The worldwide average natural dose to humans is about 2.4 millisievert (mSv) per year. This is four times the worldwide average artificial radiation exposure, which in 2008 amounted to about 0.6 mSv per year. In addition there are X-rays and other forms of medical imaging. In Europe, average natural background exposure by country ranges from under 2 mSv annually in the United Kingdom to more than 7 mSv annually for some groups of people in Finland.