An assessment of ultraviolet radiation components of light emitted from electric arc and their possible exposure risks

Abstract

The study of Ultraviolet Radiation has of recent become interesting because of the health hazards it poses to human. Apart from its intensity reaching the earth from the sun, other man-made sources have been identified. We have undertaken the measurement of UV radiation from electric arc welding light generated by 240 TURBO Clarke weld arc operated at a voltage of 120 V using the National Institute of Standard and Technology UVX radiometer and sensors of UVP Company, Upland, USA. Three sensors UVX-25, UVX-31 and UVX-36 were used to measure the three components of UV radiation namely UV-C, UV-B and UV-A respectively. Each of these sensors or probes was set at the same varying distances in turn from the emitted arc light. The result showed that the UVX-25 probe (for UV-C) recorded the highest intensities going from 3.4 to 0.2 mW/cm²; the UVX-31 probe (for UV-B) recorded intensities ranging from 3.2 to 0.8 mW/cm² while UVX-36 probe (for UV-A) recorded intensities from 1.60 to 0.96 mW/cm², all measured at distances from 25.0 cm to 350.0 cm respectively from the UV light. Converting mW/cm2 to mJ/cm², our recorded values clearly showed that for 1.0 second the UVX-25 recorded UV radiation 3.4 to 0.2 mJ/cm², UVX-31 recorded 3.2 to 0.8 mJ/cm² and UVX-36 recorded 1.60 to 0.96 mJ/cm² from a distance of 25 to 350 cm respectively. According to American Conference of Governmental Hygienist (ACGH), the Threshold Limit Value (TVL) of exposure for UV-C and UV-B radiations ranges from 3.0 mJ/cm² to 1000 mJ/cm², for exposure to the eye not exceeding 8 hours period, while for UV-A, the TLV should not exceed 1.0 mW/cm² for period greater than 16 seconds. These values are therefore high for exposure limits of 8 hours for UV-B and UV-C and the 16 minutes for UV-A. The investigation showed that UV-radiation emitted from arc welding machine of the type used in this work could indeed pose harmful health risk to the occupational electric arc worker if no serious precaution is undertaken in the course of performing his work.

KEYWORDS: Ultra-violet radiation, Intensity, Exposure, Health, Distance.