The Dangers Of Power Lines
By Michael Forbush
March 9, 1994
Abstract
An alternative hypothesis for the increased occurrence of childhood leukemia in residences located near power lines is discussed. Three substances with carcinogemic or mutagenic properties known to occur in the vicinity of high voltage power lines are considered: Polychlorinated Biphenyls, Ozone, and Nitrogen Oxides. It is shown that increased exposure to all three may increase the risk of leukemia more than the sum of the risks to each substance individually. Quantitative measurements of the exposure levels of each of these substances should be used in further epidemiological studies.
Introduction
The relationship between low frequency electromagnetic radiation and biological systems has been studied extensively and many review articles have summarized the studies [1, 2, 3]. Consistently the conclusion of these reviews has been that the studies have been inconsistent. In this paper I will present an alternative hypothesis for what I believe to be the most statistically significant study which links low frequency electromagnetic radiation to childhood leukemia by studying the proximity of powerlines to the clusters of leukemia cases.
As Neville J. Woolf [4] presented in a little known letter to the editor in Nature, there are other considerations that must be made before one can draw the conclusion: Low frequency electromagnetic radiation causes leukemia. He mentions highly reactive chemicals and the presence of NO2 or O3 around power lines. I will clarify this hypothesis and present new considerations for future studies.
As recently as November 1993 [5] results for an increased risk of childhood leukemia has been linked to residences in the neighborhood of power lines. Unfortunately, the conclusion has emphasized the effect of non-ionizing electromagnetic radiation as the source of this risk. Instead, the presence of polychlorinated biphenyls, ozone and nitrogen dioxide should be considered before drawing this conclusion.
Polychlorinated Bophenyls and Cancer
In 1977 the US terminated the production of electrical equipment containing Polychlorinated Biphenyls (PCBs) because of the toxicity and accumulation property of PCBs was recognized [6]. The most noted health effect of PCBs at the time was correlation of low birth weights with PCB contamination.
The accumulation of PCBs in biological tissues was discovered during the DDT research of the 1960s. It was shown that, like DDT, PCBs accumulate in biological systems. This is because PCBs are very stable molecules, and they are readily soluble in lipids and stored in all parts of the body especially in the fatty tissues and the liver. It has been shown very high doses of PCBs have caused neoplasms in the livers of small animals, and more recently PCBs have been linked to the promotion stage in cancer development [7].
In modern theory of cancer development there are multiple stages in the development of the disease. These stages can be grouped into the initiation, the promotion and the progression of the disease [8]. It has been shown [7] that PCBs may play a weak role in the initiation stage; they are established as promotors in the promotion stage, but they do not play a role in the progression of cancer. It is possible to imagine accumulation of PCBs in the body continuously until the concentration reaches some threshold concentration such that they function in the role of a promoter. At this point the biological system is ripe for the intervention of an initiator. Therefore, if a second material were present in the environment which could act as an initiator and possibly a third substance which increases progression. The sum effect would be an increased risk of cancer observed in the population.
Polychlorinated Biphenyls Near Power Lines
PCBs were used in electrical equipment because they have a high dielectric constant, and they do not burn easily. This allows them to be used in the cooling and electrical insulation of transformers and as the dielectric in high power capacitors. Both of these components are used in the transmission of electrical power. The typical locations of these components are utility poles and towers.
Although the manufacture of electrical equipment containing PCBs ceased in 1977, nearly all transformers and capacitors manufactured between 1930 and 1977 contained PCBs. Furthermore, all existing electrical equipment containing PCBs has remained in existence with the condition that transformers have their PCBs replaced with non-PCB fluid when this fluid would normally be replaced. Since the lifetime of a typical transformer is 40 years and the lifetime of a typical capacitor is 20 years, all of the PCB containing electrical equipment associated with power lines will not be replaced until well into the next century.
Since the replacement of a transformer or capacitor is contingent on the failure of that device I will consider the failure modes of transformers and capacitors as presented in the Canadian handbook on PCBs in electrical equipment [6]. It should be noted most failure modes allow for the escape of PCBs into the environment.
Failure modes of transformers:
1) Lightning or high voltage sparks cause a build up of pressure within the tranformer. The excess pressure forces the PCBs out of the transformers through pressure release valves or weak gaskets.
2) Contamination of the insulating PCBs results in arcing. Arcing produces pressure build up and the release of PCBs.
3) Weakening of the seals or gaskets allows the release of PCBs.
4) Physical damage resulting in leaks or failure.
5) Overheating leads to decreased life expectancy and possible leaks.
Failure modes of capacitors:
1) The metal can containing the capacitor may rust resulting in a rupture or leak.
2) Physical damage may result in a rupture or leak.
3) Overheating may result in a rupture.
4) Internal insulation fails which may result in a rupture.
I would like to point out PCBs are expected to be released into the environment as a method of pressure equalization. In addition, even though PCBs have a low vapor pressure there are some conditions in which PCBs become airborne, for example, pressure relief. Even though the Canadian government regulates the release of PCBs to 1 gram per day the accumulation of PCBs in the environment around power lines is likely to be higher than the accumulation of PCBs in areas further away from power lines.
Ozone and Nitrogen Oxides
It is a well known fact electrical sparking in air ionizes the air. In doing this both ozone and nitrogen oxides are produced. [9, 10]. Additionally one may frequently observe the buzzing and sparking of a high voltage cable at a power line. In some cases the smell of ozone can be sensed which indicates that the concentration of ozone is at least 0.2 ppm [9]. This does not mean every tower has a sparking cable; however, it does mean if you live near a power line the probability of higher than average ozone concentration near your house is likely.
It has been documented both exposure and concentration affect the toxicity of ozone with no threshold for the onset of effects aside from the nominal amount of ozone naturally present in the environment [9]. Regardless of this level of toxicity there are several known facts about ozone which lead us to believe it could be an initiator in cancer development [9].
1) Aberration of chromosomes caused normally by X-ray radiation is also induced by ozone.
2) Ozone contains a bi-free radical so it is capable of initiating a series of free radical reactions.
3) Repeated exposure to ozone leads to premature aging of small animals in a manner similar to that of UV radiation.
4) Similarity between the effects of ozone and of ionizing radiation to myocardial fibers were also detected in animals. This is the result of the daily exposure to a 0.2 ppm concentration of ozone for 5 hours per day for 3 weeks.
Consideration of the above facts in the light of the three stages of cancer development could suggest the role of ozone to be a initiator. It has been documented [11] particular chromosome aberations are identified with specific types of cancer. In fact hematological malignancies such as leukemias have been attributed to X-ray exposure [12]. Since it is known ozone and X-ray exposure have similar effects on blood cells it would be natural to consider ozone as a possible contributer in childhood leukemia around power lines.
In addition to the role of ozone in the development of cancer it has been documented one of the nitrogen oxides, nitrogen dioxide, has been shown to aid in cancer metastasis [13]. In this experiment melanoma cells were released in the blood stream while the subject inhaled between 0.3 - 0.8 ppm Nitrogen Dioxide. This resulted in the transfer of the cancer to the lungs of the animal. Similar concentrations of Ozone were administered to another group of subjects showed no effect.
Conclusion
In conclusion I would like to suggest the inconclusive studies in the area of low frequency electromagnetic radiation's carcinogenic effects are flawed by an error in the linkage between cause and effect. Particularly in the area of powerlines and the increased risk of childhood leukemia where the increased risk of leukemia from epidemeological studies could be the result of increased exposure to PCBs, ozone and nitrogen oxides. Although the exposure to any one of the above substances may have minimal effects on the risk of contracting leukemia, exposure to all three would have an amplified risk because each substance effects a different stage of cancer development.
In review of the literature I believe the strongest case for a correlation between low frequency electromagnetic radiation and cancer has been from epidemiological studies of power lines. At this point an unstubstantiated link is made between powerlines and low frequency electromagnetic radiation without consideration of of other known pollutants in the neighborhood of powerlines. In the 1974 Denver study it is certain all of the capacitors and most of the transformers along the power lines contained PCBs which are expected to be released into the environment. Subsequent studies may have included new or repaired power lines which were free from PCB contamination skewing the statistics. In addition, being in the vicinity of power lines does not guarantee exposure to ozone, but it does increase the likelihood of exposure. If quantitative measurments of these substances were made along with the epidemiological studies many of these questions would be answered.
