# Noise Sources and Control, and Exposure Groups in Chemical Manufacturing Plants
## 5 Conclusions  
Chemical manufacturing plants, and the manufacturing sector in general, operate plant equipment and machinery that emit noise levels exceeding regulated exposure levels. The US manufacturing sector is the largest when compared to the UK or SA, and has the highest number of noise-exposed employees. Within the chemical and petroleum industry, refinery units emit the highest average noise levels. In terms of specific noise sources within chemical manufacturing plants, vents emit the highest noise levels. The manufacturing sector inclusive of the chemical manufacturing industry is a major source of employment for different occupations such as process operators and maintenance personnel, who are inherently exposed to the emitted noise. The majority of NIHL cases reported in SA emanates from the manufacturing sector whereas the sector also contributes a sizeable number of these cases in the US. In the UK, NIHL cases are low as a proportion of total occupational illnesses reported. For the noise sources identified in chemical manufacturing plants, there exists alternative engineering noise control solutions for each source. Case studies of implemented engineering noise control measures show that engineering control remains the only option for reducing noise levels, at the point of generation, to below the regulatory levels. Regulatory initiatives such as noise regulations and regulation of machinery have seemingly not had a tangible effect on noise control at the workplace. Increased inspections and enforcement by the regulatory authorities can help arrest the continuation of the status quo. The South African inspection and enforcement regime relating to noise remains vague compared to that used by OSHA in the US. In general, the UK's noise control efforts through regulation have seemingly been more effective than those employed in SA and the US based on the NIHL statistics highlighted in this paper. The cost of achieving compliance with the noise regulations will vary based on the number of noise-exposed employees per enterprise [140]. The greatest expenditure in health and safety programmes relates to training and personal protective equipment provision but excludes health and safety personnel costs [143; 144]. The investments made in the preventative aspects of health and safety such as training, enforcement and inspection, and medical surveillance are however not easily isolated when determining the cost-benefit of regulations [145]. For enterprises, decision makers are therefore required to consider the enterprises' fiscal position when selecting and prioritising noise control measures for implementation [146]. In SA, a new approach can be to consider the adoption of new noise regulatory levels for both existing and new plant installations. As an example, new installations should be regulated on a 75 dBA rating level, whereas existing plants can be regulated based on setting continuous targeting of noise reduction up to 80 dBA. On a regulatory level, SA can also do well by clearly defining conditions required for demonstrating legal compliance with the NIHL regulations by inclusion in the DEL inspection manual, as is the case in the US. The DEL in SA can also consider adopting the Department of Mineral Resources' approach of setting short-term noise reduction targets for identified noise sources. Another important aspect that can be considered in the SA regulatory environment is the formalisation of a peak noise-rating limit as is the case in the UK, which is regulated at 140 dBC. The current 85 dBA noise rating limit assumes that workers are only exposed to continuous type of noise. Although the enforcement and inspection regime in SA is largely self-regulatory, the DEL can also initiate initiatives such as the buy quiet programme and incentivising industry for implementing effective noise control, approaches already advocated by NIOSH in the US. There exists a body of knowledge relating to noise exposure, noise sources, exposure groups and control options for chemical manufacturing plants.