Radiation safety

	Overview   |   Generation of the image   |   Standards   |   User Safety   |   Light emissions   |   Notes

Standards
Manufacturers must meet an array of national and international safety standards. Both the ionizing and non-ionizing levels of radiation from VDTs are typically well below established safety limits. Figure 4 shows the safety factors of a typical Lenovo VDT as compared to the most conservative worldwide safety standards. Under conditions of artificially increased voltage to a point (and beyond) where the unit is designed to shut down, the amount of ionizing radiation measured is 6/1000 of the permissible level recommended by the Bureau of Radiological Health (1981) and Underwriters Laboratories (1989).

Lenovo VDT Emission Levels
Type of Radiation *	Lowest Applicable Health Standard *	Fraction of Standard From Lenovo VDT *
IONIZING
X-Ray ( < 100 nm)	0.5 mR/hr (FDA)	6/1000
NON-IONIZING
Ultraviolet (UV)
100 < < 270 nm	0.0001 mW/cm2 (ACGIH)	1/1000
270 < < 400 nm	0.001 W/cm2 (ACGIH)	1/1000
Visible
400 < < 750 nm	1 cd/cm2 (ACGIH)	1/1000
Infrared (IR)
750 < < 1000nm	10 mW/cm2 (ACGIH)	1/1000
Microwave (MW)
0.3 < f < 300 GHz	10 mW/cm2 (ACGIH)	1/10,000
Radiofrequency (RF)
0.1 < f < 300 MHz	1 mW/cm2 (ANSI)	1/10,000
Very Low Frequency (VLF)
1 < f < 100 kHz	2.1 Gauss (ANSI)	1/10,000
Extremely Low Frequency (ELF)
5 < f < 1000 Hz	1.0 Gauss (IRPA)	2/1000

Our main exposure to ultraviolet radiation is from the sun and indoor fluorescent lighting. The measured level of ultraviolet radiation from the VDT is 1/1000 of the level recommended by the American Conference of Governmental Industrial Hygienists (ACGIH, 1990) and the National Institute for Occupational Safety and Health (NIOSH, 1977).

The visible radiation, appearing as the image on the screen, is minute. It is 1/1000 of the safety level recommended by the ACGIH, or about 200 times lower than the light outdoors on a cloudy day.

Sources of infrared radiation are primarily those pieces of equipment which are designed to provide heat, such as baseboard and electric heaters, stoves and electric blankets. The amount of infrared radiation from a VDT is negligible compared to the many sources of infrared radiation we typically receive. It is 1/1000 of the safety level recommended by the ACGIH.

Uses of microwave radiation include high-speed data transmission, microwave ovens and satellite communications. The design of VDTs effectively inhibits the emissions of microwave radiation.

Radio frequency radiation is associated with all radio communications and broadcasting and is found near many electrical appliances. The levels of radio frequency from VDTs are significantly lower, at most 2/1000 of the safety limit.

Over the last 2 decades,ELF and VLF electric and magnetic fields have become the subject of increasedand intense scientific interest. Until the early eighties, the majority of the scientific community believed that these fields were capable of producing biological effects only through the heating of tissue, much like that which occurs with the use of diathermy and microwave ovens.

Later in the eighties and into the nineties, however, there has been considerableresearch some of which suggested that non-thermal effects were possible. Scientific research on this subject has continued at a rapid pace throughout the nineties.

During this period, various organizations around the worlddeveloped efforts to establish maximum exposure standards for ELF and VLF emissions.

Sweden has taken on a leadership role in setting maximum emanation standards and establishing consistent measurement standards for VDTs. This work is not based on established biological threshold limits for health. Instead, it seeks to minimize levels and provide repeatable measurement methods with which to reference research.

There are two well-known measurement and emission guidelines. In the first case, a Swedish governmental agency, the Swedish National Board for Measurement and Testing, has pioneered the introduction of ergonomic and emission standards for VDUs in the form of guidelines popularly known as MPR II (a more recent version is MPR III). These guidelines prescribe limits on electric and magnetic field emissions in the ELF and VLF ranges, as well as the electrostatic field.

A second and more restrictive set of guidelines has been actively, promoted by the Swedish Confederation of Professional Employees (TCO). The initial version issued in 1992 and then revised in 1995 was limited to monitor emissions. Subsequent versions have expanded to cover the entire computer. The latest version, issued in 2002, includes guidelines for energy consumption, screen flicker, luminance and keyboards and environmental considerations.

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