Electrical Welding Work Radiation and Health Hazards

Welding has been an important industrial process since the early twentieth century and become widespread after 1940. There are approximately 60 different forms of welding, but only six of these are commonly used. Gas welding, flux-shielded arc welding, gas-shielded arc and electric resistance welding are the most frequently used.

Radiation is a mechanism for transport of energy from a source to receiver.

The effect of such radiation on living tissue is variable. The ability of this energy to ionise the target tissues distinguishes two main types of radiation, i.e. ionising radiation and non-ionising radiation. Radiation from the welding belongs to the non-ionising radiation. Ultraviolet and the visible (400-780 nm) radiation are the main components of the emission though IRR is also present in the emission. Factors like arc current, shielding gas and base metal influence the emission spectrum.

UVR spans the wavelength from 100 to 400 nm. The UVR is further divided into three regions: UVC (100-280 nm), UVB (280-315 nm) and UVA (315-400 nm). Among them, UVB and UVA are more prevalent in the welding light emission.

IRR: IRA: 780-1400 nm, IRB: 1400-3000 nm, IRC: 3000 nm -1 mm
UVA and IRB may penetrate into cornea where as visible light and IRA can penetrate into the retina of the eyes.

To evaluate the hazard associated with UV exposure during welding processes, the spectral irradiance must be measured and weighted in terms of biological effectiveness.
Spectral irradiance = Irradiance/ wave length (W/m². nm) [Irradiance = power/area (W/m²)]

Occupational and public exposure limits for UV radiation is 180-315 nm (NIOSH) and 180-400 nm (ACGIH), and all TLV values are referred to the wavelength in these ranges. Special calculation formulae and tables are present for the calculation of UV radiation TLV.
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Health effect of non ionising radiation
The number of workers world-wide whose work involves some welding is estimated to be about three million.

The brilliant light emitted by an electric arc contains a high proportion of ultraviolet radiation. Even momentary exposure to bursts of arc flash may produce a painful conjunctivitis, known as arc eye. Excessive exposure to UV radiation may also cause overheating and burning of the skin. Because of the limited penetrative ability, the biological effects of the non-ionising radiation are largely limited to eyes and skin. Well-documented health disorders caused by non-ionising radiation are:

Eyes:
· Burn in cornea, lenses and retina (conjunctivitis, photokeratitis, maculopathy etc.)
· Cataracts
· Glaucoma
· Mechanical damage


Skin:
· Burn damages on skin
· Erythema
· Exacerbation of atopic dermatitis
· Premature ageing
· Cancer of skin: malignant melanoma
Immune system depression
Deformities in offspring
Leukaemia
Lung cancer ,Five studies conducted in the USA and Europe indicated an increased risk for lung cancer by 30%.
Damaging co-effects of medicines: e.g. welding arc maculopathy and fluphenazine (drug for depression): drug accumulated in the retinal pigment epithelium may lead to susceptibility to retinal photic damage.
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Protection from radiation from welding
Control at source:
· Use of less hazardous materials (electrodes and flux etc.) for welding
· Proper cleaning of welding surfaces
· Studies show that use of thoriated tungsten electrodes has advantages of easier arc starting, greater stability and reduced weld metal contamination. The results during the welding and grinding operations for personal and area air samples were generally below the derived air concentration.

Control at path:
· All arc-welding operations should be screened to protect other people.
· Fixed welding benches and workshop should contain permanent opaque screen.
· The use of black paints inside the welding booths.

Control at receiver:
· A shield or helmet fitted with a correct grade of filter should be used.
· For the gas-shielded arc welding processes, flat hand shields can not provide protection from reflected radiation, helmets should be used. Filtered goggles or eyeglasses should be used under the helmet.
· The nape of the neck and other exposed part of the body should be covered.

Note:
It should be noted that radiation from welding does not act independently to cause adverse health effects. They act side by side with welding fumes and gases. Fumes and gases should be removed at source by LEV.

Metal oxides from:
- metal alloy
- flux material
- surface treatment

Gases:
- From the gas shield: argon, helium, carbon dioxide
- From the arc: Carbon dioxide, nitrogen oxides, ozone
- From the surface treatment: HF, HCl, phosgene, CO

Metal fumes from - Alloyed steel: iron, manganese
- Alloyed steel: Cr, Ni, molybdenum, Cu, Co, vanadium
- Aluminium: Al, Mg, Mn, Beryllium
- Surface treatment: Zn, Ni, cadmium, Cr, Pb

Ionising radiation
In welding shops where welds are tested radiographically with x-ray or gamma ray equipment, instructions should be strictly observed. Workers must be kept in distance from such equipment.
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IARC Evaluation:
There is inadequate evidence in human for the carcinogenicity of the sources of artificial ultraviolet radiation.
There is sufficient evidence for the carcinogenicity of ultraviolet radiation in experimental animals.
Ultraviolet radiation is probably carcinogenic to humans (Group 2A).

Dr. Sunil Kumar Joshi
Occupational and Environmental Medicine Specialist
Asst. Professor of Community Medicine,
Kathmandu Medical College, Sinamangal