EMF and your Health

Learn how electronic and magnetic fields (EMF) may affect your health

Executive Summary


The EMF and Your Health 2019 Update brochure addresses basic aspects about environmental EMF and contemporary issues related to potential concern over health effects from EMF exposure. It was prepared as an update to the National Institute of Environmental Health Sciences (NIEHS) booklet entitled, “EMF: Electric and Magnetic Fields Associated with the Use of Electric Power – Questions & Answers,” published in 2002.

Electricity and EMF

  • Voltage may be thought of as electrical ‘pressure’; the voltage on a conductor or appliance produces an electric field, expressed as volts per meter (V/m) or thousands of volts per meter (kV/m)

  • Current is the flow of electricity through a conductor; current produces a magnetic field, with typical fields expressed in milligauss (mG; 1 gauss=1,000 mG). The international unit is microtesla (μT) and 1 μT= 10 mG.

  • Electricity is generated and supplied at a frequency of 60 Hz in the U.S. (50 Hz in Europe); hertz means cycles per second, thus voltage and current go through one full cycle 60 (or 50) times every second. These are ‘power frequencies’ (50/60 Hz).

  • Power frequency fields neither damage cells like ionizing radiation, nor heat tissue like radio-frequency fields.

Electrical Transport

  • At the generating station, voltage is stepped up feeding transmission lines that usually travel long distances to bring power to local substations.

  • In the U.S., high voltage transmission lines operate from between about 115 kV to 765 kV

  • At the substation the voltage is stepped down for distribution to neighborhoods.

  • Distribution lines operate from between 4 kV and 35 kV.

  • The distribution voltage is stepped down to the voltages that power our lights, electronics and appliances.

Environmental Magnetic Fields

  • Directly beneath a high voltage transmission lines, the magnetic fields may reach from 10 to over 100 mG, depending on voltage class and current (load).

  • Directly beneath a distribution line, the magnetic field may reach roughly between 10 and 30 mG.

  • In most homes in the U.S. average magnetic field exposure is less than 3 mG, but activities near appliances and other sources can increase one’s overall exposure level.

  • A person’s exposure over time can vary significantly depending on

    • the power lines in proximity to the home and activities within a home that involve local sources (appliances and electrical equipment), and

    • activities and sources at locations away from home, including work, school, retail stores and recreational facilities.

Environmental Health Research

  • The evaluation of potential health risks that may be linked to environmental agents relies on a ‘weight-of- evidence’ evaluation, which factors in the results of

    • Epidemiology studies,

    • Studies in whole animals, and

    • Studies of isolated cells and tissues and analyses of potential mechanisms of action

  • To evaluate environmental agents, government agencies and risk assessment organizations recruit scientific panels whose members have proven expertise and represent the diverse specialties required for an objective evaluation.

EMF Health Research

  • Over the past 40 years, thousands of scientific articles concerned with EMF health research have been published.

  • In 2001, International Agency for Research on Cancer classified power frequency magnetic fields as “possibly carcinogenic to humans” on the basis of ‘limited’ epidemiologic evidence.

  • In 2002, after the completion of the U.S. RAPID program and report to the U.S. Congress, the NIEHS Q&A booklet concluded that, “For most health outcomes, there is no evidence that EMF exposures have adverse effects.” With respect to ‘limited’ evidence of an association of residential magnetic fields with childhood leukemia, NIEHS stated, “This association is difficult to interpret in the absence of reproducible laboratory evidence or a scientific explanation that links magnetic fields with childhood leukemia.”

  • Since the 2002 booklet was published, a variety of duly constituted expert scientific panels and governmental agencies have reviewed the EMF health literature, and collectively find no evidence of risks for pregnancy outcome, neurodegenerative diseases, cardiovascular disease and any other health condition. With respect to cancer, they see no persuasive evidence of risk for any adult or childhood cancers, with the sole uncertainty related to childhood leukemia.

Update on Childhood Leukemia Research

  • Since 2002, several epidemiologic studies have examined the occurrence of childhood leukemia with respect to residential proximity to overhead transmission lines.

  • Positive associations were reported for living close to transmission lines, but the association extended beyond the distance at which magnetic fields from the lines are negligible. A follow-up study reported decreasing risks by decade from the 1960s through the 1980s with the incidence of childhood leukemia close to transmission lines falling to background levels since the 1990s. These observations point to some other factor beside magnetic fields responsible for the positive associations reported in the epidemiologic literature.

  • A pooled analysis of children with leukemia with data from eight countries reported no relationship between magnetic fields and relapse or overall survival, despite suggestive evidence from two earlier studies.

  • Based on findings from several pooled analyses and recent studies, a 2019 meta-analysis of magnetic fields and childhood leukemia studies assessed the hypothesis of a decline in the association over time. The findings suggest that the associations were stronger during early time periods (late 1980s), and that risk of childhood leukemia in relation to magnetic fields has weakened in more recent studies (2000s).

Guidelines and Standards

  • Recommendations for electric and magnetic field exposure limits have been issued by the International Commission for Non-Ionizing Radiation Protection (ICNIRP) and the Institute for Electrical and Electronic Engineers (IEEE).

  • The limits protect against adverse ‘electrostimulation’ (stimulation of nerve tissue by an electrical stimulus). Electrostimulation occurs in a threshold manner at exposure levels that people do not ordinarily encounter.

  • For the general public, ICNIRP’s magnetic field exposure limit at power frequency is 2.0 G, and IEEE’s limit is 9.1 G.

  • The World Health Organization (WHO) has stated that: Compliance with these guidelines [exposure limits] provides adequate protection for acute effects.”

National Policies

  • Agencies in the U.S. and Canada have not established nationwide regulations limiting EMF exposure, although several states in the U.S. limit electric and/or magnetic fields on the right-of-way.

  • Over 50 countries around the world have adopted EMF exposure limits in some form.

  • WHO has stated that, “…it is not recommended that the limit values in exposure guidelines be reduced to some arbitrary level in the name of precaution.”

  • The California Public Utilities Commission (CPUC) has implemented a ‘4% rule’ whereby the state’s investor-owned utilities must invest up to 4% of a transmission projects costs for low-cost magnetic field mitigation.

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