In this paper, the procedure for calculating the level of the electric field generated by an overhead transmission line is processed. Two examples of transmission lines were selected, on which the mentioned calculation procedure was carried out. The difference between ionizing and non-ionizing radiation and their impact on living organisms is explained. It is shown how public concern about exposure to electromagnetic fields has developed throughout history. The effects of static and low-frequency and high-frequency electric fields on the human body are listed. Limit values of variable electric fields to which a person can be exposed are also shown. It is given the general procedure for calculating the electric field for the case of one conductor and the case of several conductors. A Matlab program was created to obtain the distribution of the electric field under selected examples of transmission lines. Selected examples were used to be able to compare the obtained distribution of the electric field with that of the standard. In this way, we got the correct calculation code that we can use, with small modifications, for a transmission line of any configuration. The influence of some transmission line parameters on the amount of electric field under the transmission line is also shown. The obtained results were compared with the limit values of variable electric fields to which a person can be exposed, and the conclusion was reached that there is a possibility of harmful consequences for health for one example of a transmission line, while it does not exist for another.