LEVELS, TRENDS AND EXPOSURE DOSES OF NOISE EMITTED BY SMALL SCALE ENTERPRISES IN ABEOKUTA, SOUTH-WESTERN NIGERIA

Abstract

Monitoring of noise levels and their impact are common in large scale and corporate industrial establishments while the small scale industries have not received sufficient attention. Consequently, the present study examined the levels and pattern of noise emission from small-scale enterprises that are generally ignored from compliance monitoring of the relevant agencies. The study utilises the results of noise emission quantification, determination of safe distance to the selected small-scale enterprises and impact on human as input for noise policy formulation. Three types of small-scale enterprises sampled from seventy-five (75) sites in Abeokuta were selected for noise measurement using a portable noise meter. Questionnaire and field observation were employed to assess the impact of noise on machine operators and their apprentices. Mean noise emission from the aluminum slitting machines ranged from 103.9 – 118.4 d(BA), iron welding machines; 97.0 – 108.8 d(BA) and food grinding machines; 91.6 to 108.2 d(BA). Daily Noise Dose (DND) from these three types of machine workshops were 800 – 19230% (aluminum slitter), 200 – 2400% (iron welder), and 100 – 3305% (food grinder). Time Weighted Average (TWA) for 8 hours noise exposure values were 94.0 – 107.8, 88.0 – 98.8 and 85.0 – 100.2 respectively. The spatial dimension of noise emission from the studied machines showed that acceptable levels were obtained at 20 meters from the machines sites. As predictors of variations in noise emission, the age of the machines explained 8.3 – 13.6%, 17.2 – 17.8% and 29.1 – 55.4% of noise emitted by food grinders, aluminum slitters and iron welders. The capacities of the studied machines predicted 7.9 – 13.5%, 18.4 – 30.5 and 43.9 – 56.3% of the noise emitted by iron welders, aluminum slitter and food grinders respectively. While the noise levels at the sites of the machines were significantly higher than the permissible limit, 25% of the workers were exposed for upwards of 10 hours daily and 30% for more than five years. The array of health problems; stress, dizziness, tinnitus, sleep disturbance and speech interference, experienced by the machines operators may not be unconnected to their non-use of Personal Protective Equipment (PPE) to minimize noise hazard. Policy formulation for public protection from noise pollution should prescribe limit for small scale enterprises, enforce noise level compliance, monitor wearing of appropriate PPE by machine operators and maintained a minimum of 20 meters between the sites of these machines and other human activities.