Thursday 8 September 2011

Transmission Power Lines: Should You Worry?

When you want to buy or rent a property, and you can see some special "Eiffel Towers" with transmission power lines in close vicinity, you may be worry. You then ask your friends, some say that they have stay below such power lines for years and nothing happen, some say that better don't stay near it as it can cause cancer. Who should you believe in?

    High voltage power lines transmission towers

Transmission power lines carry power from power plants to substations or between substations. It emits electromagnetic wave, which consists of both electric and magnetic field (EMF). Electric fields are produced by electric charges and magnetic fields are produced by the flow of current through the lines.

Electromagnetic (EM) waves are divided into 2 big groups: ionizing and non-ionizing. Ionizing EM waves such as X-ray, ultraviolet, gamma ray etc have sufficient energy to knock off electrons in our body cells and can cause cancer. Whereas non-ionizing EM waves such as natural light, infra red, microwave, radiowave etc are not known to cause cancer by knocking off electrons in the cells.  

    Electromagnetic waves spectrum

EM waves radiated from power lines has long wavelength and thus very low energy. It is a non-ionizing radiation. So it is accepted that it won't cause cancer by knocking off you cells' electrons. So if you are worry that the transmission power lines can have the "radiation effect" similar to X-ray or nuclear plant explosion, then you are totally wrong. However, are there any other way it can be harmful to human body?

The electric fields from a high-voltage transmission lines are generally safe unless if you have a pacemaker or defibrillator for your heart and you go extremely close to the lines. Otherwise the electric field can be easily shielded off by walls. However, there are some research which claim that the electric field may ionize particles in the air and turn them into cancer-causing agents. This is unproven and nothing is confirmed.

The main concern on the transmission lines is actually its magnetic waves. There are some reports mentioning that exposure to higher level of magnetic wave (>2 milliGauss or 0.2 microTesla) increases the risk of certain health problems especially childhood leukemia.

The strength of magnetic wave that affect you depends on the current that flow through the power lines and the distance between the line and you. The further the distance the weaker the magnetic field and the safer it is as the wave strength will fall exponentially. Some authority recommends to stay at least 400 meter away from high voltage power lines. It is known that even the strongest high voltage high current transmission lines will produce less than 0.3mG at 400m. Some say 150m away is adequate. If the power lines are not "strong" enough, then staying nearer can still be safe.

However, the higher the voltage of the lines, the lesser is the current that flow through and the less magnetic field it will produce. This does not always means that the higher the voltage in the lines, the safer it is, because the power transmitted is huge so the current is also relatively high. (Power = Voltage x Current).

Magnetic wave can penetrate through building and human body at the speed of light. The further from the source, the lesser is its effect. The best way to know how much magnetic field you are exposed to is to measure it using a Gauss meter. Any reading below 0.5mG should be alright.

     A digital Gauss meter

Not only transmission power lines, everything that has electrical current flowing through it will also radiate magnetic wave. This includes power lines on the streets/in the house and electrical home appliances such as hair dryer, microwave oven, television, computer etc. Though the magnetic field from them is not as strong, but they are very close to us. Our exposure from computer screen could be up to 2.5mG!

So far the outcome of study that look into transmission power lines and its health effects has been mixed. Some give positive findings and some give negative findings. Study on health matter is always not easy as one disease may have many causes and people are moving around, doing different things and exposed to different things everyday.

If you read a website by someone or some groups who are "not favoring" the transmission power lines, then you will see lots of evidence on its negative health effects. If you read a website which is "favoring" it, then you will see lots of researches saying that the transmission lines do not have any negative health effects.

It is confirmed that smoking cigarettes can cause cancer and eating junk food is bad for our health, and yet how many people are doing these daily? It is not confirmed that living near the transmission power lines can cause cancer or other  health problems, should you be worry? Well, it's all up to you.

A few negative notes
  • There is extremely strong evidence finding a relationship between ELF magnetic fields greater than 2 mG and childhood leukemia.  This relationship has been a matter of scientific inquiry since 1979. Sixteen out of nineteen studies conducted since 1995 are now viewed as identifying a statistically significant relationship between magnetic fields greater than 2 to 4 mG and a two to four-fold increase in a child’s risk of contracting that disease.
  • There is very strong evidence finding a relationship between maximum ELF magnetic field exposure greater than 16 mG and a 6-fold increase in miscarriages.
  • There is strong evidence linking ELF magnetic fields and Alzheimer’s and Lou Gehrig’s disease (ALS).
  • There is substantial evidence linking ELF magnetic fields greater than 12 mG and breast cancer and strong evidence linking magnetic fields and the suppression of the therapeutic effects of the anti-cancer drug, tamoxifin.

After reading the above examples, you may want to know how many mG of magnetic field you are or are going to exposed to. However, it seems like no one will answer you unless you get someone or yourself to measure it with a Gauss meter.

Positive notes from US's National Cancer Institute
  • Overall, there is limited evidence that magnetic fields cause childhood leukemia, and there is inadequate evidence that these magnetic fields cause other cancers in children.
  • Studies of magnetic field exposure from power lines and electric blankets in adults show little evidence of an association with leukemia, brain tumors, or breast cancer.
  • Past studies of occupational magnetic field exposure in adults showed very small increases in leukemia and brain tumors. However, more recent, well-conducted studies have shown inconsistent associations with leukemia, brain tumors, and breast cancer.

Is statement from "National Cancer Institute" suppose to be more "scientific" and should be used as the ultimate guidelines? It still depends on you whom to trust. There may be thousands of studies carried out on this subject and may be less than 10% has harmful health effects and 90% has no harmful health effects. If someone only show you this 10% of harmful findings then no one will ever want to stay near the transmission power lines. But if you look at all this 100% of studies, perhaps this is what they called "inconsistent findings" or "inadequate evidence".

To be able to say that the high voltage transmission lines cause certain health effect, at least the majority of studies done on it must be consistent. It cannot be a few positive and mostly negative.

If you look at the google map in Malaysia, you can see that there are many housing areas or apartment built just next to the transmission power lines. There are people staying there, may be more than 30 years. You can interview them if you can.

So, whether to invest in a property near transmission power lines or not, it's up to each individual to decide.

In Malaysia, the power transmission network is known as the National Grid and is managed by TNB. The voltage of the power lines are 132 kV, 275 kV and 500 kV. Distribution lines of 33 kV, 22 kV, 11 kV, 6.6 kV and 415/240 volt in the Malaysia distribution network connect to the National Grid via transmission substations where voltages are stepped down by transformers.


An article taken from "Health Physic Society":

Health Risks Associated with Living Near High-Voltage Power Lines

Gary Zeman, ScD, CHP

Potential health concerns about power lines were first raised in a 1979 study which associated increased risk of childhood leukemia with residential proximity to power lines. More recent studies such as that by Draper et al., confirm a reported association between elevated risk of childhood leukemia and proximity to resdiential power lines, but failed to clarify whether the observed association is causal or coincidental. Some scientists have argued the physical impossibility of any health effect due to weak ambient levels of EMFs, while others maintain that the potential health risks should not be dismissed even though the evidence remains equivocal and contradictory.

To address public concerns about power-line EMFs, a national program in electric and magnetic field research was authorized by Congress in the Energy Policy Act of 1992. This program was called EMF-RAPID (Electric and Magnetic Fields Research and Public Information Dissemination).

In 1995, the American Physical Society (APS) spoke out on the question of power-line EMFs and health effects. The APS policy statement reads, in part: "The scientific literature and the reports of reviews by other panels show no consistent, significant link between cancer and power line fields. While it is impossible to prove that no deleterious health effects occur from exposure to any environmental factor, it is necessary to demonstrate a consistent, significant, and causal relationship before one can conclude that such effects do occur. From this standpoint, the conjectures relating cancer to power line fields have not been scientifically substantiated." (See APS Policy Statement 95.2 reaffirmed in 2005.)

In 1999 the National Academy of Sciences, National Research Council (NRC) published a review of the evidence from the EMF-RAPID program and concluded: "An earlier Research Council assessment of the available body of information on biological effects of power frequency magnetic fields (NRC 1997) led to the conclusion ‘that the current body of evidence does not show that exposure to these fields presents a human health hazard. . . .' The new, largely unpublished contributions of the EMF RAPID program are consistent with that conclusion. . . . In view of the negative outcomes of EMF RAPID replication studies, it now appears even less likely that MFs [magnetic fields] in the normal domestic or occupational environment produce important health effects, including cancer." (The NRC reports are accessible by searching for EMF at the NAS website.)

While the NRC review is fairly decisive in giving power-line EMFs a clean bill of health, a 1999 report by the National Institute of Environmental Health Sciences (NIEHS) concluded, "The scientific evidence suggesting that ELF-EMF exposures pose any health risk is weak" but goes on to state, "The NIEHS concludes that ELF-EMF exposures cannot be recognized as entirely safe because of weak scientific evidence that exposure may pose a leukemia hazard." (The NIEHS report is available on its website.)

In conclusion, there are no known health risks that have been conclusively demonstrated to be caused by living near high-voltage power lines. But science is unable to prove a negative, including whether low-level EMFs are completely risk free. Most scientists believe that exposure to the low-level EMFs near power lines is safe, but some scientists continue research to look for possible health risks associated with these fields. If there are any risks such as cancer associated with living near power lines, then it is clear that those risks are small.

Typical magnetic field values (from wikipedia)
  • 10−9–10−8 gauss: the human brain magnetic field
  • 0.31–0.58 gauss: the Earth's magnetic field on its surface
  • 25 gauss: the Earth's magnetic field in its core
  • 50 gauss: a typical refrigerator magnet
  • 100 gauss: a small iron magnet
  • 2000 gauss: a small neodymium-iron-boron (NIB) magnet
  • 15,000-30,000 gauss: a medical magnetic resonance imaging electromagnet
  • 1012–1013 gauss: the surface of a neutron star
I mention above that exposure of 2 milli gauss (or 0.002 gauss) and above from transmission power lines is dangerous. However, look at the earth magnetic field on its surface where we stand on, it's 0.3 gauss, much much more than the 0.002 gauss level. Look at the magnetic wave from our refrigerator which we switch on 24 hours a day, 365 days a year, and stay very near to, it's 50 gauss!! Isn't it interesting? Can anyone explain?

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