Abstract

Petrol-engine-driven grass (and brush) trimmers are widely used for cutting long grass in Taiwan, and the workers performing these tasks are generally contract workers with little or no awareness of the occupational hazards. In this study, the noise, vibration, and heat exposure of operators are measured in the field, and suggestions are proposed regarding potentially viable countermeasures to reduce hazards during operations.

More than half of all operators are exposed to time weighted average (TWA) sound levels greater than 85 dBA, meaning it is necessary to implement a hearing conservation program and wear hearing protectors during operations. The situation is aggravated when a number of machines are operated simultaneously, as it results in still higher levels of noise exposure, thus, operators should be separated by 15 m in order to avoid the combined level of noise exposure while working with these machines. Vibration measurements are conducted in accordance to ISO 5349 under realistic field conditions. The vibration acceleration value a_xyz of the studied trimmer lay between 2.41 m/s² and 5.74 m/s², and the equivalent value of 8 hours would be 2.08 m/s² ~4.97 m/s²; hence, typical use greater than 2.5 m/s² would require reasonably practicable exposure reduction measures to be taken. In this study, heat stress level is determined based on the Wet Bulb Globe Temperature (WBGT) Index, which found that level of heat stress, as defined by WBGT, exceeded 28°C and 28.5°C, as recommended by the ISO 7243 Standard and ACGIH Standard, respectively.