Monitors and Radiation

Many people are concerned about reports of potential health hazards caused by computer monitors, also known as video display terminals (VDTs) and cathode ray tubes (CRTs). 

Because we at OCLI are concerned about the growing misinformation on the VDT issue and products addressing it, the following information about VDT radiation may help you separate fact from fiction, and to keep you informed about what OCLI is doing to address this issue. 
 
 

Why All the Concern?

VDTs generate a wide range of electromagnetic fields. For several years, scientists have been studying whether exposure to these fields is harmful to our health. Studies are conflicting, but some research has identified potential health hazards from long-term exposure to non-ionizing electromagnetic radiation in the extremely low frequency (ELF) and very low frequency (VLF) range. 

VDTs, like television sets, give off non-ionizing electromagnetic radiation, which is composed of electric (E-field) and magnetic (H-field) fields. In the electromagnetic spectrum, the ELF frequencies (30Hz to 300Hz) and the VLF frequencies (3kHZ to 30kHz) are causing the concern. 

VDT screens also give off static electric fields, which have been indicated as the cause of skin rashes and dermatitis in VDT operators. 
 
 

Electric Field Shielding Effectiveness of OCLI GlareGuard® Filters

OCLI sponsored a 1994 Electric Field Shielding Effectiveness Test to determine how well OCLI GlareGuard filters block E-field radiation. The testing was performed by Emaco Product Service, Inc., San Diego, California, specialists in electronic interference control. 

Testing shows that the GlareGuard® Maximum Plusª filter blocks up to 99.9% of the ELF/VLF electric field radiation, while the GlareGuard® Maximum™ filter blocks up to 99% of the ELF/VLF E-field radiation. 
 
 

Magnetic Field Shielding Effectiveness of Anti-Radiation/Anti-Glare Filters

Because of the questions surrounding VDT magnetic radiation and anti-radiation filters, OCLI sponsored a 1990 "Magnetic Field Shielding Effectiveness" study. The report describes how well anti-radiation/anti-glare shields block (attenuate) electromagnetic radiation. 

The testing was led by Kimmel Gerke Associates, Ltd., specialists in electronic interference control, and was performed at Amador Corporation, an electromagnetic interference test laboratory in New Brighton, Minnesota. 
 
 

Don't Be Misled

The testing indicates that anti-radiation screens do NOT block magnetic fields at the ELF/VLF levels. Changes must be made within the computer monitor itself to reduce low frequency magnetic radiation. "None of the anti-glare/anti-radiation screens tested show any sign of magnetic field attenuation in the major frequency range of concern, that is, the low frequency range of 30Hz to 30kHz," reported Daryl Gerke of Kimmel Gerke Associates, Ltd. 

Some anti-glare filter manufacturers claim to block the magnetic portion of the electromagnetic spectrum. Don't be misled by such claims. No anti-radiation/anti-glare filter available today blocks magnetic radiation at the ELF and VLF levels. 
 
 

Practice "Prudent Avoidance"

Granger Morgan, a professor of engineering and public policy at Carnegie-Mellon University, coined the term "prudent avoidance" to describe ways to limit ELF/VLF exposure without spending a lot of money or time.1

Here are a few steps you can take to practice "prudent avoidance":

• To eliminate 99.9% of the ELF/VLF E-field radiation from the front of your display, install a GlareGuard® Maximum Plusª anti-glare/anti-radiation filter on the front of your monitor. The optically coated tempered glass Maximum Plus filter, with a conductive metal coating, also eliminates static charge and dust buildup. The patented multi-layer anti-glare coatings eliminate 99 percent of glass glare, enhance contrast and improve display viewability.

 
• Magnetic radiation drops off with distance. If you are concerned about possible health risks from magnetic radiation, stay at least 28 inches from the front of your VDT. Since magnetic fields are normally stronger near the back and sides of a VDT, you should work at least 3 feet away from the back or sides of a VDT.

 
• To eliminate 99.9% of the ELF/VLF E-field radiation from the front of your display, install a GlareGuard® Maximum Plusª anti-glare/anti-radiation filter on the front of your monitor. The optically coated tempered glass Maximum Plus filter has a conductive metal coating which also eliminates static charge and dust buildup. The patented multi-layer anti-glare coatings eliminate 99 percent of glass glare, enhance contrast and improve display viewability.

 
• Turn off the monitor when not in use. If you have more than one computer at your desk, turn off the CPU not in use.

 
• Keep laser copiers or laser printers at least 5 feet from your body. 

 
• Since color television sets emit the same electromagnetic fields as VDTs, you should watch television or play video games from at least 3 feet away.

1 Fortune, "Technology: A Quick Course in What They Call 'Prudent Avoidance,'" Dec. 31, 1990. 
 

Sources:

Terminal Shock, The Health Hazards of Video Display Terminals, Bob DeMatteo, NC Press Limited, Toronto: 1986. 

The VDT Book: A Computer User's Guide to Health and Safety, Mark Pinsky, The New York Committee for Occupational Safety and Health (NYCOSH), New York: 1987. 
 
 

More Helpful Information About VDTs and Radiation

Some people try to address the ELF/VLF problem with mesh screens. Conductive mesh screens do attenuate a portion of ELF/VLF E-field emissions, but mesh screens create their own ergonomic problems such as blurred images on the display and moiré patterns on color monitors which can cause fatigue, eyestrain and stress. 

Computer monitors do not emit microwaves. 

VDTs do emit a small amount of X-rays. However, they are blocked by the monitors' display screens and cases. Experts agree that leaded shields or aprons do NOT block ELF/VLF radiation. It is also quite possible that because these lead aprons are so heavy they could cause other health problems. 

Adjusting your monitor's contrast or brightness controls won't reduce the amount of radiation you are exposed to. 

Screen savers or blankers on your monitor won't reduce the amount of radiation coming from the front of your monitor. 

GlareGuard® is a registered trademark and Maximum Plus™ is a trademark of OCLI-Optical Coating Laboratory, Inc.