The Definition of Non-Ionizing Radiation

Definition of Non-Ionizing Radiation

Non-ionizing radiation is electromagnetic energy that does not have enough energy to remove electrons from atoms, which is what ionizing radiation such as X-rays and gamma rays does. It includes ultraviolet (UV) radiation, visible light, infrared (IR) radiation, microwaves, radio frequency (RF) energy and extremely low frequency (ELF) fields from electrical power systems. Lasers can produce non-ionizing radiation at UV, visible or IR wavelengths.

Although non-ionizing radiation does not damage DNA in the same way as ionizing radiation, it can still cause serious harm. Depending on the type and strength, it can burn the skin and eyes, cause cataracts, heat body tissues and, in the case of sunlight, contribute to skin cancer.

Workers exposed to non-ionizing radiation include welders, outdoor workers, foundry and glass workers, telecommunications tower climbers, broadcast engineers, workers using RF heat sealers or induction heaters, healthcare staff using UV disinfection or medical lasers, and laboratory staff.

Types and Health Effects

Ultraviolet radiation

Sources include sunlight, welding arcs, UV curing lamps and germicidal lamps. Short exposures can cause sunburn and photokeratitis, a painful eye injury known as welder's flash or arc eye. Long-term exposure to sunlight raises the risk of skin cancer and cataracts.

Visible and infrared radiation

Intense visible light and IR from furnaces, molten metal, glassmaking and welding can cause eye strain, retinal injury, skin burns and, over time, cataracts. IR also adds to heat stress.

Radio frequency and microwave radiation

Sources include broadcast and cellular antennas, radar, RF heat sealers, induction heating and microwave drying equipment. At high exposure levels, RF energy heats body tissue and can cause deep burns. The eyes and testes are especially sensitive to heating.

Extremely low frequency fields

Power lines, transformers and electrical equipment produce ELF electric and magnetic fields. At typical workplace levels, health effects are not well established, but very strong fields can interfere with pacemakers and other implanted medical devices.

Lasers

Lasers concentrate light into a narrow beam that can cause eye and skin injuries. See laser safety.

Regulations and Guidelines

OSHA has limited specific standards for non-ionizing radiation. Its radio frequency rule in 29 CFR 1910.97 is old and widely considered outdated, so employers usually rely on more current guidance, such as ACGIH threshold limit values, IEEE C95.1 for RF exposure, FCC exposure limits for antenna sites, ANSI Z136 for lasers and ANSI Z87.1 for welding filter lenses. The OSHA General Duty Clause also applies.

Controlling Non-Ionizing Radiation

• Shielding and enclosures: enclose UV lamps, use welding screens and curtains to protect nearby workers and shield RF equipment.
• Distance and time: exposure falls quickly with distance from the source. Limit time spent near high-intensity sources.
• Energy control: power down or reduce transmitters before tower climbers work near antennas, using lockout/tagout and coordination with carriers.
• Monitoring: use RF survey meters and personal RF monitors at antenna sites and near industrial RF equipment.
• Signs and access control: mark areas where exposure limits may be exceeded.
• PPE: welding helmets with the correct filter shade, UV-blocking safety glasses, IR-filtering goggles for furnace work and sun protection for outdoor workers. See eye protection.
• Medical devices: identify workers with pacemakers or implants and restrict their access to strong field areas.

Example of Non-Ionizing Radiation

A telecommunications contractor sent a two-person crew to replace a cable on a rooftop with several cellular antennas. The crew assumed the antennas had been powered down, but the carrier's shutdown request had been sent for the wrong date. One worker's personal RF monitor alarmed as he approached the antenna face.

The crew backed away and contacted the carrier, which confirmed the antennas were transmitting at full power. Work resumed only after the sectors were shut down and the shutdown was verified with an RF meter. The contractor changed its procedure to require written confirmation of shutdowns and a meter check before any work within antenna exclusion zones.

Frequently Asked Questions: Non-Ionizing Radiation

What is the difference between ionizing and non-ionizing radiation?

Ionizing radiation, such as X-rays and gamma rays, has enough energy to remove electrons from atoms and damage DNA directly. Non-ionizing radiation has less energy and mainly causes heating, burns and eye injuries.

Is welding arc light non-ionizing radiation?

Yes. Welding arcs produce intense UV, visible and IR radiation that can cause arc eye and skin burns, so welders and nearby workers need proper filters and screens.

Are cell towers dangerous to workers?

Exposure on the ground is usually very low. Workers who climb towers or work close to active antennas can be exposed to high RF levels, so antennas should be powered down and exposure monitored.