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IntroductionEnvironmental issues are addressed in the permitting process of every transmission line project, whether it be a new line or an upgrade of an existing line. In recent years, the most controversial issue associated with alternating current lines is the potential effects of electromagnetic fields on human health. However, environmental effects on animals, plant life and other electrical and communication systems also must be assessed in every case. Although different from ac lines, high voltage direct current (HVDC) lines also produce environmental effects that warrant review and assessment in every project. This report strives to define the various environmental effects associated with HVDC lines, discusses the current knowledge of their potential effects on biological and non-biological systems, and compares these effects associated with ac lines where appropriate.
The Environment Near an Electric Power LineThe electrical environment of a high voltage transmission line can be characterized by three electrical parameters: 1) the electric field, 2) the air ion and charged aerosol concentration, and 3) the magnetic field. The electric field arises from both the electric charge on the conductors and for an HVDC transmission l i e , charges on air ions and aerosols surrounding the conductor.In addition, corona may also produce low levels of ozone, audible noise, electric field and radio interference. A magnetic field is produced by current flowing through the conductors.
Summary of Key FindingsIons. Neither the animal nor human studies provide any reliable evidence for the proposition that air ions produce any harmful effects. In fact, there is considerable uncertainty as to whether there are any biological responses to air ions. At the levels produced by HVDC transmission lines, the possibility of risk to human health appears remote, if not vanishingly small. There are no published guidelines for maximum ex...
