I have been an active researcher on biological effects of
electromagnetic fields (EMF) for over twenty five years at Columbia
University. I was also one of the organizers of the 2007 online
Bioinitiative Report on the subject. Because of this background, I have
been asked to provide background information regarding current
discussions about the proposed cell tower.
There is now sufficient scientific data about the biological effects of
EMF, and in particular about radiofrequency (RF) radiation, to argue
for adoption of precautionary measures. We can state unequivocally that
EMF can cause single and double strand DNA breakage at exposure levels
that are considered safe under the FCC guidelines in the USA. As I
shall illustrate below, there are also epidemiology studies that show
an increased risk of cancers associated with exposure to RF. Since we
know that an accumulation of changes or mutations in DNA is associated
with cancer, there is good reason to believe that the elevated rates of
cancers among persons living near radio towers are probably linked to
DNA damage caused by EMF. Because of the nature of EMF exposure and the
length of time it takes for most cancers to develop, one cannot expect
'conclusive proof' such as the link between helicobacter pylori and
gastric ulcer. (That link was recently demonstrated by the Australian
doctor who proved a link conclusively by swallowing the bacteria and
getting the disease.) However, there is enough evidence of a plausible
mechanism to link EMF exposure to increased risk of cancer, and
therefore of a need to limit exposure, especially of children.
EMF have been shown to cause other potentially harmful biological
effects, such as leakage of the blood brain barrier that can lead to
damage of neurons in the brain, increased micronuclei (DNA fragments)
in human blood lymphocytes, all at exposure rates well below the limits
in the current FCC guidelines. Probably the most convincing evidence
of potential harm comes from living cells themselves when they start to
manufacture stress proteins upon exposure to EMF. The stress response
occurs with a number of potentially harmful environmental factors, such
as elevated temperature, changes in pH, toxic metals, etc. This means
that when stress protein synthesis is stimulated by radiofrequency or
power frequency EMF, the body is telling us in its own language that RF
exposure is potentially harmful.
There have been several attempts to measure the health risks associated
with exposure to RF, and I can summarize the findings with a graph from
the study by Dr. Neil Cherry of all childhood cancers around the Sutro
Tower in San Francisco between the years 1937 and 1988. Similar studies
with similar results were done around broadcasting antennas in Sydney,
Australia and Rome, Italy, and there are now studies of effects of
cellphones on brain cancer. The Sutro tower contains antennas for
broadcasting FM (54.7 kW) TV (616 kW) and UHF (18.3 MW) signals over a
fairly wide area, and while the fields are not uniform, and also vary
during the day, the fields were measured and average values estimated,
so that one could associate the cancer risk with the degree of EMF
exposure.
The data in the figure are the risk ratios (RR) for a total of 123
cases of childhood cancer from a population of 50,686 children, and
include a 51 cases of leukaemia, 35 cases of brain cancer and 37 cases
of lymphatic cancer. It is clear from the results that the risk ratio
for all childhood cancers is elevated in the area studied, and while
the risk falls off with radial distance from the antennas, as expected,
it is still above a risk ratio of 5 even at a distance of 3km where the
field was 1μW/cm2. This figure is what we can expect from prolonged RF
exposure. In the Bioinitiative Report, we recommended 0.1μW/cm2 as a
desirable precautionary level based on this and related studies,
including recent studies of brain cancer and cellphone exposure..
As I mentioned above, many potentially harmful effects, such as the
stress response and DNA strand breaks, occur at nonthermal levels
(field strengths that do not cause a temperature increase) and are
therefore considered safe. It is obvious that the safety standards must
be revised down to take into account the nonthermal as well as thermal
biological responses that occur at much lower intensities. Since we
cannot rely on the current standards, it is best to act according to
the precautionary principle, the approach advocated by the European
Union and used by the scientists involved in the Bioinitiative report.
In light of the current evidence, the precautionary approach appears to
be the most reasonable for those who must protect the health and
welfare of the public.
Martin Blank, Ph.D.
Associate Professor of physiology and cellular biophysics