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Citation: Nieto-Álvarez, R.; de la
Hoz-Torres, M.L.; Aguilar, A.J.;
Martínez-Aires, M.D.; Ruiz, D.P.
Proposal of Combined Noise and
Hand-Arm Vibration Index for
Occupational Exposure: Application
to a Study Case in the Olive Sector.
Int. J. Environ. Res. Public Health 2022,
19, 14345. https://doi.org/10.3390/
ijerph192114345
Academic Editor: Paul B. Tchounwou
Received: 7 September 2022
Accepted: 31 October 2022
Published: 2 November 2022
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4.0/).
International Journal of
Environmental Research
and Public Health
Article
Proposal of Combined Noise and Hand-Arm Vibration Index
for Occupational Exposure: Application to a Study Case in the
Olive Sector
Raquel Nieto-Álvarez 1, * , María L. de la Hoz-Torres 2, Antonio J. Aguilar 3, María Dolores Martínez-Aires 2
and Diego P. Ruiz 3
1Department of Architectural Graphic Expression and Engineering, University of Granada,
Av. Severo Ochoa s/n, 18071 Granada, Spain
2Department of Building Construction, University of Granada, Av. Severo Ochoa s/n, 18071 Granada, Spain
3Department of Applied Physics, University of Granada, Av. Severo Ochoa s/n, 18071 Granada, Spain
*Correspondence: rnieto@ugr.es; Tel.: +34-958243110
Abstract:
In many production and industrial sectors, workers are exposed to noise and hand-arm
vibrations (HAV). European directives have established the maximum limit values or exposure
action values for noise and vibration independently. However, in many cases, workers who endure
hand-arm vibration also receive high noise levels. This research suggests a procedure to aid the
establishment of precautionary measures for workers with simultaneous exposure to both physical
agents. This procedure defines a combined index based on the energy doses for both noise and HAV.
From this combined index, the suggested methodology allows a recommended exposure time for
workers with simultaneous noise and HAV exposure to be calculated. This methodology can be
adapted to tackle the relative importance assigned to both agents according to the safety manager
and new knowledge on combined health effects. To test this method, a measurement campaign under
real working conditions was conducted with workers from the olive fruit-harvesting sector, where
a variety of hand-held machinery is used. The results of the study case show that the suggested
procedure can obtain reliable exposure time recommendations for simultaneous noise and HAV
exposures and is therefore a useful tool for establishing prevention measures.
Keywords: physical agents; noise; vibration; HAV; workers; olive sector
1. Introduction
Scientists, experts and numerous official bodies such as the World Health Organisation
(WHO) or the European Economic Community (EEC) have recognised noise and vibration
as a health hazard and their effects have been regarded as an increasingly important health
problem [
1
,
2
]. In terms of noise, for example, health effects of environmental noise exposure
(i.e., noise in the living environment such as road traffic, railway, aircraft, building and
construction noises or industrial noise) have been extensively studied in scientific literature.
These effects range from purely physiological disorders, such as progressive hearing loss,
to psychological disorders, such as irritation and fatigue, leading to dysfunctions in daily
life [3–5].
In addition, other research has focused on health effects of occupational noise exposure
(in the working environment) specifically. Indeed, workers are exposed in their workplace
to various environmental factors that can affect their health. These factors include physical
agents such as vibration [
6
–
8
] and noise [
9
–
11
], which can cause various pathologies and
adverse effects. Nowadays, the exposure of workers to both physical agents has increased
as all productive sectors have evolved towards mechanisation, and so the probability of
suffering from these adverse health effects has increased. For example, the increased use
of hand tools (electric, combustion, pneumatic and hydraulic) causes exposure to noise
Int. J. Environ. Res. Public Health 2022,19, 14345. https://doi.org/10.3390/ijerph192114345 https://www.mdpi.com/journal/ijerph
Int. J. Environ. Res. Public Health 2022,19, 14345 2 of 23
and HAV. For this reason, their effects have been analysed in many productive sectors
such as construction [
12
,
13
], agriculture [
14
–
16
], forestry [
17
,
18
], metallurgy [
19
], textile
industry [
20
], chemical manufacturing [
21
], automobile manufacturing [
22
], mining [
23
], the
mining industry and mechanical engineering [
24
] etc. The issue of occupational noise and
vibration exposure is so relevant that the Sixth European working conditions survey [
25
]
reports that 28% of all workers are exposed to high noise levels for more than a quarter
of the working day in different labour sectors. Furthermore, 20% of workers are exposed
to vibrations produced by tools or machines for more than a quarter of the working
time. These data show the relevance and importance of the problem in the occupational
risk assessments.
Despite advances in preventive and protective measures to limit such effects, they are
still present today in a large number of occupational activities. This research focuses on
the establishment of preventive measures in workers with simultaneous exposure to both
physical agents as a reinforcement of safety.
In terms of health effects, on the one hand, it is well established that exposure to
occupational noise also causes health effects such as vascular problems [26], heart disease
and cardiovascular disease [
27
–
29
], insomnia [
30
], achievement and memory problems [
31
].
In this matter, a causal relationship between noise exposure and hearing loss has been
clearly demonstrated [
11
,
32
–
35
]. One of the most usual consequences is tinnitus [
36
,
37
].
Boger et al. [
38
] indicated the prevalence of tinnitus of workers exposed to occupational
noise could be as high as 66%. Another problem commonly reported is the extended
high-frequency hearing loss and poor speech perception [34].
On the other hand, exposure to vibrations can cause other health effects. One of
the most studied and best-known effects with regard to exposure to hand-arm vibration
(HAV) is Raynaud’s syndrome [
39
–
41
], also known as white fingers syndrome. Raynaud’s
syndrome is an ischemic response in the skin of the fingers, which reduces blood flow and
causes discoloration [
42
]. Burström et al. [
43
] also demonstrated that cold environment
also increases the risk of white fingers in workers occupationally exposed. In addition
to this effect, HAV may cause other health effects; among the most commonly reported
are musculoskeletal disorders [
44
,
45
], vascular problems [
46
] and neuro-sensory problems
with loss of manual dexterity [47].
1.1. Simultaneous Exposure to Noise and Vibration
Numerous studies have also reported research on the combined effects of noise and
other factors. Golmohammadi, R. and Darvishi, E. [
9
] presented a thorough review of
effects of combined exposure to noise and other exposures, such as chemical agents and
physical factors (i.e., lighting, heat, etc.). In their review they also paid attention to the
state-of-the-art insights in differences in effects of noise exposure by personal characteristics
such as age, gender, genetic background, etc. From this research, an increased incidence of
health effects in workers exposed to simultaneous vibration and noise has been reported.
This increased incidence has been described from several aspects.
On the one hand, relevant and early attention was paid to study the possible as-
sociation between Raynaud’s syndrome and hearing loss, i.e., Iki et al. (1987) [
48
] and
Miyakita et al. in (1990) [
49
] found a decrease in finger temperature when hearing protec-
tors are not used at the same level of vibration. In this line of research, Pyykkö et al. [
50
]
studied the shipyard workers, forestry workers, metal workers and patients referred to
a clinic. They reported that workers with vibration-induced Raynaud’s syndrome were
more susceptible to hearing loss at 4 kHz than workers exposed to noise alone. In the same
regard,
Turcot et al. [18]
concluded that combined exposure to noise and vibration should
be considered as possible risk factors for developing hearing loss.
Other studies in the same research topic led to similar conclusions.
Duan D. P. et al. [22,51]
detected the increased risk of adverse effects on hearing function when the worker is
additionally exposed to vibration under the same noise conditions in the workspace. In the
same sense, other authors such as Pettersson et. al. [
52
–
55
] detected a higher probability
Int. J. Environ. Res. Public Health 2022,19, 14345 3 of 23
of hearing problems in workers who already suffered Raynaud’s syndrome. In terms
of the influence of noise in probability of appearance of the Raynaud’s syndrome, other
studies by Stjernbrandt et al. [
56
] found a higher probability of developing Raynaud’s
syndrome among individuals exposed to occupational noise than only under the effects
of HAV exposure. Turcot [
18
] confirms previous findings of greater hearing loss at higher
frequencies in workers with Raynaud’s syndrome.
In terms of the association of Raynaud’s syndrome and hearing loss, current research
shows that the appearance of this association is highly likely when both physical agents
are involved, but more research is needed to quantify these effects.
On the other hand, a large number of studies in this subject have also been focused
on the effect on workers’ comfort or psychological effects [
57
]. It has been suggested
that the psychological and stressful problems created by both noise and whole-body
vibration may lead to accidents in professional drivers [
58
] and affect the ability to work,
leading to reduced physical and mental performance [
59
]. Other researchers such as
Huang and Griffin [
60
] showed that the sensation of discomfort increases when there
is simultaneous exposure to noise and whole-body vibration. Another study by Kim
et al. [
61
] detected increased headaches and visual fatigue under the combined effect of
noise and vibration in workers. Psychological effects have also been found in workers
subjected to HAV and noise simultaneously, such as psychological anxiety and neurological
problems [
62
], nervous system related disorders [
63
], mental health problems such as
depression [
57
] and insomnia problems [
64
], even at levels under the recommended limits
by the standards, and they may also lead to other disturbances which, although they might
seem less important, cause discomfort to the operator, such as an increased sweating of
the hands when handling hand tools in the presence of noise [
65
]. Nari et al. [
64
] revealed
an association between occupational noise and vibration exposure and insomnia, both
individually and simultaneously.
In terms of comfort and psychological effects, current research shows that increased
discomfort is highly likely when both physical agents are involved, but more research is
also needed to quantify these effects and additional studies and research are required to
further understand this relationship.
Accordingly, since the appearance of health effects from combined exposure to both
noise and vibration is highly likely, some interesting research has looked into the assessment
of the possible association between them, assessing both the possible increase in health
effects on workers and the appearance of new effects. If the literature review focuses on the
effects of combined exposure to noise and specifically hand-arm vibration, the first research
study on the effects of combined exposure was the research of Petterson et al. [
55
]. They
suggested that the combined exposure effects could be due to the additional noise of the
vibrating tool. Finally, they underlined that these results cannot be generalized to elderly
and unhealthy subjects exposed at the workplace because the sample they analysed was
constituted of healthy young subjects with no history of occupational exposure. A further
insight in the published literature into the possible relation or quantification of this effect
in simultaneous exposure to noise and vibration in general is found in several interesting
research studies. As illustrative examples of the findings in this subject, the research by
Sisto R. et al. [
66
] and Ljungberg and Neely [
59
] is remarkable. Sisto R. et al. [
66
] conducted
an experimental study with 12 volunteers. They concluded that a synergistic effect of
noise and vibration in inducing cochlear damage seems to be present and it is possible to
make quantitative estimates of this effect. This idea contradicts those of Ljungberg and
Neely [
59
] who claim neither synergistic nor antagonistic effects were observed from the
combined noise and vibration exposure. Other work carried out by Zhu et al. 1997 [
67
]
concluded that noise exposure is essential to produce an increase in temporary threshold
shift of hearing and, together with noise exposure, hand-arm vibration can enhance the
effect of noise on hearing by producing a higher sympathetic activity which might cause
greater vasoconstriction in the inner ear, but no clear quantification on exposure limits
was reported.
Int. J. Environ. Res. Public Health 2022,19, 14345 4 of 23
A more in-depth review about the combined effects of occupational exposure to noise
and other risk factors carried out by Golmohammadi and Darvishi [
9
] concluded that the
current research evidence shows that there is high evidence that the exposure to vibration
exacerbates all noise effects. Nevertheless, the possible various interactions between noise
and HAV should be studied further. In the same sense, Sisto et al. [
66
] concluded that there
is a risk that exposure to mild noise levels could interfere with the exposure to vibration,
enhancing the adverse effect on the hearing function. This should be considered to optimise
prevention strategies at the workplace.
1.2. Standards and Regulations
International standards define two exposure values for these physical agents. On the
one hand, Exposure Action Value (EAV) is a daily amount of vibration or noise exposure
above which employers are required to take action to control exposure. The Exposure Limit
Value (ELV) is the maximum amount of vibration or noise an employee can be exposed
to on any single day. In this regard, the EU Directive [
68
] establishes the limit values for
vibration; the Exposure Limit Values (ELV) are set up in 5 m/s
2
and Exposure Action Value
(EAV) in 2.5 m/s
2
. The same values are recommended by The American Conference of
Governmental Industrial Hygienists (ACGIH) [
69
], in its latest publication of TLVs and
BEIs [
70
]. Unlike the previous ones, NIOSH [
71
] does not provide a limit value but it
establishes recommendations to protect the health of workers. In terms of measurement
procedure, international standards also establish the HAV vibration measurement pro-
cedure; in this case both ISO 5349-1:2001 and ISO 5349-2:2002 [
72
,
73
] as well as ANSI
S2.70 [74].
In noise regulations there are more differences in ELV, with values ranging from
85 to 90 dBA.
Thus, the European Directive [
75
] establishes 87 dBA as (ELV) value while
USA-OSHA raises it up to 90 dBA. The strictest recommendations are established by
NIOSH and ACGIH in TLVs and BEIs [
70
], since they both establish the ELV equal to 85
dBA. This is the same value that the Directive-2003/10/CE [
75
] establishes for the EAV
as well as ISO 1999:2013 [
68
], so these values for noise are widely applied to perform
exposure assessments. Since these EAVs in international standards are widely used, in this
research they are adopted as a basis of providing a reference, but in case other occupational
standards are used, the EAV should be substituted in the combined index proposal.
In Europe, manufacturers, suppliers and importers are affected by Directive 2006/42/CE [
76
]
relative to machinery. It establishes that machinery must be designed and constructed in
such a way that risks resulting from the emission of airborne noise are reduced to the lowest
level. In the same way, the machinery must be designed and constructed in such a way that
risks resulting from vibrations produced by the machinery are reduced to the lowest level.
The values supplied by the manufacturers allow establishing protection measures at work
but some studies such as [
77
] find some differences between the values provided by the
manufacturer and those measured in real working conditions, which may cause the risk to
be underestimated. This fact makes it necessary to carry out experimental risk assessments
in order to design safe working procedures that minimise the exposure of workers to these
risks. For this design, it is essential to establish recommendations or criteria based on time
exposure, taking into account the combined exposure to both physical agents.
It should be noted that noise regulations established for occupational settings do
not protect 100% of workers from NIHL, but rather strike a balance between hearing
conservation and economic development (Shepard et al. [34]).
1.3. Main Hypothesis and Objectives of This Research
The main objective of this research is to reinforce the preventive measures in workers
with simultaneous exposure to both noise and HAV in their occupational activities, i.e.,
as a reinforcement of safety in work. The main aim is to propose a combined index to
suggest a maximum exposure time to both agents, thus providing a way to calculate this
Int. J. Environ. Res. Public Health 2022,19, 14345 5 of 23
precautionary exposure time based on physical measurements, and so discouraging the
use of rule-of-thumb criteria.
With this objective, this research aims to propose a combined index which accounts for
the total energy received by the worker coming from both noise and HAV. The proposed
index is based on the calculation of the combined energy dose calculated from the EAV
prescribed by the standards. On this basis, a methodology is proposed to allow recom-
mendations on exposure time to be adopted for minimizing the adverse health effects
on workers.
Thus, the proposed index is based on the additive energy dose coming from both physi-
cal agents. The foundation of this proposal relies on the following main
hypotheses 1 and 2
:
Hypothesis 1.
The current occupational noise and HAV regulations independently applied may
underestimate the adverse health effects of combined exposure, so it is advisable to reinforce the
preventive measures in workers with simultaneous exposition to both noise and HAV in their
occupational activities.
Hypothesis 2.
The interaction between noise and HAV exposures should be considered as additive
in terms of exposure to energy in developing the suggested procedure (i.e., the combined index).
At the current state of the research, there is not an unambiguous relationship and quantification
of this association between both physical agents, so a cautious approach is taken and a reasonable
approximation to the total effect caused by a combination of noise and vibration can be determined
from a summation of the effects of the individual agents.
The rationale of these hypotheses was previously discussed in the preceding section.
The first hypothesis comes from the health effects reported upon the scientific literature
review where there are many signs and evidence of health effects of these agents in inter-
action. As a specific example to support this hypothesis, the work of Shepard et al. [
34
]
concludes that the current occupational and environmental noise regulations may signifi-
cantly underestimate the adverse health and societal cost of noise-induced hearing loss.
The second hypothesis is taken as a starting point for the combined index proposal.
From the literature review on combined effects on noise and vibration, it can be concluded
that the current research evidence shows that there is high probability that the exposure to
vibration increases some noise effects, and vice versa, i.e., the noise exposure could interfere
with the effects of exposure to vibration (Hypothesis 1). At the current state of the research,
there is not a clear relationship and quantification of this association between both physical
agents. At this stage of the research, it is advisable to optimize prevention strategies at
the workplace until research on health effects of combined exposure can clearly establish
the nature of the association between these agents. For the sake of implementing such
a prevention strategy, a systematic literature review was performed on combined health
effects in the preceding section. This review leads to the conclusion that the interaction
between these two exposures is not well known at the current stage of research, and there
is a lack of undeniable combined exposure models, i.e., there is no clear evidence that
these effects should be considered as synergistic or not and how this could transfer to the
exposure models.
In this context, the rationale of the proposed approach in this research lies in the
current dose–response assessment methodology used previously in other risk assessment
contexts, such as in the chemical agents’ case [
78
]. The conceptual framework supporting
this proposal comes from the limited current knowledge on health effects coming from
combined exposure. In this case a cautious approach is recommended to ensure that
simultaneous exposure to noise and vibrations under their respective exposure limit values
is properly addressed. In this case, an exposure index based on the sum of the energy
exposures to each of the component divided by their respective exposure limits in terms
of energy is a logical choice. These exposure limits are taken from the workers’ energy
exposure based on the noise energy dose (Directive-2003/10/CE) [
75
] and HAV energy
Int. J. Environ. Res. Public Health 2022,19, 14345 6 of 23
dose (ISO 5349-1:2001 and ISO 5349-2:2002) [
72
,
73
]. Thus, the energy dose concept and the
criteria levels used in this research rely on the international standards. In summary, at the
current stage of knowledge, this combined effect could be considered as additive, unless
new information becomes available to indicate that the effects are synergistic, for example.
With the available information, this cautious approach is adopted, and the combined
effect is considered additive in terms of exposure energy to develop the proposed method.
As an example of the application of the proposed methodology, an experimental study
is carried out in the olive sector, specifically in olive harvesting, analysing the exposure to
both noise and HAV from a hook type olive harvester with combustion. To this aim, some
measurement sensors and equipment were used to obtain data from noise and HAV, and
some time exposure recommendations are given for this study case.
2. Occupational HAV and Noise in the Olive Oil Sector
One of the sectors in which mechanisation has been most evident throughout history
has been agriculture. Among the sub-sectors, the olive oil sector has been no exception.
Olive oil consumption has increased in all countries, even in Spain, where it was
already traditionally consumed as the main dietary fat (Berbabeu et al. [
79
]). Spain is the
world’s leading producer of olives, with a third of the total production according to data
from the International Olive Council IOC [
80
]. The cultivated area of olive groves in Spain
extends to 2.7 million hectares, of which Andalusia accounts for 60% according to data
from the Survey on Surface Areas and Yields ESYRCE 2020 [81].
The sector has increased its productivity and competitiveness by incorporating ma-
chinery that reduces harvesting times. Deboli et al. [
82
] show that productivity can be
tripled with the use of hand-guided electric machines. Machinery manufacturing compa-
nies offer a wide range of hand-guided tools (comb, hook, flap, beater, comb, hook, flap
and beater). The most commonly used in Andalusia are hook and comb type harvesters.
This fact is very relevant from an economic point of view, as olive harvesting costs
can account for up to 50% of the sale price of the product, according to Bernardi et al. [
83
].
Increased mechanisation can reduce these costs by 40–48% if handheld portable equipment
is used, as demonstrated by Sperandio et al. 2017 [84].
Many workers are involved in these tasks. The number of working days in harvesting
in an average production season in the region of Andalusia can amount to about 19 million,
according to data from the “Olive grove production capacity 2021/2022” report in [85].
There are few studies on the impact of noise and HAV exposure in the olive sector.
Some studies on hand-harvesters [
86
–
96
] only assess the HAV exposure received by the
worker, with values almost always above the EAV set by Directive 2003/10/EC [
75
] and
sometimes above the ELV.
Studies on the effects of both physical agents in olive harvesting work are scarce and
give different results depending on the type of tool analysed and its power source. In
comb-type harvesters with electric motor flap type portable harvesters, Cakmak et al. [
97
]
found noise values lower than EAV (80 dBA) and vibration values above EAV (2.5 m/s
2
).
Saracoglu et al. [
98
] evaluated hook type olive harvesters with combustion engine and
obtained different vibration results for the right and left hand, but above EAV and higher
noise values ELV (87 dBA).
In a previous study, the authors of the present article [
99
] presented the first results
of the evaluation of the physical agents in olive harvesting, where the most commonly
used hand-harvesters were evaluated. The noise values obtained were above EAV and
ELV depending on the machine and the HAV levels were higher than ELV. In addition, all
values were higher than those declared by the equipment manufacturer.
In general, the studies found on the machinery used during olive re-picking give
varied results, exceeding the permitted values in most cases, but in any case, they are
limited to measuring noise and vibration. Therefore, the high levels of exposure to noise
and HAV in this sector justify their choice for the application of the proposed combined
assessment index in the present study.
Int. J. Environ. Res. Public Health 2022,19, 14345 7 of 23
3. Materials and Methods
3.1. Data Acquisition and Testing Method
The testing method for determining the HAV and noise dose and the sampling time
depends on the type of machinery being measured. Since the HAV and noise levels received
by the worker are going to be assessed, different noise and vibration measurement sensors
shall be placed on the worker themselves, as described below.
The level of vibration received by the operator has been carried out in compliance
with the standard measurement and evaluation of human exposure to hand-transmitted
vibration (Practical Guidance for Measurement at the Workplace. ISO 5349-1:2001 and
ISO 5349-2:2002 [72,73]).
The measurement should last long enough to ensure reasonable statistical accu-
racy and for the vibration to be typical of the exposure being evaluated. The standards
ISO 5349-1:2001 and ISO 5349-2:2002 [
72
,
73
] establish that the total duration of the vibration
signal must be at least 1 min. For hand-guided tools and machines with all types of power
sources (electric, hydraulic, pneumatic, internal combustion, etc.), ISO-20643:2008 [
100
]
states that the measurements should be carried out in three series of five tests each, with a
different experienced operator for each series.
For this reason, three series have been selected, each with one operator. The selected
operators are experienced in the handling of the tool. In the work process, for each series,
or, in other words, for each operator, five periods of at least 15” were taken, so that each
sample lasted at least 75”, with a minimum of 1 min duration.
The noise assessment was carried out according to ISO 1999:2013 [
101
]. It does not
state the measurement time of the noise signal received by the worker, but it should be
measured for a representative time of the dose. It has been measured in parallel during the
same 15”, i.e., in simultaneous periods.
In order to measure the noise and vibration values received by the operator, the
measurements were made when the hand tool was used during the actual working day,
under normal conditions of use.
3.2. Equipment Used for Data Acquisition
The equipment chosen to measure vibrations exposure was a human vibration meter
(SVAN 106 equipment, SVANTEK) (Figure 1b). The vibrations transmitted to the hand–arm
system was measured with a triaxial accelerometer (SV 105, Svantek). Accelerations were
measured for both right and left hands. The accelerometer was placed on the handgrip (See
Figure 1a) in the centre of the grip area of the machine handle, as this is where the most
representative evaluation of the vibrations transmitted to the hand is obtained.
Int. J. Environ. Res. Public Health 2022, 19, x FOR PEER REVIEW 8 of 24
(a)
(b)
Figure 1. (a) Sensor placed on the worker’s hand; (b) SVAN 106 Four-Channel Sound and Vibration
Analyser.
Vibration is measured in the three orthogonal axes according to ISO 5349-1:2001 and
ISO 5349-2:2002 [65,66] standards. Subsequently, the Wh-weighting is established to ana-
lyse the signal and obtain values comparable with the maximum doses established in the
standard. The values are studied in the frequency range covered by the octave bands from
8 Hz to 1000 Hz.
In the case of noise measurements, a SQuadriga I analyser was used to made binaural
recordings at the worker position (Figure 2). The headset was placed over the worker’s
ears. Noise level measurements were analysed with Artemis software.
(a)
(b)
Figure 2. (a) SQuadriga Headphone Booster; (b) SQuadriga Headset BHS.
3.3. Calculation of Exposure Level
The assessment of the exposure level to HAV is based on the calculation of daily
exposure, which can be measured using the method of ISO 5349-1:2001 and ISO 5349-
2:2002 [72,73].
The measured vibration magnitudes are expressed in Equation (1). The daily expo-
sure A(8) is expressed as the equivalent continuous acceleration over an eight-hour pe-
riod, calculated as an rms value.
𝐴𝑖(8)=𝑎ℎ𝑣 √𝑇𝑒𝑥𝑝
𝑇0
(1)
where 𝑎ℎ𝑣 is the magnitude of the vibration from the source producing it in m/s2; 𝑇exp is
the duration of exposure to vibration 𝑎ℎ𝑣 in seconds; 𝑇0 is the 8-h reference period
(28,800 s) and 𝑎ℎ𝑣 is expressed as shown in Equation (2).
Figure 1.
(
a
) Sensor placed on the worker’s hand; (
b
) SVAN 106 Four-Channel Sound and Vibra-
tion Analyser.
Int. J. Environ. Res. Public Health 2022,19, 14345 8 of 23
Vibration is measured in the three orthogonal axes according to ISO 5349-1:2001
and ISO 5349-2:2002 [
65
,
66
] standards. Subsequently, the Wh-weighting is established to
analyse the signal and obtain values comparable with the maximum doses established in
the standard. The values are studied in the frequency range covered by the octave bands
from 8 Hz to 1000 Hz.
In the case of noise measurements, a SQuadriga I analyser was used to made binaural
recordings at the worker position (Figure 2). The headset was placed over the worker’s
ears. Noise level measurements were analysed with Artemis software.
Int. J. Environ. Res. Public Health 2022, 19, x FOR PEER REVIEW 8 of 24
(a)
(b)
Figure 1. (a) Sensor placed on the worker’s hand; (b) SVAN 106 Four-Channel Sound and Vibration
Analyser.
Vibration is measured in the three orthogonal axes according to ISO 5349-1:2001 and
ISO 5349-2:2002 [65,66] standards. Subsequently, the Wh-weighting is established to ana-
lyse the signal and obtain values comparable with the maximum doses established in the
standard. The values are studied in the frequency range covered by the octave bands from
8 Hz to 1000 Hz.
In the case of noise measurements, a SQuadriga I analyser was used to made binaural
recordings at the worker position (Figure 2). The headset was placed over the worker’s
ears. Noise level measurements were analysed with Artemis software.
(a)
(b)
Figure 2. (a) SQuadriga Headphone Booster; (b) SQuadriga Headset BHS.
3.3. Calculation of Exposure Level
The assessment of the exposure level to HAV is based on the calculation of daily
exposure, which can be measured using the method of ISO 5349-1:2001 and ISO 5349-
2:2002 [72,73].
The measured vibration magnitudes are expressed in Equation (1). The daily expo-
sure A(8) is expressed as the equivalent continuous acceleration over an eight-hour pe-
riod, calculated as an rms value.
𝐴𝑖(8)=𝑎ℎ𝑣 √𝑇𝑒𝑥𝑝
𝑇0
(1)
where 𝑎ℎ𝑣 is the magnitude of the vibration from the source producing it in m/s2; 𝑇exp is
the duration of exposure to vibration 𝑎ℎ𝑣 in seconds; 𝑇0 is the 8-h reference period
(28,800 s) and 𝑎ℎ𝑣 is expressed as shown in Equation (2).
Figure 2. (a) SQuadriga Headphone Booster; (b) SQuadriga Headset BHS.
3.3. Calculation of Exposure Level
The assessment of the exposure level to HAV is based on the calculation of daily
exposure, which can be measured using the method of ISO 5349-1:2001 and ISO 5349-
2:2002 [72,73].
The measured vibration magnitudes are expressed in Equation (1). The daily exposure
A(8) is expressed as the equivalent continuous acceleration over an eight-hour period,
calculated as an rms value.
Ai(8)=ahv sTexp
T0(1)
where
ahv
is the magnitude of the vibration from the source producing it in m/s
2
;
Texp
is
the duration of exposure to vibration
ahv
in seconds;
T0
is the 8-h reference period (28,800 s)
and ahv is expressed as shown in Equation (2).
ahv =qa2
hwx +a2
hwy +a2
hwz (2)
where
ahwx
,
ahwy
and
ahwz
are the rms values of the acceleration of the vibrations to the
hand, weighted in frequency after measuring the vibratory surface in contact with the hand
on three orthogonal axes x,y,z, expressed in m/s
2
, see Figure 3. In the proposed scheme in
this research, vibrations are considered in the three directions and measured accordingly to
obtain the ahv value.
Int. J. Environ. Res. Public Health 2022, 19, x FOR PEER REVIEW 9 of 24
(2)
where and are the rms values of the acceleration of the vibrations to the
hand, weighted in frequency after measuring the vibratory surface in contact with the
hand on three orthogonal axes x, y, z, expressed in m/s2, see Figure 3. In the proposed
scheme in this research, vibrations are considered in the three directions and measured
accordingly to obtain the value.
Figure 3. Axes direction defined in relation to the body hand (hand reference system).
On the other hand, a magnitude frequently supplied by the manufacturer is the
equivalent vibration, . This value is calculated based on the acceleration values of
vibration for each handle, as well as the mode of machine operation Equation (3).
(3)
The assessment of the exposure level to noise is based on the Directive-2003/10/CE
[75], and measures noise exposure defined in the ISO-1999:2013 [101] standard.
The A-weighted equivalent continuous level is obtained from Equation (4).
(4)
where PA is the weighted sound pressure and is the reference pressure value (20 μPa),
during a specified time interval of duration T ( = 0 is the time at the beginning and is
the time at the end of the measurement).
To obtain the daily noise exposure level () for an 8-h working day, the following
equation is used (5):
(5)
where () is obtained from Equation (4), T is the actual time duration and is the
reference time duration of the working day ( = 8 h).
The daily noise exposure level () is the parameter used as a risk predictor. The
is dependent on time and noise exposure levels during a nominal eight-hour work-
ing day. The ELV and the EAV with respect to the are fixed in the Directive-
2003/10/CE [75].
On the other hand, Directive 2002/44/EC [68] also establishes these limits for vibra-
tions exposure. Both Directive 2002/44/CE and 2003/10/EC define the exposure limit val-
ues: the daily ELV and the daily EAV. Table 1 show the values defined in both directives.
Figure 3. Axes direction defined in relation to the body hand (hand reference system).
Int. J. Environ. Res. Public Health 2022,19, 14345 9 of 23
On the other hand, a magnitude frequently supplied by the manufacturer is the
equivalent vibration,
ahv,eq .
This value is calculated based on the acceleration values of
vibration ahv for each handle, as well as the mode of machine operation Equation (3).
ahv,eq =s1
T
n
∑
i=1
a2
hwi ti(3)
The assessment of the exposure level to noise is based on the Directive-2003/10/CE [
75
],
and measures noise exposure defined in the ISO-1999:2013 [101] standard.
The A-weighted equivalent continuous level LAeq,Tis obtained from Equation (4).
LAeq,T=10log"1
TRt2
t1PA2(t)dt
P2
0#dB(A)(4)
where PA is the weighted sound pressure and
P0
is the reference pressure value (20
µ
Pa),
during a specified time interval of duration T(
t1
= 0 is the time at the beginning and
t2
is
the time at the end of the measurement).
To obtain the daily noise exposure level (
LAeq,d
) for an 8-h working day, the following
equation is used (5):
LAeq,d=LAeq,T+10logT
T0dB(A)(5)
where (
LAeq,T
) is obtained from Equation (4), Tis the actual time duration and
T0
is the
reference time duration of the working day (T0= 8 h).
The daily noise exposure level (
LAeq,d
) is the parameter used as a risk predictor.
The
LAeq,d
is dependent on time and noise exposure levels during a nominal eight-hour
working day. The ELV and the EAV with respect to the
LAeq,d
are fixed in the Directive-
2003/10/CE [75].
On the other hand, Directive 2002/44/EC [
68
] also establishes these limits for vibra-
tions exposure. Both Directive 2002/44/CE and 2003/10/EC define the exposure limit
values: the daily ELV and the daily EAV. Table 1show the values defined in both directives.
Table 1.
The daily limit values EAV and ELV defined by Directive 2002/44/EC [
68
] and Directive
2003/10/EC [75].
Directive 2002/44/EC Directive 2003/10/EC
Daily Limit Values A(8) Daily Limit
Values
LAeq,d
[dBA]
LPpeak
[dBC]
EAV 2.5 m/s2Upper EAV 85 137
ELV 5 m/s2ELV 87 140
The Directive 2006/42/CE [
76
] establishes that the manufacturer must declare the
different emission values of the machine: the A-weighted emission sound pressure level
at workstations, where this exceeds 70 dB(A), the peak C-weighted instantaneous sound
pressure value at workstations, where this exceeds 63 Pa (130 dB in relation to 20
µ
Pa),
and the A-weighted sound power level emitted by the machinery, where the A-weighted
emission sound pressure level at workstations exceeds 80 dB(A). It must also indicate under
what conditions the test has been carried out. In the case of HAV, the manufacturer must
indicate the vibration total value to which the hand-arm system is subjected, if it exceeds
2.5 m/s
2
. In the case of the type of hand-guided machinery that is going to be assessed,
the measurement conditions are carried out according to ISO 11201:2010 standard [
102
]
and for vibration ISO-20643:2008 standard [
100
]. However, these values are not always
clearly declared and shown by the manufacturer, as shown by Nieto-Álvarez et al. [
99
].
This makes it difficult for safety managers to take adequate measures to protect workers.
Int. J. Environ. Res. Public Health 2022,19, 14345 10 of 23
4. Results: Proposal of a Combined Index and Methodology for Its Calculation
The response of the human body to noise and vibration (health effects and annoyance)
is related to the energy transmitted to the body by both the vibrations and noise. Based on
this fact, much research has been made in developing dose–response relationships between
the noise or vibration exposure and annoyance or health effects (for example in the recent
books by Murphy E., 2014 [
103
] and Mansfield, N.J. 2004, [
104
] there is a comprehensive
explanation on this topic). Therefore, since Directive-2003/10/CE [
75
] established the
upper EAV for the daily (8 h) Equivalent Continuous Noise Pressure Level in dB(A)) and
Directive 2002/44/EC [
68
] established the EAV for the daily (8 h) Acceleration Exposure
A(8) (Table 1), it can be interesting to establish a criteria for the Combined Exposure Time
(
TCexp
). This combined time will be established by considering both physical agents, since
often there is a combined exposition in workers, such as in the olive sector.
For the sake of clarity, the following Figure 4shows a flowchart of the proposed
methodology for the main two cases of only one source of exposure (i.e., a machine
generates both noise and HAV), and the case when the exposure to these physical agents
originates from different noise and HAV sources.
Int. J. Environ. Res. Public Health 2022, 19, x FOR PEER REVIEW 11 of 24
Figure 4. Flowchart of the proposed methodology.
To propose a method for the calculation of the for noise and HAV, firstly the
energy dose for noise and HAV physical factors, and the combined energy dose index are
defined as (in the subsequent derivations all time units are in hours):
• Noise Energy Dose. The noise energy dose received by a worker is defined as:
(6)
where stands for the average noise intensity (watts per square meters, W/m2) re-
ceived by the worker in his/her working time and is the average noise intensity
establishes by standards. In our case, based on Directive-2003/10/CE [75], this is set
up as the average intensity equivalent to the criterium level (Upper EAV = 85 dBA) for a
daily (8 h) exposure. If a worker has been exposed to a single exposition level
during a measurement time (measurement time used to calculate the equivalent
noise level ), the received intensity in the time reference period (8 h) is equivalent
to Equation (7).
Figure 4. Flowchart of the proposed methodology.
Int. J. Environ. Res. Public Health 2022,19, 14345 11 of 23
From this figure, it can be followed that if one source generates both noise and vibration
there will only be one maximum exposure time to meet the combined index below the
EAV values. In case of two sources, the first step is to calculate the maximum time for
noise on the one hand, and for vibration on the other hand, assuming that there is only
one of these physical agents. The third step would be to establish the pairs of exposure
times, depending on the doses (the higher the noise dose, the lower the vibration dose and
vice versa).
To propose a method for the calculation of the
TCexp
for noise and HAV, firstly the
energy dose for noise and HAV physical factors, and the combined energy dose index are
defined as (in the subsequent derivations all time units are in hours):
•Noise Energy Dose. The noise energy dose received by a worker is defined as:
Dnoise =Irec
Istd
(6)
where
Irec
stands for the average noise intensity (watts per square meters, W/m
2
) received
by the worker in his/her working time
Te
and
Istd
is the average noise intensity establishes
by standards. In our case, based on Directive-2003/10/CE [
75
], this
Istd
is set up as the
average intensity equivalent to the criterium level (Upper EAV = 85 dBA) for a daily (8 h)
exposure. If a worker has been exposed to a single exposition level
LAeq,Ten
during a mea-
surement time
Ten
(measurement time used to calculate the equivalent noise level
LAeq,Ten
),
the received intensity in the time reference period (8 h) is equivalent to Equation (7).
Irec =10−12 1
8Te10LAeq,Ten/10 (7)
The Noise Energy Dose (Dnoise) for this case becomes:
Dnoise =Te
810LA eq,Ten−85
10 (8)
A value of 1 or 100% means that, in terms of energy, the worker has received the total
amount of energy allowed by the chosen standard.
•
HAV Energy Dose. The HAV energy dose is defined as the assessment of the exposure
level to HAV is based on the calculation of daily exposure, which can be measured
using the methods of ISO 5349-1:2001 and ISO 5349-2:2002 [72,73].
Dvibration =Erec
Estd
(9)
where
Erec
stands for the average HAV average energy measured during the use
of a given machinery by the worker during his/her working usage time
Te
and
Estd
is the HAV average energy derived from the standards. In our case, Directive
2002/44/EC [
68
] establishes the EAV for the daily (8 h) Acceleration Exposure A(8)
as 2.5 m/s
2
and this value is chosen as a criterion. Therefore, if a worker has been
exposed to a single exposition level using a machine that generates HAV equivalent
continuous acceleration over an
Tev
(h) period, calculated as a rms value,
ahv,eq
, the
HAV energy dose in the time reference period (8 h) is equivalent to Equation (10).
Dvibration =a2
hveqTev
2.528(10)
A value of 1 or 100% means that in terms of energy, the worker has received the total
amount of energy allowed by the standard chosen.
•
Combined Noise and HAV energy dose. This index is defined by a combination of the
two indexes defined above. Since a value of any of the above indexes equal to 1 means
Int. J. Environ. Res. Public Health 2022,19, 14345 12 of 23
that in terms of energy, the worker has received the total amount of energy allowed
by the regulation. The combined noise and HAV energy (
Dcombined
) dose is defined
consequently as the weighted arithmetic mean of both energy doses:
Dcombined =kw1Dnoise +w2Dvibration
w1+w2(11)
where
w1
and
w2
stand for the selected weighting factors for the noise and HAV energy
dose respectively, and
k
is a normalizing factor. These factors can be selected by the
prevention professionals as a value ranging from 0 to 1, depending on the relative
relevance assigned to each physical factor by the prevention professionals, so the ratio
w1
/
w2
means the relative relevance of one physical agent compared to the other one.
The prevention professional, according to the worker health record, can adjust the
weights so the relative importance of both agents can be taken into account at the
discretion of the practitioner. In our case, we consider that both agents have the same
relevance, i.e., the same relevance is given to noise and HAV energy exposure.
For this reason, both weighting factors are chosen as the same ones, and to maintain
the maximum recommended energy exposure as the value of 1 (as in the case of individual
doses), in this case the Dcombined is finally defined as the arithmetic sum of both doses.
Dcombined =Dnoise +Dvibration (12)
Once the
Dcombined
index has been defined, the next step is to propose a method
to obtain the
TCexp
. To this aim, if the worker is exposed both to noise (measured as the
noise exposition level
LAeq,Ten
) and HAV (measured as the HAV equivalent continuous
acceleration ahv,eq over the time Tev ), the following requirement should be fulfilled:
Criterion for action: Dcombined ≤1
This criterion in fact also implies that Dvibration <1and Dnoise <1
If this criterion is chosen, the occupational risk prevention professional should select
exposure times for HAV and noise to assure the
Dcombined
is less than 1. These times will
be denoted as
TCexp Noise
and
TCexpVib
and they will be connected. In this case, let us assume
that one worker is exposed in their workplace to noise (characterised by the equivalent
noise exposition level
LAeq,Ten
, measured over a prescribed time (
Ten
) and HAV (measured
as the HAV equivalent continuous acceleration
ahv,eq
over a prescribed time
Tev
). Our goal
is to select the subsets of matching pairs (
TCexp Noise
,
TCexpVib
) that will keep the
Dcombined
index under 1, as the criteria we established.
The proposed method works as follows:
Step. 1. Given the noise exposition level of the worker
LAeq,Ten
, the maximum time
allowed with this agent alone is calculated, i.e., the value corresponding to this pair
(TCexp Noise, 0). For this calculation Dnoise is equal to 1 and TCexp Noise is given by:
TCexp NoiseMa x =8∗1085−LAeq,Ten
10 ; for the case TCexpVib =0 (13)
Step. 2. The equivalent continuous acceleration
ahv,eq
over a prescribed time
Tev
is
shown in Equation (1) and it is calculated as the maximum time allowed with this agent
alone, i.e., the value corresponding to this pair (0,
TCexpVib
). For this calculation
Dvibration
is equal to 1 and TCex pVib is given by:
TCexpVibMax =2.52∗8
a2
hveq
; for the case TCexpNoise =0 (14)
Step. 3. Once the maximum numbers of the matching pairs have been established
(TCexp NoiseMa x
,
TCexpVibMax)
, the intermediate values of the time matching pairs are calcu-
lated. For this task, one can proceed as follows:
Int. J. Environ. Res. Public Health 2022,19, 14345 13 of 23
Step. 3.1. In the intervals of numbers ranging from 0 and
TCexpVibMax
, there is fixed
a set of values (namely N values) for which it is desired to calculate the matching pairs
(
TCexp Noise
,
TCexpVib
). These values are denoted as
TCexpVibi
=
TCexpVibMax
* i/N, i =1
. . .
N.
For each one of the N values of
TCexpVibi
, the corresponding pair of
TCexp Noisei
is calculated
as follows:
•HAV Energy Doses Dvibrationiare calculated for the TCexpVibi, i =1 . . . N.
Dvibrationi=a2
hveq TCexpVibi
2.52∗8(15)
Noise Energy Dose
Dnoisei
are calculated for i =1
. . .
N, maintaining the criterion that
the Combined Noise and HAV energy dose must be 1 at the most.
Dnoisei=1−Dvibrationi(16)
•
Finally
TCexp Noisei
is calculated, i.e., the maximum time given the calculated dose
Dnoisei
, i.e., the value corresponding to this pair (
TCexp Noisei
,
TCexpVibi
). For this calcu-
lation, TCexp Noiseiis given by:
TCexp Noisei=8∗Dnoisei∗1085−L Aeq,Ten
10 (17)
This procedure can be also replicated for the other case, i.e., when the fixed set of
values comes from times of noise exposure. In this case, the procedure will be as follows:
Step. 3.2. In the intervals of numbers ranging from 0 and
TCexp NoiseMa x
, it is fixed
a set of values (namely N values) for which it is desired to calculate the matching pairs
(
TCexp Noise
,
TCexpVib
). These values are denoted as
TCexp Noisei
=
TCexp NoiseMa x
* i/N, i =1
. . .
N.
For each one of the N values of
TCexp Noisei
, the corresponding pair of
TCexpVibi
is calculated
as follows:
•Noise Energy Doses Dnoiseiare calculated for the TCex pN oisei, i = 1 . . . N.
Dnoisei=TCex pNo isei
810LA eq,Ten−85
10 (18)
HAV Energy Dose
Dvibrationi
are calculated for I = 1
. . .
N, keeping the criteria that
the Combined Noise and Noise energy dose must be 1 at the most.
Dvibrationi=1−Dnoisei(19)
•
Finally, the it is calculated
TCexpVibi
, i.e., the maximum time given the calculated dose
Dvibrationi
, i.e., it is calculated the value corresponding to this pair (
TCexp Noisei
,
TCexpVibi
).
For this calculation, TCex pVibiis given by:
TCexpVibi=Dvibrationi∗2.52∗8
a2
hveq
(20)
Finally for each specific case of a worker, the matching pairs (
TCexp Noisei
,
TCexpVibi
) are
calculated that will keep the
Dcombined
index under 1. If the worker maintains below their
exposure times in these pairs, it is assured that the combined dose will be kept less than
1, and so the energy received by both vibrations and noise is below the values that the
standards consider as exposure values that give rise to an action. This is a safety measure
that safety managers may adopt to protect the workers from adverse health effects.
In the case that the worker’s exposure originates from a given machine that generates
both noise and vibrations, the procedure for the calculation of the recommended exposure
time based on the combined index becomes as follows:
Int. J. Environ. Res. Public Health 2022,19, 14345 14 of 23
1.
Let us suppose that a given worker uses a machine that generates noise and HAV
exposure to the worker. This machine is characterized by the noise level
LAeq,Ten
(noise equivalent level during a measurement time
Ten
) and HAV (measured as the
HAV equivalent continuous acceleration ahv,eq over the measurement time Tev).
2.
The criterion is that the Combined Noise and HAV energy dose becomes lesser
than 1, i.e.,
Dcombined =Dnoise +Dvibration =TCexp
810LA eq,Ten−85
10 +a2
hveqTCex p
2.52∗8≤1 (21)
So, the recommended exposure time TCexp can be obtained as:
TCexp ≤8
10LA eq,Ten−85
10 +a2
hveq
2.52
(22)
3.
The maximum exposure time
TCexp Max
can be calculated from the equation above
when the equality is accomplished:
TCexp Max =8
10LA eq,Ten−85
10 +a2
hveq
2.52
(23)
In this case the combined dose will be kept as 1, and so the energy received by both
vibrations and noise is below the values that the standards consider as exposure values
that give rise to an action. This can be a safety criterium that preventionists may adopt to
protect the workers from adverse health effects in case of combined exposure.
5. Application Example: Study Case in Workers in the Olive Sector
The proposed index can be applied to any activity where workers are exposed to both
noise and HAV simultaneously. As an example of its use the activity of olive harvesting by
hand-guided machines was selected in this research.
This study was carried out in Andalusia, a region located in the south of Spain, during
the harvesting period from November to March. As mentioned above, the number of
working days are accounted for as about 19 millions [
85
] in an average production season.
5.1. Data Acquisition and Measurement
In the olive sector there are a wide variety of hand-held machines that achieve fruit
detachment. In Andalusia, the most common used are the hook type olive harvesters, due
to their productivity and the minimum damage to the tree shoots (see Figure 5).
Int. J. Environ. Res. Public Health 2022, 19, x FOR PEER REVIEW 15 of 24
5. Application Example: Study Case in Workers in the Olive Sector
The proposed index can be applied to any activity where workers are exposed to both
noise and HAV simultaneously. As an example of its use the activity of olive harvesting
by hand-guided machines was selected in this research.
This study was carried out in Andalusia, a region located in the south of Spain, dur-
ing the harvesting period from November to March. As mentioned above, the number of
working days are accounted for as about 19 millions [85] in an average production season.
5.1. Data Acquisition and Measurement
In the olive sector there are a wide variety of hand-held machines that achieve fruit
detachment. In Andalusia, the most common used are the hook type olive harvesters, due
to their productivity and the minimum damage to the tree shoots (see Figure 5).
Figure 5. Hook type olive harvesters.
The hook type olive harvesters consist of a one-piece rod of variable length ranging
from 1.5 to 3 m with an inverted v-shaped end covered with shock-absorbing material.
The operating system differs from one brand to another, and most of them are petrol-
powered, with a two-stroke combustion engine of between 1 and 3.5 HP. The characteris-
tics of the measured machine are shown in Table 2.
Table 2. Measured machine. Noise and vibration values declared by the manufacturer.
Model
Engine cc
Power
Noise 1
Vibration 2
1
48.7 cm3
(3.0 HP)
(2.2 KW)
𝐿𝑒𝑞 = 102 dB(A)
𝐿𝑤 = 113 dB(A)
𝑎ℎ𝑣,𝑒𝑞 left = 5.7 m/s2
𝑎ℎ𝑣,𝑒𝑞 right= 5.7 m/s2
1 ISO 11201:2010 [102] Noise emitted by machinery and equipment. 2 ISO-20643:2008 [100] Mechan-
ical vibration. Hand-held and hand-guided machinery.
During the measurements, the worker was provided with the sensors and equipment
described in Section 3.2 Equipment Used. Figure 6 shows where the sensors were placed:
the vibration sensor in the palm of the hand and the noise sensor over the ears to register
the worker exposition. The data logger is placed in a bag to allow the operator to perform
his usual work operations. The vibration values of harvesters were measured and ana-
lysed for both right and left hands and the noise pressure level was measured at ear place
of the operator.
Figure 6. Worker equipped with hook type olive harvesters and measurement sensors.
Figure 5. Hook type olive harvesters.
The hook type olive harvesters consist of a one-piece rod of variable length ranging
from 1.5 to 3 m with an inverted v-shaped end covered with shock-absorbing material. The
operating system differs from one brand to another, and most of them are petrol-powered,
with a two-stroke combustion engine of between 1 and 3.5 HP. The characteristics of the
measured machine are shown in Table 2.
Int. J. Environ. Res. Public Health 2022,19, 14345 15 of 23
Table 2. Measured machine. Noise and vibration values declared by the manufacturer.
Model Engine cc Power Noise 1Vibration 2
148.7 cm3(3.0 HP)
(2.2 KW)
Leq = 102 dB(A)
Lw= 113 dB(A)
ahv,eq left = 5.7 m/s2
ahv,eq right = 5.7 m/s2
1
ISO 11201:2010 [
102
] Noise emitted by machinery and equipment.
2
ISO-20643:2008 [
100
] Mechanical vibration.
Hand-held and hand-guided machinery.
During the measurements, the worker was provided with the sensors and equipment
described in Section 3.2 Equipment Used. Figure 6shows where the sensors were placed:
the vibration sensor in the palm of the hand and the noise sensor over the ears to register
the worker exposition. The data logger is placed in a bag to allow the operator to perform
his usual work operations. The vibration values of harvesters were measured and analysed
for both right and left hands and the noise pressure level was measured at ear place of
the operator.
Int. J. Environ. Res. Public Health 2022, 19, x FOR PEER REVIEW 15 of 24
5. Application Example: Study Case in Workers in the Olive Sector
The proposed index can be applied to any activity where workers are exposed to both
noise and HAV simultaneously. As an example of its use the activity of olive harvesting
by hand-guided machines was selected in this research.
This study was carried out in Andalusia, a region located in the south of Spain, dur-
ing the harvesting period from November to March. As mentioned above, the number of
working days are accounted for as about 19 millions [85] in an average production season.
5.1. Data Acquisition and Measurement
In the olive sector there are a wide variety of hand-held machines that achieve fruit
detachment. In Andalusia, the most common used are the hook type olive harvesters, due
to their productivity and the minimum damage to the tree shoots (see Figure 5).
Figure 5. Hook type olive harvesters.
The hook type olive harvesters consist of a one-piece rod of variable length ranging
from 1.5 to 3 m with an inverted v-shaped end covered with shock-absorbing material.
The operating system differs from one brand to another, and most of them are petrol-
powered, with a two-stroke combustion engine of between 1 and 3.5 HP. The characteris-
tics of the measured machine are shown in Table 2.
Table 2. Measured machine. Noise and vibration values declared by the manufacturer.
Model
Engine cc
Power
Noise 1
Vibration 2
1
48.7 cm3
(3.0 HP)
(2.2 KW)
𝐿𝑒𝑞 = 102 dB(A)
𝐿𝑤 = 113 dB(A)
𝑎ℎ𝑣,𝑒𝑞 left = 5.7 m/s2
𝑎ℎ𝑣,𝑒𝑞 right= 5.7 m/s2
1 ISO 11201:2010 [102] Noise emitted by machinery and equipment. 2 ISO-20643:2008 [100] Mechan-
ical vibration. Hand-held and hand-guided machinery.
During the measurements, the worker was provided with the sensors and equipment
described in Section 3.2 Equipment Used. Figure 6 shows where the sensors were placed:
the vibration sensor in the palm of the hand and the noise sensor over the ears to register
the worker exposition. The data logger is placed in a bag to allow the operator to perform
his usual work operations. The vibration values of harvesters were measured and ana-
lysed for both right and left hands and the noise pressure level was measured at ear place
of the operator.
Figure 6. Worker equipped with hook type olive harvesters and measurement sensors.
Figure 6. Worker equipped with hook type olive harvesters and measurement sensors.
The measurements were carried out under real working conditions during a normal
working day in several plantations, all located in the region of Andalusia. The type of
plantation being studied is that of traditional olive tree plantations, with one or several
trunks, but with a single crown; the height of the top is variable, ranging from 3 to 5 metres,
and the worker moves around the tree (see Figure 7). The worker holds the tool with
both hands and places the hook on the medium-thick tree branch, the operation shortens
and lengthens the pole producing vibration on the tree to release the fruit (olives). In this
operation, the tool transmits HAV to the worker in both hands, and it emits noise.
Int. J. Environ. Res. Public Health 2022, 19, x FOR PEER REVIEW 16 of 24
The measurements were carried out under real working conditions during a normal
working day in several plantations, all located in the region of Andalusia. The type of
plantation being studied is that of traditional olive tree plantations, with one or several
trunks, but with a single crown; the height of the top is variable, ranging from 3 to 5 me-
tres, and the worker moves around the tree (see Figure 7). The worker holds the tool with
both hands and places the hook on the medium-thick tree branch, the operation shortens
and lengthens the pole producing vibration on the tree to release the fruit (olives). In this
operation, the tool transmits HAV to the worker in both hands, and it emits noise.
(a)
(b)
Figure 7. (a) Diagram of the worker’s position in the lateral view; (b) diagram of the worker’s posi-
tion in the front view.
The workers participating in this study were selected because they are qualified
workers with a large experience in the operation of selected machinery, according to the
characteristics included in the ISO 5349-1:2001 and ISO 5349-2:2002 [72,73]. The measure-
ment was carried out during their working day. The only criteria to select the workers
were those based on the experience regardless of their physical condition, sex or age. In
this case all the workers were male and aged between 30 and 60 years.
5.2. Measuring Results and Exposure Time Calculation
First of all, the process of characterization of the hook type olive harvesters in terms
of noise emission and HAV was performed. The measurements were taken according to
the ISO 5349-1:2001 and ISO 5349-2:2002 for HAV [72,73] and ISO 1999:2013 [101] for noise
assessment. The results obtained from the measurement of the model 1: hook type olive
harvesters are shown in Table 3.
Table 3. Noise and vibration values measured in simultaneous time periods (for each operator).
Operator
X m/s2
Y m/s2
Z m/s2
Vibration
𝒂𝒉𝒗
Arithmetic
Average
Noise
𝑳𝑨𝒆𝒒,𝑻
logarithmic
Average
1
2.707
5.609
2.553
6.731
97.3
3.105
3.508
2.506
5.312
93.8
4.069
3.926
2.239
6.081
94.2
6.714
5.176
3.010
8.996
96.7
2.698
2.767
2.104
4.400
90.6
6.304
95.1
2
2.917
3.999
1.409
5.146
96.4
2.301
3.720
2.352
4.966
97.7
1.455
2.633
0.985
3.165
82.6
1.834
1.869
1.070
2.828
94.2
5.135
12.488
3.560
13.964
97.1
6.014
95.6
Figure 7.
(
a
) Diagram of the worker’s position in the lateral view; (
b
) diagram of the worker’s
position in the front view.
Int. J. Environ. Res. Public Health 2022,19, 14345 16 of 23
The workers participating in this study were selected because they are qualified
workers with a large experience in the operation of selected machinery, according to the
characteristics included in the ISO 5349-1:2001 and ISO 5349-2:2002 [
72
,
73
]. The measure-
ment was carried out during their working day. The only criteria to select the workers were
those based on the experience regardless of their physical condition, sex or age. In this case
all the workers were male and aged between 30 and 60 years.
5.2. Measuring Results and Exposure Time Calculation
First of all, the process of characterization of the hook type olive harvesters in terms
of noise emission and HAV was performed. The measurements were taken according to
the ISO 5349-1:2001 and ISO 5349-2:2002 for HAV [
72
,
73
] and ISO 1999:2013 [
101
] for noise
assessment. The results obtained from the measurement of the model 1: hook type olive
harvesters are shown in Table 3.
Table 3. Noise and vibration values measured in simultaneous time periods (for each operator).
Operator X m/s2Y m/s2Z m/s2Vibration
ahv
Arithmetic
Average
Noise
LAeq,T
Logarithmic
Average
1
2.707 5.609 2.553 6.731 97.3
3.105 3.508 2.506 5.312 93.8
4.069 3.926 2.239 6.081 94.2
6.714 5.176 3.010 8.996 96.7
2.698 2.767 2.104 4.400 90.6
6.304 95.1
2
2.917 3.999 1.409 5.146 96.4
2.301 3.720 2.352 4.966 97.7
1.455 2.633 0.985 3.165 82.6
1.834 1.869 1.070 2.828 94.2
5.135 12.488 3.560 13.964 97.1
6.014 95.6
3
4.074 9.057 4.534 10.917 99.3
5.495 6.516 2.884 8.998 100.1
1.288 1.991 1.660 2.894 100.1
2.415 3.681 2.941 5.294 97.6
2.701 3.627 2.645 5.238 103.2
6.668 100.4
According to Equation (2) the obtained value of
ahv
is 6.33 m/s
2
. Likewise, the value
of LAeq,Tis 97.7 dB(A).
Once the hook type olive harvesters are characterized, two types of calculations are
performed. Firstly, the maximum exposure time for each one of the physical agents is
calculated independently. The criterion used was that of the previous Section 4, by keeping
the energy dose for noise and HAV physical agents up to 1 independently. Therefore,
Texp
for HAV was calculated in order not to exceed the EAV value of A(8) according to Table 1
(i.e., 2.5 m/s
2
) and in accordance with Equation (14). The same procedure was applied
to the calculation of
Texp
for noise. These calcultated exposure times coincide with the
so-called TCexpVibMax and TCex pNoiseMax according to Section 4(see Table 4).
Table 4. Maximum exposure times for noise and vibration taken independently.
Noise (Equation (13)) HAV (Equation (14))
TCexp NoiseMax =0.421 h TCexpVibMax =1.248 h
Int. J. Environ. Res. Public Health 2022,19, 14345 17 of 23
In this case, the recommended exposures times will be 0.421 h if noise is considered
and 1248 h if HAV is considered. However, in this case the worker is exposed to both
noise and HAV since the worker’s exposure originates from a given machine that generates
both noise and vibrations. In this case, the suggested procedure take into account both
exposures and the recommended maximum exposition time
TCexp Max
shall be calculated
according to Equation (23), the result being 0.315 h.
As can be expected, if we take into account both exposures, the recommended com-
bined exposure time
TCexp Max
is less than
TCexpVibMax
or
TCexp NoiseMa x
. Table 5lists the val-
ues of the
Dvibration
and
Dnoise
for this combined recommended exposure time
TCexp Max
,
by ensuring that the sum of both noise and HAV doses becomes equal to Equation (21).
Table 5. Dvibration
and
Dnoise
achieved for the combined recommended maximum exposure time
TCexp Max .
Dnoise (Equation (8)) Dvibration (Equation (10))
0.748 0.252
The value of A(8) according to Equation (1) is 1.3 m/s
2
and the value of
LAeq,d
is
83.7 dBA. As can be seen, both are below the EAV values listed in Table 1.
6. Discussion and Limitations of the Suggested Approach
Simultaneous exposure to HAV and noise is common in different industrial and
construction or production sectors. There are two possible situations where the worker
becomes exposure to both physical agents:
(1)
There are two different sources that may affect the worker; one being workers who
are exposed to HAV through the normal operation of machinery and the other being
another source not in contact that emits noise whose wave propagation reaches the
worker. Since there is simultaneous exposure to both noise and HAV, the activity
implies the worker receives exposure to both agents and it should be considered
preventively.
(2)
The second general possibility is that there is one single source or machine, which
transmits both agents simultaneously to the worker.
Of course, both situations may also appear in some specific situations.
The proposal in this research seeks to propose a recommended time exposure in both
cases considered above. In the first case, when the worker is exposed to two or more sources,
but the activity implies that they operate simultaneously, the maximum exposure time for
noise and HAV can be calculated for both sources, so as not to exceed the maximum dose
values. In this case two maximum recommended times are obtained for the two agents,
so the safety manager should choose the lower of the two to maintain the combined dose
as less than one. Another situation in this case can also arise if during a working day the
worker receives HAV from one machine and noise from another source, but the activity
does not involve simultaneous operation. The safety manager will allow each machine
to be used for the maximum time calculated for an 8-h working day and which does not
exceed the EAV values shown in Table 4.
In the second case, the noise and HAV comes from the same source as is usual in most
sectors the machinery that transmits HAV also emits noise, so the worker receives both
energies at the same time. The suggested procedure calculated a recommended exposure
time using this machine to avoid the combined dose to be exceeded. This case was the
study case shown in the preceding section where the recommended time was 0.315 h, less
than the 0.421 h if only noise is considered or 1248 h if only HAV is considered.
It should be pointed out that this research was made considering real data in the olive
sector, where the workers’ exposure comes from hook type olive harvesters such as those
considered in the preceding section. Nevertheless, it can be considered for other cases
where the reduction in the recommended exposure time becomes greater.
Int. J. Environ. Res. Public Health 2022,19, 14345 18 of 23
Concerning the underlying assumptions of the proposed procedure,
Hypotheses 1 and 2
summarise the main results on which the proposed approach is based. The main assump-
tion is that the total effect caused by a combination of noise and vibration can be determined
from a summation of the energy received by the worker coming from noise and vibration
sources. This does not deny the possibility of synergistic effects on combined health effects,
but it assumes that the sum of energies from noise and vibration sources limits the exposure
time in an additive way. This approach may be logical, unless further information related
on that the effects are synergistic or complex interaction model are available. At the current
stage of knowledge, this combined effect could be considered as additive as an initial
approach. This approach is similar, for example, to that assumed with chemical agents in
those cases where there is not established a complex interaction model.
In this regard, the literature on health effects on combined exposure to both noise and
vibration is not conclusive. Most of the research establishes the appearance of combined
effects, and some of them indicates the possibility of synergistic effects but without a clear
underlying model or pattern. For this research, we adopt the main ideas suggested in the
literature review, i.e.,
(a) There is a relationship between noise and HAV, and so there are combined effects
that demand efforts aimed at reducing and managing occupational noise and vibration
exposures. The current occupational and environmental noise regulations may signifi-
cantly underestimate the adverse health and societal cost of noise-induced hearing loss
Shepard et al. [34], and so other approaches as suggested in this proposal may be useful.
(b) The results indicate that there are interactions between noise and vibration, but the
effect may not be simple or consistent in some studies. A reasonable approximation to the
total annoyance caused by a combination of noise and vibration can be determined from a
summation of the effects of the individual agents Howart H, Griffin M. [
105
]. This is the
approach followed in this research.
The hypothesis that the energy levels are summative represents a valuable measure of
combined exposure while no other specific information is available or tested. Nevertheless,
if synergistic effects are considered or more complex interaction models are proven or
needed in some cases, the proposed additive model on energies may be no longer valid and
it may underestimate effects of combined exposure. This fact results in a limitation of the
proposed model and for those cases where these synergistic effects are clear, this procedure
should be applied with caution, and its results should be considered as a first guide to
reduce exposure. In this case, the suggested procedure should be revised introducing a new
index definition based on the more complex interaction models from the synergistic effects.
Therefore, this suggested index and this proposal should be applied with caution in
those cases where it is suspected the appearance of complex or synergistic interactions
between noise and vibration. In this case, an approach taking into account not only energy
of signals but also some other parameters could be a good starting point to tackle the
problem of specific health effects or more complex interactions. For example, differences in
exposure characteristics of the physical signals in terms of peak levels, number of peaks,
frequency of peak levels, noise and HAV spectrum etc., specific energy levels for a certain
noise exposure or a certain HAV level as occupational stressors could be some interesting
parameters to deal with in these cases and a future field or research.
In summary, this paper has suggested a procedure for the calculation of a recom-
mended maximum exposure time, taking into account the amount of energy received by
the workers. The effects of noise and HAV on the workers’ health depend on the energy
dose received by the workers. The Directive-2003/10/EC [
75
] established the Upper EAV
for the daily (8 h) Equivalent Continuous Noise Pressure Level in dB(A)) and Directive
2002/44/EC [
68
] establishes the EAV for the daily (8 h) Acceleration Exposure A(8). These
limits are defined for the analysis of individual agents based on the wave and vibration
energy received by the workers. The assumption of the simultaneous exposure should be
considered, and as the energy dose is coming from both agents, the suggested procedure
proposes a recommendation to limit the time exposure of the worker when both agents are
Int. J. Environ. Res. Public Health 2022,19, 14345 19 of 23
present, to be sure that the values for an action to be taken are not exceeded for both agents.
The proposal should be considered as a recommendation based on the amount of total
energy received with reference to the total dose for both agents, and it does not consider
possible synergetic effects or combined health issues arising for combined expositions,
since in this case most tighter recommendations should be taken into account.
Finally, although equal relevance has been established in the suggested procedure in
Equation (11) for the two physical agents, the safety manager could decide to apply different
relevance to one or other of the agents, based on the data or medical record of the worker.
For example, in cases of previous hearing impairment or hand-arm vascular problems,
different values for the weighting w
1
or w
2
in Equation (11) could be selected for the process
of calculating the combined dose. Thus, the exposure times can be calculated taking into
account this different relevance of both physical agents using the same procedure described
in the application example. It should be noted that this research does not seek to define
or establish any new criteria levels or standards, but only a combined use of energy doses
from these standards is suggested as a tool to establish recommendations for exposure
in workers. As it was commented in the introduction, this approach is similar to other
well-established procedures in the scientific literature based on the current knowledge on
the combined health effects. It provides a method to calculate exposure times beyond other
hands-on criteria or broad guides based on practice rather than theory. In future research
it will be studied how the weighting factors
w1
or
w2
in Equation (11) can be selected to
take into account particular variables such as the specific tasks performed by the worker,
previous pathologies and susceptibility of the worker to any of these physical agents. In
this future approach, the safety manager expertise will be embedded in a procedure based
on multicriteria decision-making techniques.
7. Conclusions
This paper suggests a combined energy dose index to be taken as a basis for the calcu-
lation of a recommended maximum exposure time based on the criterion of not exceeding
the Exposure Action Value for noise and HAV. Based on this combined index, several
situations can arise, and the suggested procedure allows the maximum recommended
times for noise or HAV in the case of multiple sources operating simultaneously or not,
and the maximum recommended exposure time in the case of one source simultaneously
generating HAV and noise to be calculated.
The application of this index in either of the two situations would always offer expo-
sure times below the exposure times calculated if both agents are considered independently.
This procedure should be considered as an aid to the safety manager to ensure the health
of workers and as a precautionary measure for workers with simultaneous exposure to
both agents.
Future research will be devoted to further characterise and analyse the use of this
methodology based on this energy dose combined index in workers not only in the olive
sector, but also from other industrial sectors which operate with different machinery
generating both noise and HAV. In addition, how to provide a way to integrate specific
health issues of workers in the combined index will be explored.
Author Contributions:
R.N.-Á., M.L.d.l.H.-T. and A.J.A.: conceptualization, performed the experi-
ments, formal analysis and carried out the post-processing; M.D.M.-A. and D.P.R.: conceptualiza-
tion, project administration, drafting of the manuscript; funding acquisition and supervising the
manuscript. All authors have read and agreed to the published version of the manuscript.
Funding:
This work has been supported by the State Research Agency (SRA) of Spain and European
Regional Development Funds (ERDF) under project PID2019-108761RB-I00.
Institutional Review Board Statement: Not applicable.
Informed Consent Statement: Not applicable.
Data Availability Statement: Data are provided upon request to the corresponding author.
Int. J. Environ. Res. Public Health 2022,19, 14345 20 of 23
Acknowledgments:
Authors wish to thank the anonymous reviewers whose interesting comments
helped to improve the paper.
Conflicts of Interest: The authors declare no conflict of interest.
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