Rapporteurs: Robert P. Liburdy, Ph.D. and William S. Baldwin, Ph.D.

Introduction

The breakout group was tasked to review relevant literature and assess scientific findings relating to specific EMF effects on cellular replication. Cellular replication is a fundamental and complex process that involves the interaction of a wide variety of biological processes. The study of replication itself as an endpoint in experimental studies is, therefore, one of the critical factors scientists have evaluated in assessing potential effects of EMF on human health.

Questions Discussed by the Breakout Group

1. Can EMF alter cellular replication by itself or by acting synergistically with other agents?

a. EMF altering cellular replication by itself

The group felt that at fields above approximately 10 gauss (G, 50/60 Hz) there exists evidence from a number of studies in the peer-reviewed literature to suggest that EMF can alter cellular replication; these reports derive from a number of laboratories involving different cell lines and different investigators. In the aggregate, when the peer-reviewed studies in this high-field exposure range of >10 G are reviewed, these studies indicate that effects on cellular replication are observed across a number of different laboratories and cell types.

b. Perhaps the simplest and most direct mechanism is that the magnetic fields prevent melatonin from entering the cell; this would explain the field associated blocking effect on melatonin's action. This is possible, but perhaps not likely; a marked alteration in cell membrane fluidity or permeability would most likely have wide reaching and global effects on cell function. Melatonin is known to be freely diffusable across the cell's plasma membrane, and it rapidly reaches an equilibrium concentration within the cell, so permeability issues do not appear to have the potential to play a critical role.

e. Extend cell replication findings to a variety of different cell types.

It is important to determine if a) a given cell type is characteristically responsive to EMF and b) how many different types of cells are responsive to EMF. For example, it was discussed that other human breast cancer cell lines may be sensitive to melatonin and these model systems should be investigated.

B.Conclusion Statements

1. At magnetic fields above 10 Gauss there is laboratory evidence that EMF alters cellular replication. Although no findings have been independently replicated, this body of evidence represents data across a number of different laboratories, utilizing different cell types, and a variety of exposure durations. These studies could be technically strengthened by employing multiple techniques that are currently available to assess cell replication such as quantitative flow cytometry and automated cell proliferation assays.
2. At magnetic fields below about 2 Gauss, available literature suggests there is evidence EMF alone does not alter cellular replication, but "synergistic" effects between EMF and melatonin have been reported and independently replicated.
3. "Environmental-level" magnetic fields of 12 mG block or inhibit the oncostatic action of melatonin, tamoxifen, and ICI 182,780 on human breast cancer cell growth. This field action involves co-treatment of cells with the field and the drug/hormone; the field alone does not influence cell growth. These melatonin findings have been independently replicated in two laboratories which adds significant weight to the credibility of these findings. An apparent dose "threshold" exists between 6-12 mG for the melatonin findings.
4. "Environmental-level" melatonin/tamoxifen studies may have potential for relevance to human health risk. Factors that play a role in this assessment are: a) melatonin is a naturally occurring hormone; b) tamoxifen is currently a drug of choice for management of breast cancer and is used by a large number of women; c) milliGauss field strengths are associated with these biological effects; and d) EMF is hypothesized to play a role in reducing available melatonin levels experienced at peripheral target cells such as human breast tissue via the "melatonin hypothesis."
5. Further research is recommended in a number of important areas. Further investigation is recommended to address a) the "generalization" of EMF effects on cell replication to a variety of different cell lines, including melatonin and tamoxifen sensitive cell model systems, utilizing multiple methodological approaches, b) the "synergizing" effect of EMF with other growth regulating hormones and drugs that are know to alter cell growth and replication, and c) the characterization of a dose "threshold" and an exposure duration "threshold" as well as studying the possible effects of chronic exposure and reversibility.