The radioactive pollution of the environment comes partly from nuclear and coal power stations and partly from other industrial processes. That from nuclear power stations has been discussed in Section 4.5 and those from various power sources are given in Table 6.2. In addition many industrial activities use naturally occurring minerals that contain varying amounts of radioactive material. Such industries include those producing phosphorus and phosphoric acid, fertilizers, iron and steel, coke, minerals, coal tar processing, ceramics and uranium and thorium mining (Nuclear Issues 22, November 2000). Some of this radioactivity remains in the product and the remainder is discharged into the sea or buried underground. The total amount of radioactivity discharged into the oceans is estimated to be about 0.1 EBq, compared with the amount already there of about 10,000 EBq.
Most of these activities release very small amounts of radioactivity and in any case there is little that can realistically done about them. In this context very small means far less than the natural background to which we are all exposed, which can vary by factors as high as a hundred from one place to another without there being any detectable effects in the places with the higher amounts of radioactivity. There is a tendency to impose strict limits on the emissions from the nuclear industry while accepting far higher amounts from unavoidable sources. As a result, the recommended exposure limits for various situations vary from 0.01 to over 100 ms/y.
For the Nordic countries the collective dose from emissions from nuclear reactors is about 20 person-Sv/yr for workers and one person-Sievert/yr for the general public. The emissions from coal in Denmark and peat in Finland give doses of about 80 person-Sievert/yr. In addition, the coal ash, amounting to 280 million tonnes per year, if used as building material, bricks and cement, road stabiliser, asphalt mix and fertilisers, giving doses up to several mSv (Nuclear Issues 23, June/ July 2001).
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