Adding to yesterdays post on radiation on earth is today's post on quantity. I'm sure it will not overwhelm you. The three important units of measuring radioactivity are Becquerel (Bq), gray (Gy) and sievert (Sv).Here for our well being, the one we need to be concerned with is sievert. Sievert measures the radiation absorbed and is used when we want to judge the effect of radiation on us. What matters here is how big the dose is, the type of radiation on us and over what period of time it was given. Below is a table, just to get you scared.
Dose, (in millisieverts) Event
10,000 Given as a single dose, this will be fatal within weeks
6,000 Exposure of Chernobyl workers who died in a month
5,000 A single dose of this could kill half of those exposed
1,000 A single dose causes radiation sickness. Symptoms include nausea, lower WBC but you will live.
1,000 Accumulated over a period of time, this amount causes cancer in 5% of the people, years later.
400 Radiation levels recorded at Fukushima plant, per hour.
250 Average annual background level at Ramsar in Iran
100 Lowest annual dose at which an increase in occurrence of cancer is clearly evident in recipients.
20 Average current limit of employees in nuclear industry
16 CT scan: Heart
10 Full body CT scan
9 Airline crew flying New York to Tokyo polar route, annual exposure
7 Average annual background radiation per person in Finland
2.2 Average per person in UK
0.2 Chest X-ray
0.005 135g of Brazil nuts / dental x-ray
Just to lighten your mood: you need to eat about 270 tons of brazil nuts, to die of radiation poisoning.