Assessment of Ultraviolet Radiation Exposure in the Wood Surface Coating Industry

Abstract

Abstract Ultraviolet (UV) radiation curing of paints and lacquers has rapidly increased in the furniture industry. Exposure to UV radiation involves a potential health hazard to workers in this industry and there is little information on UV radiation spectra and exposure levels under these working conditions. We have investigated the intensity and spectral distribution of UV radiation and determined the maximum permissible exposure times (MPETs) at different fixed points surrounding the UV curing units. The spectral irradiance was measured between 250 and 400 nm using a calibrated diode array spectrograph, and the intensity of the UV radiation was measured using a radiometer equipped with UVA and UVB detectors. The spectral power distribution was weighted for biological effect using Wester's approximation equations of the spectral effectiveness curve adopted from the International Radiation Protection Association/International Non-Ionizing Radiation Committee. The intensity of the UV radiation at the substrate passage level ranged from 100 to 200 mW/cm2, giving MPETs of 0.6 to 0.03 seconds, respectively. MPETs varied between 8 and 126 seconds at entrance and exit openings and between 0.5 and 2.3 hours at 0.8 m from the UV curing units. Direct UV radiation from holes and fissures in the units was detected at four of the six plants; MPETs varied from 6 seconds to 3 minutes. High intensity UV radiation was measured below the unshielded bottom of a UV curing unit at one plant (2 seconds MPET). The proportion of UV radiation in different wavelength regions varied moderately (UVA, 38 to 56%; UVB 21 to 40%; and UVC, 12 to 24%). We conclude that UV curing units must be equipped with proper radiation shields, including the holes and fissures, and routinely checked and maintained in order to afford adequate protection from high intensity UV radiation at biologically hazardous wavelengths. Adequate eye and skin protection is required for workers during maintenance of unshielded equipment in order to prevent harmful effects.