Working with non ionizing radiation

Introduction

Non-ionizing radiation is a collective term for several types of radiation which are not harmful in low dosages and without long-term exposure. Non-ionizing radiation cannot cause ionization in biological systems (body cells), even at very high intensity levels. This is the major difference with ionizing radiation. However, certain effects can arise: Heating or causing electrical currents in tissues and cells.

Exposure to higher dosages or concentrations can, however, be dangerous for humans, such as radio frequency radiation of heat sealers and transmitting equipment, infrared radiation of welding arcs, hot objects and lasers (a laser pen, for example!) and UV radiation of welding processes and sterilization lamps. Even less is known about effects such as fatigue, drowsiness and carcinogenicity. Discussions are running high in this area, for example, when it concerns the safety of mobile phones, GSM masts, radars and the like.

Legislation

The Dutch Working Conditions Act and the Working Conditions Decree do not contain norms with regards to non-ionizing radiation as laid down by the law. However, this does not mean that everything is allowed in the area of non-ionizing radiation. The employer is responsible for a safe and healthy working evironment and will, therefore, have to counter any damaging effects of non-ionizing radiation. Appliances and machines that emit non-ionizing radiation are required to be of sound construction.

Health limits have been determined for each type of radiation. Tracing and assessing sources of non-ionizing radiation is part of the statutorily required hazard assessment that an organization has to perform. Employers are required to take measures in order to prevent exceeding the limits.

Specific information

UV radiation (frequency between 750x1012 and 3000x1012Hz):

The most important organs that are 'affected' by UV are the skin and the eyes. UV-A radiation penetrates the furthest and is therefore the most dangerous type. Acute effects include burning of the skin ('sunburn') and keratitis and conjunctivitis ('welder's flash'). Long-term effects may include skin cancer and cataracts (clouding of the lens in the eye).

UV light with a wavelength of less than 240 nm can convert oxygen into ozone. Ozone is an extremely harmful substance (TLV is 0.06 ppm TWA 1 hour).

The National Health Council has given recommendations about the maximum exposure to UV radiation (1993). The occurrence of unintended UV radiation is required to be as limited as possible.

Visible light (frequencies between 385x1012 and 750x1012Hz) and Infrared (frequencies between 3x1011 and 385x1012Hz)

The damage that can occur in the visible part of the spectrum is limited. Eyes have their own mechanism for protection ('squeezing your eyes shut'). Damage to the eyes can only occur when they are exposed to too much visible light. The odds of damage to the retina are greatest at a wavelength between 400 and 500 nm ('blue light hazard').

Infrared is divided into three frequency areas: IR-A, IR-B and IR-C. Infrared radiation with a small wavelength (IR-A) can penetrate deep into the skin and eyes and can cause thermal (heat) damage to the retinas. Chronic infrared exposure to the eyes can cause cataracts. Wavelengths belonging to IR-B and IR-C cannot penetrate deeper than the corneas and cause less damage. The skin can be burned by excessive exposure to infrared.

The standard for this part of the spectrum is very complicated, because the sensitivity of the body is strongly dependent on the wavelength that is being emitted. Furthermore, not all body parts are equally sensitive. More information on this can be found in the National Health Council recommendation (1993).

Microwaves (frequencies between 3x108 and 3x1011Hz) and radio waves (frequencies between 3x105 and 3x108 Hz)

Microwaves cause the temperature of the exposed tissue to rise. The organs that are most sensitive to this type of wave are the eyes, the skin and the testicles. There is no clear evidence for additional (subjective) complaints such as headache, irritability and drowsiness, but these are nevertheless often mentioned in the literature.

The effects of radio waves are largely comparable to the effects of microwaves. Touching an object in an area with strong radio frequency radiation can even cause burns. A lot of subjective complaints are attributed to radio waves: headaches, sleeping disorders, fatigue, general weakness, and the like.

In determining the limits, the levels of current density (in mA/m2) and the absorption capacity of the body with regards to this are taken into account. This variable is called the Specific Absorption Rate (the "SAR"). However, both the SAR and the induced current in humans are not measurable. The exposure limits have therefore been determined to be derived variables that are measurable: the strength of the electric and the magnetic field.

The National Health Council recommendation (1997) about microwaves and radio waves provides exposure limits for radio frequency radiation and microwave radiation per frequency area.

Static electric and magnetic fields/ELF fields (frequency lower than 3x105 Hz)

Electromagnetic fields can be divided into static and ELF fields. Static electric fields are often 'natural' fields, such as Earth's magnetic field and fields created during thunderstorms, while the 'technical' fields (i.e. generated by human action) are mostly alternating fields with a frequency of 50 Hz. These fields are caused by high voltage wires and electrical equipment.

A lot is unclear about the effects brought about by electromagnetic fields and magnetic fields. It is certain that people who use electronic aids (pacemakers, hearing aids) can experience discomfort or damage from ELF fields.

In exceptional situations - with very high field strengths - instant health effects may arise in humans.

The National Health Council states that, according to the current insights, health complaints are not to be expected from ELF fields under normal circumstances. Recommendations about the maximum exposure can be found in various National Health Council recommendations (see bibliography).

Persons with a pacemaker should observe a limit value of 0.5 mT. Measures with regards to the dangers of flying metal are required to be named at flux densities higher than 3 mT. Analogue watches, credit cards and computer floppy disks can be influenced negatively at an exposure higher than 1 mT (this is mostly an inconvenience but offers no health risks).

Implementation at the UT

Within the UT there are many sources of non-ionizing radation. In practice it becomes apparent that almost everyone has been exposed to one or more sources of non-ionizing radiation. For the most part, that exposure is not significant when looking at possible harm to a person's health. However, it is important to note that there is sufficient insight into the presence or absence of sources that emit non-ionizing radiation, on purpose or by accident.

Hazard identification and risk assessment (RI&E)

The RI&E should focus on recording the harmful sources of non-ionizing radiation and the situations in which exposure to these sources can take place. The boundary between harmful or not is not easy to determine, but further identification will be necessary in case of uncertainty.

It should be considered that exposure is often the consequence of an unintended emission of radiation (for instance UV radiation in welding). An identification is always necessary if:

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ultraviolet radiation is emitted or used: with lasers (see also 'Guidelines and Regulations when using lasers'), with welding and with disinfection by means of UV light;

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infrared radiation is emitted: welding, lasers;

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work is performed with radio frequency sources such as (radio) transmitters, industrial microwaves, plastic sealers;

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staff is working with: large static electromagnetic fields (NMR), electrolysis equipment, high-voltage cables.

I Information about the sources:

·

What is the non-ionizing source?
Iindicate what type of source it is (UV, IR, etc.)

·

Information about the size of the source
What are the relevant frequencies of the radiation and what is the corresponding wavelength? The information can be known (manufacturer, supplier). Measurements may have to be performed. Expertise in the field of performing such measurements is necessary; contact an occupational hygienist or safety expert from the Health, Safety and Environment department;

·

Effects that may occur
Possible harmful effects that can occur due to contact with non-ionizing radiation (risks for skin and eye especially or the release of other gases such as ozone). In these cases it is required to use the most recent information received through National Health Council publications (see bibliography and ww.gr.nl).

II Information about operations

Which operations have a chance of releasing non-ionizing radiation? Is this:

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Intentional emission of radiation (transmitter, UV disinfection)?

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Unintentional emission of radiation (released during, for example, welding or when a laser is used (continuous, periodically)?

III Group(s) exposed to risk(s)

·

Which (groups of) members of staff, students or other persons present can come into contact with the source?

·

Are there any possible high-risk groups that are at greater risk when exposed (for example, people with pacemakers)?

IV Action Plan

·

Indicate the measures taken to prevent the occurrence of harmful effects. Consider the following:

Optic radiation/IR radiation/UV radiation:

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Enclose the source. Almost every material can be used for this: glass, perspex, curtains;

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Maintain distance from the source (radiation decreases proportionally to the square of the distance);

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Limit the amount of time in which work is performed with the source;

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Protect eyes and skin (use personal protective gear). Remember to check that the glasses being used protect against the correct wavelength;

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As a consequence of heating, ozone or other harmful gases can be released as a by-product. If this is the case, use proper exhaustion.

Radio frequency radiation/microwave radiation

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Add facilities to equipment to ensure that the maximum level of radiation can never rise higher than is strictly necessary for proper functioning;

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Provide the source with a metal enclosure (Faraday cage, properly grounded);

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Turn off equipment when not in use;

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Add zoning to a room to ensure that people cannot step into a high radiation field unnoticed;

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Maintain distance from the source (radiation decreases proportionally to the square of the distance);

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There are few options with regards to personal protective gear.

ELF radiation

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Try to keep the distance between the source of radiation and the staff member as large as possible;

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Turn off equipment when not in use;

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Apply maximum screening by means of confining radiation beams, screening of reflections and enclosing parts that are under power;

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Mark areas that may possibly be dangerous to people with pacemakers.

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Mark areas that are dangerous in connection with, for instance, attracting metal, or cards that can be scrambled;

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There are few options with regards to personal protective gear.

Literature/further information

1.

Gezondheidsraad, Optische straling, gezondheidskundige adviezen voor blootstelling aan elektromagnetische straling met golflengten tussen 100 nm en 1 mm, Publicatie 93/09. (in Dutch)

2.

Gezondheidsraad UV-straling, Blootstelling van de mens aan UV-straling, Publicatie 86/09. (in Dutch)

3.

Gezondheidsraad, Blootstelling aan elektromagnetische velden (0 Hz - 10 MHz), Publicatie 00/06. (in Dutch)

4.

Gezondheidsraad, Gevaren van microgolfstraling en de daaruit afgeleide aanvaardbare stralingsniveaus, Publicatie 75/21. (in Dutch)

5.

Gezondheidsraad Radiofrequente elektromagnetische velden, Publicatie 97/01. (in Dutch)

6.

Elektromagnetische straling in arbeidssituaties, Ministerie van SZW, 1995. (in Dutch)

7.

www.gr.nl (National Health Council website).

8.

Brochure of the Ministry of Social Affairs and Employment: 'Veilig werken met niet-ioniserende straling en velden; (in Dutch, see www.minszw.nl).

Annex 1: Information about non-ionizing radiation

Radiation is characterized by the frequency of the radiation (in Hertz) and the wavelength of the radiation (in metres). Non-ionizing radiation has a frequency lower than 3x1015 Hertz (Hz), which corresponds with a wavelength larger than 100 nm.

Nomenclature

The nomenclature of non-ionising radiation is often very confusing. Different types of radiation are described in different terms (visible light is expressed in a wavelength, while microwaves are expressed in frequency). In the frequency area where very large wavelengths occur, it is common to speak not of 'electromagnetic radiation' but of 'electric and magnetic fields'. A good rule of thumb is that when the distance between the source and the exposed is shorter than one wavelength, it is called a 'field'; if this distance is longer than a wavelength it is called 'radiation'. The boundary is approximately at waves with a frequency of 100 MHz.

The table below has arranged the various types of radiation according to wavelength and frequency. In addition, the most common denotation is provided.

Type of radiation

Wavelength

Frequency

Most common denotation

ELF fields

> 3000 m

< 0.3 MHz(1)

Electromagnetic field (V/m) and magnetic flux density (T)

Radio waves

1 – 3000 m

0.3 - 300 Mhz

Electromagnetic field (V/m)

Microwaves

1 – 1000 mm

0.3 - 300 GHz

Frequency (Hz)

Infrared radiation

0.78 – 1000 µm

0.3 - 385 THz

Wavelength (m):

IR-A: 780 – 1400 nm

IR-B: 1400 – 3000 nm

IR-C: 3000 - 106 nm

Visible light

400 – 780 nm

385 - 750 THz

Wavelength (m):

UV radiation

100 – 400 nm

750 - 3000 THz

Wavelength (m):

UV-A: 315 – 400 nm

UV-B: 280 – 315 nm

UV-C: 100 – 280 nm

(1): M (mega) = 106

G (giga) = 109

T (tera) = 1012