Non-ionising radiation (NIR) is the term given to the part of the electromagnetic spectrum where there is insufficient quantum energy to cause ionisations in living matter.
The non-ionising radiation part of the electromagnetic spectrum can be divided into three approximate regions namely:
|Slow time-varying fields:
Alternatively referred to as static magnetic, static electric, and ultra-low frequency fields (i.e. ELF, VF, VLF, LF). Frequencies are generally accepted to be below 10 kHz and with wavelengths ranging from 103m to infinity.
Radio-frequency fields: includes radiofrequency (RF) and microwave (MW) radiation. RF banding is between 10 kHz to 1 GHz frequency, wavelengths approximately 103m down to 10-2m. Microwave banding is between 1 GHz and 100GHz frequency, wavelengths approximately 10-2m down to 10-4m.
Optical radiations: range from infra-red through visible light to ultra-violet. Conventionally, wavelengths rather than frequencies are used to define optical radiation band. The bands represent comparatively only a very small part of the electromagnetic spectrum. Infrared radiations range from approximately 10-4m to 7x10-7m, the visible light spectrum ranges from 7x10-7m at the red end to 4x10-7m at the blue end. Ultraviolet radiation is sub-banded into UVA, UVB and UVC and ranges from 4x10-7m to approximately 10-7m.
Below wavelengths of approximately 10-8m i.e. at and beyond the limit of UVC radiation, radiations have sufficient energy to become ionising.
The most important information for those working with non-ionising radiations are Hazards associated with the use of non-ionising radiations and Essential actions for work with non-ionising radiations. Please ensure that you read through both these documents before commencing any work with or in areas where there is Non Ionising Radiation.
Each of the different types of non ionising radiation has a further specific page as listed below:
Essential actions for work with non-ionising radiations
Responsibility rests with the Principle Investigator and or the Manager whose work area involves use of non-ionising radiations and or equipment capable of emitting non-ionising radiations.
The University Radiation Protection Supervisor can be contacted for further advice and guidance.
- Occupational exposures to non-ionising radiations must be kept as low as reasonably practicable (ALARP).
- A risk assessment for use of an emitter must be prepared. A risk assessment must be:
- Suitable & sufficient;
- Made by competent persons;
- Identify controls;
- Reviewed as necessary;
- Significant conclusions must be recorded;
- Technical protective measures such as engineered controls should be applied to the source of non-ionising radiations where practicable.
- Operational protective measures such as administrative controls (including authorisation for using a source) must be implemented as appropriate for the emitter.
- Source–specific safety instructions must be developed and implemented.
- Controlled, restricted or forbidden areas near emitters must be delineated and secure and with clear warning and instruction signs where necessary.
- If control of exposure cannot be achieved by other means appropriate personal protective equipment must be worn.
- Potentially exposed personnel must be provided with training about the safe use of an emitter or safe work procedures near an emitter, and must be informed about any appropriate health protection precautions.
The Regulatory framework for the 8 actions is: -
- A general Duty of Care requirement under the Health and Safety at Work etc Act 1974.
- A risk assessment requirement under the Management of Health and Safety at Work Regulations 1999.
- The Control of Artificial Optical Radiations at Work Regulations 2010.
- The European EMF Directive 2004/40/EC which sets Exposure Limit Values (ELV) for defined physical parameters associated with electromagnetic radiation.
EMF Directive 2004/40/EC requires employers to assess the risks to employees by assessing, and if necessary measuring, the relevant ELV action levels of non-ionising radiation fields (electric and magnetic fields) to which employees are exposed. As part of this risk assessment, employers must also consider any indirect effects, such as interference with medical electronic devices (e.g. cardiac pacemakers). The Directive also requires employers to provide appropriate information and training for employees, consult with employees and their representatives, and initiate health surveillance where appropriate. It is likely that the Directive will be incorporated into specific UK legislation on electromagnetic radiation in April 2013.
Hazards associated with the use of Non-Ionising Radiations
There is evidence that some non-ionising radiations cause unwanted effects on the human body. For example the nervous system can be affected causing feelings of nausea and dis-orientation, harmful heating of body tissue can occur, and optical radiations can burn skin and damage the eyes.
• In the lower frequency range (300Hz to 1MHz) induction currents may interfere with the functioning of the central nervous system.
• In the intermediate frequency range (100KHz to 10GHz) the absorption of electromagnetic energy generates heat.
• At the upper frequency range (10GHz to 300GHz) heating of superficial tissues is possible.
• From optical radiations (infra-red, visible light and ultra-violet) there can be the harmful consequences of heating of tissues and of damage to the eyes.
The nature, extent and physiological importance of biological effects from non-ionising radiations exposure is complex and depends on factors such as the energy of incident radiation (which determines the penetration depth), the power density of a field or beam, source emission characteristics, duration of exposure, environmental conditions and the spatial orientation and biological characteristics of the irradiated tissue (e.g. molecular composition, blood flow, pigmentation, functional importance, etc.).
Apart from the optical region, non-ionising radiations are not perceived by any of the human senses unless the intensity is so great that it is felt as heat. Therefore in workplace situations where there is potential for non-ionising radiations to be generated, protection measures must be in place to prevent against unsuspected exposure. A risk assessment must be carried out to anticipate where a hazard might exist and to identify controls.
Infra-red radiation, also known as IR, is named because the wavelength is slightly longer than red light in the visible light spectrum.
Infra-red is usually divided into near (IR-A), mid (IR-B) and far-infrared (IR-C) regions;
• Near IR-A: 700 nm–1400 nm (215 THz - 430 THz) and the region closest in wavelength to the red light visible to the human eye
• Mid IR-B: 1400 nm–3000 nm (100 THz - 215 THz)
• Far IR-C: 3000 nm–1 mm (300 GHz - 100 THz)
Mid and far-IR are progressively further from the visible spectrum and nearer to microwave radiation.
There are two potentially significant hazards associated with IR radiation:
- Thermal effects.
Infrared waves are given off by all warm objects and produce heat in all objects they strike. The waves cause heat by exciting molecules (increasing their movement) in the substances they strike. The earth is warmed by infrared radiation from the sun.
Sources of IR radiation are used as artificial heating devices e.g. printing ink driers, food warmers in restaurant kitchens, cold weather outdoor heaters and for therapeutic heat treatments. These present minimal risks of harm to health, but other sources of IR from ‘hot’ work applications such as work with molten metals, welding and glass blowing can cause serious burns to unprotected skin.
- Eye effects.
The use of furnaces, powerful heating and drying processes and high powered LED's which use IR can result in cataracts developing and flash burns to the cornea - these are the main biological effects of IR-A radiation due to temperature rise in the tissue. But IR-A radiation wavelengths are close to the visible light wavelengths and are transmitted to a small extent to the retina; permanent retinal damage can occur if the source is high powered (produces heat) and the exposure is prolonged. As wavelengths increase into the IR-B and IR-C regions the radiation is no longer transmitted to the retina but corneal flash burn injuries can still be caused.
Where a work activity is known or suspected to generate significant IR radiation, a risk assessment must be carried out and control measures put in place. The supplier or manufacturer of the IR source will be able to provide technical information on the power, flux density etc. to allow an informed assessment to be carried out.
Typical control measures are provision of enclosures and shielding around the source to prevent exposure, use of protective clothing to prevent skin exposure and use of IR-opaque eye protection to prevent eye exposure.
Microwave radiation is electromagnetic radiation in the frequency range of from 30MHz to 300GHz. The frequency range is further subdivided into the microwave bands of VHF (30 – 300MHz), UHF (0.3 – 3GHz), SHF (3 - 30 GHz) and EHF (30 – 300 GHz). Television, microwave ovens and meteorological radar equipment operate in the UHF; satellite communication and navigational radar operate in the SHF bands and radio astronomy in the EHF band.
Microwave generators include radar, radio transmission equipment, jammers, RF induction and dielectric heating equipment and microwave ovens.
Before any type of microwave generator is installed a risk assessment must be undertaken. This does not apply to domestic microwave ovens.
A maximum exposure limit is set at 10mW.cm-2 for all microwave sources (including ovens). The present state of research suggests that no injuries of any kind should occur below 1mW.cm-2.
Microwave ovens must be checked for leakage if damage is suspected (contact the Safety Office). There are no specific UK regulations governing microwave ovens used in food preparation, but it is recommended that the current USA regulations are adopted. These state that all ovens must have two interlocks switches, and that the maximum permitted leakage radiation shall not exceed 1mW.cm-2 for new ovens or 5mW.cm-2 for existing ovens.
Harm (biological effects) can be caused by overexposure to microwave radiation usually a consequence of heat generated in tissues by the radiation. The most heat sensitive body organs are the lens of the eye, the gall bladder and the testicles. In the case of the eye, visible signs of damage are apparent in the form of white flecks due to coagulation of lens protein. Temporary sterility due to damage to the spermatic duct can also occur and if radiation density is high and/or prolonged the sterility can become permanent.
Radiofrequency radiated energy is more harmful in pulse form than in uniform mode. Normal clothing offers little protection to microwaves. The eyes can only be protected by glass or plastics covered with a thin film of metal, e.g. gold.
Reflections are a major problem for microwaves, but these can be reduced by wire netting or perforated metal sheet. Walls, partitions etc. can be lined with absorbent material such as graphite-impregnated mats.
Ovens can be damaged in several ways. The use of metal objects inside the oven may result in high-voltage arcing, damaging the enclosure or causing a fire. Interlock connectors or switches may fail in an unsafe condition through abuse of the door, allowing microwave leakage. Finally the oven may be dropped, damaging the door seal, enclosure, switches or power supply
Mobile Phones, Base Stations and Health
Useful information can be found by searching ‘mobile phones’ on the Health Protection England website.
Key information on mobile phones.
• Radiate powers up to around ¼ watt.
• Typically held with their antenna around 2cm from the users head.
• Mostly expose the tissues of the head nearest to the phones antenna.
• Localised exposure is measured as the Specific Absorption Rate (SAR) of energy in the head.
• Guidelines advise localised SAR should not exceed 2watts per kilogram when averaged over any 10grams of tissue and any 6 minute period.
• All phones sold in the UK produce SAR values below 2watts per kilogram.
Key information on base stations.
• Radiate powers up to around 100watts.
• Antennas are typically tens of metres away from the general public.
• Exposure is more even over the body but at a very much lower level than with a mobile phone (because of greater distances from the antennas and inverse square dependence of exposure on distance).
• The power density of the radio waves incident on the body is a good measure of whole body exposure.
• Guidelines advise reference levels of either 4.5 or 9 watts per square metre depending on frequency band.
• In addition to their obligations under UK safety law, the Network Operators have voluntarily agreed to comply with lower international guidelines.
• Typical exposures at locations accessible to the public are thousands of times lower than guidelines
Mobile phones at work.
The Health and Safety Executive advises employers that they should instruct staff not to use mobile phones while driving or doing anything where safety is important and their use might interfere with concentration. Where employers require staff to use mobile phones and concerns about possible health risks are raised, employers could respond by, for example:
(a) explaining that mobile phones operate within international guidelines.
(b) discussing with concerned staff ways to reduce mobile phone use.
On construction site, use of mobile phones must be restricted to site cabins, compounds or other areas where safety will not be compromised. Mobile phones must not be used by workers or supervisory staff on scaffolding, areas where equipment, cranes or hoists are being used overhead, confined spaces or areas where there are potentially explosive atmospheres.
Solar Radiation and Outdoor Workers
Exposure to solar radiation from the sun (ultra-violet) can cause skin damage including sunburn, blistering, skin ageing and in the long term can lead to skin cancer. Skin cancer is the most common form of cancer in the UK, with over 40,000 new cases diagnosed each year. UV radiation is an occupational hazard for people who work outdoors.
People with pale skin are most at risk of skin damage, especially those with fair or red hair, with lots of freckles or with a family history of skin cancer. People with brown or black skin are at low risk but people of all skin colours can suffer from overheating and dehydration.
A skin protection six-point code for employees and others exposed to sun should be followed.
- Skin should be kept covered. Clothing forms a barrier to the sun’s harmful rays – especially tightly woven fabrics.
- A hat should be worn - with a brim or a flap that covers the ears and the back of the neck, areas which can easily get sun burnt.
- Stay in the shade whenever possible, during work breaks and especially at lunch time.
- A sunscreen of at least sun protection factor 15 (SPF15) should be used on any exposed skin. Apply as directed on the product.
- Plenty of water should be drunk to avoid dehydration.
- Skin should be regularly checked for unusual moles or spots. A doctor should be consulted if anything is found that is changing in shape, size or colour, itching or bleeding.
Managers of employees whose work involves outdoor activities must provide the following:-
- Give advice on sun protection in routine health and safety training.
- Inform workers that a tan is not healthy – it is a sign that skin has already been damaged by the sun.
- Encourage workers to keep covered up during the summer months – especially at lunch time when the sun is hottest.
- Encourage workers to use sunscreen of at least SPF15 on any part of the body they can’t cover up and to apply it as directed on the product.
- Encourage workers to take their breaks in the shade, if possible.
- UV is the electromagnetic radiation covering the range 100 to 400 nm. It is commonly divided into 3 ranges of varying wavelength:
- UV-A 315-400 nm
- UV-B 280-315 nm
- UV-C 100-280 nm
The direct potential radiation hazard to health arises from UV with wavelengths greater than 180 nm. UV at lower wavelength is readily absorbed in air and only exists in a vacuum. Generally the shorter the wavelength the more biologically damaging is the UV radiation. UV-A is the least damaging (longest wavelength) form of UV and reaches the earth from the sun in great quantities. While UV-B exposure can be very harmful, stratospheric oxygen and ozone absorbs 97-99% of the sun’s light with wavelengths between 150 and 300 nm. UV-C is almost never observed in nature because it is completely absorbed by the atmosphere. However some equipment can generate concentrated UV radiation in all the spectral regions that if used without appropriate shielding can cause injury after only a few seconds of exposure.
There are several common sources of UV radiation in laboratories including germicidal lamps in biological safety cabinets, nucleic acid trans-illumination boxes and nucleic acid cross linkers activated by UV radiation.
In workshops etc. arc welding generates high levels of UV radiation. Curtains etc. must be used to shield non-operators. It is not possible to protect the arc weld operator other than by use of appropriate protective equipment – visors, gloves etc.
Hazards associated with exposure to UV radiation.
An unfortunate property of UV radiation is that there are no immediate warning symptoms to indicate overexposure. Symptoms of exposure including varying degrees of erythema (sunburn) or photokeratitis (welder’s flash) typically appear hours after exposure has occurred.
Skin injury by UV.
UV radiation can initiate a photochemical reaction called erythema within exposed skin. Certain individuals have abnormal skin responses to UV exposure (i.e. photosensitivity) because of genetic, metabolic or other abnormalities. Effects are exaggerated for skin photosensitised by a variety of chemical agents including birth control pills, tetracycline, sulphathiozole, cyclamates, antidepressants, coal tar distillates found in antidandruff shampoos, line oil, some cosmetics and certain foods (e.g. celery root). Chronic skin exposure to UV radiation has been linked to premature skin aging, wrinkles and skin cancer.
Eye injury by UV.
UV radiation exposure can injure the cornea, the outer protective coating of the eye. Photokeratitis is a painful inflammation of the eye caused by UV radiation-induced lesions on the cornea. Symptoms include a sensation of sand in the eye that may last up to two days. Chronic exposure to acute high-energy UV radiation can lead to the formation of cataracts.
UV safety and risk assessments
The following guidance will assist carrying out a risk assessment for work involving UV radiation.
• Determine the type of UV source (e.g. UV-A, UV-B or UV-C). This can be obtained from the manufacturer or it may be listed on the equipment. The type of UV determines the type of risk (e.g. skin, eye, etc).
• Determine the intensity of the source. Many UV bulb suppliers provide the bulb intensity in μW.cm-2 at a specific distance.
• Determine the exposure duration (hours per week or minutes per week).
• Compare the intensity and exposure duration with threshold limit values for skin and eye exposure. For UV-A (315 – 400 nm), total irradiation incident upon the unprotected eye should not exceed 1.0 mW.cm-2 for periods greater than 103 seconds.
• Identify suitable controls e.g.
o Shields, e.g. UV-opaque Perspex polycarbonate, blinds, curtains etc.
o Protective equipment e.g. lab coat, protective gloves,
o UV-opaque eye / full face shields. Ordinary prescription glasses may not block all UV radiation. UV certified goggles and safety glasses will protect the eyes, but it is common for lab workers to suffer facial burns in the areas not covered by goggles and glasses.
o Label equipment. Any equipment that emits UV radiation must be conspicuously labelled with a caution label e.g.
UV RADIATION HAZARD
USE ONLY WITH SHIELDING IN PLACE
PROTECT EYES AND SKIN FROM EXPOSURE TO UV LIGHT
- Consider use of warning lights to show when equipment is energised.
- Where sources are used which emit UV radiation of less than 242 nm, there must be adequate ventilation because of the hazard of ozone production. An extractor system may be required in some cases.
DO’s and DON’Ts
- NEVER allow the skin or eyes to be exposed to UV radiation sources.
- DO wear a fully buttoned lab coat, full leg covering and closed top shoes.
- DO be vigilant to prevent gaps in protective clothing that commonly occur around the neck and wrist areas.
- DO wear disposable nitrile gloves to protect exposed skin on the hands. Ensure wrists and forearms are covered between the tops of gloves and the bottom of the lab coat sleeves.
Biological Safety Cabinets and Germicidal Lamps.
NEVER work in a biological safety cabinet while a germicidal lamp is on.
- Germicidal lamps emit UV-C and typically the effective irradiance from a 15W germicidal strip lamp is 600 μW.cm-2 at 200nm and 40 μW.cm-2 at 1m.
- Lamps of this type must only be used inside closed cabinets with interlocked doors. The paint near these fixtures must not be reflective, and the cabinet must be constructed of suitable materials.
NB UV lamps are not recommended as they are no longer considered an effective sterilising method. Current standard BS EN 12469 references that UV lamps are not recommended for use in MSCs.
Portable UV sources.
ALWAYS mount portable UV sources in such a way that the radiation is directed away from the eyes.
These are used in biotechnology for visualisation of agarose and polyacrylamide gels. Samples are placed on the illumination window and illuminated by UV light. Devices operate at one of several wavelength bands depending on the type of sample. Standard wavelength bands are: 254nm, 312 nm and 365nm.
• NEVER use a transilluminator without its protective shield in place.
• ALWAYS keep shields clean and replace if damaged.
• NEVER use a UV Crosslinkers which does not have a door safety interlock.
• ALWAYS use curtains etc to shield other persons from the arc radiation.
• The operator must ALWAYS wear protective equipment, i.e. visors, gloves etc.