Musculoskeletal Disorders of Refuse Collectors emptying ...

Human Factors & Ergonomics Society of Australia 42nd Annual Conference 2006 1

Musculoskeletal Disorders of Refuse Collectors emptying litter bins which
are housed inside street furniture.

Jennie Window
Safety Advisor, General Motors Holden
(formerly OH&S Consultant, Adelaide City Council)
Postgraduate Student: Occupational Health & Safety Management, University of Adelaide
Human Factors & Safety Management Systems, University of South Australia

Valerie O’Keeffe
Lecturer, University of Adelaide, Public Health, Thebarton, South Australia.

Keywords: Workplace Musculoskeletal Disorders, Nordic Questionnaire, Rapid Entire Body
Assessment, Manual Tasks Risk Assessment

ABSTRACT

The purpose of the paper is to identify and analyse potential Workplace Musculoskeletal
Disorders for workers collecting refuse from litter bins, and test the hypothesis that “A low entry
vehicle will significantly reduce the incidence of Workplace Musculoskeletal Disorders
experienced by refuse collection workers”. A small cohort of refuse collection workers employed
by Local Government participated in the study. Refuse worker's shoulder and lower back regions
were identified in the literature review as high risk areas for developing Workplace
Musculoskeletal Disorders. This finding was supported by the results of the Nordic Questionnaire.
The quick ergonomics assessment tools Rapid Entire Body Assessment and the Manual Tasks
Risk Assessment identified the leg, arm and back regions as being the body areas most at risk of
developing Workplace Musculoskeletal Disorders. The Manual Tasks Risk Assessment also
identified the shoulder area as being at risk. The worker entering and exiting the driver's cabin of
the garbage truck was identified as the task with the highest risk of developing Workplace
Musculoskeletal Disorders.

1. Introduction

Waste Management Industries in many countries have addressed the manual handling problems
associated with the lifting and/or carrying of awkward items by changing the refuse collection containers
from bags and bins to two- or four-wheeled containers (Schibye et al. 2001). Automated, side arm refuse
trucks have virtually eliminated the incidence of manual handling tasks from domestic refuse collection.
However, refuse collection in the business sector and public domain (parks, streets, shopping precincts)
has not eliminated manual handling tasks, but merely altered manual handling processes from lifting,
carrying and lowering to pushing and pulling.

2. Background

Manual handling activities and complex/awkward postures are closely associated with Workplace
Musculoskeletal Disorders. The emptying of refuse from litter bins, which are housed inside street
furniture, requires the worker to adopt awkward postures for short periods of time when entering/exiting
the vehicle, and performing various manual handling tasks with the street furniture, the bin and the
controls of the garbage compactor.

Litter bins located on pavements, close to roadways are relatively easy to access. The two wheeled bin
can easily be pushed or pulled along the path to the garbage compactor. However, litter bins located in
parks and gardens are more difficult to work with. Higher forces are required to push or pull a full wheelie
bin across soft or wet lawn, pine bark, mud or soil than over paving.

Human Factors & Ergonomics Society of Australia 42nd Annual Conference 2006 1

In the past, Local Government Organisations used metal bins housed inside cylindrically shaped street
furniture in parks and streets. The manual handling processes used to empty these bins (bending, lifting
and carrying) presented a relatively high risk of developing Workplace Musculoskeletal Disorders.
Alternative street furniture housing wheelie bins are being introduced in an attempt to eliminate or reduce
these risks.

Photo 1.Cylindrically shaped street furniture Photo 2.Street furniture containing two-wheeled
containing metal bins. plastic bins.

2.1 Workplace Musculoskeletal Disorder Research Literature

Extensive electronic searches for Workplace Musculoskeletal Disorders in the Waste Management
Industry were carried out via the Internet resource MedLine and the Google search engine. Although six
research articles/ reports relating to Workplace Musculoskeletal Disorders in the Waste Management
Industry were found, none of them had information about refuse collection from litter bins.

The six sighted refuse collection research articles/reports dealt primarily with manual handling. None of
these studies addressed the ergonomic issues of work flow or the psychosocial environment.

The investigators at the Florida Centre for Solid and Hazardous Waste Management found that the rates
of injury for municipal workers in Florida and Denmark were six to seven times greater than those of the
general work force (BOMEL 2004). Poulsen et al (1995) is quoted in BOMEL (2004) as stating that refuse
collectors are 1.9 times more likely to develop musculoskeletal problems than the rest of the population.

Pinder & Milnes (2002) quoting a study by Stassen et al. (1992) claim that waste collection using
domestic sized wheelie bins can result in unacceptably high metabolic loads. However, Pinder & Milnes
(2002) goes on to state that the study carried out by Markslag et al (1993) showed that the metabolic
demands were greater during carrying and throwing 7kg bags than during pushing and pulling wheelie
bins.

De Looze et al (1995) reports that the frequency of stressful events in the field is lower in the mini
container (wheelie bin) method than the bag method.

3 Historical Injury Statistics

Historical injury statistics for the Waste Management Services Business Sector were sourced from
WorkCover SA. Employer injury statistics were provided by the Adelaide City Council.

During 2003/04 in the South Australian Waste Management Services Business Sector, 14% of the injury
claims were made by garbage collectors. This increased to 25% for long term injury claims. During
2003/04 in the South Australian Waste Management Services Business Sector, 14% of the injury claims
were made by garbage collectors. This increased to 25% for long term injury claims. The recorded
mechanism of injury for these long term injury claims are: body stressing (37%); handling objects other

Human Factors & Ergonomics Society of Australia 42nd Annual Conference 2006 2

than lifting (13%); and handling refuse or waste bins (22%)

Between January 2003 and November 2005 the City Operations Department of the Adelaide City Council
recorded fifteen injuries which are relative to this study. Forty seven percent of these relevant injuries
resulted in muscular strain. Back injuries accounted for 25% of these injuries; leg injuries 20%; hand
injuries 9% and shoulder/neck injuries 21%. No injury data was available from the other Local
Government Organisation that participated in the study.

4. Methodologies Used

The methodologies used are (a) the Nordic Standard Questionnaire; (b) Stress Satisfaction Offset
Questionnaire; (c) Rapid Entire Body Assessment (REBA); and (d) Manual Task Assessment Tool
(ManTRA). To facilitate the use of REBA and ManTRA, the litter bin refuse collector’s work was
separated into eight different tasks, six of which are shown in the photographs below.

(1) exiting truck cabin (2) open litter bin surround (4) operating compactor

(5) closing litter bin surround (6) entering truck cabin (7) mounting riding platform

Photo 3. Work Tasks performed during the collection of refuse from litter bins.

These work tasks are : (1) exiting the truck cabin; (2) opening the litter bin surround; (3) wheeling the bin
to the compactor; (4) operating the compactor; (5) wheeling the bin back to the litter bin surround; (6)
entering the truck cabin; (7) mounting the riding platform; and (8) dismounting the riding platform.

Each of these work tasks were further broken down into a number of actions. The assessments of these
actions were entered into the REBA data table, and the ManTRA data table. The REBA and ManTRA
results were then compared with the results of the Nordic Standard Questionnaire.

The Stress Satisfaction Offset Questionnaire was used to identify if there were any underlying
psychosocial issues contributing to Workplace Musculoskeletal Disorders.

Human Factors & Ergonomics Society of Australia 42nd Annual Conference 2006 3

4.1 Difficulties With The Methodologies Used

Workers exhibited a reluctance towards participating in the study. The majority of these workers had
experienced a departmental restructure twice in the past eighteen months and initially treated any attempt
at observations or questionnaires with suspicion or mistrust. Only a small number of people (7) agreed to
participate.

It is difficult to ascertain if all of the Workplace Musculoskeletal Disorders experienced by the workers
were reported. Experience has shown that the rate of reporting minor physical problems is quite low
unless encouraged (Safetyline Institute 1998). Also, reliance on the accuracy of the information
presented by participants in the historical data section of the Nordic Standard Questionnaire tends to be
low due to the trend that participants could not recall symptoms in the past, in particular the symptoms of
low severity (Kaewboonchoo et al 1998).

Historical injury statistics may be inaccurate. A common problem in interpreting injury statistics is that
sudden on-set injuries (such as sprains and strains resulting from a fall) are often in the same category as
gradual-onset injuries diagnosed as some kind of musculoskeletal disorder, for example repetitive strain
injury (Macdonald 2004).

5. Results

It is assumed that the participants of the study are an accurate representation of refuse workers who work
with two wheeled bins. The results of the Stress Satisfaction Offset Questionnaire indicated that 68% of
the participants do not have a compounded risk of developing Workplace Musculoskeletal Disorders due
to psychosocial factors.

5.1 Results - Nordic Standard Questionnaire

All of the participants are male. All of them have been working with wheelie bins for over 12 months. Four
of the seven participants work 100% of the time collecting refuse from litter bins. The other 3 participants
work at the Adelaide Central Market where approximately 40% of their work involves the emptying of
refuse from 2 wheeled bins.

Three of the seven participants are aged between 25-30 years old. Four of the seven participants are
aged between 40-45 years old. All of the participants have played in a football or soccer team. Six of the
seven participants have sustained an injury (in the past) while playing sport. Two of the participants have
sustained a sports injury in the same body region (shoulders) as the location of the pain experienced in
the 12 months prior to the study and also during the participation of the study.

All of the participants remember experiencing pain in at least one body region during the 12 months prior
to the study and also during the participation of the study. Pain in the ankles and feet has been
experienced by five of the seven participants during the twelve months prior to the study, with three of the
participants also experiencing pain in this region during the study. Shoulder pain was experienced by five
participants during both time frames.

During the seven days prior to the study, six of the participants experienced pain in the wrists and hands,
five of the participants experienced pain in the shoulders, and four of the participants experienced pain in
the lower back (refer Table 1).

During the seven days prior to the study, one participant perceived his muscular aches/pains as being at
a higher level or intensity than the other participants. Five of the seven participants perceived muscular
problems in the neck, shoulders, and wrists/hands as being a niggle or annoying. Four of the seven
participants perceived muscular problems in the ankles/feet, knees and lower back as being an
ache(refer Table 1). Only two of the participants have reported a Workplace Musculoskeletal Disorder.

Human Factors & Ergonomics Society of Australia 42nd Annual Conference 2006 4

Body Participant ID

Location 123 4 5 6 7

Elbows 4

Ankles/ Feet 34 3

Knees 4

Lower Back 35 2 3

Upper Back 3

Neck 2

Upper Arm

Wrist/ Hand 2 22 1 2 1

Shoulders 2 23 3 2

Severity of Pain Niggle Annoying Ache Pain Very Painful
Corresponding No. 1 2 3 4 5

Table 1. Severity of pain experienced at work by participants in the 7 days prior to the study.

During the seven days prior to the study and also during the study participant number 4 perceived
muscular aches/pains in more body areas than any of the other participants. Participant number four also
perceived his muscular aches/pains as being at a higher level or intensity than the other participants.

Four of the seven participants perceived muscular problems in the shoulders as being an ache. Two
participants perceived their shoulder muscular problems as a pain. Five of the seven participants
perceived muscular problems in the lower back, with four of them identifying it as an ache. Five of the
participants perceived muscular problems in the upper arm. Three of these participants identified the
muscular problem as a niggle. Three of the participants perceived muscular problems in the ankles and
feet. Two identified the problem as an ache, however one identified the problem as very painful (Table 2).

Body Participant ID

Location 123 4 5 67
3
Elbows

Ankles/ Feet 35

Knees

Lower Back 1 3 3 3 3

Upper Back

Neck

Upper Arm 1 1 4 13

Wrist/ Hand 4

Shoulders 333 4 3 4

Severity of Pain Niggle Annoying Ache Pain Very Painful
Corresponding No. 1 2 3 4 5

Table 2. Severity of pain experienced at work during the study.

5.1 Results - Rapid Entire Body Assessment & Manual Task Assessment Tool

Each of the work tasks were further broken down into a number of actions. In the majority of cases the
Rapid Entire Body Assessment (REBA) and the Manual Task Assessment Tool (ManTRA) identified the
same work task action as having a high risk factor for developing Workplace Musculoskeletal Disorders.
However, the REBA and the ManTRA did not, on all of these occasions, allocate the same level of risk to
the work task.

In over 50% of the observed postures for entering and exiting the truck cabin, the legs and arms are

Human Factors & Ergonomics Society of Australia 42nd Annual Conference 2006 5

identified as being at risk of developing Workplace Musculoskeletal Disorders by both REBA and
ManTRA.

When the worker was opening and closing the litter bin surround, REBA identified the arms, wrists and
hands as being at risk of developing Workplace Musculoskeletal Disorders. For this work task, ManTRA
identified that the neck and shoulders are at risk of developing Workplace Musculoskeletal Disorders.
These results for both REBA and ManTRA were observed in 75% of the observed postures for opening
and closing the litter bin surround.

When the worker was operating the controls of the garbage compactor, both REBA and ManTRA
identified that the arms, hands and wrists are at risk of developing Workplace Musculoskeletal Disorders.
ManTRA identified this in four of the nine (44%) observed postures. However the REBA only identified
this in one of the postures (11%).

When the worker was mounting and dismounting the riding platform of the garbage compactor REBA
identified that all body regions are at risk of developing Workplace Musculoskeletal Disorders during 25%
of the observed actions. ManTRA identified that only the legs were at risk of developing Workplace
Musculoskeletal Disorders for 25% of the time and the back 50% of the time.

5.2 Results Summary - Rapid Entire Body Assessment & Manual Task Assessment Tool

To facilitate the comparison of data obtained from REBA and ManTRA, it was decided to convert the
percentage data into a number to represent low, medium, high or very high posture risks (Table 3). The
summary results are for REBA in Table 4 and ManTRA in Table 5.

1 = low 2 = medium 3 = high 4 = very high
0 – 29% 30 – 59% 60 – 84% 85 – 100%

Table 3. Percentages representing the four levels of risk.

All body areas were identified having a medium risk of developing a Work Place Musculoskeletal Disorder
when the worker was entering and exiting the truck cabin (Tables 4 and 5).

Work task Legs Back Shoulder arms

Entering truck cabin 2 2 2 2
Exiting truck cabin 2 2 2 2
Opening bin surround 0 0 0 3
Closing bin surround 0 0 0 3
Operating compactor 0 0 0 1
Mounting riding platform 1 1 1 1
Dismounting riding platform 1 1 1 1

Table 4. High risk posture areas identified by REBA

Work task Legs Back Shoulder arms

Entering truck cabin 22 2 2

Exiting truck cabin 22 2 2

Opening bin surround 00 3 0

Closing bin surround 00 3 0

Operating compactor 00 0 2

Mounting riding platform 20 0 0

Dismounting riding platform 1 2 1 1

Table 5 High risk posture areas identified by ManTRA

Human Factors & Ergonomics Society of Australia 42nd Annual Conference 2006 6

During all work tasks, REBA identified the arms as having a high risk of developing a Work Place
Musculoskeletal Disorder (Table 4). The high risk was identified during the third and fourth task which
involved opening and closing of the litter bin surrounds (Graph 1).

Arm Injury Risk Levels Shoulder Injury Risk Levels

REBA ManTRA REBA ManTRA

3.5 3.5
3 3

2.5 2.5
2 2

1.5 1.5
1 1

0.5 0.5
0 0
T1 T2 T3 T4 T5 T6 T7 T1 T2 T3 T4 T5 T6 T7

Work Task Work Task
Injury Level
Injury Level

Graph 1. Arm injury risk level comparisons Graph 2. Shoulder injury risk level comparisons

During five of the seven work tasks ManTRA identified the shoulders as having a high risk of developing a
Work Place Musculoskeletal Disorder (Table 5). The high risk was identified during the third task and the
fourth task which involved opening and closing of the litter bin surrounds (Graph 2).

6. Discussion

Complex/ awkward postures and manual handling activities are closely associated with Workplace
Musculoskeletal Disorders. Waste Management Industries in many countries have addressed the manual
handling problems associated with the lifting and or carrying of awkward items by changing the refuse
collection containers from bags and bins to two - or four - wheeled containers (Schibye et al 2001). This
has not eliminated the manual handling tasks, but merely altered the manual handling process from
lifting, carrying and lowering to pushing and pulling.

Observations made during the work task analysis for the emptying of litter bins identified that the pushing
and pulling of wheelie bins does not occur in isolation. The work process also requires the worker to
adopt awkward postures for short periods of time when entering/exiting the vehicle, and performing
various manual handling tasks with the street furniture, the wheelie bin and the controls of the garbage
compactor.

Two of the Internet accessed reports found that the acts of pushing and pulling wheelie bins are a causal
factor of lower back pain (Pinder & Milnes 2002; and Schibye et al 2001). Larsen et al (2002) claim that it
is the shoulders and not the lumbar area that is affected by pushing and pulling wheelie bins. This is
supported by the findings of Dr Frings-Dressen (e-mail November 2005) where the main musculoskeletal
complaint experienced by 94 refuse collectors was in the shoulder region. Hoozemans et al (2002) and
Larsen et al (2002) also concluded that the container weight affected the magnitude of the load on the
shoulders.

It is not the intention of this study to prove or disprove the findings in published studies, but to build upon
these findings by taking into account the ‘real-life’ work postures and activities carried out before and after
the two-wheeled bins are pushed or pulled from the litter bin surround, to the compactor and then back
again.

The Standard Nordic Questionnaire identified that five of the seven participants (71%) experienced pain
in the shoulders. This supports the findings of Larsen et al (2002) and Dr Frings-Dressen (e-mail
November 2005) that the main musculoskeletal complaint experienced by refuse collectors was in the

Human Factors & Ergonomics Society of Australia 42nd Annual Conference 2006 7

shoulder region. The Standard Nordic Questionnaire also identified that four of the seven participants
(57%) experienced pain in the ankle/feet, knees and lower back. It is interesting to note that the memory
of pain severity experienced in the past (Table 1) was at a higher level for five of the seven participants
than the pain severity experienced during the study (Table 2).

The REBA and ManTRA results (Tables 5 & 6) identified that the postures used when entering and
exiting the truck cabin produced a medium level of Workplace Musculoskeletal Disorder risk for all body
regions. However, for the postures used when the worker opened and closed the street furniture, a high
level of Workplace Musculoskeletal Disorder risk was present for the arms (REBA – Graph 1) and the
shoulders (ManTRA – Graph 2).

Unfortunately, the results of this study can not be used with any confidence due to the small cohort size
used in the investigations. The REBA and ManTRA results indicate that postures used when opening
and closing of the litter bin surrounds may be a contributing factor in the development of shoulder
discomfort experienced by the workers. Also, the postures used when climbing in and out of the truck
cabin may be a contributing factor for all of the body regions.

7. Conclusion

Refuse collectors are 1.9 times more likely to develop musculoskeletal problems than the rest of the
population (Poulsen et al 1995 quoted in BOMEL 2004). In South Australia, the handling of refuse bins
accounts for 22% of long term injury claims. The handling of the two wheeled garbage bins was not
identified as a contributing factor in the development of Workplace Musculoskeletal Disorders. However,
the postures associated with the opening and closing of litter bin surrounds was identified as a cause of
pain in the shoulder region. The action of entering and exiting the truck cabin was also identified as a
contributing factor for developing Workplace Musculoskeletal Disorders in all regions of the body. Due to
the small cohort size used in the investigations, the hypothesis “A low entry vehicle will significantly
reduce the incidence of Workplace Musculoskeletal Disorders experienced by refuse collection workers”
could not be tested. Further work, using a larger cohort needs to be carried out to determine the
Workplace Musculoskeletal Disorder risk levels for refuse collectors handling two wheeled bins.

REFERENCES:

BOMEL (2004) Mapping Health & Safety Standards in the UK Waste Industry. HSE Report 240.

de Looze MP, Strassen AR, Markslag AM, Borst MJ, Wooning MM, Toussaint HM (1995) Mechanical
loading on the low back in three methods of refuse collecting. Ergonomics. 1995 Oct;38(10)1993-2006.

Kaewboonchoo O, Yamamoto H, Miyai N, Mirbod S, Morioka I and Miyashita K (1998) The Standardized
Nordic Questionnaire Applied to Workers Exposed to Hand-Arm Vibration. Journal of Occupational Health
1998; 40:218-222

Laursen B, Schibye B (2002) The effect of different surfaces on biomechanical loading of shoulder and
lumbar spine during pushing and pulling of two-wheeled containers. Applied Ergonomics 2002 March;
33(2):167-74.

Macdonald W. (2004) Workload, stress and psychosocial factors as hazards for musculoskeletal
disorders. Journal of Occupational Health Safety - Aust NZ 2004, 20(1):37-47.

Pinder A & Milnes E (2002) Manual Handling in refuse collection. H&S Laboratory. Sheffield.

Safetyline Institute (1998) Manual Handling - Self Reporting: Consult with employees and Supervisors.
www.safetyline.wa.gov.au/institute/level2/course17/lecture49/148_03.asp

Schibye B, Sogaard K, Martinsen D, Klausen K (2001) Mechanical load on the low back and shoulders
during pushing and pulling of two-wheeled waste containers compared with lifting and carrying of bags
and bins. Clin Biomech (Bristol, Avon). 2001 Aug; 16(7):549-59.