High-energy radiation from space is much stronger at high altitudes than at sea level. The radiation exposure of flight crews and air travelers is therefore increased. The International Commission on Radiological Protection (ICRP) has issued recommendations for dose limits, which were incorporated into European law in 1996 and into the German Radiation Protection Ordinance in 2001. Radiation exposure is particularly high when flying in the polar regions or over the polar route. The average annual effective dose for aviation personnel was 1.9 mSv in 2015 and 2.0 mSv in 2016. The highest annual personal dose was 5.7 mSv in 2015 and 6.0 mSv in 2016. The collective dose for 2015 was about 76 person-Sv. This means that flight personnel are among the occupational groups in Germany with the highest radiation exposure in terms of collective dose and average annual dose. This group also includes frequent flyers, with Thomas Stuker holding the "record" - also in terms of radiation exposure - by reaching the 10 million mile mark with United Airlines MileagePlus on 5,900 flights between 1982 and the summer of 2011. In 2017, he passed the 18 million mile mark.