Possible adverse health effects from electromagnetic fields chevron_right
- What are electromagnetic fields?
- Do electromagnetic fields effect health?
- How are health effect studies carried out?
- What is the epidemiology?
- What do the EMF studies show?
- Are there any Australian guidelines to limit exposure?
- What are typical exposure levels around homes?
- What are typical exposure levels in workplaces?
- What can be concluded?
There is a general perception amongst many in the community that there are health risks resulting from exposure to electromagnetic fields (EMF) from power lines. All alternating electric currents generate electric and magnetic fields, collectively known as EMFs (sometimes, incorrectly referred to as electromagnetic radiation). The electric field is proportional to the voltage (which can be considered as the pressure with which electricity is pushed through the wires). The magnetic field is proportional to the current, that is, to the amount of electricity flowing through the wires. The direction of the current, and therefore that of the magnetic field, changes 50 times per second (that is, at 50 Hz).
These fields emanate from the wires delivering electricity to our homes and all devices which use electricity in the home. Many people are concerned about the alleged link between exposure to magnetic fields, in particular, and an increased risk of contracting cancer. These concerns are raised when stories appear in the media in which the words radiation and cancer are emphasized, especially when children are also involved.
Electric fields can be easily shielded, but the shielding of magnetic fields is technically difficult and therefore very expensive. Buried power lines generate lower magnetic fields than overhead power lines because of their design, not because the earth eliminates the field. The easiest way to reduce exposure to magnetic fields is to increase the distance from the source, particularly for fields generated by appliances.
Power lines include transmission lines (mounted on large steel towers) and distribution lines (mounted on concrete or wood poles placed on the road reserve).
Transmission lines generate both strong electric fields and strong magnetic fields. Distribution lines generate weak electric fields, but can generate strong magnetic fields.
Human studies have consistently shown that there is no evidence that prolonged exposure to weak electric fields (such as those found in the home or in most workplaces), results in adverse health effects. Whether chronic exposure to weak magnetic fields is equally harmless remains an open question. There is no evidence that these fields cause immediate, permanent harm.
Laboratory studies on animals and cell cultures have shown that weak magnetic fields can have effects on several biological processes. For example, they may alter hormone and enzyme levels and the rate of movement of some chemicals through living tissue. By themselves, these changes do not appear to constitute a health hazard. We do not know if, in the long term, they may have an effect on the incidence of cancer or other adverse health effects. While most studies have produced inconclusive results or no increased cancer incidence in laboratory animals following exposure to EMFs, a few studies have indicated an increased incidence.
Another way to find out whether EMFs affect human health is to conduct relevant studies on human populations.
To determine if there is a health risk from some, as yet, unknown cause, science uses the discipline called epidemiology. Epidemiology is the study of occurrence and distribution of disease in the population (or community). The first major benefit to mankind from this science came in 1855. John Snow, a British physician, observed that death rates from cholera were particularly high in areas of London which were supplied with drinking water which had been extracted from the Thames River at points adjacent to sewage outfalls. He proposed that cholera was transmitted by an unknown agent through sewage. This discovery eventually led to proper treatment of sewage.
To do this type of study for EMFs and cancer, two groups of people need to be compared: one group which has, in the past, been exposed to EMFs while another group (the control group) has not. Because everyone in the community has been exposed, to some extent, to these fields, the exposed group is usually made up of people who live near to power lines, while the non-exposed group live further away. An observation is then made as to whether there are more cancers in the exposed group than in the non-exposed group. Simple? Unfortunately, it is not and that is why the controversy remains.
The epidemiology of cancer is difficult for the following reasons:
There is a long latency period (delay) of 5 to 20 years or more between exposure and onset of the disease. Cancer usually occurs in old age because of the long latency period.
Cancer is found amongst people who have not been exposed to the causative agent because the disease is naturally occurring. For this reason carcinogenic (cancer causing) agents are often given a relative risk ratio. Cigarette smokers for example have 10 to 30 times the risk (relative risk ratio) of contracting lung cancer as do non smokers.
Not everyone who is exposed will get a cancer. Cancer incidence is relatively rare, except amongst the elderly.
There are many factors which can increase the risk of cancer. For example; poverty, cigarette smoking, alcohol consumption, occupation, sex, race, lifestyle and age.
The cause of most cancers is not known. The occurrence of cancer in an exposed group seems to be a random process. Not all cigarette smokers get lung cancer and perhaps that is why people continue to smoke despite the warnings. They are playing a lottery with their lives.
For the above reasons, to do an epidemiological study between an exposed and non exposed group for a possible cancer risk factor, one needs to meet the following criteria:
- A large number of people must be included in the study (not everyone exposed gets a cancer).
- The two groups must be matched in every respect except exposure to the agent under test (there are many risk factors for cancer).
- The two groups must be monitored for a long time (long latency period for cancer).
Since cancer incidence is random, a statistical (mathematical) analysis of the results must be performed. This analysis will result in a relative risk factor (see above).
There are several ways in which these studies can be performed. Because of the time and cost savings involved, a retrospective cohort (group of associates) study is the most common method for EMF exposure. In this type of study a group of people who have been exposed to the agent under test and a similar group who have not been exposed are compared. One might choose electrical linesman and compare them with their next door neighbour, for example. This type of study is fraught with pitfalls, such as:
The exposed group have not had their exposure, to the agent under test, measured. It is assumed because of their occupation or proximity (say to powerlines) that they are more exposed than the control group.
It is difficult to find a control group which has the same mix of characteristics so that confounding (confusing) factors do not interfere with the result.
The results of all EMF studies to date have indicated either no association or a weak association with adverse health effects. Those studies which do indicate an increased risk of health effects claim a relative risk ratio of 2 to 3. That is as a result of exposure to powerline electromagnetic fields the risk of contracting a cancer is two to three time the risk for a non exposed person. Because of the small risk ratios found (most epidemiologists consider a single study with a relative risk ratio less than 3 as not significant) there is room for debate about whether a health hazard exists at all.
At this point it is necessary to discuss the meaning of the word association as it is used in epidemiology. Association does not mean causation. The fact that the air temperature rises when the cock crows is an association. We know that it is the rising of the sun that causes the temperature to rise, not the cock. To pass from association to causation the results of these studies should meet most if not all of the following criteria:
- The risk ratio should be high, usually 5 or greater.
- The studies should consistently demonstrate an association.
- There should be an association between the exposure and a specific disease. The association should not refer to cancer in general but a specific cancer; eg leukemia and brain cancer together is acceptable but not leukemia in one study and brain cancer in another.
- There should be a demonstrable dose effect. A dose effect means that as you increase exposure to EMF the number of cancers increases.
- There is a biological mechanism by which the agent under test can cause the associated disease; eg. cholera is caused by a bacterium, lung cancer is caused by the chemical carcinogens in tobacco tar.
- To date all of the epidemiological studies on exposure to EMF do not meet these criteria. The evidence is either weak or absent. In particular:
- The relative risk ratio for those studies which do show an association is usually less than 3.
- The studies are inconsistent. Many studies show no effect.
- The health effects vary. Some studies show an increase in brain cancer while others show an increase in leukemia.
- No dose effect has been demonstrated.
- No biological mechanism is known for induction of cancer from exposure to EMF’s.
It is for these reasons that the majority of scientists, and Australian radiation health authorities in particular, do not regard chronic exposure to 50 Hz electric and magnetic fields at the levels commonly found in the environment as a proven health risk. Moreover, the evidence we have is inconclusive and does not allow health authorities to decide whether there is a specific magnetic field level above which chronic exposure is dangerous or compromises human health.
Some authorities advocate a policy of minimizing exposure wherever possible, providing this can be achieved at reasonably modest cost. Since this is essentially a question of judgement, such decisions are best left to the individual. Simple steps to reduce exposure are:
- using an electric blanket to warm the bed and switching it off before climbing in will virtually eliminate what could be a significant exposure;
- locating bedrooms towards the rear of the house reduces dramatically the exposure due to distribution lines in front of the house;
- moving a bed away from an external wall which has an electric hot water service on the other side will also reduce exposures;
- a distance of about 50 cm between a video screen and the user usually results in an exposure not very different from those found elsewhere in the environment.
There are currently no Australian standards regulating exposure to these fields. The National Health and Medical Research Council has issued Interim guidelines on limits of exposure to 50/60 Hz electric and magnetic fields. These guidelines are aimed at preventing immediate health effects resulting from acute exposure to these fields. The recommended magnetic field exposure limit for members of the public (24 hour exposure) is 1,000 mG (0.1 milliTesla) and for occupational exposure (whole working day) is 5,000 mG (0.5 milliTesla).
The NHMRC notes that "although there are limitations in the epidemiological studies that suggest an increased incidence of cancer among children and adults exposed to 50/60 Hz fields, the data cannot be dismissed. Additional study will be required before these data can serve as a basis for risk assessment". In other words, because the research data do not indicate an exposure level at which a cancer risk exists (assuming that such a risk exists at any level), it is simply not possible to determine an exposure limit below which that risk would disappear. Hence, the above NHMRC limits do not apply to the avoidance of cancer risk resulting from chronic exposure to 50 Hz magnetic fields.
Exposure levels to EMFs around the home are in the range of 0.1 - 2.5 mG. For homes near powerlines, these levels may be as high as 5 - 10 mG. Immediately under the powerline, magnetic field levels of 60 - 100 mG may be found.
The widespread use of electricity means that in all workplaces, there will be levels of magnetic fields that would be considered "normal". However, there are also localized sources of magnetic fields in the workplace such as electrical substations in the basement, power cables in the walls or floor and distribution lines close to the building. The field levels close to these sources will be relatively high and may cause computer screens to shimmer, for example. These levels may exceed the NHMRC limit .
The only remedies currently available to reduce these fields, and the resultant exposure, is a combination of shielding and relocating the source (both very costly), or relocating the employees (also potentially costly). The general aim of any field reduction program is to minimize the exposure level for all staff. However, particular situations may require particular solutions and the local electricity supplier or the Electricity Suppliers Association of Australia should be consulted.
On balance, the scientific evidence does not indicate that exposure to 50 Hz EMFs found around the home, the office or near power lines is a hazard to human health
The earth’s magnetic field has a strength of about 500 mG. This figure is included to help the reader obtain a feel for what the units mean. The earth’s magnetic field is not changing direction at 50 to 60 times per second and is therefore not comparable to power line fields as far as health effects are concerned.
Radiation emissions from microwave ovens chevron_right
- Who assesses risks from microwaves?
- What are microwaves?
- What are microwaves used for?
- How do microwave ovens work?
- How safe are microwave ovens?
- Are cardiac pacemakers safe near microwave ovens?
- What precautions are required with cooking containers and foils?
- What inspections should the user undertake?
- What precautions are required for radiation safety in the use of microwave ovens?
- What other precautions are needed for the safe use of microwave ovens?
- Are there any Australian Standards that apply to microwave ovens?
- What other references provide information on microwave ovens?
The Australian Radiation Protection and Nuclear Safety Agency maintains a close watch over potential radiation hazards arising from technical and consumer products and evaluates any possible public health risk arising from their use. Ovens which utilize microwave radiation for cooking of foodstuffs either in the home or in commercial or other premises have a potential to create radiation hazards if they are incorrectly used or are not maintained in good working order. Some features of microwave ovens and precautions in their use are described below.
Microwaves, like visible light are a part of the electromagnetic radiation spectrum and are extremely high frequency radio waves. Microwaves travel in straight lines and may be either reflected, transmitted or absorbed by matter in their path. Metallic materials totally reflect microwaves. Non-metallic materials such as glass and plastics are partially transparent to microwaves. Materials containing moisture such as foods absorb microwave energy and produce heat.
Some of the more common uses of microwaves include satellite communications, radar, car phones, air and sea navigational aids. Other applications include use in industry for thawing and drying materials and in medicine for diathermy treatment. The use of microwave ovens in industrial, commercial, domestic and other premises has increased substantially over recent years.
In the microwave oven an electronic tube called a magnetron is used to produce the microwaves. The microwaves then pass through a wave guide into the metal oven cavity where they are reflected around the oven walls. Uneven reflections may cause localized hot and cold "spots" in food. This is minimized by the use of a mode stirring fan and rotating carousel. The microwaves penetrate into the food and cause water molecules within the food to vibrate at the frequency of the microwaves (2450 MHz). The vibration causes considerable molecular friction which produces heat and results in a rapid rise in temperature. The cooking time is therefore much shorter than in a conventional oven. The rate of heating depends on the moisture content, shape, volume and mass of food present. This can produce uneven heating with some foods where the outside may be only warm while the inside may be close to boiling (jam filled donuts are an example). The oven walls and most cooking utensils are not directly heated by microwaves because they do not absorb microwave energy. However, they frequently get warm from being in direct contact with the hot food.
Microwaves generated in microwave ovens, like visible light from light globes, cease to exist once the electrical power to the magnetron is turned off. They do not remain in the food when the power is turned off and they cannot make the food or the oven radioactive. Therefore, food cooked in a microwave oven presents no radiation hazard.
All microwave ovens have at least two safety interlock switches which stop the generation of microwaves immediately the door is opened. The design of microwave ovens is such that the microwaves are contained within the oven, but it is possible for some leakage to occur around the door. However, the design of oven door seals limits this leakage to a level well below that recommended by the National Health and Medical Research Council.¹
In Australia, all State Electricity Authorities have gazetted domestic microwave ovens as prescribed items. That is, before any domestic microwave oven is sold, a sample of each model has to be tested and approved to the particular requirements for microwave ovens as per the Australian Standard². Such testing and approval requires the oven to be surveyed for microwave leakage.
There are a number of microwave oven leakage detectors, designed for household use, marketed within Australia of which unfortunately few work satisfactorily. Only detectors showing that they comply with the Australian Standard³ for microwave oven leakage detectors for household use should be used. Unless these detectors are used strictly in accordance with instructions, they may indicate a false result. Surveys by testing authorities have shown that microwave oven leakage levels in excess of the recommended limits are very rare and an oven in good condition and used correctly is safe. However, when an oven appears to have deteriorated or is damaged, then a qualified serviceman should inspect the oven before it is used and check the leakage to ensure that it does not exceed the recommended level.
Modern pacemakers are not susceptible to microwave radiation interference from microwave ovens having leakage within the limits of the Australian Standard. Therefore, there is no reason for concern. People who are unsure or experience any discomfort in the vicinity of a microwave oven should contact the doctor who implanted the pacemaker.
Plastic containers considered suitable for holding foods at room temperature may not necessarily be suitable for use in a microwave oven. The high cooking temperatures may cause the plastic’s chemistry to break down and thereby contaminate food in the container. Since it is difficult to determine the composition of plastic from its appearance, it is recommended that plastic containers or wraps not be used in a microwave oven unless clearly designated for such use by the manufacturer Research shows that ceramics, glass-ceramics, some plastics and papers are satisfactory. Dishes with metallic glazes should not be used. If fast food foil containers and aluminium foil are used, the oven manufacturer’s directions should be carefully followed. Do not let fast food foil containers or aluminium foil touch the sides of the oven as this may cause sparking.
A microwave oven should only be used if an inspection confirms all of the following points.
- The surface of the door is not damaged.
- The door fits squarely and securely and opens and closes smoothly.
- The door hinges are in good condition.
- The door seals are not covered with food or do not have burn marks.
- No corrosion is evident on the door or the oven interior.
- Follow the oven manufacturer’s instructions on recommended operating procedures and safety precautions.
- Never tamper with or inactivate the interlocking devices.
- Never poke an object, particularly a metal object into the oven.
- Never use the oven without the trays provided by the manufacturer unless specifically allowed in the manufacturer’s instructions.
- Never operate the oven without a load (i.e. an absorbing material such as food or water) in the oven cavity unless specifically allowed in the manufacturer’s instructions.
- Never rest heavy objects such as food containers on the door while it is open.
- Clean the oven cavity, the door and seals with water and a mild detergent at regular intervals.
- Supervise children using microwave ovens.
- When thawing frozen foods in the microwave oven it is important to thaw the food thoroughly before beginning to cook. Always ensure the food reaches a temperature sufficient to destroy micro-organisms that may be present.
- Do not use microwave ovens for sterilizing baby bottles or other food utensils.
- Ensure that all food prepared in a microwave oven is at the correct temperature to allow it to be consumed safely. Cases have been reported where babies have received severe burns from boiling milk heated in a microwave oven.
- Use only cooking containers designated as suitable for microwave cooking.
The National Health and Medical Research Council recognises that some microwaves may escape from ovens and has laid down a standard of safety for leakage radiation. It believes that compliance with this standard will ensure the public health is not affected by the use of microwave ovens. This standard of safety states that the power flux density of microwave radiation from any microwave oven shall not exceed 5 milliwatts per square centimetre at any point 5 centimetres or more from the external surface of the oven.
- National Health and Medical Research Council, Seventy-third Session, Canberra, October 1971.
- Standards Association of Australia. Australian Standard 3301-1980. "Approval and Test Specification for Particular Requirements for Microwave Ovens"
- Standards Association of Australia. Australian Standard 2889-1987. "Microwave Oven Leakage Detectors for Household Use".
Radiation emissions from video display terminals chevron_right
- What are some of the concerns associated with VDTs?
- What types of radiation do VDTs emit?
- What type of health effects are linked to VDTs?
- What studies have been done?
- What conclusions can be drawn?
Video display terminals (VDTs) serve as a convenient way for people to interact with a computer system. The widespread use of VDTs has been accompanied, however, by expressions of concern from VDT operators, trade unions, and the media about possible adverse health effects associated with VDT use. Adverse pregnancy outcomes, eye problems and skin disorders have been blamed on the electromagnetic radiation emissions from VDTs.
Most VDTs currently in use are based on cathode-ray tube (CRT) technology and the information in this bulletin applies only to this type of VDT. The VDT is designed to emit visible radiation (light) with a brightness that is adjustable by the operator. In creating the display, however, other types of electromagnetic radiation are also generated, in particular, extremely low frequency, radiofrequency, infrared, ultraviolet and X-ray radiation.
The CRT is an evacuated glass tube which has a source of electrons at one end and a screen, which is coated on the inside with a phosphor, at the other. When a sufficiently high voltage is applied to the CRT, a focussed beam of electrons is produced which is then scanned across the screen. The beam is switched on and off in order to generate the display. The interaction of these electrons with the phosphor causes the emission of visible radiation, plus a small amount of ultraviolet radiation, from the screen. This interaction also produces low energy X-rays which are absorbed by the thick glass envelope. Some infrared radiation is emitted as a result of heat generated within the electronic circuitry during VDT operation.
Radiofrequency radiation is emitted by the horizontal deflection coil which moves the beam across the screen, by the CRT itself and by the extra high voltage transformer which supplies the voltage necessary to accelerate the electron beam in the CRT. Extremely low frequency electromagnetic fields (EMF) surround the AC power connection and the vertical deflection coil. Radiofrequency emissions and extremely low frequency EMF’s are not confined to the VDT screen - they occur in all directions from the VDT.
1. Eye problems
Many surveys have shown that VDT operators suffer from eye strain, nausea, headaches and blurred vision more often than other office workers. These subjective complaints are also described by people performing other close-visual tasks and indicate that either the display needs adjusting, the screen should be relocated, or the operator’s eyesight needs correcting. VDT emission levels of radiation known to cause cataracts are either not detectable or are very low. Indeed, no survey has shown that VDT use causes cataracts.
2. Skin disorders
Almost all cases of skin disorders among VDT operators have occurred in northern Europe. There, the typically dry atmosphere may be an important factor. The build-up of electrostatic charges on the operator’s body, the presence of atmospheric aerosols in office environments and the susceptibility of the operator to skin problems may all be contributing factors. The VDT’s electrostatic field is not considered to be involved, although further studies are being undertaken. The humidity in Australian offices is somewhat higher, which could explain the lack of reports of local incidence. Ultraviolet radiation emissions from VDTs are not considered to cause skin disorders either.
3. Adverse pregnancy outcomes
Allegations that adverse pregnancy outcomes among VDT operators are due to radiation emissions are tested by two types of study. The results of animal studies, where chicken eggs or pregnant mice are exposed to radiation similar to that from a VDT, are inconclusive. In any event, they cannot predict human experience. Reliable epidemiological studies conclude that the incidence of adverse pregnancy outcomes among VDT operators and women who do not operate a VDT are not significantly different. So there is no firm evidence to support the above allegations.
The Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) has measured the radiofrequency, microwave, ultraviolet and X-radiation emissions from 108 different models of monochrome and colour VDTs. These measurements were made at ARPANSA using very sensitive and accurate equipment, generally with the VDT screen filled with "M"s and set at maximum brightness. The results have been published in an ARPANSA Technical Report, "Video Display Terminals - Health Concerns and Radiation Emissions" (ARPANSA/TR092), where the emission levels are compared with exposure limits recommended by the International Radiation Protection Association (IRPA) and the Standards Association of Australia. This Report also reviews the studies into the alleged adverse health effects.
The above measurements showed that:
- radiofrequency radiation was detected, but at levels which were low compared to recommended exposure limits,
- no microwave radiation was detected,
- ultraviolet radiation was detected, but at levels which were very much lower than recommended exposure limits, and
- no X-ray radiation was detected.
The levels of infrared radiation emitted from nine VDTs have also been measured at ARPANSA and found to be less than that emitted from a human hand.
Extremely low frequency (ELF) electromagnetic fields were not measured at ARPANSA as they were not considered to be a hazard. Other studies have reported that these VDT fields are less than the 50/60 Hz IRPA exposure limits. Still, concerns about the health implications of long-term exposure to ELF magnetic fields have recently been expressed. Current scientific opinion about these implications is in dispute by minority groups and further studies are in progress.
The electromagnetic radiation emissions from VDTs that were measured by ARPANSA are alleged to be responsible for adverse health effects among VDT operators. These allegations are not supported by either animal studies or reliable epidemiological studies. Furthermore, the emission levels from VDTs used in Australia are less (and, in most cases, very much less) than the relevant recommended exposure limit. It is therefore concluded that these emissions are not a hazard to the health of VDT operators or to the foetuses of pregnant operators.
Mobile telephones and health effects chevron_right
- What part of the mobile phone emits radiation?
- Is there a basis for health concerns?
- What are the known effects of microwave exposure?
- What is the evidence for cancer?
- What research is being funded?
- What conclusions can be drawn?
Mobile telephones have transformed the telecommunications industry. These devices can be used to make telephone calls from almost anywhere. There are two types - one has the antenna mounted on the handset and the other has the antenna mounted on a separate transmitter or, if the telephone is installed in a vehicle, mounted on the roof or rear window. Communication between a mobile telephone and the nearest base station is achieved by the microwave emissions from the antenna.
Concerns have been raised about the type of mobile telephone that has the antenna in the handset. In this case, the antenna is very close to the user’s head during normal use of the telephone and there is concern about the level of microwave emissions to which the brain is being exposed.
Those telephones that have the antenna mounted elsewhere are of no concern, since exposure levels decrease rapidly with increasing distance from the antenna. Cordless telephones, which need to be operated within about 20 metres of a base unit that is connected directly to the telephone system, do not have any health concerns associated with their use because exposure levels are very low.
Reports have appeared in the media linking the use of mobile telephones with, among other things, headaches, hot spots in the brain and brain cancer.
Media reports have claimed that up to 70 percent of the microwave emissions from hand-held mobile telephones may be absorbed in the user’s head. This is not supported by the evidence, but nevertheless leads to speculation that hot spots may be created in the user’s brain, thereby raising concerns that the telephones may be a health risk. Other reports have indicated that mobile telephone users suffer localised headaches when they use their telephone. At this stage, it is difficult to evaluate the evidence supporting these reports, since they have not been published.
The brain cancer reports originated in the USA where a number of lawsuits have been lodged against mobile telephone manufacturers and suppliers. These claims for damages allege that the microwave emissions from mobile telephones used by the claimants caused their (in some cases, fatal) brain cancers. Those few cases that have been tried have been dismissed for lack of supporting evidence.
Microwaves are but one type of electromagnetic field. (For the purposes of this Information Bulletin, "fields" and "radiation" are equivalent.) One of the ways that these fields are described is by specifying their frequency. The range of frequencies that are useful for telecommunications include microwaves.
Some public concern about mobile telephones is erroneously based on media attention to the possibility of adverse effects from exposure to power-line electromagnetic fields, which have a much lower frequency than the microwaves emitted by mobile telephones. The physical properties and biological effects of these fields are very different from microwaves and it is meaningless to extrapolate the results of those studies to the subject of this Information Bulletin.
The current Australian exposure Standard is based on the well-established thermal effects of exposure to microwaves. That is, when tissue is exposed to sufficiently high levels of microwaves, the tissue is heated and damage may occur. The exposure limits are set well below levels where any significant heating occurs. The Standard also sets limits for pulsed radiation that are intended to eliminate possible effects where heating is not evident (non-thermal effects).
All mobile telephones marketed in Australia must satisfy the regulatory requirements of Austel (the Australian Telecommunications Authority), as well as that part of the Australian Standard that sets limits on the power output of a mobile telephone. Therefore, use of a mobile telephone is not expected to cause significant heating in any part of the body, including the brain.
Some research has indicated that non-thermal effects resulting from low-level microwave exposure also occur. However, the existence of these effects has not been sufficiently established to allow for them in the Standard.
A few animal studies suggest that exposure to weak microwave fields can accelerate the development of cancer. Further studies are required to establish their reproducibility and the existence or otherwise of a dose-response relationship. Whether these results are relevant to users of mobile telephones is not clear. In any event, these results cannot be dismissed at this stage.
The very few studies that have been conducted on human populations (epidemiological studies) do not provide any direct information on possible mobile telephone hazards and hence are of limited value. The results of these studies are difficult to interpret because exposure levels were either not measured or impossible to determine from the data provided. In general, however, this type of study will be useful in identifying possible links between mobile telephone use and cancer risk. Complementary cellular and animal research is required to establish any cause-and-effect relationship and the biological mechanisms involved.
The Australian Radiation Protection and Nuclear Safety Agency continues to closely monitor the research being conducted in this area.
On the specific issue of brain cancer occurring in users of these telephones, it is important to note that such cancers existed before the introduction of mobile telephones. It is simply not possible to identify the cause of any single case of cancer. Long-term studies to investigate whether mobile telephone users have a greater incidence of, say, brain cancer than the general population have not been completed.
The Commonwealth Government has established the "Electromagnetic Energy Public Health Issues Committee" to examine and advise on the adequacy of health exposure standards, compliance procedures, local and overseas research results and the potential for further research, all with respect to mobile telephone use, among other things. The Committee includes representatives from the Department of Health and Family Services, the Department of Communications and the Arts, Spectrum Management Agency, CSIRO, Austel, ARPANSA and the Therapeutic Goods Administration. Mobile telephone companies and service providers are not represented.
Late in 1996, the Commonwealth Government announced that $4.5mil would be provided for an Australian research and public information program over the next 4-5 years. This research program will be managed by the National Health and Medical Research Council.
There is no evidence that microwave exposure from mobile telephones causes cancer, and inconclusive evidence that such exposure accelerates the growth of an already-existing cancer. More research on this issue needs to be carried out.
Users concerned about the possibility of health effects can minimize their exposure to the microwave emissions by: limiting the duration of mobile telephone calls, using a mobile telephone which does not have the antenna in the handset or using a ‘hands-free’ attachment.
There is no clear evidence in the existing scientific literature that the use of digital or analogue mobile telephones poses a long-term public health hazard (although the possibility of a small risk cannot be ruled out).
Laser pointer hazard chevron_right
- What are Laser Pointers?
- What is LASER radiation?
- What are the categories of lasers?
- What are the hazards with Laser Pointers?
- What precautions are needed?
Laser pointers are battery-powered lasers which can produce a small spot of light hundreds of metres away, but which are small enough to be concealed in the closed hand. They were first used by demonstrators to point out features in their visual aids. The latest models can project shapes like stars, circles and squares, in addition to the conventional dot. They are now more widely available, particularly to children, resulting in them becoming a nuisance and an unlikely, but possible, hazard to the eye. There have been numerous reports of people shining the laser beam into the eyes of others with the intention of, at least, distracting them. Laser beams directed at vehicle drivers or machinery operators, while not causing them eye damage, could result in serious accidents.
Laser devices are sources of light which differ from all other sources of light in both the mechanism of operation and in the quality of the light produced. The word "laser" is an acronym referring to a device that operates by the process of -
The term "light" is used in the broadest sense to include the entire electromagnetic spectrum - from radiowaves to gamma rays.
Most lasers emit light in the form of a narrow beam of low divergence many times brighter than the sun. The light emitted from a laser differs from that emitted by a light bulb in that it is monochromatic (a pure colour) and it can be readily confined to a narrow beam (typical of a laser pointer) which diverges only slightly with distance. The radiant energy in a narrow laser beam can travel efficiently over large distances and may easily enter the eye and cause damage to it. The colour of light is determined by the wavelength of the light. Most laser pointers emit red light at a wavelength of about 630 nanometres.
Lasers are classified according to the hazard associated with their emissions, as defined in the Australian/New Zealand Standard AS/NZS 2211.1:1997 Laser Safety Part 1: Equipment classification, requirements and user’s guide:
- Class 1 lasers are considered safe under reasonably foreseeable conditions of operation.
- Class 2 lasers emit visible light at higher levels than Class 1, but eye protection is provided by aversion responses such as the human blink reflex.
- Class 3A lasers have higher power levels than Class 2 and the beam has a larger cross section such that the power of the beam entering the eye does not exceed the power of Class 2. This class of laser can be a hazard if optical devices such as binoculars focus the beam onto the retina.
- Class 3B (Restricted) lasers are similar to Class 3A except that the irradiance (power density) limit is increased by a factor of two.
- Class 3B lasers are sufficiently powerful to cause eye damage in a time shorter than the human blink reflex (0.25 seconds). Laser products with power output near the upper range of Class 3B may also cause skin burns.
- Class 4 lasers are high power devices capable of causing both eye and skin burns, and diffuse reflections may also be hazardous.
In 1993, the Radiation Health Committee of Australia’s National Health and Medical Research Council determined that laser pointers (and other consumer laser products) should not exceed Class 2. For visible laser emissions, a Class 2 laser is limited to a maximum power level of 1 milliwatt (mW) continuous wave emission. Unfortunately, there are laser pointers on the market with output powers well above 1 mW (that is, Class 3B). To make matters worse, some of these products are incorrectly labelled and hence their hazard potential is not known to the user. In particular, owing to different classification criteria in the U.S.A. and Australia, some lasers imported into Australia may be labelled as Class 3A when they are actually Class 3B.
Deliberate staring into a 5 mW beam is potentially damaging to the eye, although most laser pointers are of lesser power. Laser pointers should be kept away from infants and children who do not understand this risk. The natural aversion response of adults will protect their eyes from such lasers, although common sense says not to stare into the beam of any laser.
The most serious hazard from laser pointers is accidents resulting from temporary effects on the eye. Momentary viewing of the beam from a laser pointer may cause temporary flash-blindness, similar in effect to viewing a photographic flash at close range. However, unlike the photographic flash, a laser pointer can cause flash-blindness up to 50 metres or more away. For example, a driver, whose vision is unexpectedly affected, may loose control of their vehicle and have an accident, perhaps involving loss of life.
As with other types of laser products, laser pointers should always be used safely and in accord with relevant user guidelines as specified in AS/NZS 2211.1:1997. Glass surfaces and mirror-like targets should be avoided. Children should not have unsupervised access to these devices - if such access is possible, the batteries should be removed when the pointer is not being used. Adults should be provided with training on the safe use of laser pointers.
In particular, laser pointers should never be intentionally directed towards any person and should not be used outdoors where bystanders may accidentally view the beam. Intentional exposure of another person may be treated as an assault, resulting in serious legal consequences.
Visible light lasers used for surveying, levelling and alignment chevron_right
- What are the risks?
- How does this equipment operate?
- What are the biological effects?
- What are the Laser classifications?
- What precautions should be taken?
- What regulatory controls are in place?
- What references are available?
The growth in the number of laser devices used in Australia for surveying, levelling and aligning applications has increased the potential risk of workers being exposed to laser radiation through carelessness, misuse of equipment or ignorance of the hazards involved.
This bulletin is intended to explain the hazards and provide broad guidelines for the safe use of visible light lasers employed for surveying, levelling and alignment purposes.
Helium/neon gas laser devices which are most commonly used for surveying, levelling and alignment purposes consist of a high voltage gas discharge tube with reflecting mirrors at each end. One of the mirrors is partially transparent and the laser beam emerges from the discharge tube as a fine pencil of red light about 1 millimetre in diameter.
Lenses may be added to expand the beam diameter and to decrease the beam divergence. Helium/neon laser devices usually produce their light continuously and are referred to as continuous wave (c.w.) lasers, but the laser light may be pulsed (either electrically or mechanically).
Surveying, levelling and alignment laser devices all use the property that light travels in a straight line through air over long distances. For pipe laying or tunnelling applications the direction of the laser beam is fixed and used to guide the work; if accurate level measurements over a large area are required (e.g. laying concrete slabs, installing ceiling tiles), a motor driven prism reflector may be used to continuously rotate the laser beam.
A pulsed laser light allows the distance to be measured between a reflecting target and the laser measuring equipment by determining the time taken for a laser pulse to reach the target and reflect back to the laser measuring instrument. (Light travels in air at a constant velocity of about 300 million metres per second).
Most laser damage is due to the heating of the absorbing tissues. This thermal damage is usually confined to a limited area extending either side of the energy absorbing layer and centred on the irradiating beam.
Lasers which produce light in the visible region of the spectrum are potentially hazardous to sight. This is because the eye will focus the laser beam onto the retina and a retinal burn may result, in much the same way as a magnifying glass using the sun’s rays will burn paper. The power density of the laser spot focussed on the retina is typically about 100,000 times the power density incident on the cornea. Therefore, although it may be quite safe to expose the skin to a moderately low power visible laser, it is often hazardous to look into the beam. Laser burns on the retina may cause serious impairment of vision or even blindness in the eye affected.
Where the eye receives minimal exposure to a laser beam, temporary blindness may occur (similar to that caused by a photographic flash unit). The duration of the flash blindness is a measure of the severity of exposure and if the flash blindness lasts for an hour or more, it is an indication that permanent eye damage may have occurred.
Australian Standard 2211 - 1981 requires that laser products used for surveying, levelling or alignment purposes should preferably be either Class 1 or Class 2 (refer to section 6.3). The Standard allows use of Class 3A, but more stringent safety precautions are required than with Class 2. Class 3B and Class 4 laser products are too dangerous for general surveying, levelling or alignment purposes and are therefore not allowed for these applications.
Users and manufacturers of laser devices should consult Australian Standard 2211 - 1981 "Laser Safety" (AS 2211 - 1981) which lists detailed requirements of procedures and requirements necessary to protect persons from laser radiation. Users of lasers employed for surveying, levelling and alignment tasks in the construction industry, should also consult Australian Standard 2397 - 1980 "Guide to the Safe Use of Lasers in the Construction Industry". AS 2397 - 1980 reproduces and supplements the user precautions outlined in AS 2211 - 1981.
- Precautions should be taken to ensure that persons do not look directly into the laser beam.
- Direct viewing of the laser beam through optical instruments (theodolite, binoculars, telescope, etc.) will generally increase the hazard and should not be permitted.
- The laser beam should be terminated at the end of its useful beam path and must in all cases be reduced to less than the recommended maximum permitted exposure (see AS2211 - 1981) if the beam path extends beyond the control area (construction site, etc.).
- The laser beam path should be located well above or below eye level wherever practical.
- Precautions should be taken to ensure that the laser beam is not directed at specular (mirror-like) surfaces.
- When not in use the laser device should be stored in a location where unauthorized personnel cannot gain access.
- The laser head should be rigidly fixed in place so that the direction of the laser beam cannot be accidentally altered.
- Where laser devices are used indoors, room lighting should be as bright as practical in order to constrict the diameter of the pupil of the eye and consequently lessen the hazard.
- A responsible person should be appointed as a Laser Safety Officer to assess and implement controls appropriate to the class of laser, the type of installation and the associated hazards.
- Only suitable trained employees approved by the Laser Safety Officer should be allowed to install, adjust and operate the laser equipment.
- Warning signs (as designated by AS2211 - 1981) should be placed in conspicuous locations both inside and outside the work area and in locations giving access to the area.
- Laser devices used on building construction sites, which employ ROTATING LASER BEAMS, often have a beam rotation rate adjustable from about 6 revolutions per second down to a completely stationary beam. Accidental viewing of a STATIONARY beam must be avoided; however whilst the beam is rotating at more than a few revolutions per second, then accidental viewing should not cause any permanent eye damage (even when Class 3A laser devices are used).
In Victoria approval for the use of a laser on a construction site must be sought from the Department of Labour and Industry who enforce laser safety regulations.
Department of Labour and Industry
National Bank House
500 Bourke Street
MELBOURNE VIC 3000
- Charschan, S.S. (ed.)., Lasers in industry. New York: Van Nostrand, 1972.
- Harry, J. E., Industrial lasers and their applications. New York: McGraw-Hill, 1974.
- Standards Association of Australia. Laser Safety. North Sydney, 1981. A.S.2211.
- Standards Association of Australia. Guide to the safe use of lasers in the construction industry, 1980. A.S.2397.
- Sydenham, P. H., Laser gauging - reference guide to the use of laser based measurement systems. Armidale, N.S.W.: Department of Continuing Education, University of New England, 1976.
- Victoria. Labour and Industry (Laser Safety) Regulations 1983. Statutory Rules No. 361, Government Printer, Melbourne.
Laser Bar chevron_right
- What are Laser Bar-code Scanners?
- What are the hazards associated with scanners?
- What is the level of risk with scanners?
Laser bar code scanners are used in applications where the accurate identification of many articles in a short time is necessary, for example, in supermarkets, libraries and warehouses. These devices use a low powered laser to read the bar code attached to the article in question.
The laser beam is rapidly scanned in one or more planes usually by vibrating or rotating mirrors inside the bar code scanner. A sensor detects the time dependent pattern of reflected laser light as the beam is scanned across alternate light and dark bands on a bar code. This information is processed electronically to produce a digital interpretation of the bar code that a computer will understand.
To meet design safety requirements, the scanner incorporates fail-safe detection circuitry that turns the laser off in the event of a component failure or when output limits are likely to be exceeded during a given time interval. Many handheld scanners used for low volume bar code reading (such as in libraries) do not use a laser light source - they use a low power visible or infrared light emitting diode similar to those used in remote controls for TV or video equipment.
This document discusses the special characteristics of laser light and the inherent safety aspects of lasers used in bar code scanners.
Laser bar code scanners are either Class 1 or Class 2 lasers, and operate at relatively low power levels (outputs measured in milliwatts) and produce visible red beams (most common) or near-infrared beams.
The vast majority of supermarket bar code scanners are classified as Class 1 under ANZS 2211 and so are therefore safe. The risks associated with handheld Class 2 laser bar code scanners, as used in larger variety stores, are small owing to the strong aversion response that normally sighted people have to bright light sources2. However, temporary flash blindness (similar to the effect of an electronic camera flash seen at close range) may occur following a brief accidental exposure to a laser scanner. Such flash blindness will usually occur only within about 500 mm from the scanner head in a dull lighting environment. A person effected by temporary flash blindness could have other accidents while this visual impairment persists.
No injuries from Class 1 or Class 2 bar code scanners used either in Australia or overseas have been reported. In view of the relatively low output power from these devices, this lack of injury reports is not unexpected. By comparison, there have been injury reports from high power Class 3B and Class 4 laser systems used in research, industry or medical surgery around the world.
Currently, there are no mandatory legal requirements in any Australian States or Territories for bar code scanners to comply with Class 1 limits. However, it is highly likely that all supermarket checkout scanners used in Australia are Class 1. Some handheld laser bar code scanners intended primarily for use in warehouse environments (inventory and stocktaking purposes) are classified as Class 2.
- It is worthwhile noting that viewing the sun so that the image is fixed on a single region of the retina for exposure times of about a second can cause retinal burns. In practice, people avoid solar retinal injury through very strong aversion responses such as blinking, tearing and looking away with rapid eye movements
Clothing and solar uv protection chevron_right
- What is UV radiation?
- Why is UV radiation dangerous?
- How can you protect yourself from UV radiation?
- What does a UPF rating mean?
- How can you choose a good sun protection garment?
- Where can you purchase sun protective garments?
- Is there a Standard for garments?
- What is the UPF certification scheme?
- Where can I get further information?
- What other precautions can I take to protect myself?
Of the many types of radiation emitted by the sun, mainly visible (light) and infrared (heat) reach the earth’s surface. Ultraviolet radiation (UVR) is also present but we cannot see it or feel it. Ozone in the atmosphere absorbs much of the dangerous UVR before it reaches the ground but we can still receive enough to cause sunburn and more serious health problems.
Exposure to UVR can cause not only sunburn but also lasting skin damage. This may result in premature skin ageing and skin cancer. UVR can also cause eye disorders such as cataracts.
Australians have the highest rate of skin cancer in the world. Our country has high UVR levels and relatively clear skies. Poor use of sun protection measures during outdoor work and leisure, means our mainly fair-skinned population has a high exposure to UVR. The risk of a person eventually developing skin cancer is related to the amount of UVR they are exposed to over their lifetime, particularly in childhood.
- Avoid going outdoors in the middle of the day (10am to 2pm) when the sun is highest (11am to 3pm during daylight saving). This practice can dramatically reduce your UVR exposure.
- When outdoors, choose shaded areas where you cannot directly see the sun or the open sky.
- Wear well designed clothing that covers the arms and legs as well as the body.
- Wear a broad-brimmed hat which shades the face, ears and back of the neck.
- Wear sunglasses when outdoors.
- Apply at least SPF 15 sunscreen to all areas of the body that are not covered by clothing. Reapply sunscreen every two hours and after swimming or activities causing heavy perspiration as sunscreens do wear off.
- Young children do not understand the dangers of UVR. Protect them with shade, suitable clothing, hats, sunglasses, and sunscreen. Well designed sun protective clothing is available in children’s sizes.
In Australia on clear summer days people with unprotected fair skin can receive enough UVR to exceed recommended exposure limits and cause a sunburn in about 15 minutes. If their skin is covered with a garment, the UVR exposure they accumulate will be significantly reduced.
For example, wearing a well designed garment with a UPF rating of 20 will reduce solar UVR exposure to the skin beneath the garment by a factor of 20.
Another way of looking at UPF ratings is that a fabric with a UPF rating of 15 will only allow one fifteenth of the UVR to pass through it; A UPF 20 fabric will only allow one twentieth of the UVR to pass through it, and so on.
The aim of sun protective clothing is to reduce a person’s UVR exposure.
What affects the UPF of a fabric?
- Different fabrics have different UVR-absorbing properties.
- Less UVR passes through tightly woven or knitted fabrics.
- Darker colours usually block more UVR.
- Heavier weight fabrics usually block more UVR than light fabrics of the same type.
- Garments that are over-stretched, wet or worn out may have reduced UVR protection
The UPF rating on many garments indicates clearly how good the fabric is at blocking UVR but the design of the garment also needs to be considered. Shirts with long sleeves and high collars, hats that shade the face and protect the back of the neck and ears are most effective. Loose fitting clothing is usually more protective than tight fitting clothing.
Many state anti-cancer authorities, department stores, children’s stores and sports stores stock UPF rated garments.
Published in July 1996, AS/NZS 4399 describes standard laboratory procedures for measuring the UPF of fabrics and for labelling UPF rated clothing. Fabrics are assigned a UPF rating number and also a protection category depending on how much UV radiation they block out. This table shows the rating system.
UPF Rating Protection Category % UVR Blocked 15 - 24 Good 93.3 - 95.9 25 - 39 Very Good 96.0 - 97.4 40 and over Excellent 97.5 or more
This was developed by the Australian Radiation Protection and Nuclear Safety Agency to guide purchasers of sun protective clothing. Garments made from fabrics tested by recognised laboratories are labelled with a tag showing the garment’s UPF rating which assures consumers of the protective ability of the fabric.
Most State anti-cancer authorities and the Australian Radiation Protection and Nuclear Safety Agency produce a range of publications on radiation related matters. The Resource Guide for UVR Protective Products lists sources of UPF rated fabrics, clothing and other UVR protective products and is available from the Australian Radiation Protection and Nuclear Safety Agency.
- Avoid outdoor activities in the middle of the day when the sun is highest.
- Choose outdoor areas shaded from direct sun and open sky.
- Wear well designed clothing that covers the body, arms and legs.
- Wear a broad-brimmed hat which shades the face, ears and back of the neck.
- Wear well designed sunglasses.
- Use at least SPF 15 sunscreen.
Sunglasses and protection from solar uv chevron_right
- What are the health effects of solar UV radiation?
- How is UV radiation transmitted?
- What part of the UV radiation spectrum causes concern?
- Why do we need to wear sunglasses?
- When do we need to wear sunglasses?
- Is there a Standard for sunglasses?
- What should we look for when purchasing sunglasses?
Both the skin and eyes are at risk from solar ultraviolet radiation (UVR). It is well known that overexposure to UVR from the sun can cause sunburn, skin damage and, ultimately, skin cancer. This UVR can also cause cataracts, a clouding in the lens of the eye which obscures vision. As well as such damage, UVR can also cause eye damage, if the UVR intensity is sufficiently high.
In general, there is almost as much UVR scattered from the sky as there is direct from the sun. Hence staying out of the direct sun does not eliminate the hazard and still means that both the skin and the eyes can suffer long term damage from scattered UVR.
UV radiation is made up of UVA, UVB and UVC, which has the following properties:
- UVC and part of UVB are absorbed high in the atmosphere.
- UVB is very damaging to the skin and eyes, causes sunburn and is implicated in skin cancer induction.
- UVA is less damaging than UVB but lately there has been concern over long term hazards of exposure.
Sunglasses eliminate solar UVR, in particular the more-damaging UVB radiation. As the eye cannot see UVR, its transmission by sunglasses is not only undesirable, but unnecessary. Reducing the amount of UVR that the eye is exposed to over a person’s lifetime can do no harm and is likely to prove beneficial. Good quality sunglasses (particularly, the "wraparound" type) provide the eyes with substantial protection against solar UVR. These sunglasses should be worn by both children and adults. The important points to look for when purchasing sunglasses are detailed below.
Outdoors, particularly in the following circumstances:
- During Summer. The level of UVR at noon in summer is about three times as high as that for winter. More importantly, the levels of UVB can be as much as ten times higher (which is why sunburn takes such a short time in summer).
- Around noon (1 pm during daylight saving). 70% of the harmful UVB radiation that is received each day occurs within three hours either side of this time.
- On the beach or boating. There are usually few buildings or objects to block out part of the sky, so people are exposed to direct and scattered radiation from the whole sky.
- Skiing at high altitude. Solar UVR increases with altitude and, at 2000 metres (typical of Australian ski fields), can be as much as 30% higher than that at sea level. The high reflection of snow worsens the problem, so that the UVR dose to the eye can be quite large. Consequently, good eye protection while skiing is very important.
- When using medication which may act as a photosensitiser. Some medical treatments involve drugs which make people more sensitive to UVR, so that UVR exposures that would not normally be a problem are sufficient to cause damage.
Psoriasis patients undergoing PUVA therapy are extremely sensitive to UVA radiation for some time afterwards. They therefore require good eye protection and should wear sunglasses which absorb 100% of the UVR.
Standards Australia have issued the standard AS 1067 Sunglasses and Fashion Spectacles, which sets limits on the allowed transmittances of fashion spectacles, general purpose sunglasses and specific purpose sunglasses. Fashion spectacles provide the least UVR protection and are usually worn for cosmetic purposes only.
General purpose sunglasses are intended to reduce sun glare in ordinary circumstances (including driving in daylight). These offer good protection against solar UVR.
Specific purpose sunglasses are intended for situations where general purpose sunglasses may not provide adequate protection, due to the presence of higher levels of solar UVR, for example, on snowfields. The requirements of the standard are most stringent for specific purpose sunglasses and this type provides the greatest protection against solar UVR.
Sunglasses that comply with the requirements of AS 1067 should be labelled as such. Those labelled "EPF 10" (Eye Protection Factor rating 10) actually exceed the requirements of AS 1067 and thus provide even greater protection. Others may be labelled "absorbs 100% UVR" these should also carry the AS 1067 label.
Sunglasses that are to be worn while driving must also comply with the coloration limits of AS 1067. Colors, in particular traffic signals, will then still be recognisable when viewed through the lens.
Look for the following points when purchasing good quality sunglasses.
- The sunglasses are actually general or specific purpose sunglasses and not fashion spectacles.
- The sunglasses carry a label that indicates they comply with or exceed the requirements of AS 1067 or are rated EPF 10.
- The sunglasses absorb more than 95% UVR (or transmit less than 5% UVR). Some sunglasses may even provide 99% or greater UVR absorption.
If the sunglasses are to be used while driving, then colours should still be easily recognized when viewed through the lens.