Extremely low-frequency electromagnetic fields and health

Advisory report | 08-04-1992

This concern was largely triggered by the 1979 epidemiological study by Wertheimer and Leeper (Wer79) reporting a very weak relation between the 'wire code'*, a factor they considered to be an indicator for exposure to ELF EMF, and the mortality resulting from childhood leukemia. This report prompted an ever increasing number of experimental and epidemiological studies aimed at answering the questions of whether exposure to ELF EMF poses health risks and, if so, about the nature of the underlying biological mechanism.
Several major reports published in recent years summa¬rize the ELF EMF research and consider the possible health effects of exposure. They mainly focus on the possible involvement of exposure to ELF EMF in the development of certain types of cancer. These publications included the report on ELF EMF effects published in May 1989 by the Office of Technology Assessment (OTA) of the US Congress (OTA89). The Environmental Protection Agency (EPA) issued in December 1990 a draft report (EPA90) which was subsequently strongly criticized. In The Netherlands a study prepared by the State University of Limburg for the Dutch Ministry of Housing, Physical Planning and Environment was released in July 1991 (Sch91).

Conclusions and recommendations

The ELF Electromagnetic Fields Committee of the Health Council of the Netherlands was installed in order advise the Dutch Minister of Housing, Physical Planning and Environment on the possibly adverse health effects of exposure to ELF EMF. The Committee evaluated scientific literature available as per November 1, 1991 concerning the effects and influence of ELF EMF on biological systems, including humans. The conclusions of the Committee are presented in this report.
The Committee has focused its conclusions on the effects in humans, and specifically on the effects caused by exposure to EMF generated by 50/60 Hz alternating currents. As the exposure of the general population to EMF of other frequencies in the ELF range is negligible, the discussion on possibly adverse health effects pertains to the ubiquitous 50/60 Hz EMF.
The Committee gives an answer to three questions asked by the Dutch Minister of Housing, Physical Planning and Environment.

The first question asked whether present scientific knowledge is indeed insufficient to determine the existence of a relationship between exposure to ELF EMF and adverse health effects and, should this be the case, what research might be needed to fill the gaps in this knowledge.
The Committee thinks that such results of the epidemiological studies as are now available do not justify the conclusion that there exists a relation between prolonged domestic or professional exposure to ELF EMF and adverse health effects. Present knowledge concerning the biological effects of ELF EMF furthermore does not clearly indicate the existence of such a relation. In other words, the Committee thinks that any evidence from currently available research is insufficient to support the hypothesis that exposure to ELF EMF generated by the electricity distribution system and by electric household appliances and industrial electrical equipment has any influence on the initiation or growth of malignancies, or on the course of pregnancy or fetal development.
The Committee recognizes that several epidemiological studies in the US have reported a relation between the configuration of overhead distribution lines (the 'wire code') and the incidence of childhood leukemia. This relation is in itself insufficient reason for the Committee to assume a causal relationship between exposure to ELF EMF and the incidence of leukemia (or other types of cancer). A relation with the measured field strength has not been found. According to the Committee further research into the relation between the wire code and the characteristics of the ELF EMF exposure pattern (e.g. field strength, duration of exposure) might clarify the observed relation. Research along these lines is now underway in the US. Furthermore it will have to be investigated whether a relation exists between wire codes and other factors such as traffic density. In view of the present uncertainties in the interpretation of the results of scientific research in this area, and as this research is being intensified, at least in the USA, the Committee recommends that monitoring of the developments in this field be continued and the data re-evaluated in five years.
The Committee lists a number of specific points regarding which knowledge on the biological effects of exposure to ELF EMF is lacking and which might warrant research in the Netherlands.

The second question the Minister posed was whether present knowledge concerning the effects of ELF EMF on human health is sufficient to justify the development of exposure guidelines and, if so, whether the interim guidelines of the INIRC/IRPA (IRPA90) could serve as starting-point for policy making.
The Committee recognizes that exposure to ELF EMF with extremely high field strengths can result in acute effects. These may pose a potential health threat. Such high field strengths are not encountered in the domestic environment, but can be present in certain industrial work areas. The Committee considers that this is a reason to develop exposure standards. The Committee suggests that the approach used by INIRC/IRPA be followed and the standards based on the internal currents in¬duced in the body by the ELF EMF. According to the Committee, compliance with the exposure limits proposed by INIRC/IRPA offers sufficient protection against possible acute adverse health effects.

In his third question the Minister asks whether it would be relevant to gather information on the ELF EM field strengths to which the Dutch population is exposed.
 In this report the Committee gives an overview of the field strengths in close proximity to high-power transmission lines, transmission cables and to electrical appliances. These data indicate that in The Netherlands the field strengths generated by these sources are of comparable magnitude. The field strengths directly underneath and, hence, also at some Bistance from transmission lines in The Netherlands comply with the criteria from the INIRC/IRPA interim guidelines. The Committee does not at present consider that there is a need for detailed determination of the ELF EM field strengths to which the Dutch population is exposed. The main argument for this position is that it is not known which characteristics of the pattern of chronic exposure to low field strengths (electric field strength, magnetic fluxdensity, frequency, duration of exposure) have a relation, if any, to health.

Commentary to the recommendations

Environmental factors, that include exposure to chemi¬cal substances, ionizing radiation and ELF EMF, may influence human health. Whether there is any influence and, if so, to what extent, depends on the nature of the factor and on the extent of the exposure. The presence of other factors may also be important. Adverse effects of some environmental factors are not readily detectable and are basically impossible for scientific research to exclude with certainty.
In the present public awareness of the possible health effects of exposure to ELF EMF, special emphasis was placed on the alleged relation between exposure to these fields and an increase in the incidence of certain types of cancer. From a scientific point of view a relation of this type can be regarded as probable if it was determined in hypothesis-testing studies - possibly after appearing in an (hypothesis-generating) epidemiological study - and there exists a plausible biological mechanism based on the results of laboratory stu¬dies. Indications of such a relation for instante can be found in studies on the incidence of the effect in experimental animals.
 In the opinion of the Committee the results of the epidemiological studies on the effects of exposure to ELF EMF do not fullfil the conditions stated. The Committee recognizes that interactions between ELF EMF and biological systems have been demonstrated in several laboratory studies. This is not surprising, since electrical phenomena are involved in communication between cells or cellular systems. When external fields are of sufficient strength these biological systems will show the same reaction to these as to an endogenous natural stimulus. However with field strengths that occur in the environment such interactions have always been reversible, i.e., did not result in observable permanent effects after the source of EMF was shut down.

Summary

The conclusions and recommendations of the Committee can be summarized as follows:

1. There is at present insufficient scientific proof that chronic exposure to ELF EMF with low field strengths as found in the domestic or professional environment results in adverse health effects. Such exposure neither influences the initiation or development of cancer, nor results in premature termination of preg¬nancy nor adversely influences fetal development.
2. Exposure to ELF EMF with field strengths considerably higher than those that occur in the domestic environment but may be present in certain industrial work areas can result in acute health effects. The Committee therefore recommends the development of standards for the maximum exposure to ELF EMF. These standards could be based upon the interim guidelines of the INIRC/IRPA.
3. There are no compelling reasons to determine in detail the ELF EM field strengths to which the Dutch population is exposed.
4. Further developments regarding effects of exposure to ELF EMF should be followed. The Committee recommends a re-evaluation in five years.

* The 'wire code' is the grouping into a limited number of catagories of the entire set of components constituing the overhead electricity distribution system: the number of high and low voltage lines, their relative position, the localization of the step-down transformers, all in relation to the distance to a dwelling. This catagorization is related to the EM field strength near the dwelling.