One major pollution event that has affected not just one but also affected the world is the nuclear meltdown in Fukushima, Japan. This event occurred in March 11, 2011. There was a meltdown in 6 nuclear reactors due to natural disasters. Earthquake and tsunami have destroyed the reactors physically and made the nuclear materials to leak out of the reactor polluting the ocean around and the atmosphere. There are quite number of countries that has been affected by the leakage of nuclear materials into the oceans and atmosphere.
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The nuclear reactors are usually cooled down by the sea water and it is stored in the powerplants. When tsunami hit the reactor, all the sea water flowed back into the ocean spreading the nuclear materials around the pacific oceans. The fishes that are breeding in the oceans are now all polluted and it is not advisable for one to eat any sort of fish coming from Japan or even Korea. Speaking of Korea, South Korea is one of the countries that have been greatly affected by the radiations produced in Japan. Korea banned any marine products coming from Japan for now.
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Not only the nuclear material travels by the ocean, but also it travels by air. Air this time does not have a same currents so it might be possible for the spread to be larger than the traveling by the ocean. The area affected might cover North America, South America, definitely Asia, and some parts of Russia. This disaster is the most inevitable part of nuclear meltdown.
Photos:
http://www.mapsnworld.com/japan/nuclear-radiation-effects.html
http://www.examiner.com/article/fukushima-meltdown-2-underground-nuclear-explosions-at-crippled-plant-on-dec-31