The occupational exposure risk and inhalation risk due to ultrafine particles emitted during the powder-coating process

Background: Due to the rapid development of the powder-coating process and growing awareness of occupational health, the ultrafine particles (UFPs) generated during the powder-coating process have become a serious and urgent problem. However, researchers have not clearly understood the risk of exposure to the UFPs and inhalation risk of the UFPs. Results: Irregularly shaped, aggregating particles containing Si, Al, Fe, Mg, Pt, and Ca elements were sampled from the work area. The number concentration (NC), mass concentration, surface concentration, personal NC, and lung-deposited surface area concentration of the particles were high: >10 5 pt/cm 3 , 0.2–0.4 mg/cm 3 , 600–1200 μm 2 /cm 3 , 0.7–1.4 pt/cm 3 , and 100–700 μm 2 /cm 3 , respectively. In the particle number count, majority of the particles were 30–200 nm in size. The time-weighted and task-weighted levels of exposure to the particles were high. Upon inhalation, most (71.09 mg) of the particles ranging from 10.4 nm to 96.8 nm accumulated in olfactory area, and a few of the particles (0.649 mg) was taken into lung. Similarly, the majority (1195 mg) of the particles that ranged in size from 100.3 nm to 469.8 nm were deposited on the lungs, and the remaining of the particles were trapped in the nasal cavity. Conclusions: Due to the high emissions rate of the UFPs and insufficient control measures, the workers involved in the powder-coating process are at high exposure risk. Moreover, the risk of inhalation of the UFPs by the workers is high, which is suggested by the high quantities of the UFPs deposited in the lungs and on the olfactory. To protect the workers, the series of measures we proposed, including engineering control, management control, and personal protection equipment should be implemented.