The amount of absorbed radiation is called a dose and for us the most important is the so-called effective dose, which takes into account the amount of, the type of radiation and its biological effect. This is exactly what our dosimeters during your visit of Chernobyl will measure. The units of effective dose are Sieverts or more practically microSieverts (1/1 000 000 of Sievert). Our dosimeters measure both the actual level of radiation in microSieverts per hour and also automatically calculate the total dose during the time the dosimeter is switched on. As we have already mentioned during the typical excursion day in the Exclusion Zone your dosimeter will measure about 3-4 microSieverts of gamma radiation.

Talking about receiving a dose of radiation may sound threatening, but it is important to put this into perspective. We have to understand that some levels of radiation i.e. background radiation are completely natural and occur everywhere in the world. Background radiation consists of multiple sources including radiation coming from all the radioactive isotopes that naturally occur in everything around us, and cosmic radiation coming from outer space. The most significant source of background radiation is the radioactive gas called radon released naturally from the ground that we inhale with air. Particularly, inside buildings with bad ventilation this gas can concentrate and the radiation levels can easily become greater than most places in the Exclusion Zone.

In figures, the world average for all sources of background radiation is around 8 microSieverts per day. So you can see that the 3-4 microSieverts measured by your dosimeter during the 10-12 hours of our excursion are completely safe and are comparable to what you would receive normally everyday at home. Moreover, there are many places that now have naturally much higher levels of radiation than Chernobyl today. Guarapari Beach in Brazil holds the record, where, at some spots, levels of radiation can exceed the current Chernobyl levels hundreds of times.

Beside natural sources of background radiation, there are also many artificial sources that we are exposed to routinely. This includes various medical procedures, but also smoking, since cigarette smoke contains significant amounts of radioactive polonium-210 that can cause cancer. Another radioactive activity is plane travel since at high altitudes we are more exposed to cosmic radiation that is usually shielded by the atmosphere. We list the most common artificial sources in table 1 below. As you can see smoking is one of the most radioactive activities that a human can experience and by smoking one pack a day, in one year you will receive a dose 10 000 times larger than during an excursion to the Zone.