ERGONOMICS IN AGRICULTURE:

WORKPLACE PRIORITY SETTING IN THE NURSERY INDUSTRY

James M Meyers Center for Occupational and Environmental Health

University of California, Berkeley 1301 S. 46th St., Bldg 112

Richmond, CA 94804-4603

John A Miles Biological and Agricultural Engineering Department

University of California at Davis Davis, CA 95616

Julia Faucett

Occupational Health Nursing Program University of California

San Francisco, CA 94143-0608

Ira Janowitz Ergonomics Program

University of California, Berkeley 1301S. 46th St., Bldg 112 Richmond, CA 94804

Diana G Tejeda

UC South Coast Research & Extension Center 7601 Irvine Blvd. Irvine, CA 92781

John N Kabashima

UC South Coast Research & Extension Center 7601 Irvine Blvd. Irvine, CA 92781

ABSTRACT Agriculture is generally recognized as the nation's most hazardous industry and although it displays high rates of musculoskeletal disorders with evidence to suggest that ergonomic risk factors are involved, there is very little history of application of ergonomic approaches in agricultural workplaces. A three-year National Institute of Occupational Safety and Health-supported study has been initiated in California nurseries to describe and design engineering interventions for priority musculoskeletal disorders. In this article, are reported the results of the project's initial workplace job task screening for ergonomic risk factors and associated musculoskeletal disorder reports to define priority ergonomic risk factors for the nusery industry and selected priority job tasks for intervention. Revised 1/97

ERGONOMICS IN AGRICULTURE:

WORKPLACE PRIORITY SETTING IN THE NURSERY INDUSTRY

Introduction

For the past several years, agriculture has been generally regarded as the Nation's most hazardous

industry in which to work. However, there is almost no history of work on ergonomic risk

factors in agriculture. Review of reported occupational injuries in California agriculture for the

period 1981-1990 by AgSafe (1) shows that sprains and strains predominate as a major type of

injury, accounting for 43% of all reported agricultural occupational injuries. Further, it was

estimated by AgSafe (1) that nearly 40% of the reported sprain and strain injuries involved the

back. Back injuries are generally acknowledged by agricultural employers and worker's

compensation insurers as a significant problem from the perspectives of both incidence and cost.

When these data were combined with a reported citation of over-exertion as injury cause of 25%

of all injuries, interest was stimulated in a search for practical, cost-effective ergonomic

interventions which might begin to address this problem in agriculture.

For initial inquiry into the ergonomics of musculoskeletal disorders in agriculture, nurseries were

chosen for three primary reasons:

1. Nurseries feature a comparatively stable workforce from year to year;

2. Nurseries share many workplace characteristics with manufacturing industries

in which much previous ergonomic intervention research had been performed; and

3. Nurseries constitute a major sector of California agriculture, and share many

workplace and workforce characteristics with other agricultural commodities.

It should also be noted that according to the AgSafe data (1), nurseries shared with other

agricultural commodities a pattern of high rates of sprain and strain injuries. The AgSafe data

(1) suggested that 48.9% of all reported injuries in horticultural specialties (including nurseries)

were sprains and strains, slightly above the proportion for agriculture as a whole. Over-exertion

as a cause of injury for this area was cited for 30.2% of reported injuries, also above the general

proportion for the industry as a whole.

Agricultural Industry Cooperators

Three nursery companies are formally cooperating in the project. All three specialize in

container grown outdoor bedding and ornamental plants, primarily for delivery to retail

nurseries. These cooperators are all large operations by industry standards, and between them

account for some 1290 employees at the involved worksites. This industry is almost completely

non-union in California, and there is no active union representation at any of the cooperator

sites. The majority of workers in these operations are Spanish-speaking, from Mexico or Central

America. They earn an average of about $5.00 per hour. Nursery work is considered a

comparatively good job by most California agricultural workers because it is year-round,

relatively well-paid, and at these sites includes health benefits. All of these cooperators have

active and well-planned injury and illness prevention programs on-site. Provision of worker's

compensation insurance benefits is required in California.

Nursery Work Organization

Operations at most California nurseries of this type follow a similar four-part organization;

1. Propagation

New plants are started in a specialized area. Four different methods are commonly

utilized - cuttings from mature plants, tissue culture, seeds, and grafting. Propagation

includes greenhouse maturation. Characterized by highly repetitive, hand-intensive work.

2. Canning

As plants grow they are replanted in individual plastic containers called "cans" (typically

2-3 times). A powered conveyor is used from which cans are loaded onto trailers by hand

for field transport. Characterized by repetitive pinching and other hand-intensive activities,

and repetitive upper extremity lifting and bending to off-load the conveyor.

3. Field Work

Plants are held in outdoor groups until fully mature. During this period tasks include

watering,

pruning, fertilizing and weeding, tying-staking-shaping, and spacing as plants grow.

Characterized by prolonged stooping, frequent lifting, and hand-intensive tasks.

4. Shipping

When plants are fully mature, they are removed to the shipping area, labeled, organized by

order load, and loaded into trucks. This operation can also include truck unloading at retail

sites. This work is characterized by frequent stooping, lifting and carrying.

Method

This project's overall goal is to develop and assess the preventive efficacy of applications of

previously validated ergonomic approaches for agricultural work. The overall project will

employ a pre-post design to collect and analyze data from injury/illness incidence, ergonomic

risk factors, and productivity and worker acceptance measures. The necessary first step of

identification and analysis of injuries related to ergonomic causal factors and designation of

priority intervention targets is highlighted here.

Specific objectives for this phase of the project include describing and prioritizing ergonomic

risk factors and hazards for musculoskeletal disorders (including back injury and CTDs) in the

nursery industry. Once this preliminary survey was completed, the project team and cooperators

selected specific priority jobs or tasks for intervention. Following priority task selection,

continuing work will include: evaluation for nursery application previously validated task and

tool modifications used in other industries with similar tasks; development of task and tool

modifications which eliminate or significantly reduce the ergonomic hazards associatedwith that

task; and conduct and evaluate cooperative on-site intervention trials (6-12 months) for each

selected task with cooperating nursery operations. Final evaluation will include repeated

detailed ergonomics and injury analyses, and assessment of interventions as to their technical fit

in the cooperating operations, industry acceptance, and impact on productivity.

In order to gain an overall assessment of the jobs and tasks involving the greatest ergonomic risk

for musculoskeletal disorders, a triangulation strategy was evolved. Triangulation simply refers

to the use of three points of reference instead of one or two to determine a location or trend. By

extension, the comparison of three different and isolated means of identifying high risk jobs and

tasks is intended to strengthen confidence in a screening or survey exercise. In this workplace

scale study, preliminary to more detailed measurements, it was important to select economics

methods both in terms of personnel time and equipment. Once high risk job tasks were

identified by each survey method, the three different lists were compared. Those job tasks which

were identified by all survey methods made up the pool of priority job tasks for selected

intervention.

The first method involved inquiry of managers and supervisors. These employees all had long

experience in both the nursery industry and with the cooperating employers and all had achieved

supervisorial status. Their assessments were based on personal work experience, accumulated

employee opinion, and oversight of each operations injury and illness records. Each supervisor

was asked to cite jobs or tasks that in their experience constituted the highest level of risk for

identified musculoskeletal disorders. The resulting list was summarized with their participation

and approval into a single priority list.

The second survey method involved workplace screening of jobs for ergonomic risk factors.

Because this involved three very large cooperating operations with some 1290 employees, a

simple worksite screening checklist approach as described by Keyserling (2) was selected.

Three different preliminary checklists were pilot tested, with one of the ANSI Z-365 (3)

checklists being finally selected. This ANSI Z-365 checklist proved among the quickest to apply

in the worksite setting and yielded results which allowed the most useful degree of distinction

between close scoring job tasks because it was not binary (a risk factor was either present or

not). These jobs are "fluid" in their content, in that tasks required vary for many reasons,

including weather and season. Job titles or descriptions are not precise since a worker may be

assigned to do quite different tasks from day to day. For this reason, the team decided to analyze

each task falling under the four functions described above. This approach may prove useful in

other industries (such as construction) where job content varies within a given job title.

Two trained ergonomic evaluators used the checklist to evaluate the 50 identified job tasks on

each of the three cooperating worksites. The evaluators checklist practice was tested for inter-

rater error by comparing scores generated by both evaluators observing the same task performed

by the same worker at the same time. As a result of the first cut survey, the highest scoring job

tasks were selected, and submitted to a more detailed checklist modified from validated

checklists previously published by Keyserling, et al (4) and developed for use in manufacturing.

The modifications were made to make the checklists more appropriate for nursery work. The

highest scoring job tasks from this set of checklists were submitted to the triangulation

procedure.

The third survey method involved scrutiny of each cooperator's injury and illness records to

identify those job tasks which were most frequently associated with musculoskeletal disorders.

Initial inquiry revealed that most of these employers maintained separate records for OSHA

reportable injuries and for first aid (i.e., those not referred to medical care and returning to

work). Because some musculoskeletal disorders may initially present as more simple sprains or

strains, it was determined to include scrutiny of the first aid records in this initial review.

Cooperators made all records available, and a list of musculoskeletal disorders and associated

job tasks was developed.

Results

Priority concerns, as reflected by managers and supervisors are displayed on Table I below and

focused on lifting and carrying containers, repetitive hand tasks in cutting and pruning, and in

slips and falls in field work.

TABLE I

Cooperator Designated Shipping Propagation/Canning Fieldwork

Lifting/Carrying Repetitive Hand Slips &

Containers (cans) Tasks (propagation, Falls

canning, pruning)

Results from the ergonomic risk factor checklist procedure at the three cooperating worksites

resulted in similar identification of a set of jobs by job task as shown in Table II.

TABLE II

Ergonomic Risk Factors Shipping Canning Fieldwork Propagation

(checksheet analysis - Truck load/unload Transport to Field Spacing, Pruning Cuttings

ANSI Z-365) Labeling Weeding

Review of the OSHA 200 injury report logs and non-required first aid report data for 1993 and

1994 at each of the three cooperative sites suggested a list of 85 musculoskeletal disorders as

displayed on Table III. By analyzing type of injury and descriptive information on situation and

cause, those injuries which appeared to be cumulative in nature were selected. Those with

clearly acute causes such as slips, falls, or vehicle incidents were excluded.

TABLE III

TOTAL FIRST OSHA LOST SPRAINS BACK HAND & OTHER LOWER FACE/ OTHER

AID 200 DAYS WRIST UPPER EXT EXT. HEAD________

85 11 74 1246 66% 26 19 20 10 2 8

The resulting job tasks with the highest risk of musculoskeletal disorders by this indicator are

shown on Table IV, below.

TABLE IV

Injury Reports Analysis Shipping Canning Fieldwork Propagation

Truck loading/ Transport to Field Pruning, Spacing. Cuttings

unloading Weeding

As the project proceeds, this information on musculoskeletal outcomes will be supplemented by

extensive pain and symptom surveys of employees performing specific tasks selected for

intervention.

Triangulation across the three methods resulted in the following list of candidate tasks for

intervention planning:

Among the three cooperating nurseries, there are variations in tasks and how they are performed.

Some nurseries have more powered equipment (e.g., fork lift trucks, pruning equipment) than

others, which modify the risk factors to which workers are exposed. The following descriptions

delineate the most common risk factors for the development of work-related musculoskeletal

problems in the seven candidate tasks for intervention planning:

1. Plant cuttings (Propagation)

The worker stands or sits at a worktable, empties a basket of plant cuttings, and uses hand shears

to cut them into smaller pieces for propagation. The shears are held in the dominant hand; plant

material is grasped with non-dominant hand. After each piece of plant material is cut, the shears

must be disinfected by dipping them in a solution in a small container on the work bench.

When cutting, the right hand is engaged in very repetitive gripping, with an average of 50-60 cuts

per minute. Mild to moderate wrist flexion and ulnar deviation are present throughout the

cutting cycle.

The left hand is used to hold the cuttings, orient them for cutting, and discard the remains in a

bin. Moderate wrist extension and ulnar deviation are present throughout the cycle.

Additional risk factors include:

Contact stress on the front of the thighs from the edge of the work table

Contact stress from the handles of the clippers

Poorly fitting latex gloves

2. Handling cans for transport to field

a. Transporting plants from conveyor belt to trailer

The worker grasps three or four 1-gallon containers in each hand and places them on a trailer

located either to one side of him or behind him. This job cycle is repeated 13-20 times per

minute.

Risk factors include:

Highly repetitive gripping

High pinch forces (Estimated to be in excess of 66% of predicted maximum voluntary

contraction)

Awkward postures:

i. Trunk flexion when placing cans on trailer (Approximately 60 degrees of trunk flexion.

An average of 40 degrees of peak lumbar flexion as measured by the Lumbar Motion

Monitor)

ii. Shoulder flexion: Up to 90 degrees when placing cans on trailer. This represents high

biomechanical stress on shoulder when combined with trunk flexion.

Contact stress from edge of cans on the lateral surfaces of the fingers

Contact stress from edge of trailer against the thighs

High energy demand

Cold ambient temperatures (in the early mornings)

b. Transporting plants from a trailer to a planting bed

The worker grasps three or four 1-gallon containers in each hand, carries them up to 55 feet, and

places them on the ground along a predetermined row. This job cycle is repeated 3-5 times per

minute.

Risk factors:

Highly static gripping with both hands, for periods of 10-15 seconds

High pinch forces (Estimated to be in excess of 66% of predicted maximum voluntary contraction)

Frequent trunk flexion (Approximately 100 degrees of trunk flexion. An average of 50-60

degrees of peak lumbar flexion, as measured by the Lumbar Motion Monitor)

Contact stress from edge of cans on the lateral surfaces of the fingers

Contact stress from edge of trailer against the thighs

Cold ambient temperatures (in the early mornings)

3. Pruning (in the field)

The pruner works with various shears to snip off unwanted or dead parts off the top and side of

plants. He/She is usually standing or bent over to reach plants. The dominant hand holds the

shears, and is engaged in very repetitive gripping, with an average of 40-50 cuts per minute.

The fingers of the right hand are also used to pinch off small twigs or other plant parts. The non-

dominant hand grasps the can for a rapid pick and place, and also holds the cuttings in a static

grip with moderate wrist flexion and ulnar deviation present throughout the cutting cycle.

Risk factors:

Prolonged trunk flexion (up to 90 degrees of trunk flexion, 50 degrees of lumbar flexion)

Awkward posture of both wrists, primarily flexion and ulnar deviation

Contact stress from edge can, left hand

Contact stress from handle of shears, right hand

Cold ambient temperatures (in the early mornings)

4. Spacing

As the plants grow they must have adequate room to expand. Thus, spacing must be done

periodically; grasping and lifting 3-4 plants in each hand, carrying them a short distance, then

placing them on the ground in rows. This cycle is repeated 3-5 times per minute

Risk factors:

Repetitive gripping

High pinch forces (in excess of 66% of predicted maximum voluntary contraction)

Frequent trunk flexion (an average of 60-65 degrees of peak lumbar flexion)

Contact stress from edge of cans on the lateral surfaces of the fingers

Cold ambient temperatures (in the early mornings)

5. Weeding

The worker exams each plant, checks for weeds growing, and removes them. He/she pulls the

weeds by hand or uses a tool called a spoon to scoop them out.

Risk factors:

Repetitive gripping (5-6/min)

High pinch forces

Contact stresses on non-dominant hand from plant and on dominant hand from tool

Prolonged trunk flexion (90-100 degrees)

Cold ambient temperatures (in the early mornings)

6. Plant Labeling (Pre-shipping)

This operation consist of counting containers and moving each one out from its row into the

furrow. The right or left hand grabs the edge of the container (one container in each hand) and

places it in the furrow. The worker peels a label from its backing with the dominant hand and

places it on the outside of the can.

Risk factors:

Repetitive pinching of labels (dominant hand, 13/min)

Repetitive gripping (non-dominant hand, 13/min)

High pinch forces (left hand)

Prolonged trunk flexion (70-100 degrees)

Contact forces on the dominant hand when wiping off dirt and water to place label

Cold ambient temperatures (in the early mornings)

7. Load / Unload Truck (Shipping)

Each worker lifts three to four containers per hand weighing 16 to 80 lb. per hand to a flatbed

trailer truck. Up to 400 hundred plants must be moved by 1-2 workers in a period of 1-3 hours.

The workers then remove each plant (3 to 4 at a time) onto crates on the floor of the dock

according to the order form to be filled. Each crate holds up to 40 plants. The crates are moved

by hand truck or forklift from the holding dock and placed into the trailer of the truck. Another

worker then removes each container and places it on racks in the truck.

Risk factors:

Repetitive gripping (10-12/min)

High pinch forces (in excess of 66% of predicted maximum voluntary contraction)

Frequent trunk flexion (90 degrees, 7/min)

Contact stress from edge of cans on the lateral surfaces of the fingers

Very high energy demand

Cold ambient temperatures (in the early mornings)

Contact forces on the dominant hand when wiping dirt from can to place label

All of these should be considered to involve a high degree of ergonomic risk for musculoskeletal

disorders. Further, this list of tasks and the identified risk factors also leads to identification of

landmark risk factors for this industry which are now described as:

1. repetitive hand work (clipping, cutting, pruning, etc.)

2. stooped working postures

3. lifting, carrying, moving loads with awkward postures

(stoop, reach, twist, pinch grip, etc.).

To narrow the list of priority job tasks to 3-5 feasible areas for intervention, each of the seven

job tasks was reviewed using the following criteria:

1. How many workers are regularly exposed;

2. Duration of exposure usually involved;

3. Feasibility of intervention strategy;

4. Degree of risk reduction anticipated from intervention strategy?

This exercise required the engineering group to graphically present intervention strategy ideas.

A set of four job/tasks were selected as involving high risk for musculoskeletal disorders and as

presenting likely targets of opportunity for ergonomic intervention. That list is in Table V.

TABLE V

JOB TASK ELEMENT RISK FACTORS

1. Spacing of Cans (Field Work) Handling Cans Stoop, Lift, Pinch Grip

2. Loading Trailer (Canning) Handling Cans Stoop, Lift, Pinch Grip

3. Pruning (Field Work) Hand Clipping Repetition

4. Making Cuttings (Propagation) Hand Clipping Repetition

DISCUSSION

None of the survey screening methods used in this study is particularly complicated and none

requires expensive instrumentation. At the same time, these mtehods do facilitate priority

setting for intervention. Conceptually, the research team attempted to improve upon large scale

screening efforts by utilizing multiple methods, and selecting priorities through triangulation to

increase confidence. This approach can overlook a job that has a high degree of illness or injury

incidence, that for some reason is not reported in the reporting period scrutinized. It can also

eliminate a job which scores high on ergonomic risk factor checklists, but for some reason is not

reflected on the other measures. However, this type of criticism will apply to virtually any

general workplace screening method that is also practical enough to be used in similar

circumstances. By using three different measures, insulating the screening teams, and then

comparing the different results, a set of priorities was reached which reflected high scores on

each separate method, and that met the expectations of cooperating workers and supervisors,

ergonomists, and occupational health experts.

Additionally, the resulting priority job tasks involve the ergonomic risk factors one would expect

in this type of workplace: stooping, lifting and carrying loads, and repetitive hand tasks. These

risks do not differ from those found in other industries. Because they result from a multi-method

survey of the nursery workplace and because all assessment groups agree on their priority, the

team feels confident in identifying these as generally critical or "landmark" ergonomic risk

factors for this industry. This is an important distinction for the industry group and for longer-

term agricultural research planning.

Engineering strategies in the prototype stage at this time include:

1. lightweight handles for lifting and carrying cans which eliminate pinch grip and

minimize stooping;

2. handles for cans mounted on hand trucks for larger cans and greater through-put;

3. raised working platforms in the canning offloading area to facilitate use of handles;

4. hydraulic tilting trailers to minimize can lifting when loading and unloading; and

5. powered clippers and cutters for use in pruning and cutting tasks.

As the project moves into its second phase, these priority tasks are being analyzed in detail,

utilizing research scale instrumentation. Health outcomes will be assessed using structured

employee interviews with well-tested symptom batteries and analysis of hours worked before,

and between musculoskeletal symptom occurrences. Ergonomic risk factors are being assessed

using the Lumbar Motion Monitor, the Greenleaf System for wrist motion, the NIOSH Lifting

Equation, and metabolic demands through the use of heart rate monitoring and the University of

Michigan Energy Expenditure Prediction Program (5).

Work on engineering alternatives for each of the targeted tasks is underway using the

engineering design process. Multiple potential alternatives will be generated by the engineering

team, and each will be evaluated for the:

1. degree to which it reduces risk of, or risk factors for, work-related musculoskeletal disorders;

2. interaction of the intervention with other nursery activities;

3. acceptability of the intervention by the workers;

4. capital cost associated with implementation; and

5. changes in productivity associated with the intervention.

Both nursery management and selected workers are involved in the design evaluation process,

and the engineering team recognizes that any intervention that is not acceptable to management

and the workers has little chance of being implemented.

Initial designs have concentrated on tools to allow workers to do their jobs with improved

postures, better hand grips, and less metabolic energy than their jobs currently require. They

have also concentrated on developing simple inexpensive alternatives, rather than automation.

The purpose of this approach is two-fold; to reduce prevention costs and to contribute to job

preservation. The intervention phase of the project is just starting, and time will judge the

wisdom of this approach.

CONCLUSIONS

This study provides evidence that agricultural work demonstrates similar types of

musculoskeletal disorders and ergonomic risk factors already reported in other industries. It also

provides preliminary evidence that the same approach of ergonomic risk factor analysis and

intervention using known principles and demonstrated methods is readily applicable to

agriculture. Finally, this phase of the project has resulted in a set of general or "landmark" risk

factors for longer-term research and prevention consideration. Future similar projects in

different agricultural commodities are expected to reinforce the importance of these risk factors

in agricultural work.

The agricultural industry has long been insulated from much of traditional occupational health

and safety approaches. Further, agricultural audiences are quick to cite genuinely special work

circumstances and situations that militate against applying remedies from other sectors. In this

light, demonstration of how ergonomic methods apply to agricultural workplaces and can lead to

practical, productive and safe designs for agricultural tools and tasks is well worthwhile.

Finally, this study suggests that a multi-method approach to workplace survey screening for high

priority intervention targets is both productive and practical.

The preliminary research reported here is an essential first step to ergonomic improvement of

agricultural work settings. Such work is of critical importance in demonstrating to the industry

the value of ergonomic methods in practical and effective prevention of musculoskeletal

disorders. The value of doing so via cooperative demonstration trial with selected companies

that are acknowledged as industry leaders should not be understated.

ACKNOWLEDGEMENTS

This project is supported by the National Institute for Occupational Safety & Health (NIOSH)

with a three year grant (NIOSH Grant # UO5/CCU911435-02) to a University of California team

organized under the U.C. Center for Occupational and Environmental Health and is administered

from the Biological and Agricultural Engineering department at the University of California,

Davis. The project team is led by Dr. John A Miles, Biological & Agricultural Engineering, UC

Davis. Other team members are: Dr. Julia Faucett, Occupational Health Nursing, UC San

Francisco; Dr. James Meyers, Center for Occupational & Environmental Health, UC Berkeley;

Mr. Ira Janowitz, Ergonomics Program, UC San Francisco; Mr. John Kabashima, UC

Cooperative Extension, Orange County; and Ms. Diana Tejeda, Biological & Agricultural

Engineering, UC South Coast Research & Extension Center.

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