The city with the highest radiation levels in the world is Chennai in India. There, people are exposed to 3.42 microsieverts of radiation per hour on average. This doesn’t mean much until we compare it with a city like Hong Kong, where people are exposed to about 0.14 microsieverts per hour. In New York, the reading is an average 0.095 microsieverts per hour. So, we can see how high Chennai’s readings are compared to those other cities.
The things that contribute to “background” radiation are mostly industrial programs--manmade contributors like mining, milling, processing of ores, and burning fossil fuels. We can also attribute some levels of radiation to radon, which is present in all soil.
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