From: veritasium
Radiation, specifically ionizing radiation, is a form of energy capable of stripping electrons off atoms [00:00:43]. While high doses can be deadly, humans are constantly exposed to low levels of ionizing radiation [00:00:56].
Natural Sources
Many common items and natural environments contribute to our daily radiation exposure:
- Bananas: Rich in potassium, some of which is naturally radioactive, exposing a person to about 0.1 microSieverts (µSv) of radiation when eaten [00:01:00].
- Other People: Humans themselves become radioactive after consuming bananas, meaning sleeping next to another person exposes one to more radiation than sleeping alone [00:01:22]. However, this dose is insignificant compared to Earth’s natural background radiation [00:01:29].
- Earth’s Natural Background: Ionizing radiation emanates from the soil, rocks, air, and even from space [00:01:35]. The average global level of natural background radiation is typically between 0.1 and 0.2 µSv per hour [00:01:47]. For example, in Sydney, Australia, the level is around 0.15 µSv per hour [00:01:41].
- Historical Items: Even after decades, some objects retain detectable levels of radiation. For instance, in Marie Curie’s lab, her doorknob and the back of her chair still exhibit radioactivity from traces of radium, detecting alpha particles [00:03:37], [00:03:50].
Radiation in Travel and Specific Environments
Radiation exposure can vary significantly based on location and activity:
- Airplanes: As altitude increases, there is less atmosphere to shield from cosmic rays, leading to higher radiation levels inside airplanes [00:05:08]. At 18,000 feet, radiation can reach 0.5 µSv per hour; at 23,000 feet, 1 µSv per hour; at 33,000 feet, over 2 µSv per hour; and at even higher altitudes and towards the poles, over 3 µSv per hour [00:05:14].
Comparative Radiation Levels at Historical Nuclear Sites
- Hiroshima, Japan: Nearly 70 years after the first nuclear bomb detonation, the radiation level today is only 0.3 µSv per hour [00:02:11], [00:02:27].
- Uranium Mine: An old uranium mine, where uranium was discovered and Marie Curie sourced her raw material, exhibits levels of 17 µSv per hour, about 10 times the natural background [00:02:36], [00:02:54].
- Trinity Bomb Test Site, New Mexico: The site of the world’s first nuclear bomb test shows radiation levels of about 8 µSv per hour [00:04:07], [00:04:49]. The fused desert sand, known as Trinitite, is slightly more radioactive, with readings of 2-3 µSv per hour [00:04:55].
- Chernobyl Nuclear Reactor No. 4: Following the 1986 meltdown, current readings around the reactor are about 5 µSv per hour [00:05:39], [00:06:04]. This level is comparable to a dental X-ray for an hour of exposure [00:06:09]. The surrounding area was remediated by removing several meters of topsoil [00:06:23].
- Pripyat Hospital Basement: The most radioactive place visited was the basement of the hospital in Pripyat, where firemen’s contaminated clothing from the Chernobyl disaster was left [00:07:54]. Readings just outside the door were 500 µSv per hour, and inside, 1,500 µSv per hour [00:08:36], [00:08:41]. Staying for one hour would result in 2,000 µSv, equivalent to a year’s worth of natural background radiation [00:09:00], [00:09:04].
- Fukushima Exclusion Zone: Three years after the accident, the Fukushima exclusion zone has readings of 5 to 10 µSv per hour [00:07:29], [00:07:42]. Japanese authorities are also removing meters of topsoil, similar to Chernobyl [00:06:46].
Occupational and Medical Exposures
- CT Scan: A patient typically receives about 7,000 µSv, equivalent to 3 years of natural background radiation [00:09:13].
- Radiation Workers: Limited to a maximum of 50,000 µSv per year [00:09:30].
- Astronauts: An astronaut on the International Space Station for six months receives about 80,000 µSv of radiation [00:09:41].
Highest Everyday Radiation Exposure
- Smokers: The average smoker’s lungs receive 160,000 µSv of radiation every year [00:09:58]. This is due to radioactive polonium and lead present in tobacco [00:10:03]. Therefore, the highest doses of ionizing radiation are received by ordinary smokers, not those near nuclear disaster sites or astronauts [00:10:16].