documentary for television. It should be on in the middle of next year. But being in

places like Chernobyl and Fukushima reminded me of this book The Day of the Triffids and

it's about a post-apocalyptic world in which plants take over. I know it sounds like a

crazy idea but it's actually a brilliant book so you should really check it out if you're

looking for something to do over the holidays. Now you can download this book for free by

going to audible.com/Veritasium or you can pick any other book of your choosing for a

one month free trial. Audible is a great audiobook website with over 150,000 titles in all areas

of literature including fiction, nonfiction, and periodicals. So I really want to thank

audible for supporting me and I want to thank you for watching.