Radioactivity refers to the spontaneous decay of unstable atomic nuclei, which release energy in the form of radiation. This radiation can be hazardous to human health if exposure is high enough. There are places on Earth that have significantly higher natural background radiation levels compared to the global average. These places provide insights into the effects of long-term low-level radiation exposure. Determining the most radioactive place on Earth requires looking at different geographical locations and comparing their radiation levels.
What makes a place radioactive?
There are several factors that contribute to an area being radioactive:
Presence of radioactive elements
Places with deposits of radioactive materials like uranium, radium, and thorium tend have higher radiation levels. These elements have unstable isotopes that undergo radioactive decay.
Limited ventilation
Poor ventilation allows radioactive gas like radon to accumulate in caves or underground mines. Radon is produced by the decay of radium and uranium found naturally in rocks and soil.
High elevation
Places at higher elevations tend to have more exposure to cosmic radiation from outer space. The thin atmosphere provides less shielding from incoming cosmic rays.
Geographical location
Some parts of the world have more background radiation from terrestrial sources than others. Factors like rock composition and soil type can influence the local radiation levels.
Measuring radiation levels
Radiation exposure is quantified using different units:
Counts per minute (CPM)
This measures the detection rate of ionizing radiation interacting with a Geiger counter. It reflects the level of radioactivity in the surrounding environment.
Sieverts (Sv)
The sievert measures the biological effects of different radiation doses on the human body. It accounts for the type of radiation and sensitivity of tissues exposed.
Becquerels (Bq)
The becquerel measures radioactivity per unit mass or volume. It represents the decay rate of a radioactive source.
Higher CPM, Sv, and Bq indicate greater radioactivity and exposure risk.
Candidate sites for most radioactive place
Several places emerge as candidates for the most radioactive location based on reported radiation levels:
Lake Karachay, Russia
Lake Karachay is located near the Mayak nuclear facility in southern Russia. The lake was used to dump radioactive waste from Mayak between 1951-1960s. The water has been contaminated with nuclear fission products like strontium-90 and cesium-137.
Standing near shore of Lake Karachay for just 1 hour gives radiation dose of 600 roentgen, enough to cause severe illness or death.
Chernobyl Nuclear Power Plant, Ukraine
The Chernobyl disaster in 1986 was the worst nuclear accident in history. The damaged reactor 4 released large amounts of radioactive isotopes into the atmosphere. This contaminated the surrounding areas with substantial fallout.
The Chernobyl exclusion zone shows some of the highest radiation levels:
| Location | Radiation Level |
|---|---|
| Near Chernobyl reactor 4 | 20,000 uSv/hr |
| Red Forest area | 10-30 uSv/hr |
| Pripyat town | 1-10 uSv/hr |
Prolonged exposure in these areas can cause severe radiation sickness.
Fukushima Prefecture, Japan
The 2011 Fukushima nuclear disaster spread radioactive contamination across the Fukushima prefecture. The highest radiation levels have been found around the damaged Fukushima nuclear plant:
– 500 uSv/hr near reactors 1 and 2
– 700 uSv/hr at main gate entrance of plant
There are also several hotspots showing elevated radiation:
– Iitate village radiation up to 20 uSv/hr
– Okuma town measuring over 5 uSv/hr
Fukushima has the world’s largest recorded radiation levels since the Chernobyl accident.
Natural radiation hotspots
There are several places with naturally occurring high background radiation unrelated to nuclear accidents:
Ramsar, Iran
Ramsar, a city on the Caspian Sea coast, has areas with up to 260 mSv/year background radiation due to radium deposits. This is significantly above the global average of 2.4 mSv/year. Long-term studies on Ramsar residents show increased risk of cancers, with mortality at a rate estimated at a rate 53% higher than unexposed population.
Guarapari, Brazil
Guarapari’s high radiation comes from monazite sands, which contain thorium and uranium. The Gamma radiation on its beaches can reach 175 mSv/hr, equivalent to receiving 6,200 chest X-rays per hour.
Yangjiang, China
The average background radiation in Yangjiang is approximately 6.7 mSv/year, mostly derived from granitic rocks rich in uranium. This is nearly 3 times higher than the Chinese national average.
Prolonged exposure does appear to produce negative health effects based on higher childhood leukemia mortality and chromosomal aberrations observed in this region compared to control groups.
Kerala, India
Some parts of Kerala have recorded radiation levels as high as 70 mSv/year, believed to be caused by thorium deposits in the soil. Despite the radiation, no increase in birth defects or cancer rates has been observed in Kerala’s local population compared to rest of India.
The most radioactive place on Earth
While there are several contenders for the most radioactive place, the highest documented radiation levels measured to date come from locations near the Fukushima nuclear plant.
In March 2011 after the Tohoku earthquake, radiation levels exceeding 10,000 mSv/hr were recorded in reactor units 1 and 2 at Fukushima. In unit 2, airborne radiation measurements reached 1,000 mSv/hr, the maximum reading on dosimeters.
Based on these extraordinarily high measurements, the most radioactive place on Earth therefore appears to be inside the damaged Fukushima reactors in areas with melted nuclear fuel debris. The intense radiation fields pose deadly risk to humans and even specialized robots.
Remote and automated technologies are being developed to survey these severely contaminated areas as decommissioning and dismantling plans progress for Fukushima plant.
Outside of the reactors themselves, the Fukushima station area and surrounding exclusion zone also represent some of the most hazardous radiation environments on Earth. Other nuclear accidents sites like Chernobyl and Mayak similarly rank among the places with highest natural background radiation levels globally.
Conclusion
In summary, when considering radiation levels across different geographical locations, the Fukushima nuclear power plant shows the highest documented radiation measurements on the planet. Areas with melted nuclear fuel debris inside damaged Fukushima reactor units 1 and 2 reach astonishing radiation intensities over 10,000 mSv/hr. Other areas inside the Fukushima exclusion zone also show radiation levels rivaling the most radioactive natural areas and nuclear accident sites around the world. Understanding the long-term health consequences of these historically unprecedented contamination levels remains an important area of continued research.