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applied
sciences
Review
Noise Sources and Control, and Exposure Groups in
Chemical Manufacturing Plants
Oscar Rikhotso *, Johannes Leon Harmse and Jacobus Christoffel Engelbrecht
Department of Environmental Health, Tshwane University of Technology, Private Bag X680,
Pretoria 0001, South Africa
*Correspondence: oscar.rikhotso@sasol.com or luvani1723@gmail.com; Tel.: +27-79-463-8771
Received: 16 July 2019; Accepted: 20 August 2019; Published: 27 August 2019
Abstract:
The chemical manufacturing industry employs sophisticated mechanical equipment to
process feedstock such as natural gas by transforming it to usable raw material in downstream sectors.
Workers employed at these facilities are exposed to inherent occupational health hazards, including
occupational noise. An online and grey literature search on ScienceDirect, Oxford Journals online,
PubMed, Medline, Jstor and regulatory bodies using specific keywords on noise emission sources
in the manufacturing sector was conducted. This review focuses on noise sources and their control
in chemical manufacturing plants along with the receptors of the emitted noise, providing hearing
conservation programme stakeholders valuable information for better programme management.
Literature confirms that chemical manufacturing plants operate noise emitting equipment which
exposes job categories such as machine operators, process operators and maintenance personnel
amongst others. Prominent noise sources in chemicals manufacturing industries include compressors,
pumps, motors, fans, turbines, vents, steam leaks and control valves. Specific industries within the
chemical manufacturing sector emit noise levels ranging between 85–115 dBA (A-weighted sound
pressure level), which exceed the noise rating limit of 85 dBA used in South Africa and United
Kingdom, as well as the 90 dBA permissible exposure level used in the United States, levels above
which workplace control is required. Engineering noise control solutions for plant equipment and
machinery operated in chemical manufacturing plants are available on the market for implementation.
Keywords:
chemical manufacturing plants; noise; noise-induced hearing loss; noise source; noise
exposure group; noise transmission paths
1. Introduction
The manufacturing sector inclusive of chemical manufacturing transforms materials, chemicals
and components to value-added consumer and commercial goods using power-driven and
material-handling machinery in installations commonly referred as plants, factories or mills [
1
,
2
].
Chemical manufacturing plants use natural gas or refinery by-products such as ethylene, hydrogen
rich gas, tail gas and many more as feedstock to produce chemical products and many consumer
goods in downstream chemical processes [
3
,
4
]. Plastic and paper manufacturing, petroleum refining
and textile mills are but some of the industries classified under the manufacturing sector employing
millions of workers worldwide [1,2].
Noise exposure in the manufacturing sector inclusive of the chemical manufacturing plants is
widespread and amongst the loudest [
5
]. Cited reasons for the noise problem in existing installations
include the inadequate knowledge of its mechanism of generation and abatement, lack of proper
consideration during plant design phase and installation [6].
The noise sources operating in chemical manufacturing plants emits noise through acoustical
radiation and aerodynamic turbulence [
7
,
8
]. The noise is then transmitted through pathways such
Appl. Sci. 2019,9, 3523; doi:10.3390/app9173523 www.mdpi.com/journal/applsci
Appl. Sci. 2019,9, 3523 2 of 26
as turbulence, shock and pulsation, cavitation, impact and tooth meshing [
8
,
9
]. Noise regulations
require the mandatory of implementation of hearing conservation programmes (HCPs) for exposure
prevention and control in workplaces emitting noise exceeding the universal noise rating limits, 85 or
90 dBA [
10
–
12
]. However, HCPs have not eliminated excessive noise levels in some chemical industries
and have tended to shift focus away from control of noise at the source towards the use of hearing
protection devices (HPDs).
Exposure to occupational noise may lead to auditory and non-auditory health effects. Examples
of auditory effects includes noise induced temporary threshold shift, acoustic trauma, tinnitus and
noise-induced hearing loss (NIHL). Examples of the non-auditory effects include interference with
speech and telephone communication, annoyance and job performance. The auditory effects of noise
on humans result in a loss of hearing sensitivity whereas the non-auditory effects of noise affect the
psycho-social wellbeing of humans and are mainly subjective [13,14].
In the case of compensable auditory effects, the illness affects other stakeholders such as the
immediate family, co-workers, medical practitioners and insurers. In addition, there are costs associated
with noise-induced illnesses relating to general economic costs, social costs, employer and employee
costs. The understanding of the overall impact of noise sensitises all affected stakeholders to be aware
of the true impact of noise-related illnesses and a need to plan for the implementation of required
preventive actions [
15
,
16
]. Emerging issues related to noise exposure includes its effect on blood
pressure, its effect on reproduction, its association with ototoxic chemicals and ototoxic medicines
further highlighting the need for exposure prevention.
This review provides an appraisal of prominent noise sources and control, noise levels and
exposure groups in chemical manufacturing plants.
2. Materials and Methods
A web based literature search on ScienceDirect, Oxford Journals online, PubMed and Jstor
electronic databases was conducted up to July 2019 related to noise in the manufacturing sector
and chemical manufacturing industry using the following specific keywords: noise in chemical
manufacturing plants, noise in manufacturing sector, noise level database, noise sources in chemical
manufacturing industry, noise control in chemical manufacturing industry, job categories in chemical
manufacturing industry. The search was also extended to online databases of regulatory, standard
setting and research bodies such as the National Institute for Occupational Safety and Health (NIOSH),
Occupational Safety and Health Administration (OSHA), United States Environmental Protection
Agency (US EPA), Health and Safety Executive (HSE), South African National Standards (SANS),
World Health Organisation (WHO), International Organization for Standardization (ISO) and the
International Labour Organisation (ILO). These bodies form the knowledge base in noise exposure
prevention and control in industry.
The literature search was further extended to classical handbooks on occupational health and
safety as well as chemical engineering books to describe process application of noise sources operated
in chemical manufacturing processes. The Department of Employment and Labour (DEL) in South
Africa (SA) was also searched for related content.
3. Results
The online literature search on databases returned limited and fragmented results. Classical
handbooks on noise returned literature results closer to the search criteria for this review whilst OSHA,
NIOSH (Health hazard evaluations) and the US EPA were identified as bodies having noise level
records from various industries [
5
,
17
,
18
]. The online search on the DEL webpage only returned NIHL
regulations and associated forms.
Appl. Sci. 2019,9, 3523 3 of 26
3.1. Noise and the Manufacturing Sector
Noise is listed as an inherent occupational hazard for processes operated within the manufacturing
sector [
19
,
20
], emitted by an array of plant equipment [
21
]. The chemical manufacturing industry is
important in the manufacturing sector as it is interconnected to downstream sectors such as transport,
agriculture, power production, consumer goods and construction [1].
3.1.1. Noise Levels in the Manufacturing Sector
The diverse nature of plant equipment used by the manufacturing sector results in variance
in emitted noise levels due to the age of the plant equipment, wear and tear of the equipment and
operating speed of the operated machines, amongst other factors [
22
]. The emitted noise levels expose
a great percentage of the workforce employed in the sector [
23
]. Table 1shows the reported average
noise levels in literature, with references, within the manufacturing sector inclusive of the chemical
manufacturing industry.
From 1979 to 2013, noise measurements recorded in the OSHA database show that the majority
of noise levels exceeding the permissible exposure level were from the manufacturing industry [
24
].
In general, data in Table 1show that noise records from the manufacturing sector were mainly from
the textile industry and emanated from different geographies. The noise records from the US date
back to the 1970s, the period around which the enactment of the Occupational Safety and Health
Administration Act was initiated.
There were only two noise records that emanated from SA. These records are recent and show
noise levels from the chemical manufacturing industry and the iron and steel industry highlighting the
need for information sharing through publications and other research platforms. In the case of SA,
the low return on the literature search is understandable against the backdrop of a limited number of
chemical manufacturing plants. The SA chemical manufacturing sector is anchored by a few companies
concentrated close tosix refineries to enable easy access to feedstock.
The overall literature on noise for the chemical manufacturing sector retuned a low number of
search results. Due to the enormous size of the sector and the important role the sector plays in the
world economy, the literature search was expected to return a high volume of related literature but
the expectation was proven negative. Expectedly, most of the obtained literature related to chemical
manufacturing and noise emanated from the US sources. Occupational health and safety specialists
employed in the chemical manufacturing sector should fill this knowledge gap through journal
publications such as this review article and other platforms.
Appl. Sci. 2019,9, 3523 4 of 26
Table 1. Average noise levels per manufacturing industry type.
Country Industry Average Noise Level in dBA 1References
Food manufacturing
US Food manufacturing 90–92 OSHA, 1979–2006 [5]
US EPA, 1971 [18]
UK Food processing 88–94 Institute of Occupational Medicine, 2002 [25]
Textile plants
US Textile product mills 89–95 OSHA, 1979–2006 [5]
US EPA, 1971 [18]
India Textile plants 80–102 Bedi, 2006 [26]
Sudan
Textiles:
Ahmed and Awadalkarim, 2015 [27]
Weaving 88–86
Preparing 63–93
Ethiopia
Textiles:
Ejigu, 2019 [28]
Spinning mill 86–115
Weaving mill 92–101
UK
Textiles:
Institute of Occupational Medicine, 2002 [25]
Twisting area 88–92
Winding area 82–85
South Korea Textile plant 81–110 Moon and Kwon, 1976 [29]
US Apparel manufacturing 81 OSHA, 1979–2006 [5]
US EPA, 1971 [18]
Nigeria Textile industry 97–105 Odusanya, Nwawolo, Ademuson and Akinola 2004 [30]
US Leather and allied product manufacturing 90 OSHA, 1979–2006 [5]
US EPA, 1971 [18]
Wood industry
US Wood product manufacturing 92–94 OSHA, 1979–2006 [5]
US EPA, 1971 [18]
South Korea Wood industry 71–100 Moon and Kwon, 1976 [29]
US Paper manufacturing 90–92 OSHA, 1979–2006 [5]
US EPA, 1971 [18]
Printing and publishing industry
US Printing and publishing 82–93 OSHA, 1979–2006 [5]
US EPA, 1971 [18]
Ghana Printing company 79–90 Boateng and Amedofu, 2004 [31]
Appl. Sci. 2019,9, 3523 5 of 26
Table 1. Cont.
Country Industry Average Noise Level in dBA 1References
Petroleum and related industries
US Petroleum and coal products manufacturing 87–92 OSHA, 1979–2006 [5]
US EPA, 1971 [18]
US
Refinery units:
Burgess, 1995 [21]
Hydrocracker plant 93–100
Fluid cracker 89–115
Hydrofluoric alkylation unit 89–100
Catalytic hydrocracking 90–100
Crude distillation 85–111
Taiwan Oil refinery 73–89 Chen and Tsai, 2003 [32]
Chemical manufacturing
SA Chemical manufacturing company 85-95 Rikhotso, Harmse and Engelbrecht, 2018 [33]
US
Urea formaldehyde and polyurethane foam
insulation: NIOSH, 1983 [34]
Manufacturer A 83–94
Manufacturer B 81–86
US Chemical manufacturing 85–92
OSHA, 1979–2006 [5]
US EPA, 1971 [18]
Lynch, 1989 [35]
Pringle and Warren, 1989 [36]
South Korea Chemical industry 91–100 Moon and Kwon, 1976 [29]
US
Polyethylene battery separator manufacturing:
NIOSH, 2004 [37]
regrind 95–97
Extruder lines 82–94
Iran Petrochemical industry 88–93 Neghab, Maddahi & Rafeefard, 2009 [38]
US Plastics and rubber products manufacturing 86–92
OSHA, 1979–2006 [5]
US EPA, 1971 [18]
Mutchler, 1989 [22]
US Nonmetallic mineral product manufacturing 88–94 OSHA, 1979–2006 [5]
US EPA, 1971 [18]
Steel industry
US Primary metal manufacturing 91–92 OSHA, 1979–2006 [5]
US EPA, 1971 [18]
UK Steel industry 90–100 Howell, 1978 [39]
SA Iron and steel companies 78–106 Mizan, Abrahams, Sekobe, Kgalamano et al. 2013 [40]
US Fabricated metal product manufacturing 90–92 OSHA, 1979–2006 [5]
US EPA, 1971 [18]
Saudi Arabia
Beverage cans manufacturing 92–98
Noweir, Bafail & Jomoah, 2014 [41]
Steel reinforcement forming for concrete 91–95
Steel sheets forming and processing 87–91
Brazil Metallurgical company 83-102 Guerra, Lourenco, Bustamante-Teixeira & Alves 2005 [42]
Appl. Sci. 2019,9, 3523 6 of 26
Table 1. Cont.
Country Industry Average Noise Level in dBA 1References
Machinery manufacturing
US Machinery manufacturing 86–93 OSHA, 1979–2006 [5]
US EPA, 1971 [18]
India Small scale hand tools manufacturing industry 81-110 Singh, Bhardwaj, Deepark & Bedi, 2009 [43]
US
Computer and electronic product manufacturing
85–91 OSHA, 1979–2006 [5]
US EPA, 1971 [18]
US
Electrical equipment, appliance, and component
manufacturing 87–90 OSHA, 1979–2006 [5]
Saudi Arabia Industrial and household appliance
manufacturing 85–86 Noweir, Bafail & Jomoah, 2014 [41]
US Transportation equipment manufacturing 88–92 OSHA, 1979–2006 [5]
US EPA, 1971 [18]
US Furniture and related product manufacturing 88–93 OSHA, 1979–2006 [5]
US EPA, 1971 [18]
Bottling and tobacco industry
US Beverage and tobacco product manufacturing 86–96 OSHA, 1979–2006 [5]
US EPA, 1971 [18]
Nigeria Bottling industry 95–103 Odusanya, Nwawolo, Ademuson & Akinola 2004 [30]
Nigeria Bottling factory 92–99 Ologe, Olajde, Nwawolo & Oyejola, 2008 [44]
Miscellaneous manufacturing
US Miscellaneous manufacturing 87–91 OSHA, 1979–2006 [5]
US EPA, 1971 [18]
1A-weighted sound pressure level.
Appl. Sci. 2019,9, 3523 7 of 26
The average noise levels across the manufacturing industry ranges between 81–115 dBA inclusive
of the petroleum, chemical and plastics manufacturing which are sub-categories of the chemical
manufacturing sector [
1
]. Average noise levels noted in Table 1which are at and/or above 85 and/or
90 dBA would require implementation of hearing conservation or control measures depending on the
domicile (country) of the industry where the noise was measured [
10
–
12
]. The hearing conservation
and noise control levels currently used in SA, US and the UK are shown in Table 2.
Table 2. Hearing conservation and control levels [45].
Country
Permissible Exposure
Level/Noise Rating Limit in dBA
(8-h Average)
Exchange Rate
in dB
dBA Level for
HCP Institution
dBA Level for
Engineering
Controls
SA 85 3 85 85
UK
80 (lower exposure action value)
85 (Upper exposure action value)
87 (exposure value with HPD use)
140 1(Peak noise level)
3 80 87
US 90 5 85 90
1C-weighted peak noise level (dBC).
The permissible exposure levels or noise-rating limit or exposure action values listed in Table 2
are not related to the emission data that accompanies noisy equipment and machinery intended for
industrial use. The objective values in Table 2are used by regulatory bodies during enforcement and
inspection activities to determine legal compliance. In SA however, the DEL inspection manual does
not detail conditions under which legal compliance with the NIHL Regulations can be demonstrated.
Compared to the US, the OSHA Field Operations Manual (OFM) details conditions for industry and
the Certified Safety & Health Official (CSHO) under which legal compliance can be demonstrated for
the noise standard.
In the UK’s approach, the lower exposure value encourages employers to keep noise exposure as
low as practicable, as noise levels increase between the exposure action values so does costs related to
noise control. Once noise levels breach the upper exposure value, the employer will bear the costs for
providing HPDs to exposed employees as well as other related costs.
In SA general industry, the 85 dBA noise rating limit is the basis for workplace control with
regard to HCP initiation inclusive of training, noise measurement, area noise zoning, engineering noise
control, audiometric testing and provision of HPDs.
3.1.2. Process Equipment Use and Noise Levels in Chemical Manufacturing Plants
Prominent and specific noise emitting process equipment in chemical manufacturing plants,
whose noise is compounded by wall and ceiling reverberation include compressors, pipe fittings, pipes,
pumps, control valves, flare stacks, induced draft fans and turbine generator [
7
,
18
,
20
,
21
,
36
,
46
,
47
].
Table 3shows prominent process equipment and their application, noise generating mechanism and
resultant noise levels in chemical manufacturing plants along with references.
Appl. Sci. 2019,9, 3523 8 of 26
Table 3. Process equipment, applications, noise generation mechanisms and resultant noise levels in chemical manufacturing plants.
Process Equipment ProcessApplication: NoiseGeneration Mechanism Specific Process Equipment Examples Emitted Noise Level
(Range) in dBA Source or Record Type References
Duct and pipe flow Process product flow:
High velocity flow, flow resistance,flow turbulence [9,48]. Duct and pipe flow 100 Conference paper Fagerlund, Karczub & Martin, 2005 [49]
Flow machines/pumps and hydraulic systems
(Positive displacement and reciprocating pumps)
Pressurisation and movement of gases and fluids within pipelines: Tooth meshing, friction,
inertia, rolling, cooling fan, air intake [7,9,22,47,48,50,51].
Screw type
Vane type
Axial piston type
Gear (aluminium) type
Vane (mobile) type
Gear (machine stock) type
71–78
75–82
76–86
78–88
84–92
96–104
Handbooks
Miller, 1984 [7]
Burgess, 1995 [21]
Lynch, 1989 [35]
Free jets
Release of gas through nozzles. Mixing layer of the turbulence due to gas stream speed: High
velocity air and steam jets [7,9,48]Free jets (1 m from blowoffnozzle) 105 Handbook Gerges, Sehrndt & Parthey,2001 [52]
Valves and piping
(Globe and rotary valves)
Direct control or manipulation of the process through positioning of valve plug or disc from
the actuator: Cavitation, turbulence, shock and pulsation [7,53,54].
De-areator valve
Pressurised pipes and valves
Turbine admission valve
95–100
90–100
100
Handbooks
Miller, 1984 [7]
Emerson, 2005 [54]
Fans and blowers
(Axial and centrifugal fans)
Movement of high quantities of air through use of power-driven rotating impellers: Fan,
speed changer, fan motor,fan shroud [7,48,51]
Forced draft fan 100
Handbook and regulatory
database
Miller, 1984 [7]
Induced draft fan 90–100 US EPA, 1971 [18]
Compressors and turbines
Compressors (pressure generation) and Turbines(power generation): discharge piping and
expansion joint, antisurge bypass, intake piping and suction drum, air intake, discharge to air,
timing gears, speed changers [7,48,51,55–57].
Air compressor
Steam turbine generator
Turbine admission valve
Turbine drive
Turbine generator brush gear
Compressor platforms
95–100
90–95
100
95–100
95–100
90
Handbook and regulatory
database
Miller, 1984 [7]
US EPA, 1971 [18]
Steam leaks Indication of process leaks on corrodedpipelines, joints, process valves: High velocity air
and steam process leaks [7,48,58]. Steam leaks (within 25 feet radius) 100 Handbook Miller, 1984 [7]
Vents Intentionaland controlled gas or liquid release into atmosphere during emergencies, shut
down activities and absence of storage facilities: High velocity air and steam vents [
7
,
48
,
59
].
Vents(within 10 feet of vent outlet) 140–160 Handbook Miller, 1984 [7]
Motors
Power source for driving fans, pumps, generators by converting electric power to mechanical
power: Cooling air fan, mechanical and electrical motor noise [7,48,51]. Motors 90 Handbook Miller, 1984 [7]
Appl. Sci. 2019,9, 3523 9 of 26
The process equipment listed in Table 3is inter-connected and inter-dependent resulting in a
combination of noise generation mechanisms such as high velocity flow of gases and liquids, cavitation,
turbulence, shock and pulsation. The noise emitted by the identified prominent noise sources ranges
between 71 dBA up to 160 dBA with vents representing the highest noise emission sources [
7
]. The
proximity of bigger and smaller noise sources adjacent to each other can however mask the noise
emitted by the smaller equipment [
7
,
9
,
22
,
47
,
48
,
50
,
51
]. The reported noise levels in both Tables 1and 2
were derived and recorded through workplace noise surveys [
60
,
61
]. The logarithmic averages of noise
levels in Table 3adds up to reflect those indicated in Table 1in a case of chemical manufacturing plants.
Noise measurement data for both area and composite measurements resulting from industry
noise surveys is voluminous yet remains unpublished. Resources such as the Noise Levels Database
developed by the Canadian Centre for Occupational Health and Safety (CCOHS) remain difficult to
access for cost reasons [
62
]. In SA general industry there remains no noise level database, however
the Mining Industry Occupational Safety and Health has undertaken the development of the mining
industry noise level database [63].
3.2. Exposure Groups in Chemical Manufacturing Plants
Chemical manufacturing plants employ different occupational classes which have different noise
exposure profiles according to the industry type. Plant equipment used in chemical manufacturing
plants require manual operation by these employees, whom by close proximity to these equipments
are exposed to the emitted high noise levels [19].
3.2.1. Occupational Classes in Chemical Manufacturing Plants
Various job classification systems exist in the world. According to the ILO occupation classification
system, occupations within chemical manufacturing plants are grouped into craft and related trades
workers, plant and machine operators and assessmblers [
64
]. Examples of minor groups of these
occupations include electrical mechanics and fitters, electrical line installers and repairers, chemical
products plant and machine operators, helpers, plastic machine operators, locomotive engine drivers
and related workers, mobile plant operators, steam engine and boiler operators.
In SA, these job categories are clustered in job code 0805 “Chemical, gas, food and beverages
production and processing related occupations” [
65
]. According to OSHA, occupations denoted with
standard industrial classification codes 28 to 30 have been historically exposed to excessive noise
levels [5].
3.2.2. Relationship between Emitted Noise Levels and Exposure Groups
The exposure groups in chemical manufacturing plants are exposed to both the average and
composite noise levels highlighted in Tables 1and 3. Some job categories, due to proximity to noise
sources, task duration and movement patterns in relation to exposure sources, will only be exposed to
the average or a fraction of the average noise levels. Examples of the correlation between area noise
measurements and employee daily noise dosage are illustrated in Table 4. The daily exposure noise
levels are derived and recorded through noise dosimetry surveys where the worker wears a personal
noise meter for a task or a job or the full shift [60,66].
Appl. Sci. 2019,9, 3523 10 of 26
Table 4. Correlation between activity-based area noise levels and employee daily noise dose.
Country Work Activity Observed Job Category Area Noise Level
Range (in dBA)
Daily Noise Exposure
Range (in dBA) Evaluation Criteria Reference
UK
Compressed gas supply depot
Workers
85–94 80–90
Exchange rate: 3 dB, criterion
level: 85 dBA, 87 dBA
Institute of Occupational
Medicine, 2002 [25]
Paper coating (laminating) 81–88 84–88
Ship building (blacksmith shop) 90–10 90–95
Light engineering (fabrication) 84–105 85–93
Food processing 87–94 89–92
Coal fired power station 93–102 85–102
Bottling 84–92 84–97
Textiles (twisting and winding) 88–92 85–94
Ferrous foundry 81–112 86–108
Ship building (heavy fabrication) 83–106 88–99
US Stator manufacturing Process operators
Machine tapping operators -84–88 Exchange rate: 3 dB, criterion
level: 85 dBA NIOSH, 1991 [67]
78–82
US
Television manufacturing company:
Operators 83–88 Exchange rate: 3 dB, criterion
level: 85 dBA NIOSH, 1991 [68]
Metal stabilizing lehr 81–88
Frit dispensing department 86
Thump and flush department 88
US Industrial centrifugal manufacturing
Balance machine -85 **
NIOSH (Exchange rate: 3 dB,
criterion level: 85 dBA)
NIOSH, 1995 [69]
88
Basket floor operator -89 **
93
Boring mill (main bay) operator
-83 **
85
Crating operator -81 **
OSHA (Exchange rate: 5 dB,
criterion level: 90 dBA)
87
Fitting floor operator -84 **
87
Welding operator -87 **
91
Denmark
Various Danish manufacturing
industries: -
Exchange rate: 3 dB, criterion
level: 85 dBA, 87 dBA
Kock, Andersen, Kolstad,
Kofoed-Nielsen, Wiesler and
Bonde, 2004 [70]
Manufacturer of machinery 81–84
Manufacturer of furniture - 82–84
Manufacturer of basic metals - 84–87
Manufacturer of wood - 84–86
Manufacturer of minerals Workers - 84–86
Manufacturer of food - 84–86
Manufacturer of fabrication metals - 84–86
Manufacturer of motor vehicles - 83–86
Publishing and printing - 82–84
Iran Textile industry
Spinning operator - 93
Exchange rate: 3 dB, criterion
level: 85 dBA, 87 dBA
Nodoushan, Esmaielpour,
Ravandi, Mehrparvar and
Gholamezadeh, 2008 [71]
Baling operator - 98
Carding operator - 91
Combing operator - 86
US
Steel coil manufacturing plant: 76–93 84 ** NIOSH (Exchange rate: 3 dB,
criterion level: 85 dBA) NIOSH, 2017 [72]
Exit labourer 1 91
Pickling and crane cab 50–86 70 ** OSHA (Exchange rate: 5 dB,
criterion level: 90dBA)
Exit labourer 2 84
India Glass manufacturing
Coater-1 - 92 (83) *
Exchange rate: 3 dB, criterion
level: 85 dBA, 87 dBA
Prabu, Gokulram,
Magibalam, Senthilkumar
and Boopathi, 2018 [73]
Offline-2 - 91 (85) *
Cold end-2 - 89 (84) *
Offline-4 - 96 (84) *
US Urea formaldehyde and
Polyurethane foam insulation
Part-time drum washer
83–94
84–92 ˆ
OSHA (Exchange rate: 5 dB,
criterion level: 90 dBA) NIOSH, 1983 [34]
Part-time drum washer 88–97#
Electric-powered screwdriver
operator 93–96 ˆ
Foaming agent drum filling
operator 95–99 #
Europe European petroleum refineries
Crude distillation operators - 85–95 ˆ
80–95 #
Exchange rate: 3 dB, criterion
level: 85 dBA and 90 dBA Concawe, 1990 [74]
Vacuum distillation operators - 80–95 ˆ
85–95 #
Isomerisation operators - 85–95 ˆ
-
Catalytic cracker operators - 85–95 ˆ
85–95 #
Catalytic reformer operators - 80–95 ˆ
85–95 #
Hydrotreater operators - 80–95 ˆ
95 #
Sulphur plant operators - 80–95 ˆ
80–95 #
Alkylation plant operators - 90–95 ˆ
-
Utilities operators - 80–95 ˆ
80–95 #
* Values represent before and after engineering control implementation, with after measurements in parenthesis. ˆ
represent 1982–1984 data. # represent 1985–1988 data. ** Noise levels derived using the OSHA 5 dB exchange rate
and criterion level of 90 dBA.
Table 4data highlights variances in workplace noise levels and employee daily noise dosage
which ranges between a minimum of 1 dBA up to a maximum of 10 dBA, where available. Similar to
area noise levels, daily noise dosages noted in Table 4which are at and/or above 85 dBA or 90 dBA
represent rating levels at which the employer should implement specific HCP measures to achieve
regulatory compliance [10–12].
Appl. Sci. 2019,9, 3523 11 of 26
3.2.3. Compensable Claims as Indicator of Noise Exposure
The evidence of noise exposure in the manufacturing sector inclusive of the chemical manufacturing
sector is highlighted by the extent of NIHL compensable claims. Figures 1–3show occupational illnesses
including noise induced hearing loss (NIHL) reported to the United States Department of Labour, HSE
in the United Kingdom (UK) and the Compensation Commissioner in South Africa [75–78].
Figure 1. Occupational illnesses reported in the United States.
Figure 2. Occupational illnesses reported in South Africa.
Figure 3. Occupational illnesses reported in the United Kingdom.
Figures 1–3show that NIHL contributed a fair percentage of occupational illnesses between the
three countries notwithstanding differences in defining compensable NIHL by each country. In SA,
NIHL is by far the highest reported occupational illness. Current NIHL statistics however do not
differentiate sectoral origin of each case. In SA, the reported total occupational illnesses exclude those
originating from the mining sector whereas those reported in the US and UK statistics include illnesses
from the mining sector.
Employees diagnosed with NIHL have a reduced quality of life and limited employment
opportunities. These untold consequences place a burden on affected employees. In spite of the
Appl. Sci. 2019,9, 3523 12 of 26
reported NIHL statistics, there is limited knowledge on noise exposure from the workplace across
nations [79].
In the US, skin diseases or disorders, respiratory conditions and poisonings amongst others
contributed to the total reported illnesses shown in Figure 1.
In SA, other diseases in Figure 2includes tuberculosis of the lungs in health care workers,
pneumoconiosis, dermatitis, occupational asthma, mesothelioma, irritant induced asthma, occupational
cancers, chronic obstructive airways diseases, diseases caused by chemical agents and diseases caused
by biological agents (excluding tuberculosis).
In the UK, vibration white finger, carpal tunnel syndrome, osteoarthritis of the knee, other
musculoskeletal, allergic rhinitis, dermatitis and other musculoskeletal illnesses reported are reflected
in Figure 3.
In view of these reported occupational diseases, occupational health and safety regulation to
prevent these diseases is therefore justified.
3.3. Noise Control in Chemical Manufacturing Plants
Noise regulation mandates employers to implement feasible noise controls through the use of
a mixture of engineering controls and administrative controls with HPD use considered as a last
resort [
10
–
12
]. The noise sources affecting the workforce the most such as those identified in chemical
manufacturing plants should receive the highest priority of consideration for engineering control [
5
,
48
].
Table 5shows engineering noise control solutions with projected noise reduction values for prominent
noise sources in chemical manufacturing plants. Case histories of the effectiveness of the controls are
also shown.
Table 5.
Noise sources, control solution, approximate noise reduction and case history of effectiveness.
Noise Source Noise Control Solution and
Typical Noise Reduction Case History Noise Control Solution Noise Reduction
Achieved Author
Duct and pipe
flow
Lagging or acoustical insulation:
One-inch thick pipe insulation or
double thickness of pipe wall
insulation: 20 dB to 40 dB with no
acoustical leaks [51,80].
Steam line regulators
generating 97 dBA
Modification of the main valve
plug with throttling vanes with a
reduction in pressure from 555 to
100 pascal in a 2 inch steam line
Pipeline noise reduced to
85 dBA NIOSH, 1978 [48]
Flow machines
(pumps),
compressors
and turbines
Acoustic enclosure: 5 dB to 10 dB
noise reduction for sound
insulating wrapping [6].
Industrial mixer
hydraulic pump
emitting 97 dBA
Low-cost engineering
modifications Noise reduced to 80 dBA
Advanced Noise
Solutions, 2003–2019
[81]
Screw compressor
emitting 100 dBA with
tonal content
Reactive silencers fitted into
either side of pipe intake
20 dB overall noise
reduction HSE, 2017 [82]
Acoustic enclosure: 10 dB to 25 dB
noise reduction for single shell
enclosures with sound
absorbing lining.
Steam generator feed
pumps emitting high
tonal noise at
100–105 dBA, causing
noise at the turbine
hall to be 92–98 dBA
4 inch acoustical glass fibre
insulating enclosure lined with
perforated sheet steel on the
inside installed on each feed
pump
Turbine hall noise
reduction to 88–89 dBA NIOSH, 1978 [48]
Noise reduction of more than 25 dB
for double shell enclosures with
sound absorbing lining [83,84].
Free jets and
vents
Silencer: 10 dB to 20 dB noise
reduction [6,83,84].
Ordinary jet noise
exceeding 95 dBA
Proper routing of the airstream
and installing a silencer 20 dB noise reduction Mutchler, 1989 [22]
Compressors
Design stage (rotor blade alteration
or adjustment control through
design): increase in number of
rotor blades from 20 to 80 results in
10 dB noise reduction [18,85].
Motor generator
emitting 94 dBA
1
2
inch thick glass fibre lined with
plywood acoustic enclosure 10 dB noise reduction NIOSH, 1978 [48]
Gas turbines
Intake and exhaust silencer: a
noise insertion loss of 20 to 49 dB
in low frequency range and a 40 to
60 dB noise insertion loss at 40 to
60 dB [18,83,84].
Reciprocating air
compressors
generating 88 dBA
Intake silencers fitted at each
compressor
17 dB overall noise
reduction HSE, 2017 [82]
Machinery
noise
Acoustic barriers with absorbent
linings: 5 dB–10 dB noise
reduction in low frequencies
Gearbox of a 9000
steam turbine emitting
120 dBA inside engine
room
Acoustic enclosure using acoustic
panels with high transmission
properties and a silencer installed
at propeller shaft
Noise reduction unknown,
noise confined within the
acoustic enclosure with a
decrease in adjacent areas
NIOSH, 1978 [48]
20 dB noise reduction in high
frequencies [85,86].
Fans (blowers)
Fan blade design, enclosure and
silencers: locating the fan cut-offat
optimum clearance in relation to
tips of the impeller results in 12 dB
noise reduction [18,85].
High pressure,
low-volume
centrifugal fan unit
emitting 95 dBA
50 mm thick acoustical panel
enclosure 20 dB noise reduction HSE, 2017 [82]
Rotary blowers
emitting high noise
levels due to unit
rotational speed
Hybrid active silencer with
absorptive packing for both low
and high frequency noise
attenuation
42 dB noise reduction HSE, 2017 [82]
Appl. Sci. 2019,9, 3523 13 of 26
The engineering noise control options in Table 5are intended for application to identified
individual noise sources to achieve noise reduction values ranging from 5–60 dB which when correctly
applied, would be successful to reduce noise to below the regulated noise rating limit as highlighted
by the case histories. Occupational hygienists play a crucial role of advising the process team of the
adequacy of these controls [8,46].
Silencer types such as the reactive, reflective, resonator, blow-offand active-adaptive passive
provide noise control to airborne noise along the transmission path. Silencers achieve noise reduction
by preventing gas pulsation and oscillations at the source, whilst also reducing the conversion of
pulsations and oscillations into sound energy [84].
Acoustic insulation when applied to ducts or pipelines involve covering of the outer layer of a
pipe with sound-absorbing material to contain the noise within the insulation layer. Acoustic insulation
materials are denoted as Class A, B and C depending on the minimum insertion loss requirements
which in turn is dependent on the pipe diameter on which they are applied [80].
Engineering noise controls such as acoustic enclosures, silencers and acoustic insulation are cost
effective when incorporated during the design phase of new plant installations, purchasing of new
machinery and retrospective fitting on existing installations [82,86,87].
The knowledge base on noise engineering control options for noisy equipment operated in
chemical manufacturing industries is vast. However, there is limited sharing of this knowledge
amongst companies and through research publications [
62
]. In SA, the literature search could not
locate a single article detailing implementation of a noise engineering control measure and its reported
effectiveness. In 2019, the Noise Control Engineering Journal intends to publish a special issue on case
studies of industry implemented noise engineering controls which will in the future become a useful
resource for HCP personnel [88].
4. Discussion
4.1. Noise in the Manufacturing Sector
The broad manufacturing sector utilises an array of plant equipment which emit noise levels as
high as 160 dBA. Electric powered motors, an important source of noise exposure, are frequently used
at chemical manufacturing plants and during 1974 around two million motors were sold in the US
alone [
7
]. Most manufacturing industries operate plant equipment that emits noise levels exceeding the
noise rating limit for hearing conservation. Chemical manufacturing plants also generate high noise
levels which vary based on equipment model, size, type, speed of operation and material handled [
22
].
As an example, compressors used in ammonia plants generate noise levels up to 90 dBA, whereas
those used in a low-density polyethylene chemical plant generate noise levels at 100 dBA [56].
4.2. Employment and Noise Exposure in the Manufacturing Sector
The manufacturing industry remains the main employer of blue-collar workers, craft workers,
plant operators, and machine operators amongst others [
1
,
20
,
89
–
92
]. The employment statistics in
the manufacturing sectors in SA, US and UK are reported at 1.7 million, 16 million and 2.9 million
workers respectively [
89
–
91
]. According to the 2016 fourth quarter statistics on employment by
occupation published by Statistics South Africa, there were 1,977,000 craft workers and related trade,
and 1,319,000 plant and machine operators in employment SA for all sectors [91].
In the UK, about 2 million workers are exposed to noise above the lower exposure values (personal
noise exposure of 80 dBA) whilst more than a million employees are exposed to noise levels above the
exposure action levels [
93
]. By 2016, the manufacturing sector in the US employed about 15.4 million
workers with about 22 million workers are exposed to excessive noise in all industries. Of the
22 million noise-exposed workers in the US, 6 million of these workers were from the manufacturing
sector [
94
–
96
]. No estimates of the number of employees exposed to noise are currently available in
SA’s manufacturing sector.
Appl. Sci. 2019,9, 3523 14 of 26
Area noise measurements and noise dosimetry results from the manufacturing sector have been
shown to correlate with each other confirming that noise exposes employees to NIHL impacts [
97
–
99
].
Differences in noise levels as high as 5 dB are however possible within certain operations between area
noise measurements and personal dosimetry as highlighted in Table 4[99,100].
Available industry NIHL compensation statistics attribute the manufacturing sector as the highest
contributor of reported occupational illnesses, totalling about 72% in the US alone in 2010 and 82%
in 2007 [
89
,
101
]. The NIHL is particularly prevalent amongst specific job categories such as machine
operators, plant operators, mechanical fitters amongst others [
102
]. In South African general industry,
NIHL remains the highest compensated occupational illness.
4.3. Noise Control for Chemical Manufacturing Plants
Engineering noise control is the ultimate preventative measure for the prevention of NIHL
and should be the primary goal of industry implemented HCPs [
51
,
99
,
103
–
105
]. A systemic review
conducted by NIOSH in the US found no field studies evaluating the effectiveness of implemented
engineering noise controls. There is thus a great need for publishing noise control measures which
have effectively reduced worker noise doses [
106
]. In a systemic review assessing interventions to
prevent occupational NIHL in industry, it was concluded that noise reduction at the source is not
sufficiently implemented [107].
Personnel assigned roles of HCP implementation should influence industry managers to protect
employee hearing by doing “the right thing” which is to consider and implement noise controls [
108
].
A non-exhaustive reference of standards that HCP personnel should consider to guide the process of
implementing engineering noise controls during any stage of a plant installation are shown in Table 6
along with the scope, stage of consideration and assigned responsibilities.
Appl. Sci. 2019,9, 3523 15 of 26
Table 6. Non-exhaustive list of noise control standards and their scope, stage of consideration and responsibility.
Standard Scope Stage of Usefulness/Consideration Responsibility
Design Replacement Retrofitting Supplier Employer
South African National Standard
11688-1. Part 1 [8]
Defines and is intended to provide basic noise control concepts for
machinery and equipment during the entire production chain with
the aim to assist designers of the final machinery and equipment.
33333
South African National Standard
11690-2. Part 2 [6]Defines workplace technical aspects relating to noise control. - - - - 3
South African National Standard
11688-2. Part 2 [9]
Defines and is intended for use by machinery and equipment
designers and users. Also intended for use by regulators,
supervisors or inspectors with the objective of noise reduction in
existing plants.
33333
International Organisation for
Standardisation. ISO 14163:1998(E) [84]Defines practical silencer selection for use in gaseous media. - 3 3 3 3
International Organisation for
Standardisation. ISO 15667:2000(E) [85]
Defines the acoustical performance and performance criteria of
enclosures and cabins. Also defines the agreements of the acoustical
and operational requirements between the supplier, manufacturer
and end user.
33333
International Organisation for
Standardisation. ISO 15664: 2001(E)
[109]
Defines noise control design procedures for new plants, plant
modifications or during extensions. 3-333
International Organisation for
Standardisation. ISO 15665:2003(E) [80]
Defines a standardised methodology for the measurement of
acoustic performance of Class A, B and C pipe insulation. 3-333
International Organisation for
Standardisation. ISO 4871 [110]
Provides information on machinery and equipment required
declaration of noise emission values and provides a methodology
for declared noise emission value verification.
33333
International Electrotechnical
Commission. ISO 8297 [111]
Defines an engineering method for determining sound power levels
in large industrial plants containing multiple noise sources - - - - 3
International Electrotechnical
Commission 60534-8-3. Part 8-3 [112]
Addresses valve and connected piping’s noise generated through
aerodynamic processes 33333
International Electro Commission
60534-8-4. Part 8-4 [113]
Predicts control valve noise generated noise levels during liquid
flow and the resultant noise levels downstream of the valve; and
outside the piping.
3 3 - - 3
EEMUA 140 [114]
Indicates the method for specifying maximum acceptable noise
levels and describes acceptable test methods for determining
equipment noise emission
33333
International Organisation for
Standardisation. ISO 11546-2 [115]
Specifies in situ methods to the determination of the sound
insulation performance of machine enclosures. 33333
Appl. Sci. 2019,9, 3523 16 of 26
Consideration of the guidance or requirements provided in Table 6ensures that noise is controlled
before it is “born” and that due consideration is given during any point of introducing new equipment
and machinery into chemical manufacturing plants. In SA, the NIHL Regulations should incorporate
the duty of care to force employers’ hand to consider equipment listed noise emission levels before
introduction into chemical manufacturing plants as it the current case with the control of noise
regulations in the UK [10].
4.3.1. Workplace Regulation
The health impacts resulting from workplace exposures have resulted in health and safety
regulation. Workplace health and safety regulations when fully implemented, result in the reduction of
illnesses whilst also giving income security to employees [
116
]. Although workplace health and safety
regulations have not fully eliminated workplace hazards, the implementation of these regulations has
reduced workplace injuries and occupational illnesses. The noted reduction in workplace injuries
and occupational illnesses is evidence of positive enforcement and inspection outcomes conducted by
the regulator through inspectors or compliance safety and health officers [
117
–
119
]. Noise regulation
compliance means assigning a limit to the hazard level and the imposition of punitive measures in
case of non-compliance [
118
]. The NIHL regulations in SA and the control of noise at work regulations
in the UK are examples of noise-specific workplace health and safety regulations. The impact of noise
regulation on reducing NIHL cases can however only be measured in the presence of data comparing
changes in illness rates for inspected and non-inspected workplaces [120].
Regulatory Control of Plant Equipment
The legal requirement for the specification of noise emission data of tools, equipment and
machinery used in industry is an important regulatory tool in noise reduction efforts for both new
and existing plants [
121
]. Buying quieter plant equipment shifts the focus to equipment designers
and manufacturer to meet regulatory noise emission specifications. The buy quiet programme is a
NIOSH noise prevention initiative which is composed of (a) a list of existing plant machinery and
equipment along with the listed noise levels; (b) company policy statement committing to buying quiet;
(c) materials and tools for educating and promoting the buy quiet programme; and (d) cost–benefit
analysis for buying quiet. In the buy quiet programme, manufacturers are encouraged to design quieter
equipment and machinery whilst companies are also encouraged to buy or rent equipment which is
quieter [
122
]. Noise emission data specification related legislation has however been largely ignored
and both equipment designers and purchasers are said to only pay lip service to the requirement [
18
].
The noise ranges extrapolated on Table 2attest to this fact.
Additional requirements that can be built into the noise data sheets requirements for machinery
include placing additional restrictions on machinery containing tonal and impulsive noise components.
Plant owners have to consider the cost effectiveness of selecting machinery with low noise emission levels
during the design phase of a plant or selection of new machinery [
109
]. Due to the interconnectedness
of machinery in chemical manufacturing plants, noise prediction incorporating all noise emitting
machinery should be done during the design phase of new installations [80,84,85,109].
Regulatory Control through Inspection and Enforcement of Noise Regulations
Noise regulations are intended for worker protection in the workplace and are implemented by
the employer whilst the regulator conducts inspection and enforcement [
123
]. The inspection and
enforcement are conducted to ensure legal compliance to health standards [
124
]. The inspectors use
preventative tools such as risk evaluation, promotion of best practices, information and awareness
campaigns, guidance and sanctions during inspections to secure compliance to health and safety
regulations [125].
Noise regulations are intended for worker protection in the workplace and are implemented by
the employer whilst the regulator conducts inspection and enforcement [
123
]. The inspection and
Appl. Sci. 2019,9, 3523 17 of 26
enforcement are conducted to ensure legal compliance to health standards [
124
]. The inspectors use
preventative tools such as risk evaluation, promotion of best practices, information and awareness
campaigns, guidance and sanctions during inspections to secure compliance to health and safety
regulation [125].
Between October 2015 and September 2016, OSHA issued 691 citations for 370 inspections
conducted with penalties amounting to $1,665,895 for the violation of the noise standard. The chemical
manufacturing sector received 20 citations in 10 inspections with penalties amounting to $105,897
whilst the plastics and rubber producers were issued with 35 citations for 18 inspections with penalties
amounting to $157,303. [
126
]. Although evidence of enforcement and inspection in SA exists, the DEL
annual report does not detail the specific violations noted during enforcement and inspections. In
the 2015/2016 reporting year, 20,476 notices (citations) were issued to industry for health and safety
violations during 23,678 workplace inspections [
127
]. No inspection and enforcement data relating to
the citations related to the noise standard is available for the UK.
To highlight the important role of inspection and enforcement, inspections conducted by OSHA
inspectors in 1973 showed that occupational illnesses and injuries were reduced by an estimated
16 percent. Inspections conducted in 1974 however showed no statistically significant inspection
impact [
128
]. The results of studies attempting to measure the effectiveness of OSHA enforcement
however, remain mixed but point to the positive impact on the reduction of incidence of occupational
illnesses and injuries [
129
]. Incomplete enforcement of health and safety standards is identified as a
leading factor for low impact inspection outcomes [120].
Interestingly, inspections coupled with penalties conducted by OSHA are reported to have resulted
in a reduction of 19 percent lost workday injuries by 1979–1985. This percentage reduced to 11 in
1987–1991 [
130
]. An increase in the number of health and safety inspections conducted in the US’
manufacturing sector has also been shown to result in a decrease in the number of citations and worker
exposure levels, further highlighting this need [
131
]. However, increased enforcement and inspection
in the current economic climate adds additional fiscal pressure on government budgets [132].
Organisational and Administrative Controls
Similar to the mining industry, there remains limited or no evidence of the implementation
of administrative controls to reduce worker exposure in the manufacturing industry [
133
]. The
organisational aspects of noise control include consideration of work methods which generate low
noise levels. The organisation of work to reduce noise considers limiting exposure duration by
reducing exposed employees to an absolute minimum, scheduling work activities exposing few
employees accompanied by rest periods away from noise sources [
134
]. The reliance on administrative
controls should however be accompanied by continuous checks to ensure compliance and correct
application [
73
]. Administrative controls should incorporate the use of worker dosimetry, time-motion
studies and equipment noise profiling to increase effective utilisation. Despite lack of their economic
feasibility, an apparent advantage of administrative controls is that they have a low cost base and
consume less time during implementation compared to engineering controls [133].
Hearing Protection Devices
Noise regulations also prescribe the transient use of HPDs for exposure control. However, HPDs
can only be effective where users are properly trained in their use and correctly selected based on the
country’s preferred rating method to avoid misinterpretations in selection outcomes [
33
]. Compared
to other HCP elements, HPDs have been found to be the most implemented element [106].
Notwithstanding any degree of protection afforded by wearing HPDs, their real-world performance
has been shown to be highly compromised in many studies, which further highlights the need for
implementing engineering noise control [135].
Noise in chemical manufacturing plants has not been eliminated despite regulatory enforcement,
inspection and HCP institution [
136
]. The HCPs implemented by industry should include additional
Appl. Sci. 2019,9, 3523 18 of 26
aspects such as allowing for noise prediction techniques for new plant installations which are available
to assist employers in noise reduction efforts [8,48,87,137].
4.3.2. Costs and Benefits of Noise Control and Regulation
The implementation of noise control and other aspects of noise regulations place a financial and
compliance burdens on employers. However, this should not discourage employers from implementing
feasible engineering noise controls. The annual costs for the manufacturing sector in the US relating
to compliance with the occupational noise standard in 1993 were estimated by OSHA to be around
$210.3 million. The compliance costs for each enterprise in the sector were also estimated at $638
thousand based on the 1993 dollar terms. On the other hand, the costs related to HPDs required for
compliance with the same standard were estimated at $34.2 million. The overall estimated compliance
costs to OSHA-related regulations in the US in 1993 were estimated between $23.1 billion and $46.7
billion [138].
In the UK, the final regulatory impact assessment of the control of noise at work regulations
2005, also estimated compliance costs segregated into costs related to familiarisation, assessments,
information, preparation of programme, reducing exposure, HPDs, signage and audiometric testing.
On the first year on implementation, employer costs were estimated between £117 million to £202.6
million, whilst the 10 year costs were estimated to be between £477.6 million to £676.3 million. The
highest cost item predictably related to the implementation of engineering controls was estimated at
between £27.5 million to £109.9 million in the first year, and increased to between £65.2 million to £268
million for the 10-year cost period. The HSE estimates employer costs for each noise-exposed worker
at £35.60. [139].
There however remains limited studies detailing the exact overall costs of compliance to all
occupational health and safety regulations [
132
]. This is true for SA where there are no publicly
available cost estimates and benefits of implementing occupational health and safety regulations
inclusive of the NIHL regulations. Notwithstanding the costs relating to compliance to the NIHL
regulations, employers and the government in SA should play their legal roles of ensuring that the
good intentions of these regulations are met. Afterall, these regulations were enacted into law following
extensive deliberations and agreements amongst the tripartite structure inclusive of government,
labour and unions.
The benefits of noise control and regulation are however not immediately visible due to the
delayed onset of NIHL. However, an ancillary and tangible benefit of noise control and regulation is
that it highlights the important role played by professions such as occupational hygienists in workplace
health and safety programmes [
140
]. The benefit of a noise control measure to a worker however
requires noise quantification through dosimetry measurements before and after the intervention [
141
].
In general, the costs of occupational safety and health actions are easily visible compared to benefits
which tend to be underestimated. Additionally, the return on investment related to occupational health
and safety compliance initiatives is influenced by an enterprise’s current practice, implying that an
enterprise with a dismal practice in noise control and prevention will notice major spinoffs for a small
investment made to address the same issues [142].
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
Appl. Sci. 2019,9, 3523 19 of 26
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. This knowledge should be harnessed
by all stakeholders involved in various stages of HCPs, enforcement and inspection to achieve
quieter workplaces.
The future success of workplace health and safety relies on governments, researchers, employers,
employees and health and safety officers’ strong commitment [
119
]. Thus, in SA, studies addressing the
socio-economic impact of occupational diseases including NIHL and the evaluation of the effectiveness
of the noise regulations are advocated to ensure that the prevention of this workplace scourge is
prioritised [
147
]. Research is also required in the area of compliance costs related to the NIHL
regulations [
138
]. Other research areas include studies focusing on the implementation procedures
and evaluation methods of administrative controls for reducing worker noise exposures [134].
Author Contributions:
O.R. conceptualised the study, conducted the literature study, drafted and edited the
manuscript. J.C.E. and J.L.H. reviewed the technical content and layout of the manuscript. All authors read and
approved the final manuscript.
Funding: This research received no external funding.
Appl. Sci. 2019,9, 3523 20 of 26
Acknowledgments:
The primary author acknowledges Karabo Shale, Cape Peninsula University of Technology,
Faculty of Applied Sciences, Department of Environmental and Occupational Studies, for his encouragement and
support during the initial part of the broader project.
Conflicts of Interest: The authors declare no conflict of interest.
Ethical Statement:
The results presented in this paper form part of a broader study for which ethical clearance
was obtained from the Tshwane University of Technology (TUT) Ethics Committee (FCRE 2016/03/012 (SCI)).
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