Assessment of Noise Level and Distribution from Socotherm Nigeria Limited: Its Health Implications on the Workers

Introduction

Noise is one of the most common hazards in Nigerian work places. The National Institute for Occupational Safety and Health (NIOSH) estimates that 30million workers are exposed to hazardous noise. Noise can be regarded as an unwanted sound [1]. It is also an environmental pollutant. Assessment of the health risk of exposure to industrial noise demands understanding of the physics of sound and the physiology of the ear [2]. A pollutant is any substance introduced into the environment that adversely affects the usefulness of a resource [3]. Exposure to noise for a long period of time can result to adverse effects on health such as hearing loss, physical and psychological stress, reduced productivity, interference with communication and accidents. Exposure to noise for a long period of time can result to temporary or permanent shift in hearing threshold. Most sound heard in everyday life is a mixture of more than one frequency termed broadband noise [4], thus there are different types of noise as steady level noise, mixed noise, and impact noise.

Vibrations are propagated as waves in the form of pressure variations and termed sound waves if they fall within the range capable of exciting the sense of hearing [5]. Vibrations are further converted to similar and powerful mechanical vibrations. These are transmitted to the stapedial footplate which moves in and out of the oval window through which the wave motion arrives at the inner ear [6]. According to De Kluijver and Stoter [7], noise modelling makes it possible to optimize the quality and efficiency of noise effect. As a general rule, a well-designed vibration isolator will also help to reduce noise [8]. Klaeboe, Engelien and Steinnes [9] while discussing noise impact mapping as an alternative to exposure mapping pointed out that GIS-generated noise maps, serve as a tool for funding noise abatement projects and also makes it easier to “disseminate results in a form the public can understand.

Effects of noise pollution on workers therefore can be appreciated when they are placed on periodic medical examination to isolate affected workers for possible rehabilitation or redeployment [10]. This study therefore investigated the noise level and distribution of Socotherm Nigeria limited and its health implications on workers.

Study Area

The humid equatorial climate is marked by two distinct seasons, the dry season (November to March) and the rainy season (April to October). The rainy season is usually interrupted by a short dry spell in August. The area has a mean annual rainfall ranging from 1,900mm-4,000mm. The average temperature range is from 22°C-30°C.

The “upland” area was originally occupied by rainforest which has been drastically modified by human activities. In most places, economic trees particularly oil palm trees, have been preserved as “oil palm bush.” The riverine area is divisible into three main hydro vegetation zones namely, the beach-ridge zone, the saltwater zone and the freshwater zone.

The beach-ridge zone is vegetated mainly by fresh water swamp trees, palms and shrubs on the sandy ridges and mangroves in the intervening valleys or tidal flats. The saltwater zone is the tidal flat or swamps vegetated by the red stilts rooted mangrove (Flhizophora racemosa) and two other species of mangrove (Figure 1).

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The outliers of raised alluvial ground or coastal plain terrace within the swamps are vegetated by tall forest tree species and oil palm. The freshwater zone is mainly the Upper and Lower Delta floodplains of the Niger, having fresh water forest trees which are the edaphic variants of the rainforest. The Abura tree, oil palm, raffia palm, shrubs, lianas, ferns and floating grasses and reeds are the typical vegetation. The study area is surrounded by a big river which leads to the ocean and this offers a major international sea route.

The soils of the sandy ridges are mostly sandy or sandy loams and supports crops like coconut, oil palm, raffia palm and cocoyam. The drier upland area of Rivers State covers about sixty one percent while riverine area, with a relief range of 2m to 5m, covers about thirty nine per cent of the State. The entire topography of the State is also characterized by a maze of effluents, rivers, lakes, creeks, lagoons and swamps crisscrossing the low lying plains in varying dimensions [11].

Rivers State has two major oil refineries, two major seaports, airports, and various industrial estates spread across the land. More than 60% of the country’s output of crude oil is produced in the state. Other natural resources found within its boundaries are silica sand, glass sand and clay [11].

Discussion

Results revealed noise level in the morning period highest in the application area conveyor and welding spot with 95.10 and 93.66. In the afternoon period, welding spot and application area conveyor had the highest noise level of 99.20 and 92.78. In the evening period, it was observed that aggregate separator plant and welding spot produce the evening noise of 94.00 and 92.24. These two spots were the busiest spots in the evening periods because materials to be used the next business day are separated and prepared in these two spots and this accounted for the noise that was generated from these spots in the evening.

97% of the workers accepted to know that noise is a source of pollution while 3% only did not know. 84% agreed that there was no health programs like medical checkups attached to their monthly stipend. About 75% of the workers hence are exposed to noise. 106 0f 108 respondents accepted the company’s awareness program of occupational hazard. Different health challenges such as irritation, annoyance, headaches, increased heartbeat, nervousness, tiredness and fatigue were observed to have been experienced by the workers.

Higher number of the workers already have symptoms of noise-induced hearing loss as most of them could not hear at normal sound level during conversation and that confirms the report of Rilind [12] that observed that noise damages the brain, hearing power, results to poor sleep, psychological disorder, and increased risk of cardiovascular diseases.

Conclusion

The daily noise exposure of small and medium size factory workers in the study area exceeds the maximum Occupational Safety and Health Administration (OSHA) exposure limit of 90dBA. Exposure of factory workers further exceeded OSHA standards for occupational exposure to high noise levels due to long work hours. 84% reported working more than 8 hours per day and 25% more than 5 days per week. Old machines are responsible for most of the noise and more than 50% of workers are machine operators.