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Populations of humans on the planet Earth have been estimated about 6.9 billion in this year and these amounts will not going to stop but will continue to grow by each day. (Rosenberg, 2011) The increasing amounts of world's populations give rise to the energy crisis and this also affected the energy cost. Nowadays, there are a lot of High Voltage Transmission Lines (HVTL) that been used for making the transfer of electrical power became more efficient. HVTL are used to transmit electrical power (at higher voltages) over long distance transmission by reducing the energy lost. (Electric power transmission, 2011)
When these transmission are used, there will created the electric fields and magnetic fields due to direct motion and presence of electric charges. (Olden, 1999) It has been noted that electric and magnetic field have biological effects but this epidemiologic studies still be considered as contradictory and inclusive. (Haupt & Nolfi, 1984) The researchers need to do long time study and required larger sample populations to detect if this effect is actually exist. For the general information, electric and magnetic fields or known as electromagnetic field (EMF) is a physical field that been created by the electrical charges from the oscillating power systems with the currents. (Nair, Morgan, & Florog, 1989)
In addition, external EMF can alter the electric fields in the human body that can potentially effects the biological functions. Besides EMF, there is also has extremely low frequency (ELF) that appeared as a byproduct of the production of electricity. ELF can stimulate the nerve cells and also fibers by altering the electric field. (Stam, 2010) Besides that, there has an evidence shown that magnetic fields around the HVTL can reducing the melatonin levels in humans body which this effect causing increased risk of cancers. It has been studied by US National Institute of Environmental Health Sciences (NEIHS) and also the International Agency for Research on Cancer (IARC) which they concluded that EMF can bring to possible cancers. (Henshaw, 2002)
So, this EMF-ELF that been produced by the HVTL are considered to be added to the environmental agents that are potentially effects to public health list. This EMF-ELF is currently ubiquitous in the Earth's environment. Their exposure to the surroundings still in controversial issues and there are still have no valid results that concerns to the biological effects mechanisms. There have several results that shown that EMF-ELF can affect the humans' health because the continuously exposed to the fields that not came out from the HVTL itself but also in home and workplace environments. The general effects that the researchers found are mostly cancers. (Gobbaa, Bargellinib, Scaringia, Bravoa, & Borellab, 2009)
The purposes of doing this assignment are firstly, to study the effects of HVTL to humans' health. Secondly, to determine which health effects those are contributed to this EMF-ELF effect. Lastly, to evaluate all the possible health effects to occur. By doing this assignment, our group has learned a lot about the HVTL effects on public health. There still have need more prevention and precaution regarding to this matter to bring the good healthy life to all populations around the world.
Electrical power is the central to the energy systems of the world's countries. Electrical utilities required overhead alternating current (AC) transmission lines which operated at voltages of 500 kV and above if they are to economically and consistently move large blocks of power over long distances. (Rish & Morgan, 1979) Supplementary this growth in the use of very high voltage AC transmission lines is a growing concern among the public and in regulatory and technical circles about possible human health effects consequential from exposure to the EMF associated with these lines. (Rish & Morgan, 1979)
In the meantime, housing price is depreciated because of this and people try to avoid areas with HVTL. Despite the fact that our theoretical perceptive is inadequate there are numerous mechanisms by which AC electric and magnetic fields may generate health effects in human. This comprises:
Neurological or other effects generated by body currents ensuing from a continuously changing induced electric moment or from magnetic induction.
Psychological or physiological effects generated by small arc discharges which consequence when a person at one potential touches an object in the surroundings which is at a dissimilar potential.
Direct meddling in biological processes that resulted by the existence of electric and magnetic fields such as hormone and enzyme acknowledgment developments on cell membrane surfaces and bone growth processes. (Rish & Morgan, 1979)
The propagation of energy as a result of a time varying electromagnetic field in which electric and magnetic field component which described the electromagnetic radiation are connected as stated by Maxwell's equations, in the following forms: (Henshaw, 2002)
E = hc/
The wave theory of electromagnetic radiation was formalized by James Clerk Maxwell in the 1800s, when he realized that such energy was an interruption of time-varying electric and magnetic fields propagating through space and fit the wave equation. (Jones, 2011)
Radiation in the form of radio waves, emissions from visible light and mobile phones, all constitute electromagnetic radiation. Power frequencies fields, 50 Hz in Europe; 60 Hz in the USA, Canada and South America; and elsewhere are exceedingly low in electromagnetic frequency terms. (Henshaw, 2002) In fact, the possibility that exposure to low-frequency electromagnetic fields which generated by electric currents is associated with an increased risk of cancer has been debated since a link was first suggested in 1979. (Harty, Facci, Cassels, & Buynder, 2001)
Nevertheless, EMF from power lines are extremely low frequency. Physicists believe that low levels of environmental exposure are unable to generate biological effects since the amount of energy in these fields is below that required to break molecular bonds such as those in DNA. (Harty, Facci, Cassels, & Buynder, 2001) The amount of electric field, potential voltage and magnetic field should be known specifically in order to determine the real effect or danger of electromagnetic field (EMF) from the HVTL. The power lines that could provide the lowest and the desired field levels in the vicinity of the power line should be designed by the engineer. In order to optimize its electrical performance and to minimize the cost, other parameters related to the geometry for instance the placement of shield wires, conductor type and phase spacing are play a significant part in the design besides the electric and magnetic field levels. (Harty, Facci, Cassels, & Buynder, 2001)
For the HVTL electrical transmission, the total resistance of the transmission line is called R. The local population required power, P = IV and this means that the current been obtained is I = P/V. So, when the transmission line voltage is higher, the current will become smaller. The line loss is given by Ploss=IÂ²R. By substituting the current,
Ploss = PÂ²R/VÂ²
It can be concluded that the line loss decreased when the voltage is increased. There is another important parameter which is loss fraction:
Ploss/P = PR/VÂ²
This loss fraction is proportional to the load P. As the loss fraction is increased, the P is also increased. Line loss can became larger over the long distances transmission, so the power will goes into heating the transmission line cable. (Hokin, 2011)
HEALTH EFFECTS OF HVTL
It is no doubt here that electric and magnetic fields can have biological effects. Many epidemiological studies have been done with an attempted to detect related health effects in human populations. It is due to the modern technology nowadays that used a lot of electrical appliance which give more concern to researcher to study about the biological effect that might be produced.
One of the health effects regarding this matter is an increasing in childhood leukemia incidence. Ahlborn et al in D.L. Henshaw stated that there is a recent published pooled analysis of childhood leukemia in relation to power frequency magnetic field exposures. (Henshaw, 2002) Many of epidemiological studies also reported that there are possible associations between extremely low frequency, magnetic field (EMF-ELF) exposure and childhood leukemia. (Choo & Chung, 2003)
The National Institute of Environmental Health Sciences (NIEHS) report on health effects from exposure to power-line frequency electric and magnetic field stated that the scientific evidence which suggest extremely low frequency and magnetic fields (EMF-ELF) exposures might pose any health risk is weak. The strongest evidence for health effects comes from associations observed in human populations with two forms of cancer: childhood leukemia and chronic lymphocytic leukemia in occupationally exposed adults. (Olden, 1999)
Besides leukemia, EMF-ELF exposure also might causes adult cancer such as brain cancers, breast cancers (in both males and females), and testicular cancers, cancers in offspring of workers, lymphoma, multiple myeloma, melanoma, non-Hodgkin's lymphoma and thyroid cancers. In adults, the chronic lymphocytic leukemia shows only weak evidence for the exposure of magnetic fields, reported by The National Institute of Environmental Health Sciences (NIEHS). Some evidence exists for an association between brain cancers and exposure to ELF-EMF and between female breast cancers and ELF-EMF exposure. (Patty & Hill, 2006)
Unfortunately, the studies evaluating these associations are inconsistent and have limits to their interpretation making them inadequate for supporting or refuting an effect. The remaining cases show too weak support or evidence. The risks of leukemia of all types from residential exposures were evaluated in several ways and it shows mixed results for different sub-types of leukemia studied. For lymphocytic leukemia, the results of one study is inconsistent showing no increased risk and with the other showing fairly consistent dose-response with increasing cumulative exposure. (Olden, 1999)
Studies concerning Victorian public health also were done due to the publication of a UK report on the risks of power frequency electromagnetic fields, particularly high-voltage power lines. In its paper, it's stated that no convincing evidence of an increased risk of other previously implicated cancers (such as brain tumors or leukemia) in adults. The threshold exposure level of 0.4ÂµT is such that only 0.5 per cent of the UK population is estimated to face such exposures. Around 75 per cent of this share is a long way from overhead power lines. (Harty, Facci, Cassels, & Buynder, 2001)
In human body, melatonin is present as a natural anti-cancer agent and it plays an important role in affecting mood. The depression of melatonin production in the pineal gland by the action of magnetic fields has been proposed as a mechanism of increased risk of breast cancer and of depression. Research into how magnetic fields might affect pineal melatonin has been carried out in both contexts. It is found that 50Hz circularly polarized magnetic fields above 1.4ÂµT suppressed both serum and pineal gland melatonin. This observation may be important due to microtesla level rotating fields are found near three-phase electricity power lines. (Henshaw, 2002)
However, a causal mechanism by which power frequency magnetic fields may affect breast and other cancers remain unproven. (Henshaw, 2002) Changes in melatonin and changes in the immune system have been studied as the two possible mechanistic explanations for cancer findings from exposure to EMF-ELF. However, the results combined provide little supports. Numbers of cases of mood changes and hypersensitivity thought attributable to EMF-ELF exposure also were reported. (Olden, 1999)
An association between magnetic field and both depression and suicide has been seen in many epidemiological studies and is considered biologically plausible via reduced pineal melatonin. It is found that male hospital admissions for depression were increased 36% during periods of geomagnetic storms compared with normal periods. Electric and magnetic fields induce currents in the body and these may also have a bearing on depression. Some studies also have shown an effect on short-term memory which can occur at exposures as low as 28ÂµT for magnetic fields. (Henshaw, 2002)
Overall, the evidence confirms the potential for an association between power frequency magnetic fields and both depression and suicide. There is evidence that an effect occurs at a low-magnetic field threshold of approximately 0.1ÂµT. This low threshold would embrace exposures near a range of high-and low-voltage power-lines and low-voltage distribution cables. On the other hands, corona ion that is emitted from high-voltage power-lines is disperse in the atmosphere and is believe can cause lung cancer. The corona ion dispersed in two ways. (Henshaw, 2002)
First, they may disperse in their own right. Second, they may attach themselves to aerosol-sized particles of air pollution thereby increasing the electrical charge on such aerosols. When inhaled, electrically charged aerosol particles have a higher probability of being deposited in the lung compared with uncharged aerosols. Overall, there have been no specific studies of the health effects of population exposure to corona ions. However, there is tantalizing epidemiological evidence that lung cancer risk might be associated with high-voltage power-lines. (Henshaw, 2002)
Table 1 simplifies the possible number of cases of ill health in person. However, not every possible health effect was included.
NIEHS also reported that there is possibility the EMF-ELF might causes non-cancer findings in human health. Pregnancy loss is one of the investigations but there is no association was reported between measured fields (including personal exposure monitoring) and intrauterine growth, birth weight or gestational age. Low birth weight, intrauterine growth retardation, preterm birth and congenital anomalies arising from the father's exposure were not associated with occupational exposures to EMF-ELF. A study concerning an association between occupational exposure to EMF-ELF and Alzheimer's disease is considered in five studies. (Olden, 1999)
One of it shows increases in one or more exposure groups. The data obtain for this association are inadequate due to the design limitations. Amyotrophic lateral sclerosis, suicide and depression also were reported in NIEHS but the evidence supporting this is too weak. Changes in human pulse as a function of exposure to EMF-ELF showed no effect was observed. The biological mechanism is unknown, and the general effect is very small making it unlikely that this is a health risk at lower doses. (Olden, 1999)
Meanwhile, Chung-Yi Li et al. demonstrated a wide range of exposures to EMF-ELF among schoolchildren during their stay on campuses adjacent to HVTL. They conclude that EMF-ELF exposure at school did have a higher chance of having a mean exposure greater than 0.4ÂµT during school hours which consequently might risk the children health. (Chung, Fung, Fu, & Pei, 2007)
On the recent study of possible effect of occupational EMF-ELF exposure on NK cytotoxic activity in peripheral blood lymphocytes (PBL) suggest that occupational exposure to EMF-ELF, at least at TWA levels exceeding 1ÂµT, may induce a reduction of NK activity in PBL. However the biological significance of these changes is still to be elucidated, but we must consider that EMF-ELF are possible carcinogens (Group 2B) and available data suggest that they could act as promoters or progresses. (Gobbaa, Bargellinib, Scaringia, Bravoa, & Borellab, 2009).
Scientific evidence does not demonstrate a causal link between any health impact and typical exposures to electromagnetic fields. However, a precautionary approach suggest that future unnecessary heavy exposures from overhead power lines should be avoided if this is achievable without excessive costs or technical difficulties.