AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

Anthropometric data are a powerful tool for the designer of man-task equipment;

however, it is important that the data used for design are based on samples of subjects 4
similar to the end users. There are large amounts of data available for young men, e@
most resulting from military service activities. Data on people at large or the general

population exist, but data on some groups of interest are much less available.

Examples of groups whose data may be scarce are small children, elderly people,

women, and ethnic groups.

Because the number of humans that may use a particular piece of equipment is so
great, it is not reasonable or possible to measure each one. Rather, a sample that is
representative of the whole is selected and measured. If the sample is sufficiently
large, sample errors will be insignificant and the resulting design will give a reliable
fit.

As the body dimensions are measured and compiled for our sample, a data bank is
developed, ranging from the smallest measurement for each dimension to the largest.
This range represents 100% of the total with 1% the smallest size and 100% the
largest size. If the sample is sufficiently large, the measurements fall into a normal
bell-shaped probability density function, with the maximum number of measurements
occurring at the mean (or 50th percentile) (fig. 11-9).

This provides a very convenient way to refer to the size of a particular dimension with
respect to the rest of the population. For example, a man whose standing height
measures at the 70th percentile point would be larger than 70% and smaller than 30%
of the men. He would be referred to as a 70th percentile man in height. The same
procedure is used for all other dimensions.

Anthropometric data for engineering use are best presented in percentiles as discussed e@
above. These tables provide a faster, more convenient method of determining a

percentile equivalent of a dimension than does the use of normal probability density

functions. Typically, the extremes below 2% or 5% and above 95% or 98% are

disregarded for most designs, and a useful range covering the middle 90% to 96% is

used.

‘The percentile can be determined arithmetically using the standard deviation (SD) and
the mean value. The standard deviation is a measure of the scatter or dispersion about
the average:

Standard deviation (SD) = 20)

AN 718.0. «3S.

50%
16% 1, 34% M% J, 16%
Zw 47 he Atif Phe

Figure DII-9. Gaussian probability density function. Definition of percentile and standard deviation.

1-10



AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

Resource Costs

THE FARM AND
AGRICULTURAL INJURY
PICTURE

injuries, while others may include them under other machinery-related injuries. Murphy
(1990) provides an excellent discussion of concems with tractor accident data.

Collecting and analyzing farm injury data is relatively expensive compared with other
industries because of the number of farms, their geographic distribution, and the lack of
reporting or record keeping. Use of data from existing sources may be incomplete or
inconsistent from one source to another. Most farms have fewer than 11 employees, so
it is generally not possible to simply contact a few large establishments and collect
injury data for hundreds or thousands of employees as it is in many industries. If a mail
survey is desired, a sample size of over 1,000 farms will generally be needed. If phone
interviews are desired, the cost will be greater, and still more costly if on-site
interviews are desired, as considerable travel costs will be involved in visiting a sample
of farms.

Collection of data through medical sources, such as hospital emergency departments,
incurs costs for the time and paperwork necessary to collect the data. Intensive data
collection efforts could require personnel dedicated to data collection alone. Such is the
case with the Consumer Product Safety Commission NEISS system, where
participating emergency departments have a clerk assigned to the task. Existing sources
of information may also carry a cost. State agencies which collect workers’
compensation data or death certificates may provide computer searches or summaries
of data at no cost, or they may charge. Individual certificates may or may not be
available free. Newspaper clipping services generally charge a monthly reading fee plus
a charge per clipping.

Unless analyzed farm injury data are provided, time and effort will be required to
record and analyze data on individual injuries. Whether these data are collected via
survey, death certificates, newspaper clippings, medical records, or otherwise, they
must be assimilated in some orderly fashion. Inclusion criteria must be applied, missing
data located, inconsistent data verified, duplicates removed, and other quality control
methods used prior to analysis.

Fatal injury data represent some of the most long-term, scientifically collected data
available on farm and agricultural injury. This is important because over time, and on a
broad scale, fatality data become an evaluation criterion of safety and health efforts
within large segments of society, and for society as a whole.

As discussed earlier in this chapter, the NSC publishes estimates of accidental work
death totals and rates by industry. Construction and mining have historically joined
agriculture as the three most hazardous industries, based on fatality rates. Table I-1
provides a historical comparison of the total number of fatalities in these three
industries, plus the “all industry” total; table I-2 provides the death rates. As the tables
show, the number of agricultural work deaths has declined by more than 60% over the
last 30 years (2,000 fewer deaths), while the agricultural death rate has declined less
than 28%. This contrasts with the other industries, where the decrease in total deaths
has not been as dramatic. However, the death rates have declined 65% for mining, 55%
for construction, and 59% for all industries.

The National Institute for Occupational Safety and Health (NIOSH) has reported
agricultural data from its National Traumatic Occupational Fatalities (NTOF) database. .
As discussed earlier, these deaths include only those victims age 16 and older whose
death certificates indicate “injury at work” and whose usual industry is recorded as an
agricultural industry. The five sectors from the SIC Code for agriculture (01, 02, 07,
08, 09) are used. For the years 1980-1985, the annual average number of fatalities was

118



AGRICULTURAL
SAFETY AND HEALTH
FOR ENGINEERS

An ASAE Instructional Module

JERRY R. DUNCAN, Deere & Company, Moline, ill.

ROBERT H. WILKINSON, Michigan State University, East Lansing, Mich.
MARK A. PURSCHWITZ, University of Wisconsin, Madison, Wisc.
DENNIS J. MURPHY, Pennsylvania State University, University Park, Penn.
KARL C. ANDERSON, Tucson, Ariz.

EDITED BY
L. D. BAKER, JI Case, Naperville, Ill.



UNIT IV - Hazard Analysis

Minor: Unreasonable to expect that the minor nature of this failure would cause any
teal effect on the vehicle or system performance, Customer will probably not even
notice the failure.

Low: Low severity ranking due to nature of failure causing only a slight customer
annoyance. Customer will probably only notice a slight deterioration of the system or
vehicle performance.

Moderate: Moderate ranking because failure causes some customer dissatisfaction.
‘Customer is made uncomfortable or is annoyed by the failure (e.g., engine misfire,

compressor rumble, sunroof leak). Customer will notice some subsystem or vehicle
performance deterioration.

High: High degree of customer dissatisfaction due to the nature of the failure such as an
inoperable vehicle (¢.g,, engine fails to start) or an inoperable convenience subsystem

Severity of Effect Ranking

aun en ~

on

(€.g. air conditioning system, power sunroof). Does not involve vehicle safety or
noncompliance

to government regulations.

Very High: Very high severity ranking when a potential failure mode affects safe vehicle 9
operation and/or involves noncompliance with government regulations. 10

Figure IV-2. Evaluation criteria for selecting the severity value (SEV).

Step 6. Identify the potential causes of failure. A potential cause of failure is an
indication of a design weakness, the consequence of which is the failure
mode. Every possible cause of failure should be listed which is assignable to
each failure mode.

Examples of failure causes are:
Incorrect material specified Over-stressing
Incorrect assembly instruction Insufficient hydraulic capacity
Insufficient torque specified Inadequate B10 life
Insufficient lubrication capability Permissible material impurity level
Insufficient horsepower specified
Allowed casting inclusions
Step 7. Estimate the occurrence. Occurrence is an estimate of the likelihood that a

specific cause will result in a failure mode. The occurrence ranking number
has meaning rather than value. A design change is the only way to improve
the occurrence ranking number. Estimates of the likelihood that a cause will
result in a failure mode is on a 1 to 10 scale (fig. IV-3). In determining this
estimate the following questions should be considered:

How adequate is the proposed design verification (or test) program?

Is part carry-over similar to a previous-level part or assembly?

How significant are the changes from previous-level parts or assemblies?
Is the part radically different from the previous-level parts? Is the part
completely new?

What is the service history or field experience with similar parts or
assemblies?



AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

Swain, A. D. 1974. The Human Element in Systems Safety: A Guide for Modern
Management. London: Industrial and Commercial Techniques.

SAMPLE QUIZ 1. Select a system that you know in detail and for which you can identify hazards in

QUESTION -the system. Select one of the analysis techniques to review the system. Perform the
analysis. Explain why you chose the particular technique and explain the choices
made in using the technique.

IV-16



t | i 1 ot 1
AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

Death Certificates

‘Surveys

Workers’ Compensation
Records

completeness of the description of individual events depends on the knowledge of the
writer and the editorial priorities of the day. For instance, an injury incident may not be
considered “newsworthy” enough on a particular day to be included by the newspaper.

Death certificates are an important source of fatality information and one of the most
commonly used. A death certificate provides an official cause of death as well as
geographic and demographic information such as age and occupation. The description
of the injury incident depends upon the coroner or medical examiner filling out the
certificate and can vary in detail and accuracy. Usefulness of death certificates depends
upon the criteria used to select them from the large numbers of other fatalities. For
example, if occupation of farmer is used, then part-time farmers with other primary
occupations will be missed. If location of farm is used, then farm-related incidents
occurring off the farm, such as on roadways, are often missed.

Death certificates are particularly useful because they are universally required; every
state has a computerized registry of death certificates. Cause of death is classified by a
nosologist (a person who classifies cause of death) using an internationally agreed-upon
system called ICD9 (U.S. Department of Health and Human Services, 1980). This
system of ICD9 codes includes classifications for external causes of death, known as
E-codes. The ICD9 coding system is extensive, but E919.0 (injuries from agricultural
machines) is the only code specifically involving agriculture; there is no specific
E-code for falls on farms, for example. Also, because numerous codes exist for motor
vehicle accidents, a fatality involving a tractor on a public highway will be classified
under a motor vehicle E-code. Not every data field on a death certificate may be
computer searchable. Because of variations in detail recorded, and the need to examine
the narrative description of cause of death for any mention of farm involvement,
manual searching/selection may be necessary (Stallones, 1990; Field and Tormoehlen,
1982).

The advantage of using a survey is that non-fatal injuries and illness can be included.
Also, by using a representative random sample of farms, statistically sound conclusions
can be drawn about rates of injury per farm in that state. Three types of surveys have
been used: on-site interviews, mail surveys, and telephone surveys. The on-site
interview survey was very popular in the 1970s and 1980s but is no longer used
because it is a labor-intensive approach. In the 1970s and early 1980s, thirty-one
statewide surveys were conducted by state Cooperative Extension Services under the
auspices of the National Safety Council (Hanford et al., 1982). These surveys involved
mobilizing a large group of volunteers (e.g., 100 or more) who would visit selected
farms on a quarterly basis for one year. The volunteers would ask about and record
information on injuries and illness occurring to farm family members and hired
workers. The skill and devotion of the interviewer determines the accuracy of the
survey. More recently, a rigorous telephone interview methodology has been
successfully used to collect farm injury data (Gunderson et al., 1990).

The mail survey has gained recent popularity because it does not require a large labor
force. Although it does have the disadvantage of less than 100% response, and requires
follow-up to achieve an acceptable response rate, it has been used successfully
(Murphy and Huizinga, 1989). The mail survey also normally utilizes a one-year recall
period, which may introduce recall bias by participants.

The workers’ compensation system was developed to provide compensation to workers
injured on the job on a no-fault basis, i.e., regardless of whether fault lay with the
worker, the employer, or with neither. To receive compensation, the injured party must
file a claim. The database of claims can serve as an occupational injury database.
However, in many states participation by farmers is optional and typically farmers have

13



UNIT IV - Hazard Analysis

TASK ANALYSIS

Scores to a given product. Therefore, the technique is best used by teams of experts, so
that each expert’s composite score can be averaged to find a final hazard risk score.

To illustrate this procedure, an example of the development of a gasoline-powered
golf cart is used. A prototype golf cart, model XN, has been assembled. The hazard
analysis team has reviewed the machine and operated it on a local golf course. The
team has identified four potential hazards and has reached a consensus quantification
for the risk score on each hazard. The results are summarized on a hazard analysis
worksheet similar to the one shown as figure IV-8. Typically, the summary sheet also
lists the hazard type and a description, factors contributing to the hazard, potential
injury effects, and additional comments. This example suggests that the hazard
analysis team considers the risk of overturn as the most significant hazard, and
thermal or fire as the least significant.

Another area for human factors involvement in system design is that of task analysis.
Task analyses may be performed to identify error-likely situations, to describe what
should happen, and to analyze what might happen when a system is operational. A
task analysis may also be performed to document what is required of a person to
operate a system and to make judgments about whether an operator can perform what
is required.

In addressing the first question, a detailed analysis of the tasks, equipment, and work
environment is generally performed. Task performance goals are evaluated and
workloads measured. Equipment and workstations are evaluated to determine whether
they accommodate the human operator they serve. Likewise, the work environment is
evaluated to determine what it imposes on the people within it. With knowledge of the
physical, mental, social, and psychological characteristics of the population from

Product: Model XN Golf Cart Date of Review: 30 Sep 1991
Hazard Hazard Analysis Quantification
‘Type and
Descrip- Factors Contributing 10 EffectInjury Comp.
tion Hazard Potential Expo. Like. Cons. No. Comments
Impact Wor park brake latch = Bystander 7 4 3 84 Engineering -
Rolling _- Inadvertent release of | inj consider redesign,
Machine brake + Bruises Manufacturing -
= No adjustment on tatch - Contusions consider heat treat of
~ Practure part.
Thermal- Gasoline line may wear Operator - 4 3 3 36 Engineering -
me through, spilling fuel. Ist and 2nd consider rerouting
ba Routed near electrical degree burns Tine.
plesion components, potential
ignition source.
Overtarn Sharp tum redivs. Operater 6 5 6 180 Bapinceriog -
Lateral Excessive top speed. injury bons design
Stability Insufficient strength of | ~ Fractures changes 40 reduce
canopy frame. - death speed, strengthen
canopy.
Publications ~
consider safety
message in mancal,
Crushing Cos are sacked onend injury wotrack = 3 4 5 © Shipping -
Falling for shipmem, held in- — unleader consider differen,
Object. —_—_potition with sieet + Bruises stacking pater.
bending. ~ Possible
End wnit may fall over
when banding is cut.

Figure IV-8. Typical hazard analysis worksheet. Example developed by K.C. Auderson, PE.

Iv-11



UNIT I - Agricultural Hazards

or holes when operating on a side slope. More than 80% of all tractor overturns are
side overtums.

Rear overturns occur when the tractor engine powers the tractor to rotate about the
rear axle. Any condition that will stop the rear wheel from turning when the tractor is
under power to move forward will provide a lifting torque to raise the front end of the
tractor.

As shown in figure II-1, once the front end of the tractor begins to lift, and if adequate
power is available, a tractor may overturn to the rear. The “point of no retum”, the
point at which an overturn becomes irreversible, may be reached in three quarters of a
second, and many operators will not be able to recognize the danger and react in this
short of a response time.

The most common cause for rear overturns is attaching the load to some point above
the drawbar, such as attaching a chain around the rear axle or to a raised three-point
hitch. The high hitch increases the load on the tires, increasing traction such that the
rear tires may stop rotating. A high hitch also reduces the resistive torque to an
overtum that is normally produced as the product of the vertical distance between the
drawbar and rear axle times the load being pulled. If the hitch point is the rear axle,
the resistive torque is reduced to zero. If a hitch point above the rear axle is used, such
as the attachment point for the upper link, the torque produced by the load will work
to overtum the tractor, rather than resist the overturn. Driving up a steep slope will
also cause a rear overturn.

Occasionally, a tractor will overturn more or less forward when the operator drives off
of a bridge or down a steep slope when the front wheels get stuck at the bottom of the
slope (ditch).

There are three basic types of tractor runover incidents. One is when a passenger
(extra rider) on the tractor falls off the tractor when it is in motion. A second is when
the tractor operator falls off the tractor. The third type occurs when a person already
on the ground is runover by the tractor. The person already on the ground may be a
bystander (nonworking person, a small child, etc.), a coworker, or the tractor operator.
The tractor runover event often involves trailing machinery hitched to the tractor: it
may be the trailing machinery that inflicts the injury. An event of this type may or
may not be counted by statistical data as a “tractor runover” event.

Extra rider injuries occur because there is no safe location for an extra person on a
tractor, yet the practice is common. Reasons for extra riders on tractors are, among
other things, saving time, convenience, work assistance, and babysitting. Whether an
extra rider can be justified is strictly in the eye of the beholder. Safety experts and

The “Point of No Retumn*

Figure II-1. The “point of no retarn” during a rear turnover may be reached in three-quarters of a
second (Source: Deere & Company, 1983).

3


AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

the object ahead as slow moving, and then perhaps another second to brake. This

situation is often compounded by hills and curves that obstruct viewing distance,

natrow roads and berms, rural bridges, wide machinery that occupies more than one e
Jane, and on-coming traffic that may not be visible to the overtaking vehicle. By the

time the overtaking vehicle driver recognizes that he or she cannot pass safely, it is

often too late.

Aspecial emblem, appropriately named the slow moving vehicle (SMV) emblem, was
designed in the mid-1960s to uniquely identify agricultural machinery as slow moving
vehicles on public roads (see fig. II-3). The triangular orange fluorescent emblem,
with a red reflective border, was designed to be mounted on the rear of tractors and
trailing machinery. A widespread educational campaign was initiated to inform
farmers and the motoring public on the benefits of the emblem, and many states
adopted use and recognition of the emblem as a part of their state transportation laws.
Research done in the early years of the emblem’s use suggested the emblem was
effective in identifying agricultural machinery as slow moving traffic and helped to
reduce collisions between regular vehicular traffic and agricultural machinery.

Important reasons for the emblem’s effectiveness in the early years were: the emblem
was new and different, which itself drew attention; the color combination was highly
visible; and use was restricted to the purpose for which the emblem was intended.
Over the years all three of these reasons have dissipated to an extensive degree.
Farmers allow faded emblems to stay on their equipment, there are many similar
shapes of emblems and reflectors on the market today, and SMV emblems are
misused as driveway, mailbox, guy wire, telephone pole, and building markers.
Consequently, the value of the SMV emblem has been seriously eroded. This erosion
contributes to the hazards of agricultural machinery operating on public roads. @

Another serious hazard from agricultural machinery operated on public roads is
turning maneuvers. This hazard may also involve the closure-time hazard but can
exist even when an approaching vehicle has sufficiently reduced its speed. The
turning hazard stems primarily from: the lighting and marking of agricultural
machinery, obstructed views of both the machinery operator and the vehicle operator,
machinery operators not checking behind them before making a left turn, or swinging
to the left before making a right turn.

The lighting and marking of agricultural machinery refers to head lamps, tail lamps,
armber warning lights, red reflectors, and turning signals. Problem areas include old
machinery with no or nonworking lights and reflectors, an operator that doesn’t use
available lights, and trailing equipment that obscures tractor lights from the rear.
Other situations that are potentially problematic include an absence of brake lights on
agricultural machinery and a turning signal format that conflicts with the format of

POINT AT TOP: 7

ORANGE

FLUORESCENT : n :
(CENTER) > .

RED a—

REFLECTIVE ! i

i
(BORDER) q i r

Figure Il-3. A slow moving vehicle emblem (SMV) on the back of a wagon (Source: Deere &
‘Company, 1983).

I-10



PURPOSE

OBJECTIVE

SPECIAL TERMS

INSTRUCTOR
MATERIALS

TRAINEE
MATERIALS

Unit IV
HAZARD ANALYSIS

To introduce students to analysis strategies for evaluating hazards.

After completing this unit, the student will be able to:

PFene

Perform a failure mode and effects analysis (FMEA)
Perform a fault tree analysis

Perform a risk score analysis

Perform a task analysis

Failure mode and effects analysis
Fault tree analysis
Risk score analysis

Lesson plan
Chalkboard

Participant outlines made by instructor
Supplementary materials



( hoo ‘ { rod i
AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

underscore the range of ways in which an operator, a helper, or a bystander may
become injured working with or around a tractor. e@

Aged Tractors Tractors, for functional reasons, are ruggedly built. Recent surveys in several states
suggest that the average age of tractors across the United States is between 15 and
20 years of age. There are a substantial number of working tractors approaching
30 years of age, and many are over 30 years old. The design of tractors is an
evolutionary process and so is improving safety. New standards, technology, and
materials are continually incorporated into new tractor designs and manufacturing
processes, resulting in safer tractors over time. Several safety-related improvements to
tractors have been incorporated in their design. These include rollover protection,
better visibility, safer seats, easier-to-operate controls, improved lighting systems, and
more. Older, less safe machines are replaced by newer, improved machines through
mechanisms of the marketplace. This same process has replaced older, less safe
automobiles and trucks as well. What makes the tractor situation different from
automobiles and trucks is the rate at which the replacements are made. There are few
20- or 30-year-old automobiles or trucks on the road today. There are as many as a
million of these tractors that have been in use for over 20 years. Aged tractors are
more likely to be used for: hauling supplies and materials among fields, the farmstead,
and markets; mowing pastures and farmstead grounds; chores involving routing
livestock care, gathering and hauling of firewood, miscellaneous transportation, and
the like. When the untrained, inexperienced, or slowly reacting operator is placed on
an older tractor that lacks rollover protection, has a seat without back or arm supports,
a gear shift stick that is difficult to maneuver, and brakes that do not hold or cannot be
locked together properly, the risk of an injury incident increases.

MACHINERY HAZARDS There are a multitude of machines used in production agriculture, and they are @
powered in many different ways including a PTO drive shaft, hydraulic fluid power,
electrical power, internal combustion engine power, and ground traction. Components
of the same machine may be powered by two or more methods. Horse and mule
power is still the choice for certain religious sects. Regardless of how a machine is
powered, injuries do happen. This section of the chapter identifies the most common
types of farm machine hazards, and typical interactions between persons and
machines that lead to injury. It is generally accurate to state that the interaction or
exposure of workers to the hazards discussed below often occur during maintenance,
servicing, adjusting, and cleaning/clearing activities, both in the field and at the
farmstead.

Several farm machine hazards can be grouped by describing the actual machine
component's action or motion that results in injury to a person. Many machines have
several types of hazards. Pinch point hazards exist where two machine parts move
together and at least one of them moves in a circle. Pinch points are, for example,
where drive belts contact pulley wheels, drive chains contact gear sprockets, and feed
rolls mesh together. Wrap point hazards are from exposed rotating machine
components. The most commonly known example of a wrap point hazard is from the
machine’s primary PTO drive line, but, there are several other lesser-known
examples, such as secondary drive shafts, beater bars on self-unloading ensilage
wagons, and blades of some manure spreaders. The PTO wrap point hazard will be
discussed more extensively later in this section.

Shear/cutting point hazards exist where the edges of two moving parts move across
one another or a single edge moves against a stationary edge or soft material. There @
are many farm machines that contain shear/cutting hazards because the
shearing/cutting action is the purpose for which the machines exist. Examples include

0-6



AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

Potential Failure Mode

Potential Effects of
Failure

Severity

Step 1.
Step 2.
Step 3.

Step 4.

Step 5.

Complete top section of the form to provide a record of this FMEA.

Identify the part number to be analyzed and list all the functions of the part.
Identify the potential failure modes. A potential failure mode is defined as
the manner in which a part or assembly could fail to meet the design intent,
performance requirements, and customer expectations. The potential failure
mode may also be the cause of potential failure mode in a higher-level
assembly, or be the effect of one in a lower-level part. A recommended
starting point for listing potential failure modes is a review of available
failure data, such as past FMEAs, engineering test reports, quality reports,
any other available documents, and cross-functional team brainstorming.

Examples of potential failure modes:

Cracked Sticking

Deformed Short circuited (electrical)
‘Worn Open circuited (electrical)
Corroded Vibrating

Loosened Dirty

Leaking Fractured

Note: Potential failure modes should be described in technical terms, not as
symptoms noticeable by the customer.

Identify the potential effects of failure. Potential effects of failure are the
effects of the failure modes on the customer. Potential effects of failure are
described in terms of what the customer might experience. These should be
expressed in terms of product performance.

Examples of potential effects of failure:

Poor appearance Insufficient power
‘Hydraulic lines fracture Excessive operator fatigue
Noise Poor gradeability

‘Won't start Lighting failure

Vehicle control impaired Leaks oil

Poor stability

It is important to obtain data from customers. This could be in the form of
warranty reporting, service reports, dealer questionnaires, focus groups,
manufacturing improvement efforts (troubleshooting), vehicle final test
reports, and cross-functional team brainstorming.

Estimate the severity of the effect of the failure. This is a numerical
evaluation of the seriousness of the effect of failure to the next operation in
manufacturing/assembly, the vehicle, or the customer. The severity rating
applies to the effect of failure only. It is important to note that to reduce the
severity ranking there must be a design change. Severity is evaluated on a 1
to 10 scale (fig. IV-2).

Iv-4



AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

of the person’s exposure; susceptibility of exposed persons; and the type of exposure
(inhalation, ingestion, dermal). Poisoning effects from pesticides may result from
short-term overexposures and/or long-term, low-level exposures. Short-term r
overexposures may result in immediate serious illness or death. More common are
minimal overexposures that lead to headache, sweating, diarrhea, dizziness, fatigue,
muscle ache, nausea, and other common human maladies. These symptoms mimic
many other illnesses. Because minimal overexposure incidents are difficult to identify,

they may often be underreported.

Multiple episodes of long-term, low-level exposure to pesticides are reportedly
associated with many health risks to farmers. Cordes and Foster (1988) listed cancers,
birth defects, sterility and infertility problems, genetic damage, and neurological and
behavioral abnormalities that reportedly result from overexposure to pesticides.
However, reported associations between pesticide overexposures and diseases are
subject to controversy and disagreement. Diseases and chronic health problems may
neither appear, nor be detected or diagnosed by physicians, until months or years after
pesticide exposure. It is often difficult, if not impossible, to precisely attribute the
disease or health problem to the pesticide exposure. Confounding factors include
smoking, alcoholism, other occupational disease exposures, aging, poor personal
hygiene habits, a lack of medical care, and other conditions that contribute to an
unhealthy lifestyle.

Pesticides have three primary routes of entry into the human body and one less
frequent route. The primary routes are through dermal (skin) absorption, by inhalation
(breathing), and ingestion (eating, drinking). The less frequent route is eye absorption.
In production agriculture, the most common form of poisoning is by dermal contact.
The exceptions to this are small children, who are most often poisoned by ingestion.
The handling of pesticides when they are at full strength, such as the opening of e@
containers and pouring during the mixing operation, are prime times for overexposure
incidents to applicators. Children can be poisoned when they drink pesticides or
pesticide mixtures stored in soda bottles, milk jugs, coffee cans, etc., and when they
put contaminated products, such as dirt, weeds, paper, etc., in their mouths. Field
laborers may be overexposed from mixing and spraying operations, pesticide residue
on treated plants, or drinking, bathing, or cooking with contaminated water. These are
only a few of the ways in which acute overexposures and chronic, low-level
exposures may occur. For more complete listings, check the references at the end of
this lecture.

Fertilizers Production agriculture makes use of many types of fertilizers to enhance or restore
soil composition, and to increase crop yields. Nitrogen, lime, potash, and potassium
are the major fertilizers. They may be applied singularly, or in combination mixtures,
and in various forms. For instance, nitrogen may be applied either as anhydrous
ammonia, aqua ammonia, urea, or ammonium nitrate. Most fertilizers are applied in
granular form and present only low to mild hazard exposure to the eyes and
respiratory tract and to the skin as skin rashes. The exception to this last statement is
anhydrous ammonia (NH3). Anhydrous ammonia is an efficient source of nitrogen
fertilizer for crops and is widely used throughout most regions of the country. This
fertilizer exists at atmospheric pressure as a gas but is converted to liquid form when
put under pressure. Anhydrous ammonia is handled and stored through pressurized
systems. It is applied by injecting it directly into the soil through injection knives.
Once in the soil, it converts to a gaseous state and is immediately absorbed by soil
moisture.

Anhydrous ammonia is a severe irritant of the eye, skin, and respiratory tract. It can @
cause damage by freezing the skin and destroying (chemically burning) eye and

11-16



AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

Defeatability Resistance

the presence of a hazard that may cause harm. Hence, it is not an engineering solution
that should take precedence over hazard elimination or exposure reduction.

Passive protection is an effective safety engineering technique for hazard situations
that previously relied almost solely upon individual compliance with safety and bealth
practices and rules. Passive protection can be combined with an active measure to
significantly reduce the consequences of some hazards. A case in point is tractor
stability. Before the advent of rollover protective structures (ROPS), avoiding the
consequences of tractor rollover relied exclusively upon the safe operating practices
of the operator. A factory-mounted ROPS, a passive measure, combined with
fastening the seat belt, an active measure, provides very effective protection against
the crushing hazard of tractor rollover.

Even without the active measure of fastening the tractor seat belt, substantial
protection is afforded the operator by the passive portion of the protective system. The
presence of the ROPS prevents the tractor from crashing completely against the
ground during an overturn. In most cases, this is enough to prevent a life-threatening
crushing of the operator. Thus, the passive protection concept, even though not 100%
passive, can provide a relatively effective amount of protection from some hazards.

Effective product safety engineering considers reasonably foreseeable misuse of
products. This is a concer closely connected to product liability. For instance, it is
reasonably foreseeable that some farmers will misuse farm tractors as

vehicles for more persons than the operator. Another aspect of reasonably foreseeable
misuse is less well recognized. This aspect has to do with reasonably foreseeable
misuse of safety engineering features and devices.

Seiden (1984, pp. 136-138) has grouped safety engineering measures into six classes
according to their safety-defeatability quality or content. Seiden’s classes refer to
actions the product user would have to engage in to defeat the safety feature. Class 1
represents the most easily defeated safety measures and class 6 the most undefeatable.
‘Thus, class 6 safety engineering measures are more likely to remain in place and serve
their intended function. The classes are:

Class 1. Change in standard operating procedure to defeat product and/or safety
function; revert to prescribed procedure to restore safety function

Class 2. Use of simple tools and/or contrivances to defeat safety

Class 3. Use of special or complex tools or equipment to defeat safety

Class 4. Major product redesign, remanufacture, alteration, or rebuilding to defeat
safety

Class 5. Product function disruption, impairment, or damage required to defeat
safety; product repair necessary to restore function

Class 6. Product function destruction necessary to defeat safety irreversible;
impractical to reasonably reset, restore, or restart function and/or safety

Class 6 is the ideal safety-defeatability resistance class. With class 6, the engineered
safety device or feature cannot be defeated without destroying the product itself:
hence there are few actual examples of this class. This is why it represents the ideal.
At the other end of the scale, with class 1, the safety-defeatability resistance is very
low. Safety devices that can be removed or made ineffectual by hand or by changing
the way a job is completed represents class 1 safety-defeatability resistance. Many
modern walk-behind lawn mowers contain an example of a class 1 defeatability safety
feature. Modern walk-behind lawn mowers are required to utilize quick blade-stop
technology to reduce hazards to operators that leave the area behind the mower.

V-3



Unit!
AGRICULTURAL ACCIDENT STATISTICS, LIMITATIONS, AND WEAKNESSES

PURPOSE To introduce students to the sources of agricultural accident statistics that are

available and the limitations in using those statistics.

OBJECTIVE After completing this unit, the student will be able to:
1. Explain the difference between agriculture as an industry and farming as an
occupation
2. List the factors which complicate the understanding and interpretation of
statistics that are published in a variety of sources
3. List a variety of sources of injury statistics
4. List a few of the statistics of farm and agricultural injury

SPECIAL TERMS SIC Codes

Agriculture

Farming

Industry

Occupation

Production agriculture

National Traumatic Occupational Fatality (NTOF)
National Electronic Injury Surveillance System (NEISS)
Census of Fatal Occupational Injuries (CFOI)

Fatal Accidents Reporting System (FARS)

Seengavayyn

~

INSTRUCTOR
MATERIALS

Lesson plan
2. Chalkboard

TRAINEE

MATERIALS Participant outlines made by instructor

Supplementary materials

yer

oT





UNIT Il — Agricultural Hazards

Farmer's Lung Disease

Organic Dust Toxicity
Syndrome

openings through which silage is unloaded. The unloading is mostly by a powered
unloader that rests on top of the silage, though some small and older conventional
silos are unloaded manually. The hatch doors are surrounded by a metal or concrete
covering called the silo chute. The silo chute contains the silage as it is hurled out the
unloading door, allowing the silage to fall to the base of the silo.

Conventional silos do not limit oxygen inside the structure, and they do not capture
COz as does the oxygen-limiting silo. Therefore, the oxygen depletion hazard is not
the primary respiratory concer, although this hazard may still exist. The primary
respiratory hazard with conventional silos is nitrogen dioxide (NO) poisoning, a gas
that may be produced during fermentation of the forage. Factors that influence the
development of NO. include weather conditions, the type of crop ensiled, weeds
mixed in with the forage, nitrogen levels in the ground, and harvesting practices. It is
a heavier-than-air gas and may travel down the silo chute, enter livestock holding
areas, and poison animals.

Nitrogen dioxide poisoning is also known as silo gas poisoning and silo filler’s
disease. The production of the gas may begin within a few hours after the crop is
placed in the silo. It generally reaches its highest concentration during the first 48 to
60 hours but may be present in dangerous concentrations for up to two weeks, When
inhaled, NO2 combines with moisture in the respiratory tract and converts to nitric
acid (HNO3). This results in a variety of ill effects, depending on the concentration,
amount breathed, and the quickness and appropriateness of first aid and medical
treatment. These effects include a burning of respiratory tract tissue, fluid leakage in
the lungs, and death. The most serious reactions to NO poisoning are immediate.
Delayed reactions do occur and may take up to six weeks.

Hay, small grains, and silage are common livestock feeds. All three may spoil while in
storage and present respiratory hazards when later handled. The mold that develops
from spoilage can become dried, break into microscopic particles, and become
airborne when the hay, grain, or silage is handled. The mold spores, some of which
are toxic, attach themselves to like-sized particles of dust already in the air, hence the
name toxic dust. The dust is often called organic dust because it originates from
organic material. Dust particles less than 10 ym, called respirable dust, may be
inhaled into the respiratory tract, resulting in a variety of ill effects.

One of the ill effects of inhaling respirable dust is farmer's lung disease. Farmer’s
lung disease is one example of a respiratory disorder known as extrinsic allergic
alveolitis, or as hypersensitivity pneumonitis. These are generic terms describing
abnormal or extreme reactions of lung tissue to organic dusts. Farmer's tung disease
can result in both acute (short-term) and chronic (long-term) ill effects, with reactions
generally becoming more severe with each exposure. Typical responses to farmer's
lung disease include fever, shortness of breath, fatigue, muscle ache, lung
inflammation, and death. Victims who acquire farmer's lung disease are sometimes
forced to change their type of farming operation, or quit farming altogether.
Fortunately, only a small percentage of the population seems susceptible to farmers
Tung disease (Wright, 1989).

Similar to farmers lung disease, organic dust toxicity syndrome is also caused by
moldy feed dust, among other things. Acute responses by affected individuals are the
same as from farmer’s lung disease. A major difference between the two diseases is
that organic dust toxicity syndrome is thought to cause neither permanent damage to
the lungs nor death. Another difference is that all exposed persons are susceptible to
this disease. Organic dust toxicity syndrome has been identified by many other names
in the literature including atypical farmer's lung, pulmonary mycotoxicosis, toxic

IF-13



AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

a
es ©

Figure IV-6. Fault tree analysis of tractor bypass start hazard. Example developed by K.C.

Anderson, PE.

General Exposure Scale General Likelihood Scale _ General Consequences Scale

Rating Descriptor Rating Descriptor Rating Descriptor

9 ‘Continuous exposure 9 Almost certaintocom- 9 Death or complete

plete accident sequence disability

7 ‘Once daily 7 Very possible, but not. «7 ~~ Permanent partial

assured loss in work
capacity. Increased
work difficulty

5 Once peruse season 5 Some conditions favor-. 5 Hospitalization. Up
‘of once annually able to completing acci- to one month lost

dent sequence time. No permanent
Joss in work
capacity.

3 Only once in life ofa 3 Remotely possible, but 3 Doctor's office or
small percentage (10%) not likely ‘emergency room
of product treatment. Up to one

week lost time.

1 ‘Theoretically possible, 1 Practically impossible 1 Minor first aid.
highly unlikely during to complete accident Immediate return wo
life of product population sequence work.

Figure IV-7. General scales for hazard elements (Source: Madsen, 1985).

RISK SCORE ANALYSIS A different technique of hazard analysis is to score hazards by considering the
importance or impact of three hazard attributes: exposure—an estimate of how often
an operator or bystander is exposed to the hazard; likelihood—the probability that an
unwanted event will occur once there is exposure to the hazard; and consequences—
the most probable injury that might result. Each of these attributes is assigned a value
based on predetermined scales similar to those shown in figure IV-7. A composite
score is found by multiplying the values; this total score becomes the risk score for
the hazard. As shown in figure IV-7, a risk score could vary from 1 to 729. Risk
scoring is somewhat subjective because equally qualified experts may assign different

Iv-10



UNIT V ~ Engineering for Hazard Control and Injury Preventions

at a profitable price. To ensure profitability, a number of steps can be taken to
determine the anticipated selling price and the cost to produce the product. Market
surveys are made of historical total sales of a similar product that is currently being
manufactured and what percent of market penetration can be expected with the new
product. Engineering and development costs can be estimated. The cost of capital
expenditures for machine tools and buildings can be calculated. The unit cost of the
product is compiled from calculation of the materials, labor, and overhead required to
produce the product. All of these economic studies become inputs to the decision of
whether or not a particular product design will be selected for manufacture and
marketing.

There are many design selection criteria operating simultaneously during the design
process. Each of these criteria is important, and many of them can conflict. If we
consider them to be system criteria, it is obvious that it is impossible to maximize all
of them. One could make an item very easy to produce, for example, but at the
expense of size, selling price, operability, or styling. The design selection criteria in
the following list are representative of those that are generally balanced against each
other:

1. Functional performance 2. Compliance to standards/regulations
Speed ASAE, ISO, SAE, OSHA,
Maintainability/Serviceability DOT, EPA
Producibility 3. Styling
Safety 4. Cost
Human factors
Accuracy
Operability
Reliability

Once a system design has been selected and prototype units have been built, the next
step in the design process is a major one. A thorough test and evaluation program
fequires a major commitment in work force, facilities, and time. It generally includes
activities of component testing, field stress testing, durability testing, and a complete
system evaluation. During this period, further safety reviews and human factors
evaluations are conducted.

In summary, the system design process can be characterized as being 1) Multi-
faceted: There are many factors that are considered. 2) Interactive: Many different
disciplines and groups of people are involved. 3) Iterative: Many cycles occur in
which ideas are proposed, developed, tested, modified, and tested again before a final
design is established. 4) Evolutionary: As a design proceeds, it evolves into a product
that best satisfies all of the influencing factors.

The following quotation from an editorial in the December 1979 issue of Product
Engineering summarizes the system design process and the task of the design
engineer very concisely:

The design engineer must anticipate every need of the user, every stress of

the product, every economic alternative to keep costs low, every conflicting
patent, every manufactured complexity, every operating hazard, and every

maintenance problem. NOT one at a time, but all at once.

A few broadly stated principles that typically govern the application of engineering to

the safety of the user and bystander are presented. Additional principles and details
are presented in the listed references.

v-3



AGRICULTURAL
SAFETY AND HEALTH
FOR ENGINEERS

An ASAE Instructional Module

JERRY R. DUNCAN
ROBERT H. WILKINSON
MARK A. PURSCHWITZ

DENNIS J. MURPHY

KARL C. ANDERSON

EDITED BY
L. D. BAKER



PREFACE

Organized efforts to reduce the number of injuries occurring in the agricultural work
environment began about 50 years ago. The philosophical approach to this effort is evolving
slowly. The conceptual models of the three Es of safety, engineering, education, and
enforcement, and man-machine-environment are giving way to human factors and
epidemiological models. In chapter 5 of the text Safety and Health for Production Agriculture,
Dr. Dennis J. Murphy lists principles that should be considered in creating a new model:

* Injuries have identifiable causes that are either preventable or controllable.

¢ An injury incident normally derives from multiple causes rather than a single
cause. This results in multiple approaches to hazard and injury prevention and
control being more effective than any single approach.

¢ Risk is inherent and omnipresent in life.

* To be human is to err.

¢ Human perceptions of risk are not very accurate.

¢ Human behavior can be changed.

* Occupational safety and health is a function of management.

A discussion of these principles is contained in chapter 5 of the text. This evolution of a safety
philosophy is illustrative of the changes taking place through the effort to reduce injuries in the
agricultural workplace. It is the challenge of keeping pace with this evolution that will require
the instructor of this course to read and use this module.

This module is addressed to college-level faculty teaching power and machinery/systems
courses in the agricultural engineering curriculum. It is anticipated that this module will be
covered in five or six hours of class time.



Unit Il
AGRICULTURAL HAZARDS

PURPOSE To introduce students to the hazards that most commonly cause personal injury on

farms.

OBJECTIVE After completing this unit, the student will be able to identify and define:
Hazard

Power take-off (PTO)

Angle of pull

Implement input driveline (IID)

Implement input connection (IC)

Slow moving vehicle (SMV)

Farmer’s lung disease (FLD)

Nopaeye

INSTRUCTOR
MATERIALS

Lesson plan
Chalkboard

pr

TRAINEE

1. Participant outlines made by instructor
MATERIALS 2.

Supplementary materials

U1



AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

THE SAFETY
HIERARCHY

Eliminate Hazards or
Risks

is working alone, this may allow the person to seek emergency help. The
altemative — a stopped machine with a trapped victim -— may result in death from
loss of blood or shock.

* Some machines have several high-hazard areas (e.g., a PTO drive line, other
powered mechanisms, and crop intake, processing, and discharge areas). This may
Tequire several different emergency shut-off devices on a single machine because
the action in each hazard area is different.

These considerations are not easily resolved. An emergency shut-off device must have
a very high degree of reliability before it is used. Assuming that technology can solve
any problem given sufficient resources and motivation, satisfactorily engineered
reliability may raise the cost of machinery to prohibitive levels. On the other hand,
there are already some examples of simple emergency shut-off devices in use on
machines. Some activities involving the filling of silos result in workers being near
moving parts of the self-unloading ensilage wagon and the ensilage blower. Some

+ modern ensilage wagons use a combination of wire rope and grab bars as an

emergency shut-off device, and modem ensilage blowers have a handle or bar that
acts as an emergency shut-off device. Some emergency shut-off devices, of course, do
not eliminate or reduce a hazard prior to the injury incident, but only attempt to
minimize damage once the injury event occurs.

The safety hierarchy represents a conceptual prioritizing of ways to reduce hazards
and risk. Generally, some combination of priority methods are used to combat a single
problem. The safety hierarchy is:

1, Eliminate hazard or reduce risk.
2. Apply safeguarding technology.
3. Use waming signs.

4, Train and instruct.

5. Prescribe personal protection.

Safety engineering principles further identify how these priorities may be
accomplished with products. This unit is most directly concemed with the first three
Priorities of the safety hierarchy, and in particular the first two. These are the priorities
that utilize the engineering sciences most directly. Before looking again at the safety
hierarchy, we will address another safety engineering concern.

Safety engineering discussed within the framework of the safety hierarchy
demonstrates how engineering principles and priorities combine to solve real
problems. Numerous examples from production agriculture are given to illustrate how
theory is translated into practice. Some wording of the safety hierarchy terms are
altered slightly to reflect common usage of the ideas that the safety hierarchy
represents,

This is the most fundamental principle of safety engineering. However, it may not be
possible to apply this principle in real situations as directly as might be assumed. To
actually eliminate a hazard or risk means to do away with it completely. This may
often only be achievable by doing away with the product itself. Product substitution is
possible, but the product that is substituted is also likely to have associated hazards
and risks. For example, the hazards of coal mining can be eliminated by switching to
nuclear power. However, nuclear power is not without its own set of risks. In most
instances, when hazard or risk elimination is spoken of, what is really meant is
significant hazard or risk reduction. This reduction may be accomplished in many
different ways.

V-10



UNIT V - Engineering for Hazard Control and Injury Preventions

3. Safety factors and margins. This refers to the process of designing products to
withstand stresses over and above the normal functional requirement. For example
if the structural strength of a step is required to hold 300 Ib (136 kg), a safety factor
of 2 would result in the step being designed to hold 600 Ib (272 kg). Safety factors
are intended to handle unexpected events that could possibly occur, even though it
cannot be predicted when or if the event will actually occur.

4. Failure rate reduction. No operating component lasts forever. Therefore, designs
attempt to limit: failures while the system is operating, the rates of failure, and shut
downs of the system from component failures (Hammer, 1985). This is achieved
by using components with life expectancies much longer than their usage would
normally require; by timed replacements, using quality control measures to ensure
that only quality components are used; and through redundancy. Redundancy
means having two methods to achieve the same objective within the same system.
Automatic standby electrical power generators in the case of normal power failure
is one example of redundancy.

Redundancy Redundancy is a common and important safety engineering technique for improving
product reliability. The concept of redundancy cuts across many of the fail-safe design
and failure minimization principles discussed above. The two primary types of
redundancy are parallel and series. Parallel redundancy can be achieved by having
backup systems (e.g., standby generators), or by having two or more parallel
subsystems. To have parallel subsystems (components, circuits) means to have two or
more subsystems operating at the same time, each capable of functioning
independently. If one subsystem fails, the other subsystem carries on. A twin-engine
airplane, capable of flying with only one engine, is an example. Series redundancy
means that subsystems are arranged in a series in which all units must operate or fail
to allow functioning. Series redundancy is most often used to prevent damage from
inadvertent or premature operation of systems (Hammer, 1980). With series.
redundancy, all units in the series must fail if the device is to activate inadvertently.
The probability of this occurring is low, lowering the overall risk of damage.

Some systems may involve only partial redundancy (Brauer, 1990). For instance, a
single pump may be supplying fluid to two sets of hydraulic lines to actuate one
cylinder. A failure with the pump would cause the entire system to go down. However,
a failure in one set of hydraulic lines would not cause the system to go down because
of the presence of the other set of lines. Hence, the system is only partially redundant.

Redundancy is most commonly thought of in terms of hardware and automatic
equipment. However, it can also involve human operators. Cruise contro] devices on
automobiles provide speed control, as does the operator's foot on the accelerator. The
use of pilot and copilot in an airplane is another example of humans as redundant
devices.

Passive Protection Passive protection means to provide engineered protection from hazards irrespective
of the behavior of the individual being protected. Conventional wisdom indicates it is
the ideal type of hazard protection: it utilizes the more reliable and predictable
engineering sciences, rather than the less reliable and predictable human sciences. The
automobile air bag and motorized seat belt shoulder harnesses are perhaps the most
readily recognized passive protective systems. However, automatic fire extinguishing
systems, in-line ground-fault circuit interrupters, and gas line shut-off valves. for
extinguished pilot lights are other common examples. Passive protection has proven
to be especially effective, in comparison to other types of hazard protection, with
hazards that are individually and routinely encountered by consumers and the public.
Important to remember, though, is that the need for passive protection still signifies

V-5



UNIT I — Agricultural Accident Statistics, Limitations, and Weaknesses

programs are not relevant to most farmers. Sweeping engineering or administrative

solutions to common hazards may not be feasible for all situations. This reduces the
@ advantages that single locations, uniform job sites, and narrowly defined work

procedures and tasks offer in terms of hazard and injury prevention and control.

Farm Operators and The total number of farmworkers has declined by almost 70% from 1950 to 1985

Family Workers (Whitener and Munir, 1990). The farm labor force includes farm operators and unpaid
workers and hired laborers. Unpaid workers are usually family members of farm
operators and includes older workers and children. The hired labor force includes
domestic hired labor, foreign nationals, and undocumented foreign workers (illegal
aliens). Each of these groups is examined to better understand its role in production
agriculture and in issues relating to safety and health.

Family farms still dominate American agriculture. The 1987 Census of Agriculture
reports that 87% of all farms are operated by individuals or families. Another 10% are
partnerships, many with family ties. Yet, fewer and fewer farm operators devote full
time to farming; only 55% of farm operators list their principal occupation (50% or
more of work time) as farming. Thirty-five percent of all farm operators work at least
200 days a year off the farm. Other farm labor statistics also show multiple job holding
by farm workers. Oliveira and Cox (1989) report that in 1987 there were 4.4 million
farm operators and unpaid farmworkers 14 years of age and over. Over 60% of these
workers also worked in nonfarm jobs.

Older Workers As shown in figure I-1, the average age of farm operators was 52 in 1987, up from 50.5
years in 1982. Similarly, the percent of farm operators 65 years of age and over was
21.4% in 1987, compared to 17.8% in 1982. An additional 4.8% and 2.7% of unpaid
and paid farmworkers, respectively, were 65 years old or older in 1987 for a total
@ working group of 28.9%. Farm operators age 65 and over are more likely to be full-
time farmers than are other age groups of farmers, but they operate smaller farm units
with fewer and older pieces of machinery than farm operators aged 45 to 64. This
implies a greater overall exposure to farm hazards with fewer financial resources to
apply toward replacement or maintenance of older machines. Older equipment is less
likely to have guards and warnings in place, safety devices in working order, and the
safety features of newer equipment.

The 65-and-over age group is a working group not normally found in other hazardous
occupations. Forced retirement, pensions, retirement incentive programs, and failure to
meet or maintain minimum job skills or proficiency requirements normally eliminate
this age group as workers in other occupations, particularly those identified as
hazardous. Such inducements or requirements simply do not exist in most production
agriculture operations. Failing eyesight, loss of hearing, slower reaction time, and
arthritis are just a few of the age-related problems affecting the safety and health of

Source:
60 1967, 1982
50 52.0 Consus of Agriculture
H 40
wy 30 214
8 20
10
° T T
1987 1982 1987 1982
‘Average Age Percent of Operators
e@ of Operator Age 65 and Over

Figure I-1. Average age of operators and percent aged 65 and over.

LS



UNIT Il — Human Factors

Behavior Defined

STIMULI BEHAVIOR
OBJECT /SYSTEM
*Force * Bending
eerie ‘gree
* Electrical Current . Movement

Figure IlI-2a, Relationship between stimuli and behavior in objects and systems.

remedies either to reduce the frequency of errors or to make the system more tolerant
of the errors.

People will accept or take risks to achieve goals. Their experience (i.e., behavior
learned from past occurrences with the same or similar systems) affects their current
decisions, The operator’s application of knowledge from one system to another has
Jed system designers to use population stereotypes (e.g., pushing forward on a lever to
go forward or faster, etc.) to minimize operator training time and reduce the likelihood
of “negative transfer” of training.

Before we proceed to a specific example of an interruption to a hypothetical machine,
behavior and human error need to be defined and discussed. The word behavior is
used to describe responses (i.e., actions, conduct) to stimuli. It refers specifically to
responses that can be observed. Commonly used statements like, “the operator was
inattentive” or “the operator was careless”, do not describe the observed actions of an
operator and, therefore, are not descriptions of behavior. Every engineering discipline
is concerned with the behavior of objects or systems. Understanding the behavior (i.e.,
response) of objects or systems such as bridges, vehicles, buildings, and motors to
stimuli of force, acceleration, temperature, and electrical current is an important part
of the engineering discipline. Examples of these are shown in figure III-2a.

‘When people are included in the system, other stimuli, such as hunger, thirst, personal
goals, threats, and “barriers” to goals, etc., in addition to the stimuli of the physical
environment, become important design considerations. The human behavior (really,
the system behavior, because the operator’s behavior is united with the rest of the
system) resulting from these stimuli may be described only by the observed actions of
the system and by the operator’s decisions inferred to have occurred because of
observed actions. This is illustrated in figure III-2b.

As shown in figure III-3, the behavior that a system displays reflects on: how
comprehensive the designer was in considering the stimuli that affect the system, and

STIMULI BEHAVIOR
tee
——
Choser
Considered chosen
NotConsidered = = — Chosen
Unknowingly

Figure Iil-2b. Relationship between stimuli and behavior of humans,

I-5



UNIT V ~ Engineering for Hazard Control and Injury Preventions

‘SAMPLE QUIZ 1. Review a relatively new agricultural machine.

QUESTIONS (a) Determine whether there are examples of the safety principles being applied to
the machine, i.e., fail-safe designs, failure minimization, redundancy, passive
protection, and defeatability resistance. List them.

(b) Are there examples of the safety hierarchy being applied to this machine? List
them. Is it necessary, in part, to compare this machine to early versions
of the machine?

(c) Are the guards on this machine in conformance to ASAE $493 (fig. 2)?
List them.



AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

¥

en (oe) ‘Tat Ovapensen Ctr)

a | =
escpery | Ragacomnes | Regercmn | Regerecan
leniadl

I
tf

Figure IV.9, An example task analysis format.

which the system operators will be selected, judgments then can be made about
whether the operators will be able to perform as expected.

The task analysis procedure includes a step-by-step description of tasks to be
performed by the system and the operator interaction with the system. Each step
generates demands for successful completion, and these demands are compared with
what operators can do.

A typical task analysis format includes a portion for describing the task behaviors and
another for analyzing the task components (fig. IV-9). At some stage in the
development of a new system, it will be possible to define human tasks to be
performed and groupings of these tasks that will be defined as individual jobs. This
effort is normally considered to be the descriptive half of task analysis. In a task
description, operations in a system are listed. Time baselines may also be used. When
first done the data will be fairly gross; probably identification of gross tasks is all that
can be done. As the system becomes more definitive, more detail will be possible.
Ultimately, the task descriptions must be rather detailed, with each stimulus and e@
response identified in each single step in each task for each job. This level of detail
allows the analyst to describe the factors influencing performance in each task and
job. The main purpose of the descriptive material is to provide the necessary inputs
for identifying error-likely situations, helping personnel who prepare the written job
and task instructions, and serving as the basis for determining the selection and
training requirements for each job and task (Swain, 1974).

Each task may be analyzed to identify potential sources of error. The analysis involves
determining whether there are any conflicts among the various factors of tasks,
environment, equipment, and personnel. Such conflicts may result in errors. The
ultimate objective of the task analysis is to suggest system design changes. The
potential errors of greatest concern are those with an intolerable combined possibility
of occurring, going undetected or uncorrected, and causing an unacceptable system
consequence. A possible design change may reduce the possibility of an error, it may
increase the likelihood that the error, if made, will be detected or corrected; or it might
involve some way that the system could tolerate the error. The design changes may
involve changing any of the factors associated with the potential error. The changes
may be addressed to equipment design, methods of use, formal training, or personnel
selection criteria. This step is crucial, and it must be shown that any recommendation
for change represents an optimum accommodation of all the various system criteria

(including cost).
EXAMPLE OF A TASK | Figures IV-10, IV-11, and IV-12 depict a “synthesized” flow of actions and decisions,
ANALYSIS both required and possible, of an UPSAT machine operator following an interruption

caused by some material clogging the shredder unit. An UPSAT machine is a
hypothetical machine, its name an acronym for urban paper shredder and transport
machine. It is a self-propelled vehicle operated by one person and is driven along city

IV-12



UNIT H — Agricultural Hazards

all types of mowers, forage harvesters, small-grain combine heads, bedding choppers,
and grain augers. Grain augers are common on many crop and livestock farms and
have been identified as the most hazardous farm machine per hour of machine use
(Doss and Pfister, 1972). Crush point hazards are from two objects moving toward
each other, or from one object moving toward a stationary object. This type of hazard
also arises from handling animals. Machinery-related examples of crush point hazards
include standing between the front and rear tires of articulating tractors, hitching
machinery, and hydraulically controlled equipment under which a hand can be caught.

Freewheeling parts hazards arise from machine parts that continue to move after
power to the part has stopped. Usually the movement is from continuing rotation of
knife or fan blades. Many injuries result from a worker stopping power to the
machine, and then opening an access door or panel to a part that has continued to
rotate. Because many freewheeling parts hazards also involve knife blades, injuries
resulting from freewheeling parts are often associated with shear/cut point hazards.
Examples of machines with freewheeling parts are forage harvesters, feed grinders,
rotary mowers, and ensilage blowers. Thrown objects hazards result from the
chopping, grinding, cutting, and flinging motions of a variety of machines. Small
objects such as rocks, metal, glass, sticks, and vegetation may be picked up by the
machine and thrown with great force. Machines that may do this include rotary
mowers, feed grinders, combines with straw choppers, and manure spreaders,

Stored energy hazards arise from energy that is confined and released unintentionally
or unexpectedly. Stored energy involves pressurized systems or components and
serves many purposes. For example, it may be used to maintain alignment between
machine parts, lift heavy machines, force machine parts into the ground’s surface, or
speed the movement of fluids necessary for machine operation, among other tasks.
Major types of stored energy on farm machinery include springs, hydraulic systems,
compressed air, and electricity. Stored energy, in an uncontrolled or unexpected
release, may cause the initiation of hazards identified in the paragraphs above. For
instance, a crushing hazard might result from a leaking hydraulic system that allows a
front-end loader bucket to suddenly fall to the ground. Or a shear/cutting hazard
results from the movement of a knife blade when a broken bolt unexpectedly releases
the tension on a spring. Nearly all powered farm machines have several stored energy
hazards.

There are several burn point hazards associated with farm machines. Hot mufflers,
engine blocks, pipes, and fluids (fuel, oils, chemicals) are all examples of possible
burn hazards on tractors, self-propelled machinery, and pulled machinery. Machine
inspection, servicing, and maintenance are the most common types of activities that
may result in exposure to a burn hazard.

Pull-in point hazards are identified primarily with field harvesting machines. The pull-
in hazard occurs at the point where the machine takes the crop material in for further
processing. When the machine is running at full recommended PTO speed, crop
material moves into the machine at split-second speeds. Examples of machines with a
pull-in hazard includes corn pickers and combines, forage choppers, and hay balers. If
a person is holding onto crop material as it begins to enter the machine, he or she is
usually unable to react quickly enough to release the material before being pulled into
the machine. This situation most often happens when crop material plugs the intake
point of the machine. Many operators choose to unplug the machine with the power
engaged because it is easier and quicker, instead of following the recommended safety
practice of disengaging the power to the machine and shutting the tractor off. Other
practices expose workers to pull-in hazards include hand feeding or kicking crop
material into a machine.



UNIT H — Agricultural Hazards

SUMMARY

REFERENCES

Cited References

The most common hazards associated with production agriculture, identified by
nearly 30 years’ worth of injury and illness reports, studies, and investigations, were
addressed in the sections above. However, these hazards are only a part of the story,
as a complete listing of hazards would be much longer. Indeed, a complete listing may
not even be possible because nearly everything associated with production
agriculture, including ground surfaces, is a potential hazard. Many hazards overlap.
For instance, silos were discussed in relation to toxic dust particles and gases, but
falling off silos, or down silo chutes, was not. Other hazard areas not discussed
include high-pressure injections, electrical shock, fires, mental stress, drownings, and
hazards from work uses and of all-terrain vehicles, to name a few.

There are also a multitude of consumer and industrial products used in agricultural
production. Examples include chain saws, lawn mowers, power tools, welders,
ladders, etc. These products all have hazards that may produce as serious an injury or
illness as the hazards that were discussed in more detail. Readers should consult the
references and bibliographies to become familiar with the multitude of hazardous
conditions and situations that may exist at some point in production agriculture.

Hazards and “agents of injury” are numerous and commonplace in production
agriculture. Hazard characteristics associated with the operation of tractors include
tractor stability, PTO operation, and runovers; tractor age, maintenance, and
alterations; and operator variables such as age and training. Many farm machines,
whether used for stationary or field work, involve multiple hazard points. The types of
machine hazards that often result in the most serious injury include wrap point (PTO
drivelines), pull-in point, and shear/cutting point hazards. These hazards are closely
associated with the functions of farm machinery. Some hazards, such as noise and
PTO, are associated with both tractors and machinery.

Respiratory hazards include silo and manure gases, toxic dust, and oxygen-deficient
atmospheres. These hazards usually involve crop and animal storage and housing
structures. Two toxic dust hazards, farmer's lung disease and organic dust toxicity
syndrome, have been found, particularly among dairy farmers and swine confinement
workers. Animal, weather, and chemical hazard exposures are also common among
farmers and their families, as well as with migrant and seasonal farm workers.
Production agriculture health-related hazards are difficult to identify because of the
delayed appearance of symptoms or ill effects, confounding exposure variables, and
unhealthy lifestyles or behavior patterns.

This lecture was reproduced from chapter 2, Safety and Health for Production
Agriculture, Dennis J. Murphy, ASAE, 1992.

Agricultural Safety, 2nd Ed. 1983. Deere & Company.

ASAE Standards, 41st Ed. 1994, $276.4. Slow-moving vehicle identification emblem.
St. Joseph, Mich.: ASAE.

ASAE Standards, 37th Ed. 1990 ANSI/ASAE $318.10. Safety for agricultural
equipment. St. Joseph, Mich.: ASAE.

Bobick, T. G., J. R. Myers, D. L. Hard and J. E. Parker. 1991. Musculoskeletal
injuries in the major agricultural industries. In Proceedings of the Human Factors
Society 35th Annual Meeting, 867-871, San Francisco, Calif., 2-6 September.

Brauer, R. L. 1990. Safety and Health for Engineers. New York: Van Nostrand
Reinhold.



AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

“average person” for any measure of man. The lesson is: design to accommodate the ~
differences (not the mythical average man). In this same regard, it should be noted

that human performance (e.g., the interval of time to recognize and respond to an r
emergency) is not distributed “normally” with equal variance around a central mean.

Thus, the mean of the distribution of a performance measure is not a very useful

design parameter. It is better to view the “whole” distribution and design to
accommodate as much of the whole as is feasible.

People are Adaptable When systems are designed for the “average person” the real people working in those
systems must exercise perhaps one of their greatest attributes, their adaptability.
People can accommodate system deficiencies to the point that those deficiencies are
transparent or unrecognizable. As the tasks get more demanding (up to some “point”)
we just apply more effort and make judgments and adjustments to “get the job done”.
Common measures of operator or system performance such as productivity may
detect no difference between an “inconsiderate” design (one with low commitment to
human factors requirements) and a “good” design. Questionnaires and interview
techniques can be designed that are helpful in soliciting operator responses to identify
subtle, but significant, differences between altemative system designs.

Our adaptability can be observed in the way that we compensate for unwanted system.
characteristics and behavior. Compensating behavior (i.e., human actions in response
to interferences to achieving a goal) can be observed in many settings, but perhaps the
most fruitful one (for teaching someone what to look for) is in the use of personal
computers. For example, in the situation where a computer user is trying to create a
simple x-y graph using a widely used spreadsheet software product, it is common to
observe the user finally “give in” to the product and accept the graph in the form that
the product (really, the software designer) constrained it. This compensating behavior
generally stems from the user having expectations of the system that will not be r )
fulfilled—such as believing that the computer graphing program is as flexible as
pencil and paper. The lesson is: although people are adaptable, their adaptability can
compensate only to a limited degree before system performance is degraded or before
the user becomes dissatisfied and either tolerates the system as it is or searches for

another alternative.
People are Goal- Somewhere in the general sequence of performing a task a human operator may be
Oriented faced with choosing among alternative goals or perhaps coordinating conflicting

goals. For example, in operating a system, the goal of continuing to operate may
conflict with the goal of avoiding compromises in safety. A case where human
behavior, directed by a goal, has affected the performance of a safety device concems
the removal of power take-off shields. A recent article in Successful Farming
Summarized a survey conducted by Purdue University in four midwestem states. They
found that the power take-off shield is more likely to be left in place if it is of the flip-
up type (i.e., hinged at the back so it lifts up out of the way and then flips back down).
‘The flip-up shields were found in place 89% of the time. The bolt-on, fixed shields
were found in place 58% of the time, and the quick-attach shields (easily removed)
were found in place only 31% of the time. Reasons that were found for removing the
shields included: interference with the use of centrifugal spray pumps, interference
with fully mounted equipment such as posthole diggers, and interference with the
tasks of connecting and disconnecting drivelines.

Humans are agents of errors; they propagate error-likely conditions. An important
element in the system design process is to analyze the tasks performed by the
equipment operator and to classify potential human error associated with those tasks.
This analysis will likely suggest possible equipment design or operator training e@

m4



AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

Campbell, W. P. 1987. The condition of agricultural driveline system shielding and its -
impact on injuries and fatalities. M.S. thesis, Purdue University, West Lafayette,
Ind.

Cordes, D. H. and D. Foster. 1988. Health hazards of farming. Farming Family
Physician 38:233-244.

Donham, K. J. and R. Rylander. 1986. Epilogue: Health effects of organic dusts in the
farm environment. American Journal of Industrial Medicine 10:339-340.

Doss, H. J. and R. G. Pfister. 1972. Nature and extent of use of farm machinery in
relation to frequency of accidents. Report no. 30 Center for Rural Manpower and
Public Affairs, Michigan State University, East Lansing, Mich.

May, J. J., M. Marvel, M. Regan, L. H. Marvel and D. S. Pratt. 1990. Noise-induced
bearing loss in randomly selected New York dairy farmers. American Journal of
Industrial Medicine 18:333-337.

NIOSH. 1993. NIOSH wams farmers of deadly risk of grain suffocation. NIOSH
Update (April 28).

Steele, J. H. 1979. The epidemiology and control of the zoonoses. In The Theory and
Practice of Public Health, ed. W. Hoson, 332-367. New York: Oxford University
Press.

Wright, J. L. 1989. Lung disease in farm workers: Pathological reactions. In
Principles of Health and Safety in Agriculture, ed J. A. Dosman and D. W.
Crockcroft, 26-34. Boca Raton, Fla.: CRC Press, Inc.

SAMPLE QUIZ 1. Obtain farm/agricultural statistics reports from several different sources. Review

QUESTIONS any accident descriptions that are available from newspaper articles. Determine if
the agricultural hazards as described here accurately reflect the events described in
the newspaper articles and accident statistics.

2. From the best reports available, analyze the hazards encountered on a farm about
100 years ago and today. Was it safer to work on a farm then or now?

1-20



UNIT IV — Hazard Analysis

REFERENCES

Cited References

operator when the shredder unit becomes clogged, but the operator reverses the
rotation of the shredder unit using controls within the cab to eject the clog.

Four approaches to the analysis of a machine or system were presented. The FMEA is
best suited to analyze reliability issues. The fault tree analysis and task analysis are
methods of examining detailed operator-system interactions. A risk analysis is a
systematic approach to evaluating hazards in any system. The use of these techniques
provides an organized method of identifying and prioritizing hazards in the system
such that system modifications can reduce the probability of personal injury to an
acceptable level.

This lecture was primarily condensed from chapter 9, Safety and Health for
Production Agriculture, Dennis J. Murphy, ASAE, 1992, and Human Factors: A
Series of Quality Instructional Materials, No. 1 Human Factors Concepts. An
Overview, Jerry R. Duncan, ASAE, 1991. No. 11 Operator Behavior: Responses to
Interruptions of a Machine Function, Jerry R. Duncan, ASAE, 1991.

Brauer, R. L. 1990. Safety and Health for Engineers. New York: Van Nostrand
Reinhold.

Hammer, W. 1980. Product Safety Management and Engineering. Englewood Cliffs,
N.J.: Prentice-Hall, Inc.

Madsen, M. D. 1985. Quantitative safety risk assessment model. ASAE paper no. 85-
5512. St Joseph, Mich.: ASAE.

w st «
Zz
“Desc -
“Moe Seater wt contr = Move main pce bree
ever" ‘wrest (eotnet)
= nbvance rete Ete
“aamace bakes Inet og?
“Ma nped lever ormart
fasema production
Teyeometiog
a
Dperat’sEraetion: ‘Operators Eran:
Bort? “Blac?
Se? Tan?
What a ered? Wat wan erent?

Figure IV-12. Synthesized flow of actions and decisions required and possible of the operator of an
UPSAT machine when the shredder xxit plugs and the operator reverses the rotation of the shredder
anit from within the cab.

IV-15



UNIT V - Engineering for Hazard Control and Injury Preventions

Emergency Shut-off
Devices

One way manufacturers have achieved quick blade-stop is to install an additional
control lever on the mower’s handlebar connected to a shut-off switch on the mower’s
engine. To operate the mower the control lever is hand-held in the appropriate
position by the operator. If the operator leaves the rear of the mower, the shut-off
control must be released. This shuts off the mower’s engine and stops the blade. This
safety feature is easily defeated by tying the shut-off control lever to the mower’s
handle bar with a short strap. This keeps the shut-off switch from operating as
intended.

Farm machinery guards and shields that are removable by hand tools, and that do not
affect functional use of the machine, are an example of class 2 safety-defeatability
resistance. Another example is the use of a screwdriver to short across starter motor
terminals to bypass safe tractor start-up procedures. Cutting off tractor ROPS with a
torch would be an example of class 3 safety-defeatability resistance. These last two
examples (as well as the lawn mower example) obviously raise questions about the
role of operator responsibility for complying with and maintaining original equipment
safety devices.

An old safety proverb declares that “there is no smarter fool than he who figures out
how to beat a safety device”. Nevertheless, the point here is that effective safety
engineering recognizes people have tendencies to ignore or defeat safety features, and
more may do so when it is easy to do.

One issue of safety engineering that doesn’t fall neatly into the normal categories of
safety is that of machinery emergency shut-off devices. This issue has particular
relevance in production agriculture because it is already being used in some instances,
and some see an expanded role for such devices. Some machinery-related. incidents
between a person and a machine’s hazard point result in the person becoming
entangled or entrapped by the machine, with the machine continuing to run. This
situation sometimes results in additional or more severe injury to the victim. For
instance, a person’s leg may be pulled into a pinch point by a running machine. If the
machine continues to operate, another limb of the victim may become ensnared as the
person struggles to pull free. Even when only part of a victim is caught, the
continuing action of the machine sometimes inflicts considerably more damage to
skin, muscle, and bone of the victim.

An emergency shut-off device would presumably allow an immediate stopping of the

machine once:a person becomes caught by the machine. The simplest way to utilize

this technology is to have some means near enough to the point of entanglement that
the worker or a helper could activate the emergency shut-off device once a victim is
entangled in the machine. There are important factors to be considered, including:

¢ Does the emergency shut-off device encourage workers to be unnecessarily near
the hazard area? If the emergency shut-off device becomes a convenient way to
stop and start machine operation, the emergency shut-off device may create
additional risk to the operator and others nearby.

¢ A person working alone may not be able to activate the emergency shut-off device
no matter how convenient it is because of the way the person becomes entangled or
caught. For example, the incident may happen too quickly.

° Avvictim may not have the presence of mind to activate the emergency shut-off
device because of excitement or panic. On the same machine, one victim’s
entrapment position may be such that the emergency shut-off device can only be
activated by a pushing action, while a second victim's position may be such the
emergency shut-off device can only be activated by a pulling action.

+ In some instances, the continuing action of the machine results in a complete
severing of a digit or limb, in essence freeing the victim. In cases where the person

v9



AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

organic dust syndrome, and silo unloader’s syndrome. The silo unloader’s syndrome

reference is from the disease being closely associated with workers uncapping or

opening a conventional silo, an activity that often involves handling moldy silage. e
Nevertheless, in recent years, scientists from several countries have agreed to call this

disorder organic dust toxicity syndrome (Donham and Rylander, 1986).

Animal Housing The structural environment hazards discussed above occur within the structures
themselves and within animal housing buildings. Many animal housing buildings are
found directly over or under other structures such as manure storages and hay mows,
or next to such structures as silos and grain bins, where gases and dusts may travel
easily between them. Human exposure to animal feeds and bedding containing mold
spores often occurs while they are being dispersed to or among animals within
buildings. The types of animal housing most commonly identified with respiratory
hazards includes confinement housing of swine, poultry, and veal, and dairy barns.

Confinement housing and dairy barns, particularly, are associated with organic dust
toxicity syndrome, acute and chronic bronchitis, occupational asthma, chronic
obstructive pulmonary disease, and other similar respiratory disorders. The dense
stocking of animals within buildings results in large quantities of respirable dusts.
These dusts generate not only from feeding and bedding activities, but from the
animals themselves as dried urine and fecal matter, and hair and feather particles.
Diseases and disorders are most likely to appear in workers who have worked for
several years in such buildings.

Controlled-atmosphere Controlled-atmosphere (CA) storages are found on farms in those parts of the country

Storage where large quantities of fruits and vegetables are stored. A CA storage is designed to
retard the metabolic processes of horticultural crops to extend the time perishable
seasonal products will retain acceptable eating qualities such as flavor, texture, color, e
etc. The metabolic process can be slowed by lowering the temperature of the storage,
and by reducing oxygen (O2) and increasing CO. This means rooms must be
sufficiently airtight to exclude oxygen entry and maintain wanted concentrations of
CO . The desired levels of these two gases vary according to product, but as a rule,
Oz levels are always below levels immediately hazardous to life (6%). Normally,
once a CA storage is sealed, entry is not made until the end of a specified time period
when the structure is opened and completely ventilated with air, and entry is safe.
There may be exceptions when entry is required for system repair or to obtain
samples. This is when the insufficient-oxygen hazard is present.

When fossil-fueled atmosphere generators are used to initially establish the low-
oxygen atmosphere, a high carbon monoxide (CO) concentration may be produced in
the CA storage. This is harmless to the produce, but, when the room is vented prior to
produce removal, CO may seep into adjacent work areas. There is no CO danger if
nitrogen gas (N) is used to create the atmosphere.

ANIMALS Interactions between farm animals and their caretakers provide the possibilities of
both health and traumatic injury hazards to the caretaker. Many of these interactions
are in the context of production agriculture work, but not all. Injury and health
hazards also occur from pleasure-oriented activities such as pleasure riding of horses,
and showing farm animals in 4-H and FFA contests. In terms of understanding
hazards associated with farm animals, it makes little difference whether the animal
and person interaction is work or pleasure oriented. Broad categories of animal-
related hazards include animal handling and zoonotic diseases. e



Copyright © 1994 by
American Society of Agricultural Engineers
All Rights Reserved
The American Society of Agricultural Engineers is not responsible for statements and opinions
printed in its publications. They represent the views of the individual to whom they are credited
and are not binding on the Society as a whole.
This publication may not be reproduced in whole or in part by any means
(with the exception of short quotes for the purpose of review)
without the permission of the publisher.
For information, contact the American Society of Agricultural Engineers
2950 Niles Road, St. Joseph, Michigan 49085-9659 USA
Phone: 616.429.0300 Fax: 616.429.3852 E-mail: hq@asae.org

Pamela DeVore-Hansen, Editor
Acquisitions
Books & Journals
ASAE Publication 08-94
LCCN 94-72086
ISBN 0-929355-S1-2



UNIT IV — Hazard Analysis

“OLS VTA PHA, *T-AT aD

=
|

7) eH) (ct) ay (a a) ey 0) ) () ty) [) 2
N| 4] 9 | A | veya, suogoy eve (8)uonoy N 9 wousoyquen | 4 eunyes a eunyea Spow uoyouns
d/elo}te Uoyeidiuog =| pepuewuiccey d ® ubjseq N |] JO(sjesmeg | © | 40 (s)HeYS eunyye ved
wlalo|s 2 BqIsuOdseL yg ) 9 feque}og s$ #BNUE}Og jenueyog Jequinn 2 oO
PF Dy fenpiaipuyeqy e ° OWEN Ued 2
INSeY UO} a °
eta —— _ i a a ee ee SS
hq posedaug ‘sie oseajay Supsasug,
(aoe) (340) ed VERGE (S)ajoHYOA EO, [POW ‘SUTeN S8990%g 40 Ud

SISATVNV SLOG44a GNV AGOW FAN TIVA
“oseqeiep De 2p cyUt popeo] uusOS atp oABY sramyoenieM AUB ‘PosENqead Buy2q sionposd oxp 30 Artxojdwoo op Uo Suspuadap sasyoesnueUT O} amORyrUTeU Woy ATCA If WO} YW Oy) JO UORSES SILL (1)



UNIT HI — Human Factors

People are Different

The second principle is that people operate and maintain equipment in a manner
influenced by the equipment design. Thus, characteristics of the equipment design
such as the responsiveness of the steering system or brakes, or the visibility of
information displays in sunlight, or the force required to loosen a drain plug, act as
stimuli to which the equipment user must respond. If the equipment characteristics
require more from the operator than the operator is willing or capable of providing,
the operator can respond incorrectly, out of sequence, or not at all. These equipment
stimuli demand selective attention of the user; the operator cannot respond to all of
them at the same time. Thus, at any given time, the user must pay more attention to
some features of the equipment than others. Stimuli can also take the form of
procedures for operating and maintaining the equipment, such as those given in
operator’s manuals, that impose loads on the operator's memory. Just as physical
materials have certain tolerance limits within which they function effectively, the
capabilities of people are set within certain natural limits within which they function
best.

The third principle is derived from the second. Since equipment design characteristics
act as stimuli to the user, then it follows that users will respond more efficiently to (or
will accept as more preferred) certain arrangements of these characteristics over other
arrangements. Thus, if equipment characteristics are designed to match the
capabilities and limitations of the operators, the performance of the operators should
be more efficient. Because uncomfortable whole-body resonances, which are inherent
with humans, occur in the frequency ranges between 3 and 6 Hz and between 10 and
14 Hz, a seat or cab suspension design that greatly limits a vehicle operator’s vertical
acceleration in these frequency ranges will be better than one that does not (assuming
that significant vibration inputs occur in those regions).

The fourth principle is that it is easier to modify equipment characteristics to match
human capabilities than it is to modify (or select) human capabilities to accommodate
equipment requirements. It is easier to select displays with larger alphanumeric
characters or to arrange displays so that they are closer to the user than it is to add
more sensitive visual acuity to the human. It is easier to design controls to be actuated
within “human” force capabilities and to locate them within “human” limits of reach
than it is to endow the operator with greater strength or to change his physical
dimensions to a more desirable geometry.

People are different in their size and shape (anthropometric dimensions). Because of
this fact the human-factors design philosophy leads the design of a vehicle seat to
permit the operator to independently adjust the vertical and fore-aft position. This
allows the operator to determine the best viewing position for reading displays and
observing the tasks, and choosing the best position relative to the machine’s controls.

They are different in their perception of “comfort”. This fact motivates designers to
provide adjustability in the operator’s work environment (¢.g., seating, foot/leg room,
air conditioning, etc.) to accommodate these differences.

They are different in their motor capabilities (e.g., reaction time, strength, etc.). They
are different in their sensory capabilities (e.g., visual acuity, hearing ability, smell,
sensitivity, etc.). They are different in their mental or cognitive capabilities for storing
and processing information and for making decisions (e.g., learning rate, memory,
retention of skills, etc.).

They are different in their experiences, “native-training”, motivation, cultural

background, perception of risks, and many other characteristics. Even the same person
may be different at different times. Thus, the truth is: there is no “average man” or

m-3



UNIT I — Agricultural Accident Statistics, Limitations, and Weaknesses

‘Table I-1, National Safety Council estimates

for accidental work deaths, 1960-1990
@ Year Agriculture Mining* Construction All Industries
1960 3300 800 2400 13,800
1965 3000 700 2700 14,100
1970 2400 600 2800 14,200
1975 2100 500 2200 12,600
1980 2000 500 2500 13,000
1985 1600 500 2200 11,600
1990 1300 300 2100 10,500

* Includes quarrying, oil, and gas extraction.
From: National Safety Council Accident Facts, 1961-1991.

‘Table I-2. National Safety Council estimates for accidental
work death rates (deaths per 100,000 workers), 1960-1990

Year___Agriculture_ Mining* Construction _ All Industries

1960 38 123 B 2
1965 65 108 73 2
1970 67 100 2 18
1975, 58 63 61 is
1980 61 + 45 13
1985 “9 30 37 u
1990 42 43 33 9

* Includes quarrying, oil, and gas extraction.
From: National Safety Council Accident Pacts, 1961-1991.

@ 742; the death rate (per 100,000 workers) was 20.7 (National Institute for Occupational
Safety and Health, 1989). The corresponding total and rate for all industries were 6,757
and 7.9, respectively.

Fatality rates (per 100,000 workers) for individual sectors were given by Myers (1989):

Agricultural Production (SIC sector 01, 02) 21.2
Agricultural Services (SIC sector 07) 8.6
Forestry (SIC sector 08) 171
Fishing (SIC sector 09) 80.0

It was noted, however, that agricultural production accounted for the great majority of
deaths, and fishing accounted for very few, despite its high rate. Of the 742 annual
average deaths, 583 were in agricultural production, and 57 were in agricultural
services, which was said to have the second highest total. Therefore, although totals for
forestry and fishing were not given, they must have been less than 57.

‘The type of fatal accident that is occurring on farms can be estimated from the analysis
of 10 years of data as reported in the chart in figure I-2. These percentages do not
include “transport” deaths and, thus, do not exactly match figures from the National
Safety Council.

The National Safety Council estimates that about 430 fatalities a year occur from
tractor accidents. Figure I-3 shows the most common types of tractor accidents.

These estimates of the number and type of farm accident are based on nationwide data
- and 10-year averages. The number of fatalities varies from year to year. Also, the



UNIT I - Agricultural Accident Statistics, Limitations, and Weaknesses

Inconsistent Use of
Terminology

Work-related Injury

compared to nonfatal injury events. The number of fatalities nationally, as projected
from the survey data, is much less than the estimate given in Accident Facts (National
Safety Council, 1991).

The term farm accident is used to describe several different types of events. In its
broadest interpretation, it means any unintentional event that causes personal injury or
property damage on a farm. Even if farm accident is more narrowly defined, and
limited to those events involving injuries, there are two distinctly different
interpretations. One interpretation includes any injury event that occurs on a farm,
regardless of whether it was related to farm work, to recreation, or to any other activity
occurring on farm property. The second interpretation includes only those injuries
involving the farm operation in some way, such as farm work or the farm work site. It
excludes injuries involving recreation or other miscellaneous activities. The second
interpretation could also include farm work-related injuries occurring off the farm, such
as on a public road.

What is a work-related injury? When the term farm accident is used to refer to events
resulting in farm work-related injuries, the interpretation is still not clear. For example,
one interpretation of a farm work-related injury may include only those injuries
suffered while the victim was actually working. This excludes victims who are
bystanders to a work activity and are injured at that time, such as a person riding along
on a tractor to keep the operator company, a child being watched by the parent doing
farm work, or a child in the barnyard who is run over by someone backing a farm
implement. A different interpretation of work-related injury may include anyone injured
during a farm work activity. This includes the bystanders who were excluded in the
previous definition, as long as a farm work activity was occurring when the victim was
injured. However, it excludes victims injured by a machine, structure, tool, etc., related
to or used in farm work when no actual work was in progress. Therefore, a third
interpretation of work-related injury may include these victims of the farm work site.
One example could be a child playing on a tractor tire leaning against a wall; the tire
tips over and crushes the child.

A fourth interpretation or definition exists for work-related injury. This interpretation
includes only those injuries suffered in the course of working at the victim's usual
occupation. NIOSH uses this definition when compiling fatality data with its NTOF
system. An injury is considered work-related if it occurred while the victim was
working at his or her occupation; in the case of NTOF, this is the occupation stated on
the death certificate. A victim injured while performing a farm work activity would not
be included if his or her usual occupation did not involve farm work, e.g., a factory
worker, a physician, a truck driver, a teacher, etc.

In addition to the interpretations of work-related injury as it applies to farm accident
given above, there are two other issues involving farm injury data and the inclusion or
exclusion of certain cases. These are intentional injuries, and work-related injuries only
incidentally occurring on the farm.

NIOSH considers intentional injuries and fatalities, such as homicides and suicides, to
be work-related if they occur in the course of occupational work. For example, a gas
station attendant murdered during a robbery would be included in the census of work-
related injuries and fatalities. Most counts of farm injuries include only unintentional
injuries and exclude intentional injuries such as suicides. Under the NIOSH system,
they could be included if the coroner or medical examiner filling out the death
certificate concludes the death occurred “at work”.

L15



1 : i

UNIT I — Agricultural Hazards

Power Take-Off (PTO)
Stub

that will start with the tractor in gear, or on newer tractors where the starting
interlocks built into the tractor have been bypassed. Small children, usually under the
age of 5, are sometimes run over by tractors and machinery as they are moved around
the farmstead. Often, the tractor operator is unaware that the child is even near the
equipment. A loud noise, such as the start-up of a tractor, is often attractive to young
children and may draw them near and the practice of allowing extra riders may bring
them running to the tractor.

The tractor’s PTO stub shaft, often simply called the PTO, transfers power from the
tractor to PTO-powered machinery. Power transfer is accomplished by connecting a
drive shaft from the machinery to the tractor’s PTO. The PTO-driven implement’s
drive shaft slips over the tractor’s PTO. The PTO and drive shaft rotate at 540 rpm
(9 rev/s) or 1,000 rpm (16.6 rev/s) when operating at standard PTO speed. At all
speeds, they rotate in proportion to the speed of the tractor engine.

Most tractor PTO stub shafts operate independent of tractor ground speed, though
there are some exceptions. This means that the PTO can be engaged and operated
while the tractor is stationary. PTO operation independent of ground speed is one of
the fundamental reasons a tractor is the primary farm work machine. This feature
allows considerable flexibility for: basic types of work (field and stationary);
functioning of machinery (servicing, adjusting, harvesting, etc); and crop conditions
(slightly wet, course vegetation, weedy, etc.). Most incidents involving PTO stubs
stem from clothing caught by an engaged but unguarded PTO stub. The reasons a
PTO stub may be left engaged include: the operator forgets or otherwise is not aware
the PTO clutch is engaged; the operator sees the PTO stub spinning but does not
consider it dangerous enough to disengage it; or the operator is involved in a work
activity requiring PTO operation. Pant legs, overalls and coveralls, sweatshirts, and
windbreakers are among clothing items that may become caught and wrapped around
a spinning PTO stub shaft.

The PTO master shield is attached to the tractor and extends over and around the PTO
stub on three sides. This shield is designed to offer protection from the PTO stub and
the front joint of the drive shaft of the connected machine. Many tractors, particularly
older tractors, may no longer have PTO master shields. Master shields are removed or
are missing from tractors for several reasons, including: damaged shields that are
never replaced; shields removed for convenience of attaching machine drive shafts;
shields removed out of necessity for attaching machine drive shafts; and shields
missing when used tractors are sold or traded. There are many more injuries
associated with the drive shaft than with the PTO stub. Implement drive shaft hazards
and incidents are discussed in the Machinery Hazards section.

Other hazards associated with tractor operation are common to many types of self-
propelled equipment. For instance, there are slips and falls during mounting and
dismounting of tractors. Wet and muddy feet, inclement weather, steps high off the
ground for clearance purposes, difficult-to-reach handholds, and hurrying operators
are some reasons operators slip while getting on tractors. These reasons, plus difficult-
to-see steps, crowded tractor platforms, and improper exiting (facing away from steps
instead of toward them), are why operators sometimes trip or fall while. getting off
tractors. A person may be crushed between a tractor tire and a building from
inadvertent tractor rolling, or a tree limb may break off and crush an operator in his
seat during the pulling down of an old tree. Pressurized hydraulic systems, hitching
and unhitching implements, refueling, changing or adjusting heavy tires, operating
tractors on roads with faster vehicular traffic, towing heavy loads, and engine
maintenance are just some other activities and operations that may present hazards to
an operator. The point in identifying these types of miscellaneous hazards is to

5



UNIT Ill — Human Factors

Figure I11-7. Conventional anthropometric dimensions.

larger in size and weight than the corresponding general population. These data argue
that engineers/designers need to provide increased dimensions and adjustability to
accommodate these larger individuals, while still providing for the smaller user in the

population.
ANTHROPOMETRIC Measurements are made of many different parts of the body. These measurements
DATA form a data bank for the design of most equipment that interfaces with a human
(fig. HI-7).

The conventional anthropometric measurements include the following:

Standing height Seat or popliteal height

Seated height Functional arm reach

Seated eye height Upper and lower arm length
@ ‘Upper leg height Shoulder width

Knee height Hip or seat width

Seat length Weight

However, human beings must not only fit spatially in a man-task system, but they
must also be able to move and function dynamically. This requires additional room for
the operator to ingress, egress, move, turn, reach, and operate controls. Although static
body dimensions are useful for certain design purposes, the dynamic or functional
dimensions are probably more useful for most design problems (fig. MI-8). The
dynamic or functional dimensions must consider the location and movement of
operating controls as well as the forces to be exerted and the direction and frequency
of the movements.

@ sutecnin —_ bute

Figure HI-8. Static versus functional body dimensions in vehicular cab design (from Damon, Stoudt,
and McFarland, 1966).

m9



UNIT IV - Hazard Analysis

streets collecting prepackaged containers (specifically made for this purpose) of paper
trash/refuse set out along the curb by residents. The machine is built to shred the
paper refuse in a collection chamber with rotating drum knives. The shredded paper is
collected and compressed in a large holding tank that periodically is transferred to a
transport vehicle. The shredded paper is sold by the city to various customers needing
this raw material for their enterprises.

The problem to be studied is: “In what way will the operator behave (or can we expect
him to behave) when the shredder unit becomes clogged?”.

The flow charts of figures IV-10, IV-11, and IV-12 provide a means of analyzing this
problem. The beginning of each flow chart, or “event chain” as it would be for any
other kind a machine interruption, is an event that represents a functional problem of
the human-machine system. For whatever reason, the system became clogged (for.our
example, some old asphalt shingles were placed in the collection container), and the
behavior of the operator stems directly from the occurrence of the interruption. Thus,
it is necessary to recognize that interruptions to system function are characteristics of
the system. Operator activity (i.e., behavior) in response to those interruptions
depends on:

* equipment design

* other external modifiers of behavior

ACNE FUNCTION IS INTERRUPTED.
{Strader Unit Fuge)

Teeson WoORERS
‘oor
ites - Ene
“att nt foane «Cate
“ree Arab te
“theryatb Stn,
fear:
"Sond - Espn Devan
“hear "Oe Sores Oper
a ‘or .
_~ Move inain gearshit heres te “Hewtrar (eptonal) Does shred ust
“ov pre sect bere?
for bate ~ ape Ph
eo ws no
¥ +
7 ant tri mk
Sy rorrsretewtatt |_| Terme rer sree -tytopa moos
Tey to pull pig toma Tey 10 pall plug toss bideidelend
1, t ”
Bese? fevewane] [Seest fewer] [Seon owe]
Ws 6
cot “rac
“awe “mrt
‘tet “hone
howe re emt
Toren De “Awe e
reso “tigate
Howton “Mav heb oc Os
towns wean | | |e manure ew
“tween panties’ | | | “Arner ae
ower ree fee
Ata oe patio Free.
“Ae ee Forme oom
‘heme
enenig se] Tiycenenie ne]
Doers ea Opes tan
"ere “ere
Time? “tet
“ent? “ites?

[+ Learned thatthe recommended mathod doesn’ always work.

TV-10. Synthesized flow of actions and decisions required and possible of the operator of an
UPSAT machine when the shredder umit plugs and the operator turns off the power to the
shredded unit.

IV-13



UNIT I ~ Agricultural Accident Statistics, Limitations, and Weaknesses

REFERENCES

Cited References

This lecture was condensed from chapters 1 and 3, Safety and Health for Production
Agriculture, Dennis J. Murphy, ASAE, 1992. Chapter 3 written by Mark A. Purchwitz.

Agricultural Statistics Board. 1991. Farm Labor. National Agricultural Statistics
Service, U.S. Dept. of Agriculture, Washington, D.C.

Bernhardt, J. and R. Langley. 1991. Farm fatalities in North Carolina, 1984-1988.
Journal of Rural Health 8(1):60-69.

Bureau of the Census. 1984. 1980 Census of the population, vol. 1, Characteristics of
the population, chapter D, Detailed population characteristics, part 1, United States
summary. Publication PC80-1-D1-A. U.S. Dept. of Commerce, Washington, D.C.

—. 1988. Rural and rural farm population: 1987, Current population reports, Farm
population, series P-27, no. 61. U.S. Department of Commerce, Washington, D.C.

. 1989. 1987 Census of agriculture, vol. 1, Geographic area series, part 51,
United States summary and state data. Publication AC87-A-51. U.S. Dept. of
Commerce, Washington, D.C.

Bureau of Labor Statistics. 1988. Employment and earnings, vol. 35(6). U.S. Dept. of
Labor, Washington, D.C.

Consumer Product Safety Commission. 1986. The national electronic injury
surveillance system: A description of its role in the U.S. Consumer Product Safety
Commission. U.S. Consumer Product Safety Commission, Division of Hazard and
Injury Data Systems, Washington, D.C.

Deere & Company. 1993. John Deere Safety Day. (Dealer education materials).

Doss, H. J. and R. G. Pfister. 1972. Nature and extent of farm machinery use in relation
to frequency of accidents. Report no. 30. Center for Rural Manpower and Public
Affairs, Michigan State University, East Lansing, Mich.

Field, W. E. and R. L. Tormoehlen. 1982. Analisis of fatal and non-fatal accidents
involving children. ASAE paper no. 82-5501. St. Joseph, Mich.: ASAE.

Fritsch, C. F. and J. M. Zimmer. 1980. U.S. Farm accident fatalities, 1970-76.
Agriculture information bulletin no. 434. Economics, Statistics and Cooperative
Service, U.S. Dept. of Agriculture, Washington, D.C.

Fuortes, L. J., J. A. Merchant, S. F. Van Lier, L. F. Burmeister and J. Muldoon. 1990.
1983 occupational injury hospital admissions in Iowa: A comparison of the
agricultural and non-agricultural sectors. American Journal of Industrial Medicine
18:211-222.

Gunderson, P., S. Gerberich, R. Gibson, S. Adlis, P. Carr, A. Erdman, J. Elkington,
R. French, J. Melton and J. True. 1990. Injury surveillance in agriculture.
American Journal of Industrial Medicine 18:169-178.

Hanford, W. D., J. W. Burke, W. J. Fletcher, A. F. Hoskin and T. A. Miller. 1982. Farm
accident survey report. National Safety Council, Chicago, Ill.

Kelsey, T. W. 1992. Fatal farm accidents in New York: Estimates of their costs.
Northeastern Journal of Agriculture and Resource Economics 20:202-207.

Marine Safety Evaluation Branch. 1989. Printout of fishing vessel casualties reported to
the Coast Guard, 1981-1987. U.S. Coast Guard, Marine Investigation Division,
Marine Safety Evaluation Branch, Washington, D.C.

Murphy, D. J. 1990. Trends in twenty years of tractor accident statistics. ASAE paper
no. 90-1639. St. Joseph, Mich.: ASAE.

. 1991. Pennsylvania farm fatalities during 1985-89. Extension circular 390.
College of Agriculture, Pennsylvania State University, University Park, Penn.

Murphy, D. J. and M. A. Huizinga. 1989. A new approach to collecting farm accident
data. Journal of Safety Research 20(1):21-29.

Myers, J. R. 1989. The national traumatic occupational work-related deaths. NIFS
paper no. 89-9. Columbia, Mo.: NIFS.

Napier, T. L., W. R. Goe and A. R. Pugh. 1985. Incidence and predictive factors
associated with farm accidents in Ohio. Research circular 287. Ohio Agricultural
Research and Development Center, Ohio State University, Wooster, Ohio.

1-21



UNIT V - Engineering for Hazard Control and Injury Preventions

a way of communicating hazard information when products are repainted but safety

messages are not replaced, and when older products with unreadable safety messages
e are resold on the secondary market.
Prescribe personal
protection Occasionally, the operator will be exposed to hazardous conditions, such as noise

from operating a chain saw, handling anhydrous ammonia, pesticides in the air during
application of the pesticides, the absolute requirement to enter a manure storage pit, or
the requirement to enter a controlled atmosphere storage. Whenever the engineer has
the opportunity to communicate to the operator regarding these issues, instructions
should be provided that include specific information concerning the type of personal
protective equipment that is required and the general limitations of that personal
protective equipment.

‘SAFETY ENGINEERING

STRENGTHS The strengths of safety engineering as a strategy for hazard and injury prevention and
control cannot be over emphasized. Safety engineering is the most important deterrent
to unanticipated injury and death. The following summary statements and examples
represent both current and forward-looking applications of safety engineering without
regard for unresolved liability or other feasibility (costs, cultural traditions, etc.)
issues. With this caveat, safety engineering:

Utilizes the “hard” sciences rather than the “soft” sciences. The distinction between
hard and soft sciences is important because what is known about the hard sciences is
more precise, reliable, predictable, etc., than what is known about the soft sciences.
The essential difference is between understanding physical objects and things versus
the thought processes and behaviors of people.

@ Alleviates incentives to take risks. Examples: automatic coupling systems for hitching
implements to tractors eliminates the need for a second person during hitching;
stirring augers help to keep grain from bridging inside bins, reducing the need for
humans to enter the bin for that purpose.

Eliminates or significantly reduces hazards and risks. Examples: the hydraulic valve
to prevent tractor bypass starting and runover incidents; closed systems, for
transferring pesticides between original containers and mixing containers prevent
exposure to pesticides in their most concentrated form.

Offers automatic protection against hazards and risks. Examples: ROPS and a passive
Seat belt restraint on tractors; human presence-activated systems or devices that stop
moving parts if a person is in a hazardous zone.

Provides relative permanence. When engineered protection becomes a part of original
design, the protection is more likely to stay in place. Examples: hinged guards on
farm machinery; built-in ground-fault circuit interruption for electrical systems.

Provides relative efficiency. One engineering oriented solution or device may be
applicable to all or many similar products or situations. Examples: fire-resistive
coverings for cellular plastic insulation in farm buildings, oxygen level indicators in
all confined spaces (silos, manure storages, grain bins, etc.)

Combines solutions to increase protection. Examples: mechanical guards with

. interlock controls to prevent operation of hazardous machinery parts without the

@ guards in place; viewing port holes in grain bins, along with stirring augers, eliminate
the need to climb and enter the bin for observational purposes.

V-15



AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

INTRODUCTION

LANGUAGE
AMBIGUITIES

Agriculture and farming

SIC Code

Production Agriculture

One tool for assessing the safety of a new product design is data concerning the
incidence of personal injury among persons using products of similar design. This
accident history is the basis of understanding the hazards of any new product. A risk
analysis of the design options for a new product is based on understanding the hazard
exposure. The need for quality farm injury data is clear, but the data that are desired are
difficult to obtain.

Several ordinary words used to describe important characteristics of production
agriculture contribute to a lack of understanding of production agriculture by many
people. The casual use of two pairs of words, agriculture and farming, and industry and
occupation, cause particular problems from a safety and health perspective.

Agriculture and farming are often used interchangeably. Webster’s Ninth New
Collegiate Dictionary defines agriculture as “...the science or art of cultivating the soil,
producing crops, and raising livestock...”. Farming is listed as a synonymous cross-
reference, and defined as “... the practice of agriculture”. Therefore, using these terms
synonymously seems appropriate. However, when these terms are used interchangeably
within the context of safety and health, confusion and distortion often result because of
the way injury statistics are grouped by official bodies of the U.S. government.

The Standard Industrial Classification (SIC) Code is the official U.S. document for
defining and describing industrial establishments (U.S. Department of Commerce,
1989). Establishments are defined as “...economic units (places) where business is
conducted or services performed”. The SIC Code has several divisions, one of which is
division A — Agriculture, Forestry, and Fishing. Division A is divided into major
groups, often called sectors. The sectors of division A are as follows:

Ol. Agricultural Production — Crops

02. Agricultural Production — Livestock and Animal Specialties
07. Agricultural Services

08. Forestry

09. Fishing, Hunting, and Trapping

Each of these major groups is further subdivided. For example, sector 01. Agricultural
Production — Crops, has six subgroups that identify types of crop production, such as
cash grains, vegetables and melons, etc.

Only sectors 01 and 02 are synonymous with the work and activities commonly
associated with the term farming. Other terms used to describe major groups 01 and 02
are agricultural production, farm production, and production agriculture. Agricultural
production may include establishments that perform services such as operating fish
hatcheries or raising forestry seedlings. These services, or activities, fall outside the
range of activities most commonly associated with farming. Farm production may
imply that all farming activity happens on a farm, which is not true. Therefore,
production agriculture is the preferred terminology.

The assignment of establishments into the sectors within division A is not always
intuitive or consistent with popular perception. It is easy to incorrectly guess where
some types of establishments have been assigned, and there is little practical difference
among some establishments, though they may be assigned to different sectors. Fish
farming, such as raising catfish for human consumption, is a part of sector 02, while
fish hatcheries are a part of sector 09. Tree farms are a part of sector 08 and not
categorized as production agriculture. Yet, most tree farmers consider themselves to be
farmers in the popular sense of that word.

12



AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

* intemal modifiers
Thus, as is shown in figures IV-10, IV-11, and IV-12, the operator activity
immediately following the interruption basically is dictated by the equipment design. @

‘That is, there are certain actions that the operator must do before production can be
resumed. After these immediate actions are taken, the operator may then have a
number of decisions alternatives from which to choose. (Note: the more alternatives
available, the greater will be the variability of performance and, therefore, the greater
will be the potential for human error.) The choice taken by the operator is affected by
other “external modifiers”, such as the sounds or sights just prior to the interruption,
the weather, or other demands on the operator, and by “internal modifiers”, such as
motivation, experience, training, and memory of a similar situation, etc. Although it is
hoped that each item shown in the flow chart contributes to the understanding of how
operator behavior can be “synthesized”, special notice should be given to the last box,
operator evaluation. This item is a key element in each of the event chains because the
evaluation conducted of the time and effort required by the operator and what that
person learned forms the basis for subsequent decisions.

Figure IV-10 shows a flow of action and decisions required and possible by the
UPSAT machine operator when the shredder unit becomes clogged and the operator
tums off the power to the shredder unit. Figure IV-11 shows the flow of actions and
decisions, both required and possible, by the UPSAT operator when the shredder unit
‘becomes clogged and the operator leaves the power on to the shredder unit. Figure
IV-12 shows the flow of actions and decisions required and possible of the UPSAT

ACHE FUNCTION IS WTERAUPTED
(Bienen lt Pe)
‘OPERATOR ACTIONS ELISION MODIFIERS.
=the speed vers nated pnp) opener ‘urna
Mena te edocs enon speed Dean “Metaaben « Experience
apo he Lecsveanaed “tang = Met Resend - Cotere

nate ome “Tet
| cunt ree, Sores?
nas

—{~=|] P=) [C2] Le @
Figure IV-11. Synthesized flow of actions and decisions required and possible of the operator of an

UPSAT machine when the shredder anit plugs end the operator leaves the power on to the

shredder unit.



AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

SAFETY ENGINEERING
PRINCIPLES

Product Reliability

Fail-Safe Designs

Failure Minimization

Product design and product reliability go hand in hand because the reliability of a
product is built into its design specifications (Vinogradow, 1991). Product reliability
relates to safety engineering in two ways. First, if a product is not functioning the way
it is intended, or it breaks down from a component or system failure, work’ goals
become compromised. This may cause frustration or anger, which in turn, may result
in hurried and reckless work procedures, inappropriate risk taking, or an enraged
behavioral act (¢.g., kicking a control). All of these actions may lead directly to an
injury incident. A smoothly flowing work process often means a worker’s exposure to
hazards is reduced because the person can remain in a safe location (e.g., on a tractor
seat, on the outside of a silo, standing back from operating machinery, etc.). Field
crop harvesting machinery, farmstead machines to move or process crops and feeds,
and manure storage equipment are among those items for which proper product
functioning is an important means of reducing product hazards.

Product reliability also relates to safety engineering through direct failure of product
parts. For example, breakage may occur with a kicking chain being used on a young
cow or the snap on a lead shank tying a horse. In either case an injury to the handler
may result. Another example is the possibility of being injected by hydraulic oil if a
high-pressure hose ruptures.

Some safety engineering designs are referred to as fail-safe. The goal of a fail-safe
design is to ensure that a product failure will not result in damage to people, the
product itself, or the environment. There are three types of fail-safe designs (Seiden,
1984).

A fail-passive design reduces the product to its lowest level of energy so that the
product cannot operate until corrective action is taken. No further damage will result
from the hazard causing the inactivation. Electrical circuit breakers and fuses are

common examples of fail-passive designs.

In a fail-active design, the product remains energized but in a safe mode until
corrective action can be taken. Products that use monitoring systems to warn of
failure, or potential failure, have fail-active designs. A battery-operated smoke alarm
that beeps when the battery charge becomes low is one example.

A fail-operational design allows the product to continue to operate with reasonable
safety until corrective action is possible. Many view this as the most desired type of
fail-safe design because it allows the product to continue with its functional purposes.
An airplane that is capable of flying with half of its engines shut down is one example
of this type of design.

Fail-safe designs are not possible or feasible for all hazards (Hammer, 1985). In such
cases, engineering can still be used to minimize the consequences of failures of

products. The four principal methods are:

1. Monitoring devices. A specific parameter, such as temperature, noise, or toxic gas,
is kept under surveillance to ensure that it stays within acceptable limits.
Monitoring devices check operating conditions to keep dangerous situations from
developing or reaching the imminent stage. A valued monitoring device entails
four steps: detection, measurement, interpretation, and response.

2, Waming devices. This method is similar to monitoring but more directly involves a
person as the monitor. The intent of warning devices is to focus the attention of the
person on the item that constitutes the hazard or potential hazard. Warning devices
work by alerting at least one of a person's five senses. Figure V-1 illustrates how
the five senses may be used as warning devices.

V-4





AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

A SYSTEM DESIGN
PROCESS

A brief discussion of the system design process will precede the development of a few
safety engineering principles that are relevant to agricultural equipment and structure
design.

An organized product development requires that a well-planned design sequence be
followed. This sequence typically includes:

¢ Identifying a human need and creating product ideas to satisfy that need

Evaluating alternative design ideas

Designing and building prototypes

Testing and evaluating the prototypes

* Performing a preproduction “pilot” run of the product manufacturing processes.

 Full-scale manufacturing of the product

* Conducting product evaluation

Evaluating alternative designs is an important step in the process. Because of ever-
present financial pressures to be competitive, it is imperative that products be
introduced into the marketplace on schedule and within the specified budget. The
importance of meeting scheduled introduction dates is clearly recognized in highly
competitive industries. For example, a missed availability date for the Christmas
buying season can result in vast inventories that are susceptible to being outdated in a
relatively short period, possibly creating financial disaster for a toy manufacturer.
Thus, it is very important for the manufacturer to develop and evaluate alternative
designs prior to their introduction.

The evaluation of design ideas may include functional requirements review, design
group reviews, analytical methods, economic analyses, and others. A functional
requirements review includes techniques that basically work in reverse of
“brainstorming” sessions. During this type of review the soundness of the design is
scrutinized, impractical ideas are eliminated, and a check is made that the original
functional requirements are satisfied.

Design group reviews are particularly valuable in finding potential deficiencies in the
design or considerations that had been overlooked. Experienced members of the
design review group can draw upon knowledge of similar designs that can be very
valuable. On satisfactory review of design ideas for function, a general specification
for the product is established. Often, this is a joint effort between marketing and
product engineering functions. The publication and distribution of a ‘general
specification helps ensure that the development of the program starts and ends in a
product of well-defined specifications that are mutually agreed upon by all
appropriate segments of the manufacturing firm.

The analytical methods available include mathematical models and computer
simulations that provide information about concerns such as stress within a structure
for a given load condition. Other computer programs are available for simulating the
fatigue life of components, bearings, gears, shaft deflections, forces, and geometric
analyses of how parts fit together within a product. These analytical methods are
valuable because they permit the engineer to consider design changes and to evaluate
the effects of those changes with considerably less time and expense compared to
methods requiring physical testing.

Another crucial test of the product design is its cost. Since the product engineer’s
responsibility can be defined as the organized development of an idea into a profitable
product that satisfies a specified need, it will be of little consolation if a product has
Superior appearance, unmatched performance, and high reliability if it cannot be sold

V-2



UNIT V - Engineering for Hazard Control and Injury Preventions

guard and reduce its effectiveness. Guards, as well as other exposed machine parts,
are to be free from sharp edges and comers so that they do not create new hazards.

If a guard covers an area that must be accessed for lubrication or other service, a
hinged guard to discourage removal and discard is needed. If the guarded parts
continue: to rotate or move for several seconds after power is shut off, a visual or
audible warning is needed to indicate continued machine action. These are issues
covered in the voluntary consensus standards of ASAE. When the guarded area is out
of sight of the operator's station, some method to prevent power engagement by a
second party should be provided. Removing the engine key or other power source
(fuel, electrical fuse) is one way to protect against machine hazards. A more passive
measure is to include an interlock that prevents power start-up when the guard is open
or removed. In some respects, such interlocks have advantages and disadvantages
similar to emergency shut-off devices.

Human presence-activated systems are closely related to the concept of guards and
shields (Anderson and Smith, 1988). The objective of a human presence-activated
system is to detect and respond to a person entering a hazardous area. In effect, it tries
to prevent such entry. Such systems are typically equipped to sense the presence or
absence of operators in either a hazardous or safe (e.g., the operator’s station)
location. The seat switch incorporated in some lawn tractors, combines, and cotton
pickers is an example of this concept. The human presence-activated system device is
activated when the operator rises from the seat; it declutches the power train or shuts
off the engine before the operator has time to reach an area of danger. This circuitry
can have a time-delay mechanism, which would reduce the aggravation of power train
interruption caused by momentarily lifting off the seat. A complicating factor with a
human presence-activated system and cotton pickers is the periodic need to observe
the picker drums while they are functioning. This is resolved by a tether switch to
allow momentary, slow movement of the drums for observation from the ground; the
action will stop when the remote control switch is released.

Some combinations of machines are used in a stationary position while the operator is
on the ground. One example is a small tractor with a front-mounted log splitter. To
allow operation, an override switch permits the log splitter to operate while the
operator is on the ground. The override switch is installed in such a manner that it will
deactivate when the operator sits down on the seat and resumes a mobile work mode.

‘Width of Aperture Batety distance to Hazard
Ure Mustretion {Otamarer er Lotaral Length, ©, sm) em)
Finger Tip acact bois
»
*
Finger s<acds b> 120

Mand B<axa be200

0<0<250 b> 350

Figure V-2, Dimensions for openings through mesh or grille guards (adapted from ASAE Standard
$493. 1991).

V-13



UNIT Hl — Human Factors

FALLACY OF DESIGNING
FOR THE AVERAGE
PERSON

where
= = sumof
D = deviation of each value from the mean
N = number of subjects

In normal distribution, the mean (or 50th percentile)
1 Standard deviation includes 68% (16 to 84 percentile)
+2 Standard deviations include 95% (2.5 to 97.5 percentile)
£3 Standard deviations include 99.7%

The computation of a specific percentile is done as shown in the following examples:

1. To obtain the 75th percentile value when the mean value is 35.1 in. and the SD is
1.5 in., use K, = 0.674 (see table III-1).

Multiply the value 0.674 by the SD (1.5): 0.674 x 1.5 = 1.01 in.
This value is added to the mean value to give the dimensions of
the 75th percentile: 35.1 + 1.01 = 36.1 in.

2. To obtain a value below the mean, the calculated value is subtracted from the mean
value. For example, to find the value of the 10th percentile when mean value is
35.1 and SD is 1.5, use Ky = 1.282: 1.28 x 1.5 = 1.9 in.

The 10th percentile value is: 35.1 - 1.9 = 33.2 in.

: 3. To find the adjustment needed for the middle 90% of this group, use the factor K

times the SD. K, for the central 90% = 3.29
‘The adjustment required is: 3.29 x 1.5 = 4.9 in.

‘When a normal distribution is fitted to the anthropometric data, it is observed that the
most likely measurement for any dimension is at the mean. A designer might conclude
that equipment designed to fit this 50th percentile person or average person would
accommodate the largest number of persons, but designing for just the 50th percentile
person is a serious error. A control or device designed to accommodate only the 50th
percentile person will be too large or out of reach for the small half of the population
and too small to fit the large half.

Designing for the 50th percentile is also an error when the design involves muscular
strength, because a control designed for average strength could not be operated by the
weaker 50% of the users. In general, maximum control resistances should be based
upon the strength exertion of the weakest potential user. If the weakest person can
operate the control, all others will be able to do so as well. The designer should

‘Table II1-1. How to compute percentiles from standard

deviations (from Roebuck et al, 1975)
Percent
‘Confidence
Interval on.
Percentile K, —theMean K, =2K,

30 70 0524 40 1.045
25 B 0.674 50 1349
20 80 0.842 60 1.683
15 85 1.036 n 2.073
10 9 1.282 80 2563
5 95 1.645 90 3.290
25 975 1.960 95 3.920
1.0 99.0 2.326 98 4.653
OS 99.5 2576 9 5.152

FI



UNIT Hl — Human Factors

Reducing Probability of
Error

something in time. There are five major categories of human error, according to
Swain and Guttmann (1980):

1. An error of omission that occurs when a person fails to perform a task or part of a
task.

2. An error of commission that occurs when a person performs a task or part of a task
incorrectly.

3. An extraneous act that occurs when a person introduces some task or step that
should not have been performed.

4. A sequential error that occurs when a person performs some task or part of a task
out of the proper sequence.

5. A time error that occurs when a person fails to perform a task or part of a task
within the allotted time, either too early or too late.

Human performance is highly variable; we never do anything exactly the same way
twice, and no two people perform a task exactly alike. As long as the variability of the
human performance stays within the acceptable limits defined by the system, no error
will be noted. It is only when a response is outside these specified tolerance limits that
an error occurs. The narrower the limits, the more likely it is that they will be
exceeded. Thus, human variability can contribute to human error, and the greater the
variability, the greater the potential for human error. Figure III-5 depicts a
hypothetical distribution of time observed for human operators performing a task,
along with a specified tolerance limit. In this case an error occurs if too much time
elapses. In such a situation, the probability of error can be reduced two ways:

Reduce the variability of performance by selecting the operators or by intensive,
periodic training of operators so that only those people who can perform the task as
required by the system will be permitted to operate the system.

Enlarge the acceptable tolerances by redesigning the system to accommodate the
existing variability in the population of operators so that, in the case shown in
figure III-S, even the slowest operator can perform the task without an error.

Human tolerance limits, that is, limits placed on human responses to keep the
variability of human behavior within acceptable tolerances, must be used in trying to
control the potential for human error. Swain and Guttmann (1980) offer the following
list of tolerance limits arranged from the most effective to the least effective:
1) Barrier limits physically prevent unacceptable performance (e.g., interlocks,
shields); 2) Fixed limits are clearly and permanently established limits (e.g., detentes
on controls, color coding of instruments); 3) Empirical limits are limits checked by
observation or measurement during or after performance (e.g., checking an instrument
panel to see that a gauge is within tolerance); 4) Reference limits are standards to be

NOERROR | ERROR
i]
Frequency of !
‘Occurrence t
1
i)
Low Task Completion Time High

Figure III-S. A hypothetical distribution of time observed for human operators to perform a task; also
shown is a system-specified tolerance limit.

W-7



UNIT I - Agricultural Accident Statistics, Limitations, and Weaknesses

farmers, hired farm workers, and farm family members are so irregular and varied from
one person to another. One person on a farm may work 100 hours a week and another

e@ person only five or six. During planting and harvest, operations may continue around
the clock. A given piece of equipment may be used heavily for a month and not used at
all the rest of the year. As can be seen in the following discussion, no denominator data
source currently captures hours of exposure. Thus, population values are the most
frequently used denominator values.

Census of Agriculture The U.S. Department of Commerce, Bureau of the Census, conducts a Census of
Agriculture every five years; the most recent was in 1987 (Bureau of the Census,
1989). The results are typically published two to three years later. The Census of
Agriculture provides data on farms and farm operators by county, by state, and for the
nation. An interesting statistic provided is the number of farm operators whose primary
occupation (the occupation in which they spend more than 50% of their time) is not
farming. Prior to the 1987 Census of Agriculture, data were provided on the number of
hired farm workers, including the number working more than or fewer than 150 days
per year. The number of farms employing workers, categorized by the number per farm,
was also provided. These data were not collected in the 1987 census.

The U.S. Bureau of the Census considers a farm operator to be the person doing the
day-to-day management of a farm. It also considers the number of farm operators to be
the same as the number of farms. The Census of Agriculture provides data on the
number of farms by county, by state, and for the nation as a whole (Bureau of the
Census, 1989).

The farm population consists of all those who live on farms, including children. The
farm population does not represent the number of people who work on farms, as not

@ everyone who lives on a farm works on a farm. And, some people who operate or work
on a farm may not live on a farm. (See Bureau of the Census, 1988.)

USDA Farm Labor These quarterly reports from the U.S. Department of Agriculture Agricultural Statistics

Report Board provide an estimate of farm labor based on surveys taken by USDA during one
week in January, April, July, and October (Agricultural Statistics Board, 1991). The
number of workers reported includes people self-employed, unpaid family members,
and hired workers. Totals for each of these classes are provided by category for those
expecting to work 150 or more days that year and those expecting to work less than
150 days. Self-employed workers must work at least one hour on their farm during the
survey week to be counted, and unpaid workers must work 15 or more hours during
that week to be counted. The number of agricultural service workers (custom crews and
crew leaders working on farms during the survey week) is provided separately; they are
not included with the farm workers (self-employed, unpaid or hired) discussed above.

Census of the The well-known Census of the Population (Bureau of the Census, 1984), taken every

Population 10 years by the Bureau of the Census, provides a “snapshot” of employment during the
week prior to Census Day (1 April). Persons age 16 and older are asked to list the
occupation and industry in which they worked that week; if they had more than one
job, they are to respond based upon the job in which they spend the most hours. An
unpaid family member who worked at least 15 hours that week is included as if he/she
was employed. Persons not employed that week are asked to give their most recent
occupation and industry from the previous five years, if any. This total is added to the
total of employed persons to come up with the total for the “experienced civilian labor
force”.

~ r Occupations and industries do not necessarily correspond. For example, a person
working on a farm would not necessarily have the occupation of farm worker or farm

1



AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

of hay, lifting containers of produce above the head to dump into trucks, stretching
across mushroom beds, and bending over low-lying crops (cucumbers, strawberries,
etc.) are just a few examples of common work activities that may result in
musculoskeletal injury. To the extent the work environment involves vibration, cold or
dampness, a fast work pace, and forceful exertions, the hazard is increased.

Dermatoses Dermatoses refers to skin diseases. Information on production agriculture
occupational dermatoses is sketchy. Nevertheless, it is considered a leading
agricultural occupational health hazard. Among the agents that may cause dermatosis
are pesticides, zoonotic diseases, ultraviolet radiation, and the various farm chemicals
mentioned earlier. Other sources include inedible plants (poison ivy, oak, etc.), crops
(lettuce, celery, strawberries, and others), and animal feed additives. Hands are the
most commonly affected body part. Dermatoses are most closely associated with
migrant and seasonal farmworkers. One reason is the nature of their work: hand and
field work results in a high exposure to plants. Dairy farmers, from their use of
sanitizers and cleaners, have also been identified as a susceptible group for
dermatoses.

Stips and Falls One of the most common causes of minor injury on the farm, and an occasional
serious or fatal injury, is slips and falls. A variety of circumstances cause these falls,
including: ice around farm buildings, wet surfaces in the bam, including manure,
stepping up onto machinery that is wet or the boots are muddy.

Electrical Electrical power usage on the farm is still growing. Electrical hazards are created if
the electrical wiring and electrical motors are not installed according to the National
Electric Code. The other electrical hazard on the farm is contact with the high-voltage
electrical wires that supply electricity to the farm. Contact with these overhead
electrical wires can occur from moving a portable grain auger under these wires,
handling aluminum irrigation pipe, pivoting an extension ladder under these wires or
contact from unusually high farm equipment.

Flowing Grain The flow of grain inside the grain bin when the grain is being emptied from the
bottom of the bin can readily trap anyone who is on the surface of the grain. The force
created by the unloading grain is so great that once a person is waist deep in the grain,
he or she is unlikely to be able to escape, even with the aid of a safety rope. Typical
unloading rates will bury a person in less than a minute (NIOSH, 1993), and if not
removed, the person is suffocated. A similar hazard occurs for children who are inside
a grain wagon when the wagon is unloaded.

Other variations of this hazard occur when the surface of the grain has caked or
crusted as a result of moisture at the surface. The grain can bridge at the top or cake to
the walls of the bin. Once the bin has been partially emptied, a person entering the bin
can fall through this bridged surface or be trapped by grain that is dislodged from the
bin walls.

The risk of suffocation increases if grain spoils, because it gives off carbon dioxide,
which may displace the oxygen in the bin. Even if the worker is not completely
buried, he or she can suffocate because of the lack of oxygen above the grain surface
QNIOSH, 1993).

Long Work Days The seasonal nature of farming creates the pressure to work quickly and work long
hours during the planting and harvest periods. During these periods, the operator who
“is working long hours “to get the job done” may engage in risky behavior that would

not be acceptable in less stressful periods.

0-18



AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

BASIC CONCEPTS AND
PRINCIPLES

Four Basic Principles of
Human Factors

A hazard was defined in unit II as a condition or changing set of circumstances that
presents a potential for injury, illness, or property damage. An injury to a person on a
farm usually involves the interaction between an agent of injury and the person. There
is the opportunity to reduce the probability of injury by considering the agent of
injury or, separately, considering the person. The person in the human-machine
system is the subject of this lecture. The general discipline for analyzing the person in
this human-machine system is human factors.

‘One definition of the discipline of human factors is the application of behavioral
Principles and data to engineering design to do two things: to maximize an
individual’s contribution to the effectiveness of the system of which he/she is a part
and to reduce the impact of that system on the individual (Meister, 1971). The
reduction of the probability of personal injury is one element of human factors
analysis.

The basic concept in the application of human factors in the system design process is
that of the “human-machine system”. Figure HI-1 depicts a model of a human-
machine system. This model shows the closed-loop relationship between the human
operator and the equipment. For example, the operator of a corn harvesting combine
receives information from the equipment through information displays in the cab or
from the external environment in which he is operating (e.g., the position of the
header with respect to the corn rows or the amount of grain observed on the ground
behind the combine). The operator processes the information and makes certain
decisions involving it and then operates the equipment controls (e.g., turns the
steering wheel or reduces ground speed) to change the equipment status to achieve
some desired goal. The equipment consequently provides new information (feedback)
about its changed status to the operator and this cycle continues. The interaction
‘between the operator and the machine creates the system relationship.

Inherent in the application of the human factors design philosophy is the acceptance
of four principles that have been given by Meister (1971). The first principle states
that the functional effectiveness of equipment is related to the efficiency with which
people can operate and maintain the equipment. Thus, any reduction in the operator’s
performance will lead to the equipment failing to perform its function or cause the
equipment to perform that function less effectively than planned. For example,
although a self-propelled forage harvester may have been given the capability of
traveling at 9 mph (15 kph) through a field, it will fail to perform its function if the
operator feels uncomfortable traveling at that speed (i.e., is disconcerted by the
vibration, noise, and complexity of performing required tasks that are affected by the
vehicle’s speed) and selects a slower, more comfortable ride.

Figure II-1, A model of a human-machine system.

Il-2



OBJECTIVE

SPECIAL TERMS

INSTRUCTOR
MATERIALS

TRAINEE
MATERIALS

UnitV

ENGINEERING FOR HAZARD CONTROL AND INJURY PREVENTION

To introduce students to the principles of safe design.

After completing this unit, the student will be able to:

List the steps in the system design process
Explain the essential elements of the identified safety engineering

principles
List and explain the safety hierarchy

Fail-safe design
Failure minimization
Redundancy

Passive protection
Defeatability resistance

Participant outlines made by instructor
Supplementary materials



AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

Children on Family
Farms

The Hired Workforce

older farm workers. Older workers are a significant part of the total farm injury and
illness picture.

The specific effects of age-related characteristics on injuries and illness to older farm
workers appear to be the neglected area of farm safety and health research. This issue
has not generated much discussion within the popular press or professional
associations. One reason for the lack of attention to this issue may be that focusing on it
calls for examination of cultural concepts and practices deeply woven into the fabric of
American culture. Society simply may not know how to come to grips with the
underlying issues.

There is no set age group (or age) that corresponds to the word children (child) when
this group is discussed in the context of production agriculture safety and health. Other
terms such as youth, teens, and adolescents describe the same general populations,
particularly those at the upper end of the age scale. In this book, age groups are
identified by including the specific age or age parameters as appropriate. If an age is
not given, children will be persons under the age of 14. This is arbitrary but consistent
with traditional U.S. Department of Agriculture (USDA) age group delineations.

Child safety on the farm and in farm work is another one of production agriculture’s
stickier issues. Because the work site and the home site are often one and the same,
children are injured while at work and at play on farms. Some of the difficult issues to
be faced include: children working because of economic necessity, parents wanting to
instill a sense of responsibility and work ethic, a lack of childcare options while parents
work, and a cultural tradition of the entire farmstead as a giant playground for children.
Practical solutions to these kinds of dilemmas are often beyond the means of a single
farm family.

The actual number of hours per day or days per year farm family children work in
production agriculture is not well documented. A profile of agricultural workers in 1987
reported 3,129,000 households headed by farm operators with children less than
14 years of age. However, the USDA does not record production agriculture work data
for those workers under the age of 14. The U.S. Department of Labor, which compiles
occupational work data for industries, does not collect labor data on those under the age
of 16. Indirect measures of production agriculture child labor are occasionally found in
farm injury studies. For example, a tractor and machinery use study by Doss and Pfister
(1972) reported that children ages 5 through 14 operated tractors during 1971 in
Michigan a total of 2,650,000 hours, and in Ohio 2,708,000 hours. Regardless of
specific documentation, unpaid child and teenage labor in production agriculture is a
common and accepted practice. In some instances, children and teens make a
substantial contribution to a farm’s total annual hours of labor.

The hired workforce consists of contract laborers, domestic hired workers, foreign
nationals, and undocumented foreign workers. This hired workforce is often
characterized by the nature of length of their employment. For instance, there are full-
and part-time workers, and seasonal and migrant workers. Seasonal workers are those
who work particular seasons of the year but have permanent residences near where they
work. Migrant workers may also only work particular seasons, but they move from one
job site to another, far from their permanent residences.

The total number of hired workers is not precisely known. The USDA suggests the
number has remained relatively constant throughout the 1970s and 1980s, between 2.5
and 2.8 million. Advocates for seasonal and migrant workers suggest that the total
number is much higher, perhaps twice the USDA estimate. The uncertainty is attributed
to widely varying estimates of migrant and seasonal workers. The reasons estimates

1



AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

Human Error Defined

Five Categories of
Human Error

STIMULt BEHAVIOR
* Goals + Actions / Decisions
* Hunger / Thirst
* Theats
© "Barriers"

Figure IL-3. System design considers the stimuli affecting the system and the desired system behavior.

the choices made by the designer regarding the responses that the system is permitted
to make. In this context, the designer includes all the representatives that influence the
system design (i.e., legislative, judicial, producer, customer).

To change the behavior of a system, we can either modify the stimuli (redesign the
environment in which the system operates) or control or limit the responses that are
permitted to occur following the stimuli (redesign the system). In “human-machine”
systems, the human is one element of the system that generally is not within the
designer’s control. Even in military systems, where selection and extensive training of
system operators is possible, the system designer still cannot completely specify the
operator’s characteristics to match the design of the other system elements. The
operator’s behavior, however, is strongly influenced by the system design. Individual
actions and the sequence of actions permitted of, or performed by, the operator are
dictated by the system design. As such, operator behavior can be excluded or
included, as shown in figure III-4, as is done with other design parameters.

‘The other term requiring definition is human error. With regard to system design, the
definition of human error offered by Rigby (1970) is most appropriate, “Human error
is any member of a set of human actions that exceeds some limit of acceptability”.
‘Swain and Guttmann (1980) state that an error (human or otherwise) is merely an out-
of-tolerance action where the limits of tolerable performance are defined by the
system. There is no connotation of blame or fault. By convention, the definition of
human error excludes malevolent behavior but does include intentional errors. An
intentional error is one that occurs when the operator performs some act believed to
be correct or to represent a better way of performing a task but, in fact, is incorrect or
wrong. Most errors are unintentional . . . they just happen . . . such as activating the
‘wrong control because controls similar in appearance are nearby.

A human operator in a system can perform an out-of-tolerance action, that is, make an
error if the operator does something incorrectly, fails to do something, or fails to do

PERMITTED 4 NOT PERMITTED
— CO

Anite

meysniongnisares
af

Frequency of
(Occurrence

Figure I1I-4, Behavior can be excluded or included.

m6



ABSTRACT

To be effective, the designer of a product or structure to be used in production agriculture must
be aware of hazards found in agriculture. The designer must then evaluate and modify the design
to eliminate or reduce the risks associated with those hazards. A review of the injury statistics is
a first step, but the limitations of those statistics must also be known. This is the subject of unit I.

Areview of the accident statistics reveals the most common hazards in production agriculture.
These hazards are presented in unit IT.

The discipline for analyzing the person in a man-machine system is called human factors. The
person in this system serves as a controller with physical, physiological, and psychological
limitations. These issues are the subject of unit HI.

Techniques for conducting a hazard analysis are presented in unit IV.

Most products are designed using a well-defined product development sequence. During that
development cycle, the issues of managing risk are addressed. The safety hierarchy is a model
that is commonly used to manage risk. These issues are the subject of unit V.



UNIT IV — Hazard Analysis

i,
co

I> 6 ‘at hana

~

AND gate. A logical AND relation. Output A exists if and only if all
of B,, Ba, . .. B, exist simultaneously.

OR gate. A logical inclusive OR relation. Output A exists if any of
B,, By, ... By , or any combination thereof, exists.

Inhibit gate. Permits applying a condition or restriction to the -
‘sequence. The input and condition of restriction must be satisfied for
an output to be generated.

Identification of a particular event. When contained in the sequence,
usually describes the output of an input of an AND or an OR gate.
Applied to a gate, indicates a limiting condition or restriction that
most be satisfied.

Anevent, usually a malfunction, describable in terms of a specific
Circuit or component.

An event that is normally expected to occur, usually an event that
‘always occurs unless a faiture takes place.

An event not developed further because of lack of information or of
sufficient consequence. Could also be used to indicate further
investigation is intended when additional information becomes
available. Symbol W with a numerical subscript is sometimes used
also.

Indicates and stipulates restrictions. With an AND gate, the
Testriction must be fulfilled before the event can occur. With an OR.
fate, the stipulation may be that the event will not occur in the
presence of both or all inputs simultaneously. When used with an
inhibit gate, stipulation is a variable condition.

‘A connecting symbol to another part of the fault tree within the
same major branch. Has the same functions, sequence of events, and
numerical values.

A connecting symbol to another part of the fault tree within the
same major branch. Has the same functions and sequence of events,
but not numerical valves.

/

Figure IV-S, Fault tree analysis symbols and explanations (Source: Hammer, 1980).



AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

9.2% Struck by Object 3.6% Animals
2.9% Suffocation

2.2% Fire and Bums
46.7% Machines 2.8% Other Causes

2.0% Poison

4.4% Electrical
11.1% Drowning. 6.5% Firearms

8.6% Falls

Figare I-2. Nontransport deaths on farms: 10 years, 1979-1988 (Deere & Co., unpublished).

proportion of accidents will vary in different regions of the nation because of the
differences in farming operations.

SUMMARY Farm and agricultural injury statistics are neither simple to obtain nor do they compare
with other data. A variety of sources exists, each with its own strengths and limitations.
Because of variations in definitions, inclusion criteria, methodologies, and denominator
values, data must be interpreted with care. In spite of this caveat, it is clear from
existing data that:

a) Production agriculture is a relatively hazardous occupation.

b) All age groups are at risk, including children and older workers.

¢) There are many agents of injury on farms.

d) Tractors and machinery are involved in a high proportion of fatal and permanent

injuries.
€) Various occupational illnesses affect farm workers. e
f) Lack of exposure data makes developing comparable rates difficult.
8) More consistent use of terminology and inclusion criteria will improve data

collection and analysis efforts.

iN

50.8%
Overturns

Figure 1-3. Tractor accidents are the single most common farm fatal accident and tractor overturns are
the leading cause of tractor accidents (Deere & Co., unpublished).

1-20



UNIT IV - Hazard Analysis

Step 10.

Step 11.

Step 12.

Step 13.

Step 14,

Calculate the risk priority number. The risk priority number (RPN) is the
product of the severity, occurrence, and detection rankings. RPNs are
relational, therefore they have no individual value or meaning. An example
of calculating the risk priority number is:

+ Product A:
Severity - Engine misfire - Ranking 5
Occurrence = Repeated failures - Ranking 8
(1 in 20)
Detection - High (good chance) - Ranking 3
Risk priority number (RPN) = 120

Severity (5) x Occurrence (8) x Detection (3) = 120

Identify recommended actions. After the RPN has been calculated,
corrective action should be directed at the few critical characteristics. The
intent of the corrective action should be to reduce any one or all of severity,
occurrence, and detection rankings.

Areminder:

* To reduce the severity ranking the team must make one or more
design revisions and verify through testing.

* To reduce the occurrence ranking the team must remove or control one
or more of the causes of failure.

* To reduce the detection ranking the team must improve the design
verification system.

- Design of experiments

- Dynamic product simulation

~ Revised test plans

- Revised design

- Revised material specifications

Identify the responsibility for recommended actions. Enter the person(s) or
area(s) responsible to facilitate corrective actions. Include the completion
target dates.

List the actions taken. After an action has been completed successfully,
enter a brief description of the actual action, the results, and the effective
completion date. Again on complex projects, project management
techniques are a must to assure timely completion of actions that could

postpone an important FA.

Calculate the resulting risk priority number. After each corrective action has
been successfully completed the FMEA must be updated. A reevaluation of
the severity, occurrence, and detection rankings should be made. The next
step is to recalculate the risk priority number. A newly prioritized list should
be circulated to the individuals and/or areas responsible for the design and
corrective action,

The FMEA has been completed. Remember that the risk priority number has no
absolute value but is used to rank the priorities of the design changes that result from
the analysis. When the process is taken to its ultimate conclusion, design changes or

IV-7



AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

SAMPLE QUIZ
QUESTIONS

1, Analyze the most complete narrative information available for several farm
injuries to determine if there was a component of human error leading up to the
injury. What type of error was involved (error of omission,’ error of commission,
etc.)?

2. Review a combine or tractor manufactured 20 to 25 years ago and compare with
the newest tractor available. Identify design changes that will reduce the
‘probability of human error and human stress and fatigue.

3. Obtain a recent publication of anthropometric data. Compare your measurements
with that data and compute the approximate percentile for each value.



UNIT I — Agricultural Accident Statistics, Limitations, and Weaknesses

NIOSH - NTOF The National Institute for Occupational Safety and Health (NIOSH) operates the

National Traumatic Occupational Fatality (NTOF) surveillance system (Myers, 1990).

@ This system purchases all death certificates in the nation that meet all three of the
following criteria:

1... The person died of an external cause of death (injury), and thus the death
certificate has ICD9 E-codes of E800-E999.

2. © The age of the deceased is 16 years or older.

3. There is a positive response to the question “Injury at Work” on the death
certificate.

The NTOF system provides a census of all traumatic occupational fatalities in the
United States, including those due to intentional injuries like homicide and suicide. The
deaths are allocated to industry categories based upon the usual occupation and kind of
business or industry recorded on the death certificate. The selection criteria of the
NTOF system are important to farm injury statistics. The age limitation excludes
children, even those performing production agriculture work at the time of their deaths.
The “injury at work” question relates directly to the usual occupation and industry
recorded on the death certificate. For a part-time farmer, a farm accident would not be
considered an injury at work if the occupation listed was nonfarm. Since approximately
45% of U.S. farmers have a nonfarm primary occupation (Bureau of the Census, 1989),
this could be a significant factor.

CPSC —NEISS The Consumer Product Safety Commission (CPSC) operates the National Electronic
Injury Surveillance System (NEISS). This system collects information on consumer-
product-related injuries treated in hospital emergency departments (Consumer Product
Safety Commission, 1986). A relatively small sample (64) of the nation’s 6,000+
e@ hospital emergency departments is selected to be representative of the nation; they
report any injuries in which one or more of a large list of consumer products is
involved. Injuries involving certain select products under special study may be selected
for telephone follow-up or even on-site investigation.

Agricultural machines are included on the consumer product list, and 32 different
agricultural machinery codes are used. No projections are given for many agricultural
machines because of small (less than 20) sample counts of injuries involving those
machines. In 1987, only 8 of 32 agricultural machine categories were given a national
estimate. Tractors are consistently given a national estimate, but two estimates are
given: one for “farm tractors”, and the other for “tractors, other or not specified”, which
could be a farm tractor or garden tractor. If a product is not specified on the emergency
department record, the injury will not be included in the system. This approach does
have the advantage of reporting nonfatal injuries on a timely basis. Whether or not the
sample statistically represents farming areas has not been studied.

CFOl The Census of Fatal Occupational Injuries (CFOI) is a new system devised by the
Bureau of Labor Statistics. As the name implies, it is a census of all work-related
occupational injuries from participating states. A unique feature of this system is that
each case requires a secondary source for verification of the work-relatedness to an
occupation. The system was expected to be operational in all states by 1993.

NHTSA - FARS The National Highway Traffic Safety Administration (NHTSA) operates the Fatal

Accident Reporting System (FARS) to collect data on all fatal traffic accidents in the

: United States and Puerto Rico (National Highway Traffic Safety Administration, 1988).
e@ Accidents in which a person dies within 30 days of the incident are reported by state
analysts. Some 90 different data elements characterize the accident, the vehicles and the

people involved. Included in the vehicle description is a code for vehicles classified as

1-13



AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

Power Take-Off (PTO) The PTO driveline hazard is essentially a wrap point hazard. It is one of the oldest and
Drivelines most common farm machinery hazards and refers specifically to the part of the
implement (machine) drive shaft that connects to the tractor. Many farm machines e@

have additional drive shafts, so it is helpful to clarify what is meant by the phrase
“PTO driveline hazard”. The ASAE Standard $318.10, Section 2.4 (1990), defines
what is popularly known as a machine’s “PTO driveline”:

Implement Input Driveline (IID). Two universal joints and their connecting
member(s) and fastening means for transmitting rotational power from the
tractor PTO to the implement input connection. A double Cardan, constant
velocity joint is considered a single joint. The IID also includes integral
shielding (guarding) where provided.

Figure IJ-2 is a diagram of the important parts of a PTO driveline. By inference, PTO
driveline hazard means the hazard associated with the IID shaft. Less often, the
phrase is used in reference to the entanglement hazard of tractor PTO or input
connection to the implement.

The entire IID shaft is the wrapping point hazard if the IID is completely unshielded.
If the IID shaft is partly guarded, the shielding is usually over the straight part of the
shaft, leaving the universal joints, the PTO connection (the front connector), and the
implement input connection (IIC, the rear connector) as the wrapping point hazard.
Protruding pins and bolts used as connection locking devices are particularly adept at
catching clothing. If clothing doesn’t tear or rip away, as it sometimes does for the
fortunate individual, a person’s limb or body may begin to wrap with the clothing.
Even when wrapping doesn’t occur, the affected part may become compressed so
tightly by the clothing and the shaft that the person is trapped against the shaft. r)

The machine’s IID shaft is coupled to the tractor’s PTO stub. Therefore, it too rotates
at either 540 rpm (9 rev/s) or 1,000 rpm (16.6 rev/s) when at full recommended speed.
At these speeds, clothing is pulled around the IID shaft much more quickly than a
person is able to pull back or to take other evasive action. Many IID shaft
entanglements happen while the shaft is turning at one-half or one-quarter of
recommended operating speed. This may be the situation on occasions when the
tractor has been stopped but not turned off and the PTO is left engaged. Why an
operator might do this is discussed in the paragraph below. The point to be made here
is that even at slower speeds, once caught by a IID shaft, a person does not have time
for evasive action. A 540 rpm shaft makes over two complete revolutions per second
when operating at one-quarter speed. Even with a quick reaction time of one second,
the wrapping action has begun. Once wrapping begins, the person’s instinctive move

IMPLEMENT INPUT DRIVE LINE
(WITH PEDESTAL)

en ~ ‘AREAS =ry

PTO PEDESTAL IMPLEMENT
| CONNECTION | connection INPUT CONNECTION

tur MENT UT ORE UNE Tl werent @

Figure II-2. Drawing of a PTO driveline (Source: Campbell, 1987).

(PLEMENT

0-8



AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

HUMAN VARIABILITY -

compared with an output in time of doubt (e.g., samples of “good” and “bad” welds
used in quality control inspections); 5) Caution limits are limits given by warnings,
signs, etc. They are not very effective because they often are not present while the
related action is being performed or, if present, they are a familiar part of the
operator's environment and are no longer attention-getting signals; 6) Conventional
Himits are limits instilled by training or custom (but which may not be reinforced in
the work situation); 7) Forensic limits are limits subject to debate and are often
defined after some incident has occurred to assess blame.

The discipline of human factors encompasses such diverse human characteristics as
work physiology (the strength to push, pull or turn controls, the ability to lift
materials, etc.), cognitive skills and processes, and anthropometry (the physical
dimensions of people). These and other elements of the human factors discipline are
used to select the people that the Air Force will train to be jet aircraft pilots, to design
the contro] panels and instruments that are used by the operator to control a nuclear
power plant, and to design the operator controls for an agricultural machine. Time
permits only a brief introduction to one of these areas, anthropometry.

Human beings come in only two basic models, male and female. This would seem to
simplify the task of gathering data for design purposes. However, there are still wide
variations due to size, age, sex, body type, race, and country of origin, and even some
professions emphasize certain characteristics rather than others. For example, people
who do strenuous physical work are apt to be bigger and stronger than those who have
desk jobs.

The wide range in size and ability of humans makes the designer's task challenging.
‘The designer must consider the great variation of users and attempt to accommodate
as large a proportion as possible. This is particularly true in the design of agricultural
equipment. Rather than working with a specific population, such as might be found in
an industrial situation where the workers range from 20 to 65 years, the agricultural
designer knows that the design will be used by a wide spectrum of users. It will be
used by youngsters as young as 8 to 10 years of age, by older people, well into their
eighties, by women as well as men, and by people of all sizes and abilities. The
equipment will be used at night and in bright sunlight, in summer heat as well as
winter cold. It must accommodate heavy clothes, jackets, and gloves on the hands,
and have foot controls with sufficient clearance for winter boots (fig. III-6). The
designer’s task to accommodate as many people as possible under extreme conditions
is difficult and requires good anthropometric data.

Astudy by Casey (1989) gives evidence that, in addition to the wide range of people
and their sizes who use agricultural equipment, U.S. farmers tend to be significantly

Haight inches)
8:86 88 et

Sth Percentile 95th Percentile

5 Figure IIL-6. Equipment shoald fit the sunallest operator In light clothing as well as the largest in
bulky

H8



AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

Noncomparable Rates

Some work-related injuries occur on a farm but involve a victim engaged in his or her
nonfarm occupation. For example, a farm equipment mechanic may be injured while
repairing a machine on a farm. A carpenter or electrician may come to a farm for a
construction job and be injured while working. These are injuries occurring on farms
that are indeed work-related, but are related to the work of that non-farm occupation.
Whether or not these injuries are included in counts of farm injuries depends on the
inclusion criteria used. In general, these injuries are not normally counted as farm
work-related injuries because they would be included in statistics of other industries.

‘To help overcome these inconsistencies, the Farm and Agricultural Injury Classification
(FAIC) Code has been developed to provide classification guidelines based upon place
of occurrence, victim, and activity at time of injury. The code separates the injuries into
distinct categories which allow numerator data from various sources to be accumulated
in rational categories. The code allows for uniform collection and categorization of not
only production agriculture work-related injuries, but for injuries occurring on a farm
that are not related to the agricultural operation (such as a recreational injury); for
injuries related to farm work that occur off the farm (such as tractor roadway accident),
and for a number of other distinct combinations of occurrence, victim, and activity.
This code is published in appendix B of Safety and Health for Production Agriculture,
by Dennis J. Murphy.

Farm injury rates are important because they put the number of injuries into perspective
relative to the hours of exposure, the size of the population, or other denominator
values. Comparing numbers of injuries by themselves, without corresponding
information on the size of the exposed population or some other measure of exposure,
can be misleading. Farm injury rates are often difficult to compare because different
denominator populations are used in the rate calculations. Rates based upon total farm
population are different from rates based upon number of farm operators; the total farm
population is much greater than the number of farm operators. Including hired farm
labor ‘in the rates, by adding the number of hired workers to the number of farm
operators, increases the denominator value. However, the size of the increase depends
upon whether only full-time hired workers are included, or whether all hired workers
are included. Because many seasonal workers are employed, some for just a few days
at harvest time, the total number of hired workers is much greater than the number of
full-time hired workers.

Many migrant and seasonal farm workers are not hired directly by the farmer but by a
labor contractor who in turn provides labor services to the farmer. These workers are
considered to be employed in the agricultural services area and, depending upon how
the number of hired farm workers is calculated, may or may not be included in the
total. Another issue with respect to farm workers is the inclusion of unpaid family labor
and the different criteria used for such classification. For example, the USDA Farm
Labor Report (Agricultural Statistics Board, 1991) includes unpaid family labor
regardless of age if the person worked at least 15 hours on the farm during the survey
week; self-employed workers are included if they did at least one hour of work on the
farm during the survey week.

Another complicating factor involving rates and different denominator populations is
the effect denominator changes have upon the numerator. Strictly speaking, cases
should be included in the numerator only if the victims are included in the denominator
population. Thus, it would be necessary to eliminate from the numerator all those farm
injuries that involved someone not in the denominator population. Based on imprecise
information, this. task may be difficult or impossible. Conversely, if all farm injuries
were included in the numerator, it may not be possible to find an inclusive denominator
population. This is because some injuries may have involved visitors to the farm, such

1-16



UNIT V ~ Engineering for Hazard Control and Injury Preventions

For instance, suppose there may be a requirement for a service operation under a
raised element of a machine. The designer could provide a built-in swinging block
that could be positioned by the operator to positively assure that it would not fall. This
is an example of active protection. The operator must participate by positioning the
swinging block to be protected. A more passive solution is to equip the hydraulic
control with a valve that would not release oil to lower the element unless the engine
were running. This automatically protects the operator against the element
inadvertently falling even though the operator doesn’t have to take any specific
actions to receive the protection. Even with some types of passive protection, a
problem arise. For example, the operator could unintentionally sever a hydraulic
line while performing the service work. Or, an operator may intentionally open a
hydraulic line because he or she doesn’t fully understand how the hydraulic lock
system works. Therefore, it sometimes is best to incorporate redundancy by providing
both the manual block and the locking hydraulic valve.

Another example of a passive safety device is one that reduces the tractor bypass
starting hazard. A valve bypasses the pressurized hydraulic oil, which activates the
clutch until the operator cycles the clutch pedal one time. Thereafter, the clutch
actuation mechanism functions in the normal manner as long as the engine continues
to run. Since the operator must normally mount to the operator's station to actuate the
clutch pedal, this movement removes him/her from the position of risk in front of the
drive wheel. The valve does not interfere with any tractor function, it requires no
action on the part of the operator, and in fact, it may never be noticed by the operator.
Assuming adequate reliability, these are the optimum characteristics for any safety
system (Anderson and Smith, 1988).

One method of significantly reducing hazards is to change or improve the operation of
the product so the operator isn’t required to be in an exposed position. Tractor-
mounted com pickers that were commonly used during the 1930s and 1940s are an
example of this method. Under some crop and climatic conditions the machine
clogged at the crop intake area, particularly if the picking mechanism was worn or out
of adjustment. As operators became impatient with the chore of removing com stalks
with the power disengaged, they sometimes attempted to pull the stalks loose with the
engine running and the power take-off engaged. A sudden release of the clog would
then pull an arm into the rotating mechanisms. The advent of the corn head for
combines resulted in widespread replacement of pickers by combines for corn
harvesting. The com head of a combine uses a solid steel plate on the snapping roll,
instead of raised ribs, to help separate the ear of com from the stalk. Many corn heads
are also able to run in reverse. This allows these machines, in effect, to unclog
themselves in many instances. These changes and improvements have reduced this
com harvesting hazard to a great extent.

Another example is to replace a potentially harmful mechanism with one that does the
same job but is much less threatening. The substitution of a nylon filament for a steel
cutting blade made use of the hand-held power grass trimmer feasible for general use
by the public. If the whirling filament inadvertently strikes the leg of the operator, it
might sting or cause a bruise, but it is not likely to cause a serious wound. Yet it is still
able to perform its intended function. External chain or belt drive mechanisms, with
their attendant nip points, may be replaced by an internally concealed gear drive,
which provides improved reliability of machine operation, along with the reduced
exposure to risk.

Access to large tractors and self-propelled field equipment generally involves

ascending a number of built-in steps to reach the operator’s platform. An
accumulation of mud or debris can lead to a slip and injury from the resulting fall.

V-11



UNIT Il - Agricultural Hazards

Zoonoses

PRODUCTION
AGRICULTURE
CHEMICALS

Many traumatic injuries, ranging from minor bruising and crushing injuries to death,
occur during the routine handling and treatment of animals. The conditions and
activities involved in routine handling and treatment vary widely, from moving rabbits
between cages during cage cleaning, to separating small pigs from their mothers for
vaccinations, to branding cattle unaccustomed to human handling. Several factors
influence the chance of a person becoming injured while handling or treating animals.
One obvious factor is exposure: the more contact there is between an animal and a
person, the more likely that animal is to eventually cause some injury. This is true
even though some animals become more docile as they are routinely handled. Some
animals by their nature invite exposure, such as dairy cows and horses. Exposure may
also be substantially increased by the method of feeding. Some feeding methods are
heavily oriented to manual and individualized feeding while others are mechanized
and involve large groups of animals.

Other factors that influence the chance of traumatic injury from animals include:

1. Size: The larger the animal, the more probable it is to injure a person, and injure
him or her severely.

2. Familiarity with human touch: The less an animal is handled from birth, the more it
will resist being handled later in life.

3. Haste in transporting the animal: The more rushed an animal is when moved, and
the more excited it becomes, the more likely it is to resist movement.

4. Handling animals without proper restraints or handling devices such as halters,
Topes, squeeze shoots, kicking straps, etc.

5. Trusting an animal to the extent you tum your back when in close quarters with the
animal, or commit similar careless acts.

6. Remaining unaware that all farm animals have predictable behavioral
characteristics.

7. Handling beef, dairy, hogs, and horse newborn animals in the presence of their
mothers; any handling of bulls and stallions.

Zoonoses is the term that denotes diseases caused by infectious agents common to
both animals and man (Steele, 1979). A person may become infected by both direct
and indirect contact with diseased animals, their manure, urine, and bedding, or
through animal products (meat, milk, hides, hair, etc.). Indirect contacts include soil,
plants, and water contaminated by animal waste products. Intestinal diseases,
respiratory disorders, general feelings of ill health, and skin rashes and diseases
(dermatoses) are the most common manifestations of zoonotic diseases. Deaths to
livestock producers or workers in the United States from zoonoses are rare. Less rare,
though still not particularly common, are treatable dermatoses cases.

‘The term pesticide is generic for chemicals that kill, attract, repel, or otherwise control

pest plants, animals, and microorganisms. A wide range of compounds are used in
pest control including: acaracides (mites), algicides (algae), avicides (pest birds),
bactericides (bacteria), fumigants (nonselective pesticides in gaseous form),
fungicides (fungi), herbicides (weeds), insecticides (insects and related anthropods),
molluscides (snails and slugs), nematicides (worms), predacides (vertebrate pests),
pesticides (fish), and rodenticides (rats and other rodents). Pesticides are used in
nearly every type of production agriculture operation, though total use has decreased
in recent years.

Exposure to a pesticide does not, in and of itself, cause harm to humans, though this
effect is often implied. The effect or influence a pesticide has on humans depends on
various factors such as: physical and chemical properties (toxicity, degradation,
volatility, etc.) of the pesticide; the dose or concentration of the pesticide; the duration

Tr15



AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

*(panupnes) “gg61 ‘ounaN Woy padepy “sa>yA2p SujuzeM se pasn 29 WED sasuIs aay YI MOH “I-A ANB LY

“uopioeuingo UR JO JqOUR wuseM YOUISd 2uQ *>
"panned vey oui

“aaSuep # Jo WEN 01 VOI 270A °2
“Wwopioe JO

‘ovaid & Jaye 40 “janay pauluuarepasd © 01 paveaxsop fey que xp uy autevaud —aouanbou © uy date LxOU 2 2RL O1 ponqure Hey SUL HUE

‘ap voy panos my w33z7Mq UIEWOD sy2ed Je porvaxlwon awWos

‘goed ae) 01 x) Supwnjg asaym wave UE 39949 01 [auBOKIEd
sem 3}rvyen 40 uauye WUE @ UY aU WH Nay a vOME}PUY UNS y+

‘aonid omy
POUR Fu}9q peoy e SuypyNS uew ¥ wos overdo sue mp OV NUTS -y

-posooud 0) ayes sf way

SIsYoIOW Use O} says UOHLINAIHUOD PROM 1H awBEy Aq pn sBBy :2;QI514
Aipeea asow way axsus oF +2198 pus ‘vadas “sasym WO YIOI9 JO xduIW
PAlOjOD !2}9xYIA ay} JO Z¥ar ays 49A0 SurPRIO.d pect Sud; & Jo pua ay He
TRUIRALIS pas & :Uo Paxyom Sujaq x} 122 aUxpU] OF YAS BHO IY -T
“SUSIE 2yyRn revo} r>UDIUT I MUBIE VOIINED mo[[aX :¥SuJssO19 PROUTH
ye #1481] par SujSujms sxySu 19 s9pedqeg UoonyUCD UO WaysEY pay °
“pear yons SuyAuses syonn vo wus FAISOUOD 0 "TISVAWYY
“AAISOTAX S7Uts .ONIHOWS ON: ‘spzezy Supeqpuy wus} poy °2
‘majod. Suyy20f

talteyon egfry ‘aun, sqr8uaUd Jo yMEIDAY VO HBULYTR WAALS ON. “P

“aug © aBuRYD oF 2 2)
Supysef avojaq sjaaym 94) 12049 OF [MUR s,J9uN0 FD EU FUL Y *>

*hyyena parquBooas 29 wea wado x} 4 My) 128) ayn mp oF sum paruled
99 80g YOHME [EIIEIDAIa UIE OF JOOP ay JO SprEu] ay RAY BUND ypFEpUTIS
VHSO “sumo 20 mona powaynd # sy>qyps Supaou ¥ £q Ty 3q PHOS
‘Wor 199Kqo pony 40 “nrowdynbe yo aaa4d “(aod se yons) amuonE Yq

40 powsed say ous payyoods © wayt uomsad @ SUX “¢
‘ratheap Surpuadus| 40 Supsqr2 Jo Byun
‘aprncud 22,499 punos seu 20 ‘apy "uals y “

syuudys poy Y

‘satluep Jo wen 01 pom ave yo} Jo ¥a09{d 20 5B, “#

~Avatan ane2qpuy 40 puezry # 01 uonUaHE
Weane (woIayss 20) SYS SuyysEy 40 PAVO}OD 5

“SPAETRY JO LEM VOY) SPE “2

-wwauxdinbo ot payreue 30 uo pared are efuyamy -p
“epaezey 0) jauuctsad Vays 01

SERRE PUR sUOLOTUIEU] SouTUaTUTEUE PUR FuO;HEZEdO
1M pouaeyy 278 s2i0U uojINED pus SULA “>

“w0j0o Ep pun WA} Surmusaye
1 20 20409 14H 29 wo} pnezmy yeoyeAyd B NOTES “q

mous 9

amg 'q

sumy “e punog °z

‘aanous 01 vowsad ayo Wo; woHEULIE)U,
JaO pus ‘sBujuTem “suoronuisuy
weed o1 wuCpOW PURY JOY “Y

suountans pur siryy “3

smd outs

wis 3

ftuyart 9

V4

suOHORUIEUL UY FIION “2

voneuwpsrsig “q

“wuopmaqns sauoTUE ‘wean puncums snoparrmjuou
Pus “wuymns ‘v}DENGO ‘uO;osELOR Kemysiy Iit-tiem SuAeH -e UMA poreUrUUNy AjMs}4q WOU H] Bae INOPETR] YF vopeuUNT *e was ‘1
aura vonduseeg ‘Sasa onus



UNIT Ill ~ Human Factors

Design for a Worldwide
Market

more difficult and the cost is excessive. In most situations, the added complexity and
cost is not justified by the small numbers who benefit. A seat adjustment of 10.7 cm
will accommodate the middle 90% of users. Including the top and bottom 5% will
require a total adjustment range of 26.2 cm.

Increasingly, equipment is being designed and marketed for use by worldwide
clientele. Thus, the engineer/designer must choose the anthropometric data carefully.
People of different countries and races vary in size, conformation, and characteristics.
These variations may affect the design. For example, when people with a gencrally
smaller stature are expected to use the same equipment as people with a
predominantly larger size, the range of adjustment may need to be extended, or other
modifications may be needed. Foot pedal contro! must be spaced differently for
operators, with larger feet, and so on. The engineer who is aware of this full-spectrum
target market will be interested in anthropometric data with an international base.

The interaction between the operator and the machine creates the human-machine
system relationship. The functional effectiveness of the machine is related to the
efficiency with which people can operate and maintain the machine, which is
influenced by the equipment design. Operators will respond to the design
characteristics that act as appropriate stimuli, and it is easier to modify the machine
characteristics than it is to modify (train or select) the operator. The operator in a
system can perform an “out-of-tolerance”. action, i.e., make an error, by omission,
commission, an extraneous act, a sequential error or a time error.

Anthropometric issues are only one of the many human factor issues to be addressed
in the design of a human machine system.

The majority of this lecture was extracted from the ASAE publication Human
Factors: A Series of Quality Instructional Materials. No. 1 Human Factors
Concepts: An Overview, Jerry R. Duncan; No. 7 Anthropometrics and Workplace
Design, Robert H. Wilkinson; No. 11 Operator Behavior: Responses to
Interruptions of a Machine Function, Jerry R. Duncan, ASAE, 1991.

Casey, S. M. 1989. Anthropometry of farm equipment operators. Human Factors
Society Bulletin 32(7).

Damon, A., H. W. Stoudt and R. A. McFarland. The Human Body in Equipment
Design. Cambridge, Mass.: Harvard University Press

Fink, C. 1986. The great pto shield rip-off. Successful Farming (March).

Meister, D. 1971. Human Factors: Theory and Practice. New York: Wiley.

Purdue article?

Rigby, L. V. 1970. The nature of human error. Annual Technical Conference
Transactions of the ASQC. Milwaukee, Wis.: American Society for Quality
Control.

Roebuck, J. A., K. H. E. Kroemer and W. G. Thomas. 1975. Engineering
Anthropometry Methods. New York: John Wiley & Sons, Inc.

Swain, A. D. and H. E. Guttmann. 1980. Handbook of human reliability analysis with

emphasis on nuclear power plant applications. Washington, D.C.: U.S. Nuclear
Regulatory Commission.

Tichauer, E. R. 1978. The Biomechanical Bases of Ergonomics. New York: Wiley-
Interscience.

Van Cott, H. P. and G. R. Kinkade. 1972. Human Engineering Guide to Equipment
Design. Washington, D.C.: GPO.



UNIT V ~ Engineering for Hazard Control and Injury Preventions

“S861 ‘omuTEH Woy pardepy “rap Sayre se pasa aq Wes sasHIs BAY 24) MOF] (PANT|UOD) “T-A aINTyy

“woprduumsuo> 30} sadoxd

ery

2OU 5] RLaWU Mp sempUY Kew ope) Ayes KlaAiseaox9 40 “SING “DIY “B § YUNOW ay Uy CATE proMW WN aEDpO! Mey “e wopwafyy -t amen *S
“payoo3
Bujsq reawdinbs ap uy wayqod ayqrvood ® aveogpuy ARtu prny BuIj009
18 jo ammesadwar yBry Kyaatesoors truzyQand wawdynbo Jo wren Lew aonds
PavopUOD-AE we uy oreazouy amnperadusay © SKijRULIOURE SUNIE 5 FD “wayqoud
‘Suyreag 8 ammuaduinn sy fq onap 0 age 9q Kew uew aousuaeW y *> 8 jo wee und ampsaduiay Yq AjanjsssoKy “2 amaduel *
‘2ue] SHY JO 390 20 peas ap yO SujOS ‘Per 8 JO 2Aup Bama
9] 24 ay sonyp Adaaqs © wen ue pend 8 Bf sioweUL s9pinoys PU] “q ——URD PRON €  LEONpUY BOYTRAGIA 20 FUOYINOD -q
‘sdeunp -amyray Suipuaduy pore wopgoud & Jo souneand
PAR “SYS “UOLWOLIQNI JO S80] F [RUSTE WED YRYS FuIMIOL BJO VOIRIIA “E ‘Ap aeoypuT Wed Wexadinbo yo Suruuns ySnoy -v wOpEgA *& Pay
“90x JOPEIPRA U20UG # Jo J3AUP JE9 © use VED sem Supers “poresauad sop0
“yH] JO 20po ‘Buys¥2q Joy ¥ Jo uoRIZaK=p NuLtad WED 110 Jo VOYeZLOdeA “2 24) hq panlUOD—U 99 te Wowdynbs SURAPIAD "2
“BorsRQUIOD JO HHINPaud Jo sIOPO JNA IEYD
Aq pavsiep 99 sautowos UES ay) UZ0suN UE JO Souasad OU “q “wopo apeaIMRYD {yo 2418 syeoMM Fu “q
“pawzarep Aupeas 29 veo sR ~ paRERy eyo
|} OF (2opo ou sey YIU) sel jeune paul O} Poppe s KAOPO UY “B ouavaid 24 ayeoIpuT URD su snaJOpO UR Jo Buz "T Vop3a9p JOO ews “£
adwerg sorrduaeg Lica! sues

V7



AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

INTRODUCTION

Hazard

Agent of Injury

TRACTOR HAZARDS

Overturns

This lecture discusses the nature of the most common hazards identified with modern
production agriculture. Specific remedies for these hazards are not discussed; to do.so
would call for a book in and of itself. Nevertheless, it is important to keep in mind
that for each hazard identified, methods are available to eliminate, reduce, or
otherwise control the named hazard.

The word hazard is used here, consistent with the definition used by the American
Society of Safety Engineers. This definition is, “a condition or changing set of
circumstances that presents a potential for injury, illness, or property damage. The
potential or inherent characteristics of an activity, condition, or circumstance which
can produce adverse and harmful consequence”.

An injury to a person usually involves the interaction between an agent of injury and a
person. An agent of injury is that thing (item) that is involved in the injury incident.
The major agents of injury in production agriculture are machinery, structures,
animals, ground surfaces, etc. The interaction between the agent of injury and the
person takes place within some existing environment, such as a field, road, livestock
confinement building, farm shop, etc. The environment itself may have contributed to
the injury event. The following sections will incorporate all three factors (person,
agent, environment) in the discussions without regard for which factor may contribute
the most to a hazardous condition or situation, or what role a factor may play in
eliminating or reducing a hazard.

It also should be understood that most production agriculture hazards overlap into
different hazard categories. For instance, a chemical substance could be discussed in a
chemical hazards section or in an animal hazards section, depending upon how the
chemical is used. There is no set method for grouping agricultural injury and illness
hazards. The arrangement chosen here is consistent with traditional groupings of
hazards often found in the farm safety and health literature. Hazards that may overlap
into different hazard sections are discussed in the section where the interaction
between a person and the hazard most commonly occurs.

No other farm machine is so strongly identified with the hazards of production
agriculture as the tractor. The rubber-wheeled, row-crop tricycle tractor of the 1930s
Tevolutionized production agriculture. This tractor had the speed, power, flexibility,
adaptability, and handling ease that completed the move of farming from the horse
power era into the machine power era. The addition of hydraulic controls, the three-
point hitch, direct engine-driven power take-off (PTO), and, in later years, variable
shift transmissions have firmly established the tractor as the primary machine in
modem farming. Hazards associated with tractors may be grouped in the following
way: stability/instability, runovers, PTO stub, and miscellaneous. Aged tractors
warrant special attention.

Tractor overturns are the single leading cause of fatalities on the farm. Overturns
occur wherever the tractors are used, on roads, in the fields, and in the farm yard. The
most common conditions for an overtum occur when traveling on local roads. The
tractor can edge off the road for many reasons, and by the time the operator
recognizes the problem, one side of the tractor is well off the pavement. The operator
now tries to turn the tractor back onto the road and may use the individual wheel
brake to assist in making the turn. The combination of the tractor being on a slope and
the centrifugal force of the turn back onto the road causes the tractor to overturn.
While this is the most common overtum description, side overtums can also occur

from sharp turns on flat ground, especially at higher speeds, and from hitting bumps



Contents (continued)

Page
UNIT FV —- HAZARD ANALYSIS e

Purpose; Objective; Special Terms; Instructor Materials; Trainee Materials ........ Iv-1

Introduction; Hazard Analysis; Failure Mode and Effects
Analysis (FMEA) .........0. 2 0c e cece cece e cece eee e etree eee e ne eeeneeee Iv-2
Fault Tree Analysis .. . . . Iv-8
Risk Score 0.2.0.0... cece cece cece eee eee cece ee teen eect ee et ence tetnee IV-10
Task Analysis ........ 2 cece cece ccc ee ete e eee rete nee e weet eee eeeetenee Iv-11
Example of a Task Analysis . . IV-12
Summary 2.2... eee cee eee eee eee eee e nee eeeeneneeees Iv-15
References ........... Iv-15
Sample Quiz Question IV-16

UNIT V —- ENGINEERING FOR HAZARD CONTROL
AND INJURY PREVENTION

Purpose; Objective; Special Terms; Instructor Materials; Trainee Materials ......... V-1

Introduction; A System Design Process
Safety Engineering Principles

The Safety Hierarchy

Safety Engineering Strengths .



UNIT I — Agricultural Hazards

Other Chemicals

OTHER HAZARDS

Musculoskeletal
tnjuries

respiratory tract tissues. Permanent eye damage is the most serious hazard of NH3.
Inhaling an excessive amount of NH, vapors could also result in asphyxiation, but
situations where this might happen on the farm are unlikely. The risk of injury is
greatest during transfers of NH between supply tanks and applicator tanks. Ruptured
or leaking valves, cross-threaded hose connectors, damaged hoses, over-filled tanks,
or hoses that become disconnected are the main sources of accidental NH; release.

Many other chemicals are used regularly in production agriculture. Some may be used
only in certain types of operations, while others are found in almost all operations. For
instance, a variety of fuels, oils, lubricants, and degreasers are found on many farms.
These products may be flammable or explosive, and harmful to the respiratory tract,
eyes, and skin. Dairying operations use detergents, disinfectants, and sanitizing agents
for cleaning animals and equipment. Harmful vapors, chemical burns, and skin
diseases are possible hazards. Because disinfectants are not always stored properly,
small children are at particular risk. Another example includes several types of
chemicals, including acid formations, applied to forages to promote field drying and
forage preservation in storage. Eye and skin chemical bums are the primary hazards.

Hot weather hazards include sunbum, skin cancer, and heat-related illness such as
heat cramps, heat exhaustion, and heat stroke. Production agriculture work is often
done outdoors in sunny, hot, and humid weather, and may involve long continuous
hours and strenuous, physical labor. These conditions increase the seriousness of hot
weather hazards. Repeated sunburn episodes contribute to the development of skin
cancer. Two types of skin cancer, basal cell and squamous cell, are seldom life-
threatening, but a third type, melanoma, may become life-threatening if Jeft untreated.
Of the heat-related illnesses, heat stroke is the most serious and is a true medical
emergency. Heat stroke occurs when the body’s heat regulating mechanism goes out
of control, and the body’s core temperature rises to life-threatening levels.

Frostbite, which is frozen body tissue, is the most common cold weather hazard and
usually happens to the nose, ears, fingers, or toes. Hypothermia, which is a lowering
of the body’s core temperature, is less likely occur. Air temperature, wind, dryness or
wetness of skin, and length of exposure are the critical variables. Frostbite damage
ranges from mild incidents where recovery is complete, to severe incidents which
may lead to amputation of the body part. Cold weather hazards in production
agriculture are most common among livestock and dairy producers and workers.
Watering animals, wearing insufficient clothing, and looking for lost range or pasture
animals in a snowstorm are examples of reasons persons suffer from cold weather
hazards.

The term musculoskeletal refers to our body’s system of muscles, bones, joints, and
related structures (tendons, connective tissue). Many musculoskeletal injuries are
known as cumulative trauma disorders (CTD). Cumulative trauma disorders often
result from the repetitive motions of specific body parts associated with working
Movements. These working movements often involve tools and equipment, lifting,
turning, straining, etc. Some of the many types of CTDs are: carpal tunnel syndrome,
Raynaud’s syndrome, bursitis, tendinitis, hip joint arthrosis, and milker’s knee. Other
types of musculoskeletal injuries include low back pain and muscle strains and
sprains. These types of injuries are most common among those working in crop
production, particularly workers in horticultural specialties, fruits and tree nuts, and
vegetables and melons (Bobick et al., 1991).

The production agriculture work environment is conducive to many types of
musculoskeletal injuries. Tractor operation, milking cows, lifting and throwing bales

I-17



CONTENTS

Acknowledgments . .
Tilustrations .. 2.0.0... cece eect eee nnn eee eee e eee e eee eeee

UNIT I- AGRICULTURAL ACCIDENT STATISTICS,

LIMITATIONS, AND WEAKNESSES
Purpose; Objective; Special Terms; Instructor Materials; Trainee Materials .........
Introduction; Language Ambiguities .................606
Production Agriculture Work ...
Accident Reporting Systems . .

Surveillance Systems .......
Data Limitations and Weaknesses .........
The Farm and Agricultural Injury Picture
Summary .... 0... eee cece eee eee eee ene nett e ene eee e eee eenenees
References . 2.2... 6. ccc cece cece cere rere eee eee e eee e eee eeeee
Sample Quiz Questions .......... 0.2 sce e cece cece eee eee eee eee eeneeeee

UNIT 1 - AGRICULTURAL HAZARDS
Purpose; Objective; Instructor Materials; Trainee Materials ..........0. 00000 eee
Introduction; Tractor Hazards ............ 0 ee eee eee eee
Machinery Hazards .......... 0c cece cece eee eneee
Respiratory Hazards: Structures and Their Environments . . .
Amimals ....... 0... cece cece c cence cece eee eee e eee e teen teens eeeasennseeee
Production Agriculture Chemicals ...........00 00 cscs eee e eee e cece eee ee ceene
Other Hazards
Summary ......
References ............
Sample Quiz Questions

UNIT I - HUMAN FACTORS

Purpose; Objective; Special Terms; Instructor Materials; Trainee Materials .........

Introduction; Basic Concepts and Principles
Human Variability ..................008:

Anthropometric Data .............2.00

Ti-1

II-2

II-6
I-11
TI-14
TI-15
I-17
I-19
I-19
T-20



UNIT I - Agricultural Hazards

RESPIRATORY
HAZARDS

Manure Storages

regular vehicular traffic. Some newer tractors use the amber waming lights as the
signal lamps, and the amber lights may not catch the attention of the motorist.

Several of the conditions named above may compound the view obstruction hazard.
This problem exists when regular vehicular traffic nears agricultural machinery from
the rear; the machinery operator starts a lefthand turn, and neither the tractor nor
vehicle operator can see the other because of large equipment. Ensilage wagons,
produce wagons, wagons loaded with hay, and large round balers are all examples of
towed loads that obstruct the view of tractor and motor vehicle drivers. Mirrors on
tractors would minimize this problem for the tractor driver, but many tractors do not
have mirrors. The view between the two drivers may also be obstructed when the
tractor is towing large field equipment that may be folded up for road travel. When
the two drivers cannot clearly see each other, there is no way for either of them to
signal his or ber intention to the other.

Noise is unwanted sound. High levels of noise can cause permanent hearing loss, plus
a host of other problems. Farmers, as an occupational group, suffer from noise-
induced hearing loss to a greater extent than other occupational groups (May et al.,
1990).

Hearing loss depends on duration of exposure and sound intensity. High frequencies
are more damaging than low frequencies; continual noise is more damaging than
intermittent noise. Identical exposures may not lead to the same loss in two people
(Brauer, 1990). In addition to causing hearing loss, high levels of noise can interfere
with speech communication, audible warning signals, the normal sounds of
machinery, concentration on tasks, and sleep.

Potential noise sources on farms include tractors, field machinery, animals, grain
augers and dryers, silo blowers, bedding choppers, feed grinders, and more. Older
machines generally produce louder sounds than newer machines, and it may take two
or more potential sources to produce enough noise to be considered hazardous.
Unfortunately, most noise-induced hearing loss occurs gradually, with little awareness
by the affected person until permanent hearing loss has occurred.

Many structures on farms contain toxic and irritant gases, an inadequate supply of
breathable oxygen, and nuisance and toxic particulate matter (dust). Some of these
hazards regularly are present in the structure, others are only intermittently present.
Likewise, a person may be routinely exposed to these hazards, or the exposure may be
very limited. A pesticide may or may not be involved. This section will identify and
discuss the most prevalent types of respiratory hazards associated with production
agriculture structures, and the work processes that take place within or around the
structures.

Manure storage structures are designed to collect animal manure for later disposal.
Storages usually handle a several-month supply. Storages may be belowground pits or
tanks, aboveground holding ponds, aboveground holding tanks, or a combination of
these. Belowground storage pits and tanks, on occasion, contain several dangerous
gases and an insufficient supply of oxygen. Two types of belowground storages exist.
One is the storage that is entirely or partly belowground, and the other is a pit or tank
from which a pump transfers manure to an aboveground storage tank. The pump-out
pit is usually found just outside the livestock building and near the storage tank.

During manure collection there is very little hazard to exposed workers or animals.

The situation changes dramatically during pumping and emptying processes. To be
pumped, whether for transferring to a storage tank or to a liquid manure disposal unit,

I-11



AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

Employment and
Eamings

Rural and Rural Farm
Population Report

‘SURVEILLANCE
SYSTEMS

National Safety Council

manager; other possibilities could include mechanic, bookkeeper, truck driver, etc.
Landscape contractors and nurserymen are included within the occupational category
“farm operators and managers”. The broad occupational category, “farming, forestry,
and fishing” is not the same as the broad industrial category “agriculture, forestry,
fishing”. The occupational category includes logging jobs, which the industry category
does not. Care must be taken to fully understand what is included in each category.

Employment and Earnings is a report of the U.S. Department of Labor, Bureau of
Labor Statistics (Bureau of Labor Statistics, 1988). The data come from the monthly
Current Population Survey of the Bureau of the Census. The data are reported as
household data, which are collected from a sample of households, and establishment
data, which are collected from business establishments. Agricultural data are found
only in the household data. Numerous tables present data on workers age 16 and over
employed in the industry of agriculture or in farm-related occupations. Unpaid family
labor is included only for persons working at least 15 hours during the survey week.

This report provides annual averages on monthly Current Population Survey data
collected by the Bureau of the Census (Bureau of the Census, 1988). Tables are
provided on residency, occupation, and industry of employed persons. The occupations
and industries reported are those in which the respondent worked during the survey
week. The classifications are the same as for the Census of the Population. The data are
collected one week each month and are based on a sample rather than a census. Data
are only published as aggregate U.S. data: state totals are not provided.

Many organizations and agencies use systems to provide numerator and denominator
data and information on farm and agricultural injury. The data from surveillance
systems often result in national estimates of work injury, deaths, illness, etc., for several
industries, occupations, and products. The primary surveillance systems are discussed
below.

Estimates of the number of accidental work deaths in agriculture and other industries
are compiled in the National Safety Council’s annual publication, Accident Facts
(National Safety Council, 1991). These estimates are used by NSC to compute deaths
per 100,000 workers by industry, and industries are ranked by this death rate. The NSC
develops these estimates by using published national mortality totals from the National
Center for Health Statistics (NCHS). They perform three basic operations on the data:
1) the deaths are allocated among the four fatal accident reporting classes used by NSC
(motor vehicles, home, public, and work accidents); 2) the totals are projected ahead
from the most recent published NCHS figures to the current year, based upon state
reports received by NSC; and 3) the work deaths are allocated to major industry groups.
A portion of motor vehicle deaths are also considered work-related and are added to the
industry allocations.

The National Safety Council estimate for agriculture is from the sectors listed in the
Standard Industrial Classification (SIC) Code for agriculture, forestry, and fishing. The
majority of fatality cases apparently come from sectors 01 and 02, since logging is not
included in agricultural and commercial fishing, a part of sector 09 (Fishing, Hunting,
and Trapping), contributes an estimated 109 deaths per year (Marine Safety Evaluation
Branch, 1989) to agriculture’ total. It should be noted that the agricultural fatality total
includes deaths to workers under age 14, although these deaths are not included in the
rate calculation. According to instructions (National Safety Council, 1978) given to
State vital statistics agencies which report to NSC, a child fatality is only to be included
as a work fatality if the child is performing “gainful work” when the accident occurs.
This excludes deaths occurring while performing household chores or while being a
bystander in a working environment (such as riding on a tractor with a parent).

1-12



4 : '

UNIT I ~ Agricultural Accident Statistics, Limitations, and Weaknesses

ACCIDENT REPORTING
SYSTEMS

Numerator Sources and
Data

Newspaper Clippings

vary include: differing survey (estimating) methods, workers working in more than one
farm labor category; the number of illegal workers; and the contribution of seasonal
migrant children to farm labor. Though the estimates vary, there is agreement that the
contribution of the hired work force to total farm labor is increasing. The USDA
suggests that the hired labor contribution to the percent of total farm work has
increased from about 24% in 1940 to about 35% in the 1980s.

The number of days worked by the hired workforce varies greatly because of the
seasonal nature of farm work. About two-thirds of hired farm workers are casual (less
than 25 days per year) or seasonal (25 to 150 days per year) laborers. These two groups,
though comprising a majority of the workforce, are responsible for only about 25% of
the total days of hired workforce labor.

Little is actually known about the relationship between production agricultural income
and safety. and health. Conventional wisdom has it that the lower economic status
generally associated with production agriculture, particularly farm operators who work
off the farm and seasonal and migrant workers, affects safety and health in a negative
way. Some evidence has been found that suggests part-time farmers have less safe
machinery than full-time farmers (Napier et al., 1985). There is also evidence that
higher farm prices are associated with higher agricultural fatality rates (Kelsey, 1992).
The relationship between production agriculture safety and health and the farm
economy is an area that needs more exploration.

It is collectively these characteristics that have created accident reporting systems that
are not easily compared. During 1984, agriculture was credited with three different
totals of accidental work deaths by three different statistical sources. These totals were
110 by the U.S. Bureau of Labor Statistics (BLS), 710 by the National Institute for
Occupational Safety and Health (NIOSH), and 1,600 by the National Safety Council
(NSC), respectively. Underlying issues, such as inconsistent terminology, different
numerator and denominator sources, source surveillance biases, etc., have a significant
effect on enumerating farm and agricultural injury and illness cases and on injury and
illness rates. No current surveillance system is completely adequate.

There are two types of numerator data. The first type is referred to as numerator values
and is the designation of the number of cases of interest. For instance, the number of
work injuries, how many falls occurred to a group of persons, or how many times a
Person was exposed to a hazard are all examples of numerator values. The second type
of numerator data is known as descriptive data. This type of data includes descriptive
information about the injuries, the victim, and the circumstances surrounding the
injuries. Examples are age of the victim, agent of injury, time of injury, location of the
incident, and body part injured. There are many others. Appropriate descriptive data
may provide an in-depth understanding of the events of interest.

Numerator data (numerator values and descriptive data) can enumerate how often an
event occurs. These data may describe the event in detail but cannot accurately tell the
rate at which one event occurs in comparison to another event. To accurately compare
events, exposure to the hazard must be considered; exposure is not a part of numerator
data. Thus, numerator data are limited in providing a basis for ranking or prioritizing
risks. To do this, denominator data are required.

Fatalities related to farms or farm machinery typically appear in newspapers. Other
serious injuries or unusual incidents may appear as well. If a dependable newspaper
clipping service is used, and daily and weekly newspaper articles are clipped from
across a state, a good picture of that state’s situation can be obtained. The accuracy and

1-7



ACKNOWLEDGMENTS

We thank the following personnel for their review of this document: John R. Etherton, NIOSH;
Steven G. Grannes, U.S. Bureau of Mines; Stephen D. Hudock, NIOSH; John T. Talty, NIOSH;
Steven E. Taylor, Auburn University; Carroll E. Goering, University of Illinois; | Stephen J.
Marley, Iowa State University; Dennis J. Buckmaster, Pennsylvania State University; Dennis
Larson, University of Arizona; and Leonard L. Bashford, University of Nebraska.

We offer special thanks to Richard A. Carlson for standardizing the graphics.

This publication was made possible by the partial support provided by NIOSH Order No.
93-36763. Its contents are solely the responsibility of the authors and do not necessarily
represent the official views of the National Institute for Occupational Safety and Health.
Mention of company names or products does not constitute endorsement by the National
Institute for Occupational Safety and Health.

This publication was prepared in support of NIOSH
Project SHAPE (Safety and Health Awareness for
Preventive Engineering). Project SHAPE is designed to
enhance the education of engineers in the safety and
health field.



AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

Design Life

Possible

Probability of Failure Ranking Failure Rates

Remote: Failure is unlikely 1 <lin 106
Low: Relatively few failures 2 lin 10,000
3 lim 4,000

Moderate: Occasional failures 4 lin 1,000
Ss lin 400

6 lin 0

High: ‘Repeated failures 7 lin 0
8 lin 2»

‘Very High: Failure is almost inevitable 9 lin 8
10 lin 2

Step 8.

Step 9.

Figure IV-3. Evaluation criteria for selecting the occurrence value (OCCF).

Identify the steps in the design verification process. Design verifications
(DV) are all validation methods employed to verify that the design prevents
potential product failure.

Examples of design verification methods:

Design reviews Prototype testing
Mathematical studies Computer simulations
Feasibility reviews Design of experiments

Estimate the likelihood of detection of the failure. Detection does not relate
to inspection techniques in production. Detection in the sense of FMEAs
describes the ability of the proposed design verification program to identify
a potential design weakness (fig. IV-4). The detection ranking number is
used to evaluate the design verification program. In order to achieve a lower
(more desirable) ranking the planned design verification program must be
improved.

Likelihood of Detection by Design Verification Program Ranking

Very High: DV program will almost certainly detect a potential design weakness 1

High:

Moderate: DV program may detect a potential design weakness.

Very Low: DV program probably will not detect a potential design weakness

Program has a good chance of detecting a potential design weakness

DV program not likely to detect a potential design weakness.

DV program will/cannot detect a potential design weakness,
or there is no DV program 10

Figure IV-4, Evaluation criteria for selecting the likelihood ef detection value.

Iv-6



UNIT I - Agricultural Accident Statistics, Limitations, and Weaknesses

Lack of Reporting
Requirements

Agent.of Injury

as retired parents or other relatives, who are not included in the populations previously
discussed.

Because injury rates based on population values (¢.g., 100,000 workers) do not take
into account the actual exposure of these populations to farm hazards, such as hours
worked, population based rates are not as meaningful as they may seem. Rates based on
number of hours worked can be compared over time to determine whether injury rates
have truly decreased, whereas changes in rates based on population values may, for
example, be due to changes in hours worked by the subject population. Even for full-
time farm operators and hired workers, the number of hours worked per year varies
greatly.

It is estimated that 89% of all U.S. farms use only unpaid family labor or have fewer
than 11 hired workers (Myers, 1990). These farms are exempt from OSHA
requirements to keep OSHA 200 logs, listing occupational injuries. Therefore, there is
no record of injuries on the vast majority of U.S. farms. Further, these farms are also
exempt from OSHA requirements to report all fatalities and catastrophic accidents
resulting in the hospitalization of at least five workers (OSHA, 1989). The lack of
reporting requirements means that most farms are excluded from BLS statewide and
national surveys of occupational illness and injuries. Only farms with 11 or more
employees are included in these surveys, and it is not expected that their injury
experience is representative of smaller farms or of all farms. Consequently, a farmer,
hired worker, or family member may suffer a serious injury, and only family, friends,
and health care providers may learn of it.

Numerous descriptive characteristics are used in the presentation and publication of
farm injury data. These include age of victim; agent of injury; time, day, and dates of
injury; how the injury occurred; type of injury; severity; type of farming operation; and
others. However, comparison of these data between one publication or presentation and
the next is often limited by the variation in categories used to describe these
characteristics. A prime example is the age of the victim. A variety of age categories is
used, some in 5-year increments, some in 10-year increments, and some with varying
increments. For instance, the National Safety Council’s summary of 31 state surveys
(Hanford et al., 1982) uses age increments of 5-14 years, 15-24, 25-44; 45-64; and 65+.
No data are provided for children less than age 5. Murphy (1991) and Stueland and Lee
(1989) each use 5-year increments, but for different ages. Fritsch and Zimmer (1980)
use totally different age increments. Some reports define children as age 0-15; others
may use an upper age limit of 14 or 18. Comparisons of data are difficult given these
different categories.

Agent of injury is another characteristic for which differing categories and
subcategories can make comparisons difficult. Even if consistent definitions of farm
injury or work-related injury are used, as discussed earlier, agent of injury can vary
widely because there are so many potential agents of injury on a farm. In addition to
commonly used agent categories, such as tractors, or other farm machinery, there can
be categories for electrocution; tree-felling or being hit by trees and limbs; drowning;
suffocation in flowing grain; animals; tools; other vehicles; chemicals; gases/vapors;
trucks; fires; structures; falls; etc.

Within a category for agent of injury, such as tractors, or other farm machinery, there
can be varying descriptive subcategories. For example, some tractor-related injuries
involve falls from tractors and subsequent runovers by the tractors. Some authors may
categorize these as falls, while others categorize them as runovers. Another example is
the power take-off entanglement, some authors may include them under tractor-related

117



UNIT I — Agricultural Accident Statistics, Limitations, and Weaknesses

Those establishments providing custom farm services, such as custom combining, are a
part of sector 07, not 01, even though there is no practical difference in harvesting
@ machinery or technique between custom farm services and production agriculture
farmers engaged in combining. Adding to the confusion is the fact that a single
establishment owner, say a farm crop producer, could also be an agricultural services
provider. Combining his own crop of wheat is an activity within section 01; the same
activity is within sector 07 if it is done regularly for neighbors on a contract basis.

Therefore, the agricultural industry is much broader than just farming or production
agriculture. Most issues normally identified as agricultural safety and health issues
really center on production agriculture sectors 01 and 02. Similarly, books and journal
articles that use the words agricultural safety and health in their titles are usually
referring to production agriculture safety and health. The primary problem in using
such terms indiscriminately is that statistics identifying farming as a hazardous industry
(occupation) incorrectly lump statistics from all sectors in division A of the SIC Code
together. Consequently, there are more deaths and injuries than should be attributed to
production agriculture activities (farming).

Industry - Occupation Another source of confusion is the mixing of the terms industry and occupation.
Industries are defined by establishments, which are economic units where business is
conducted or services are performed. Farms are the establishment units used for
industrial classification in production agriculture. The term industry, therefore, infers a
place of business or service.

Occupation, on the other hand, refers to the type of activity performed. (U.S.
Department of Commerce, 1980). Remember that farming is defined as the “practice of
agriculture”. Thus, farming is an occupation. The activity, or occupation, can happen

@ irrespective of place, although many occupations are associated with identifiable
places, such as farms. The occupation of farming normally happens on a farm, the farm
being an establishment within the industry of agriculture. It is accurate to say “farming
is a hazardous occupation”, but it is incorrect to say “agriculture is a hazardous
occupation” because agriculture is an industry. Here again, the result of mixing these
two terms is that more deaths and injuries than should be are attributed to production
agriculture activities.

This lecture is about production agriculture safety and health. At the same time, there is
recognition that production agriculture, as defined by the SIC Code, is only a part of the
industry of agriculture. The distinctions among words such as agriculture, farming,
industry, and occupation are most important when used with injury statistics. The
literature on production agriculture safety and health is most commonly found under
the headings of “Agriculture” and “Farm”. Throughout this lecture agriculture will
denote the industry of agriculture, and farm or farming will be used synonymously with
production agriculture.

PRODUCTION Production agriculture work encompasses many things, places, and people. The nature

AGRICULTURE WORK of production agriculture work precludes simple descriptions of what it is and where it
occurs. As with the terms discussed in the previous section, accurately describing
production agriculture work is most important in discussing injury statistics. In this
section, three categories are examined that help characterize production agriculture
work.

- e@ Workplaces Most production agriculture work takes place on farms, ranches, feedlots, dairies, and

in orchards, greenhouses, and nurseries, to name just a few common production
agriculture units. These same units are most commonly referred to simply as “farms”. A

13



AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

SAMPLE QUIZ
QUESTIONS

National Center for Health Statistics. 1988. Vital statistics of the United States, 1985,
vol. II, mortality, part A. U.S. DHHS publication no. (PHS) 88-1101. Washington,
D.C.: National Center for Health Statistics.

National Highway Traffic Safety Administration. 1988. Fatal accident reporting system,
1986. USDOT HS 807 245. Washington, D.C.: Dept. of Transportation.

National Institute for Occupational Safety and Health. 1989. National traumatic
occupational fatalities: 1980-1985. Report dated March 1989 (revised) from the
Division of Safety Research, Injury Surveillance Branch, Data Analysis Section,
NIOSH.

National Safety Council. 1978. Standard reporting system for accidental deaths.
Bulletin T-072-78. National Safety Council, Chicago, Ill.

————. 1991. Accident Facts, 1991 ed. National Safety Council, Chicago, Hl.

Occupational Safety and Health Administration. 1989. Recording and reporting
occupational injuries and illnesses. CFR title 29, part 1904. Washington, D.C.:
GPO.

Oliveira, V. J. and E. J. Cox. 1989. The agricultural workforce of 1987. Agricultural
economic report no. 609. Washington, D.C. Economic Research Service, U.S.
Dept. of Agriculture.

Owens, V. J., C. Malloy, S. Schuman, S. Caldwell and D. Bellamy. 1990. Under
recognition of morbidity from stings of the red imported fire ant in the
southeastern United States. Public Health Nursing 7(2):88-95.

Rettig, B. A., D. K. Klein and J. E. Sniezek. 1987. The incidence of hospitalizations
and emergency room visits resulting from exposure to chemicals used in
agriculture. The Nebraska Medical Journal (July 1987):215-219.

Schnieder, R. D. 1987. Farm accidents in Nebraska - A new look. ASAE paper no. 86-
5512. St. Joseph, Mich.: ASAE.

Schnieder, R. D. and D. L. Morgan. 1988. Nebraska farm injury study. ASAE paper no.
MCR88-103. St. Joseph, Mich.: ASAE.

Schuman, S. H. and S. T. Caldwell. 1991. 1990 South Carolina physician survey of
tick, spider, and fire ant morbidity. The Journal of the South Carolina Medicat
Association 87:429-432.

Stallones, L. 1990. Surveillance of fatal and non-fatal farm injuries in Kentucky.
American Journal of Industrial Medicine 18:223-234. :
Stueland, D. T. and B. C. Lee. 1989. Agents associated with agricultural injuries in
central Wisconsin: An initial evaluation. NIFS paper 89-001. Columbia, Mo.:

NIFS.

U.S. Department of Commerce. 1980. Standard Occupational Classification Manual.
Washington, D.C.: GPO.

U.S. Department of Health and Human Services. 1980. International classification of
diseases, 9th revision. Publication no. (PHS) 80-1260. U.S. Dept. of Health and
Human Services, Washington, D.C.

Whitener, L.A. and Munir, R.A. 1990. Hired farm labor in seven farm input industries.
Agricultural economic report no. 635:102-113. Washington D.C.: Economic
Research Service, U.S. Dept. of Agriculture.

1, Obtain farm/agricultural statistics reports from several different sources.

(a) Determine if consistent and clear, unambiguous definitions of farm or
agriculture are used. Why is this distinction important?

(b) Who is included in reports concerning age groups, hired workers vs. family
workers, etc.?

(c) Does the report contain all of the events in a time period or are there gaps
because of the data collection method, i.e., newspaper clippings vs. death
certificate reports vs. sampling methods?

(d) Can these reports be compared to reports from other industries?

(e) Are these reports presenting qualitative information or quantitative data?

1-22



AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

Use Safety Guards and
Enclosures

‘The use of slip-resistant materials, steps with widely spaced bars to allow mud to fall
through, and the strategic placement of handholds significantly reduce the probability
of slip and falls.

Sometimes it is not possible to eliminate a hazard. The second-priority design solution
is to interpose a guard between hazards and exposed persons. A guard is any device
intended to minimize the possibility of inadvertent contact with moving machinery
Parts, or to restrict access to a hazardous area of the product. Guards and shields are
important devices for reducing hazards in production agriculture. This is because of
production agriculture’s use of field and mobile powered equipment, and the
functional requirements of machinery and material handling equipment for raw

products.

Some machinery hazards may be guarded by location. Guarding by location refers to
two things. For one, it means that there are enough other machine parts (not designed
as guards) interposed between the hazard and the operator in such manner that a safe
distance is maintained. Or secondly, there is enough distance between the hazard and
normal operation and servicing paths that risk to the operator is minimal. The
construction of a well-designed guard includes the following characteristics (Brauer,
1990):

¢ Permanently attached to the machine

Prevents access to the danger zone

* Strong and durable

¢ No additional hazards created

¢ No interference with the operation of the machine

+ Allows easy access to perform service without removal of guard
+ Easily opened and closed, or easily returned to the proper position

Experience has indicated that farm machine guards which are perceived as a nuisance
are often removed and discarded. Research conducted by Purdue University
(Campbell, 1987) showed that more than one half of all agricultural tractors inspected
did not have a power take-off master shield (the shield over the tractor PTO stub
shaft) in place, presumably because the shield made it more difficult to attach the PTO
drive line. Tractors originally equipped with bolt-on or quick-detach-type PTO master
shields had the highest percent missing, while those tractors with hinged shields that
could be raised for easier access to the PTO stub shaft were more likely to have the
shield in place.

‘Guard or shield materials may have openings, such as those found in expanded or
pierced metal or wire mesh, fora nuimber of reasons. It may be necessary to allow air
circulation for cooling, monitoring machine action, or permit cleaning of the area.
‘When guard openings are necessary, a safe distance must be provided relative to the
size of the opening. This is referred to as safety distance guarding. The ASAE
Standard S493 contains specifications for safety distance guarding for agricultural
machines. Figure V-2 is an example of the specifications for safety distances
involving mesh or grille-type guards.

The agricultural environment is severe and dictates that guards must be designed for
heavy duty service. The ASAE Standard $493 (ASAE, 1991) specifies that “guards
shall remain functional under forces that could be applied by a 270 Ib (123 kg) person
leaning on or falling against them in normal operation”. Guards must support such

weight where the guard may be used as a step. There is the possibility of corrosive

action on such machines as manure spreaders and chemical distributors. It is also |
possible that physical contact between machines or dumped loads could damage the

V-12



AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

Workplace variables vs.
Injury prevention and -
control

farm is officially defined as any place from which $1,000 or more of agricultural
Products were produced or sold, or normally would have been sold, during a census
year.

The total number of farms listed by the 1987 Census of Agriculture is 2,087,759. The
dispersion of farms across the country is uneven. For instance, Texas has by far the
most farms, 188,788; second is Missouri with 106,105. The state with the least number
of farms is Alaska with 574, Next is Rhode Island with 701. The size of farm units
across the United States also varies greatly. The average size for all farms is 462 acres,
but the range is large: a Rhode Island farm averages 84 acres, while a Wyoming farm
averages 3,650 acres. Some states have a few types of farms that dominate farming in
that state; other states are very diversified. For example, dairy operations dominate
Wisconsin farming, while California is noted for its diversity.

Production agriculture work occurs on and at locations other than farms. For instance,
homes, public roads, rural community business establishments, forested lands, and
roadside markets are all possible sites where farm work may be accomplished.
Maintaining farm records, transporting harvested crops to a rural elevator, or selling
homegrown produce at a roadside market are all work activities associated with
production agriculture. That these activities may occur off a specific farm premise is
immaterial in terms of occupational workplaces.

Not all work done on farms is related to production agriculture. Two broad categories
of work on farms are often inaccurately considered production agriculture work. One
category is work or services provided by hired or contracted agricultural services. For
example, the custom combine work referred to earlier is officially considered
agricultural service work, not production agriculture work. Contract builders of barns,
sheds, silos, etc., and veterinarians, farm equipment dealer mechanics, and volunteer
fire fighters are all groups that may engage in work on the farm but whose work should
not be counted as production agriculture work. The confusion often stems from the fact
that if the same work was done by the farmer, or a family member, or hired farm
employee, that same work would count as production agriculture work.

The other broad category of work on farms often mistakenly identified as production
agriculture work is miscellaneous work around the farm home, farmstead (buildings,
fields, pastures, etc.), and in rural areas. Examples include farm home and yard
maintenance, gardening for home use, gathering or cutting firewood for personal use,
and restoring antique machinery. For work to count as occupational, it must be directly
related to the occupation of farming. It is not enough for work to just be done by a farm
resident or on farm land.

Production agriculture work incorporates a wide variety of machinery, tools,
equipment, structures, animals, etc. Some of these, such as tractors, field machinery,
and farm animals, are strongly identified with the occupation of farming. However,
many of these things are used for nonfarming purposes. Tractors are used in the
construction industry, bams are used as meeting sites and are converted into restaurants
and other businesses, and some animals are used for recreational purposes. Adding to
the confusion is the use of equipment and structures by farmers for nonfarming
purposes. For instance, tractors pull stranded motorists out of ditches, and farm ponds
are used for recreational fishing and swimming.

The variability among workplace locations, sizes, and activities hinders our
understanding and ability to focus on important production agriculture safety and health
issues. The nature and extent of hazards and problems can be vastly different, even
among similar types of farming. This means generalized safety and health educational

4





AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

INTRODUCTION

HAZARD ANALYSIS

FAILURE MODE AND
EFFECTS ANALYSIS
(FMEA)

Reducing the probability of an injury on the farm requires that the hazards in a new
design for a machine or structure be analyzed to identify the hazards and prioritize the
fesponse to those hazards. The analysis should identify the extreme conditions, from
the high probability of a fatal injury to the low probability of a minor injury, and the
continuum in between these extremes. This analysis is improved if those who
Participate in the analysis have a good understanding of the hazards likely to be
encountered and of the injury frequency associated with these hazards.

Studies of hazards have shown that they can be divided into three broad categories:
inherent properties or characteristics of the products; failures, material or human; and
environmental stresses (Hammer, 1985). Hazard analysis is required to: identify such
hazards; determine which hazards can be eliminated through the design process; and
determine the best approach for reducing remaining hazards to an acceptable degree.
A sound analysis helps to prioritize hazards for corrective actions and demonstrate the
adequacy of subsequent safeguards. There are many different methods for conducting
hazard analyses. The textbooks of Brauer (1990) and Hammer (1985) provide many.
examples. Four hazard analysis procedures are discussed to provide examples of how
hazard analysis is used in safety engineering.

Failure mode and effects analysis (FMEA) is a systematic, analytical tool that will
help the engineer, to the extent possible, identify potential failure modes and their
associated causes, analyze customer, and develop design alternatives. In a pure sense,
all items, including sub-assemblies, should be evaluated. A rigorous FMEA is a
summary of the collective experience of the total design and development team. The
FMEA document parallels and formalizes the mental discipline that engineers
normally go through during the process of product development.

An FMEA reduces risk, supporting the design process by:

* Objectively evaluating design requirements and alternatives.

* Assuring that potential failure modes and their effects on customers have been
considered throughout the development process.

* Providing valuable information to the engineer to assure adequate testing and
development programs.

* Prioritizing product optimization efforts, based on impact to the customer.

¢ Identifying risk and aiding in developing contingency plans for failure prevention.

* Providing a reference to aid in the analysis of design changes, concerns, and
developing advanced technology.

‘The customer in an FMEA is understood to be the end user of the product being
studied. However, parts and subassemblies may have some hidden customers which,
if ignored, could be severely impacted by product failure. Such customers are other
design engineers of higher-level parts, manufacturing engineers, machinists,
assemblers, reliability engineers, and field service. These customers are most
impacted by nonmanufacturable and nonserviceable designs and should be considered
in the process of product development.

The conduct of the FMEA is guided by the form that is commonly used to complete
this analysis (fig. IV-1). Following the form makes the mechanical process of
completing the FMEA relatively simple. Several of the people most knowledgeable
about the design, manufacture, design evaluation, and service of the component
reviewed should be asked to participate in the FMEA. The challenge in completing an
FMEA is to achieve consensus of the participants on the values to be entered on the
form.



AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

design verification changes reduce the risk priority number. The probability of any
failure is reduced and the severity of any failure is reduced. e@

FAULT TREE ANALYSIS Reliability engineers have long employed a failure mode and effects analysis to
predict the probability of a mechanism meeting the design goals for reliability. The
FMEA is based upon known or projected failure rates of individual components, how
each part could malfunction, and the ultimate effect on higher-level subassemblies or
the entire product. It is a tool for analyzing hazards that result totally from the failure
of a mechanical part, but it does not consider human or environmental factors. To
overcome this limitation, the fault tree analysis technique was devised (Hammer,
1985). The fault tree analysis technique is based on the assumption that most
unintended incidents are the result of one or more sequences of events, which can be

Tepresented in a fault tree diagram.

Logic Symbols Used Beginning with the unwanted event (injury incident), a diagram is constructed
backward through prior actions that could cause the event. This task is done with the
use of fault tree logic symbols. Figure IV-S is a diagram and explanation of fault tree
analysis symbols. Events in a sequence are connected by gate symbols that indicate
whether all of the preceding conditions must be fulfilled to cause the event (AND
gate), or whether any one condition will trigger the event (OR gate). The event
symbols, because they have particular meanings, also give some indication of the type
of event. The process is continued for each branch of the tree until all available
information is applied. The lowest level of each branch is a failure or error initiating
the event.

is given in figure IV-6. In this example, the operator of a farm tractor starts the engine
by shorting across terminals on the starter motor while standing on the ground in front
of the drive wheel (an unsafe practice). If the transmission has been left engaged in
gear and the engine starts, the tractor may run over the operator. This is the top event
which is to be avoided. When bypass starting is tried on a tractor that has the
conventional dry, spring-loaded clutch, there is an immediate but slight movement of
the drive wheel when the starter is engaged. This slight movement may warn the
operator and allow him or her to move out of the way. However, when the tractor is
equipped with a hydraulically actuated clutch, there is a brief time delay while
hydraulic pressure is building up. This permits the engine to reach full speed before
the clutch is suddenly engaged, resulting in a rapid lurch of the tractor, potentially
running over the operator.

Fault tree construction for a product can be very complex. However, a simple example @

Examination of the fault tree diagram suggests various actions that may be taken to
reduce the risk of bypass starting. For instance, improved reliability of the key switch
and other-components in the electrical system may reduce the need for bypass
starting. Another engineering solution is to cover the starter motor terminals. A third
solution is to install a hydraulic valve that bypasses hydraulic pressure until the
operator depresses the tractor’s clutch at least one time. Clutch depression is a
procedure normally done from the operator’s station, thereby removing the operator
from in front of the tractor wheel. A less effective, but still helpful measure may be to
utilize a hazard waming at the starter motor. Carefeul study of the sequence of events
in the fault tree diagram shows that each of these preventive steps has some merit.



UNIT I — Agricultural Accident Statistics, Limitations, and Weaknesses

Hospitals

Physiclans’ Records

Emergency Medica!
Service (EMS) Records

insurance Companies

opted not to join. Often, this is because joining requires payment of workers’
compensation insurance premiums. Additionally, farmers without any employees may
not be required to participate even in states where all farm employees are included in
the system. In states where most farms participate in the system, the workers’
compensation system is a readily available and relatively complete source of farm
injury information.

Two sources of potential farm injury data exist in hospitals. These are hospital
emergency departments and discharge records. Hospital emergency departments treat
people injured in farm-related accidents when the injuries are severe enough to require
such treatment. Thus, the emergency department can be used to monitor farm injuries
on a prospective (starting at the present and going into the future) basis (Stueland and
Lee, 1989). If the normal emergency department records are detailed enough to include
the fact that the injury was farm-related and other desired details, the emergency
department records can be used retrospectively (starting at a point of time and looking
into the past). Unfortunately, the records are not often that detailed or available.

Discharge data are data collected and stored about every patient who has been admitted
to a hospital. These data include the injury or illness responsible for patient admission,
but may not provide the cause or source of the illness or injury. This means the data
may not necessarily be searchable to locate farm-related injuries or illness. A
supplemental questionnaire may be required from the patient (Fuortes et al., 1990).
Also, discharge data are by definition limited to patients actually admitted to the
hospital. Given the increasing emphasis on out-patient treatment and the high level of
care available in the emergency department, many agricultural injuries may be treated
without admission (Gunderson et al., 1990). Some states have statewide discharge
databases.

Theoretically, every farm injury or illness severe enough to require physician care has a
physician’s medical record. However, these are confidential and not generally available
as a data source. Public health laws in many states require reporting certain injuries or
illness, such as sexually transmitted diseases. In some states, occupational injuries must
be reported; however, uniform reporting is not assured, in spite of the law. If laws
required reporting of farm injuries, physicians’ reports could be a source of data if they
were prepared consistently. Reporting an injury based on cause rather than on a medical
diagnosis is a more complicated process, however. Physicians can be a source of data
for well-defined incidents, such as certain insect bites, via survey and/or patient
questionnaire (Schuman and Caldwell, 1991; Owens et al., 1990).

When an EMS ambulance transports a person to a hospital for any reason, a record of
that “run” is made. Depending upon the state, these run records or logs are filed with a
state agency. If the location of the victim (such as a farm) and/or the reason for the run
(such as an injury) are listed, it is possible to use these EMS run records for data.
However, many farm injury victims are self-transported, thus not showing up in the
EMS records; one farm injury study (Schnieder and Morgan, 1988) reported 68% of
emergency department cases arrived by private vehicle. A study of 48 hospital-treated
cases of agricultural chemical exposure found only one record of ambulance or rescue
squad use (Rettig et al., 1987).

Insurance companies that process medical claims resulting from farm-related injuries or
illness maintain records of such claims. However, to be of benefit to production
agriculture safety and health researchers and educators, insurance companies need to
collect information on cause, record it in a searchable manner, and then be willing to
make the files available. Insurance records are generally considered private.
Additionally, there are many health insurance companies that may provide coverage to

19



AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

NCHS

BLS Annual Survey

DATA LIMITATIONS AND
WEAKNESSES

Sensitivity

“farm equipment except trucks”, so data on fatal traffic accidents involving farm
equipment can be extracted.

The National Center for Health Statistics (NCHS) compiles and publishes national
statistics on live births, deaths, fetal deaths, abortions, marriages, and divorces
(National Center for Health Statistics, 1988). These statistics are derived from state
registration of such events; every state has laws providing for continuous and
permanent registration. States can thus provide to NCHS individual records or
computer data files of deaths. Within the published mortality data are tables of
“nontransport accidents”, in which location is provided. “Farm” is one defined location,
exclusive of the “farm home and home premises”. Accidents within a given location are
classified by ICD9 E-code. Data for E919 “accidents caused by machinery” are
provided. It is presumed that most accidents coded E919 occurring on farms involved
farm machinery. Other types of accidents occurring on farms are reported to include
falls, firearms, fires, suffocation or drowning, animals, poisoning, electrocutions and
other types and agents. There is no differentiation between work-related injuries and
non-work-related injuries.

The Bureau of Labor Statistics (BLS) of the U.S. Department of Labor conducts an
annual survey of work establishments, such as factories, offices, and stores (Bureau of
Labor Statistics, 1988). A stratified random sample of employers is drawn from each
state, and employers in the sample must summarize and report injury and illness data
from their OSHA Log 200. (The OSHA Log 200 is a record required by the
Occupational Safety and Health Administration of any workplace injury or illness
resulting in death, loss of consciousness, restriction of work or motion, transfer to
another job, and/or medical treatment, excluding simple first aid). The BLS survey
excludes farms with fewer than 11 employees. With fewer than 11% of U.S. farms
Teporting 11 or more employees (Myers, 1990), it is unlikely that the injury and illness
experience of those farms is representative of all farms across the nation.

The limitations and weaknesses associated with numerator and denominator sources,
and the data they provide, result in industry-wide problems with farm and agricultural
injury and illness data. These problems hamper communicating the nature and extent of
production agriculture risks. As will be shown in later units, an ability to accurately
describe an injury problem is the first step in mobilizing the necessary resources to
remedy the identified problems.

The sensitivity, or ability of a given data source to detect individual cases, often
involves a tradeoff between practicality and the severity of the injury. The less severe
the injury, the more difficult it is to detect because the injured person may not come
into contact with professional medical care or attract the attention of a newspaper or
other public information source. Conversely, the more severe the injury, the more likely
it will require medical attention at a hospital emergency department or, in the case of
fatalities, a coroner’s or medical examiner's investigation and newspaper coverage.
Consequently, with limited resources, it is often more practical to attempt to detect the
More severe injuries. This practice, of course, results in a picture of farm injury that is
less than comprehensive and representative. This fact sometimes gets overlooked in
discussions of farm injury statistics.

Sensitivity is particularly important when a survey is being used. While properly
planned and conducted surveys can yield representative data, surveys are often not
sensitive enough to locate infrequent events. For example, the National Safety
Council's 31-state survey compilation only includes a small number of fatalities
(Hanford et al., 1982). This is because fatalities are relatively infrequent events when

1-14



OBJECTIVE

SPECIAL TERMS

INSTRUCTOR

MATERIALS

TRAINEE
MATERIALS

Unit tl
HUMAN FACTORS

To introduce students to the concepts of human error and human limitations.

After completing this unit, the student will be able to:

1

ay

pyr

List the four principles for the application of the human factors design
philosophy as defined by Meister.

Explain the significance of people being different, people being adaptable,
and people being goal oriented.

List five categories of human error.

Define and calculate anthropometric values for a 95th percentile man or
woman.

Behavior
Human error
Anthropometry

Lesson plan
Chalkboard

Participant outlines made by instructor
Supplementary materials



AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

SUMMARY

REFERENCES

Implements solutions regardless of a complete understanding of the causes of injury
events or levels of risk. Examples: animal restraint systems can make animal handling
safer without a complete understanding of animal behavior; an ability to reverse a
machine’s crop intake mechanism can reduce the risk of an entrapping incident
without understanding why people take risks with running machines.

The challenge for any new product design is to find the effective balance of
competing issues of product performance, styling, safety, and cost. A few broadly
stated principles that typically govern the application of engineering to the safety of
the user and bystander were presented. A safe product design includes considerations
of the quality of the product. A reliable product reduces the probability of injury
because the operator is able to remain at the controls of the machine, operating the
machine. Priority should be given to designs that ensure that a product failure will not
result in an injury, a fail-safe design. Failure minimization, redundancy, passive
protection, and defeatability resistance are concepts that should also be considered in
a new design. If you address the safety hierarchy, eliminate the hazard, apply
safeguards, warn, train, or recommend personal protective equipment, you will have
addressed the priorities of a strategy to deal with safety issues in a new product
design.

The safest possible machine design begins with an understanding of the accident data
associated with similar machines. The analysis of this data provides some

jing of hazards encountered in agriculture. The designer of a new machine
should consider the broadest possible application of human factors principles.
Analysis techniques such as task analysis, failure mode and effects analysis, fault tree
analysis, and risk analysis provide methods to systematically review new designs.
Safety engineering principles provide methods to resolve issues that are identified.
The application of these concepts will lead to the safest possible design.

This lecture was condensed from chapter 9, Safety and Health for Production
Agriculture, Dennis J. Murphy, and Human Factors: A Series of Quality Instructional
Materials. No. 1 Human Factors Concepts: An Overview, Jerry R. Duncan, ASAE.
1991.

ASAE Standards, 40th Ed. 1993. $441.Safety signs. St. Joseph, Mich.: ASAE.
- 38th Ed. 1991. St. Joseph, Mich.: ASAE.
Aherin, R. A., D. J. Murphy and J. D. Westaby. 1991. Reducing Farm Injuries: Issues
and Methods. St. Joseph, Mich.: ASAE.
Anderson, K. C. and G. L. Smith. 1988. Human presence activated safety system for
mobile off-road equipment. ASAE paper no. 88-5516. St. Joseph, Mich.: ASAE.
Brauer, R. L. 1990. Safety and Health for Engineers. New York: Van Nostrand
Reinhold.

Campbell, W. P.:1987. The condition of agricultural driveline system shielding and its
impact on injuries and fatalities. M.S. thesis, Purdue University, West Lafayette,
Ind.

Hammer, W. 1985. Occupational Safety Management and Engineering, 3rd Ed.

Englewood Cliffs, NJ.: Prentice-Hall, Inc.

Seiden, R. M. 1984. Product Safety Engineering for Managers: A Practical
Handbook and Guide, Englewood Cliffs, N.J.: Prentice-Hall, Inc, .

Vinogradow, O. 1991. Introduction to Mechanical Reliability: A Designer’s Approach.
New York: Hemisphere Publishing Corporation.



AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

tractor manufacturers strongly recommend against an operator carrying an extra rider

for any reason. This advice, however, conflicts with several factors farmers must face

on a daily basis. For instance, it is human nature to want to complete work tasks as r
easily and quickly as possible; different transportation may call for added expenditure

of a meager money supply; other babysitting options simply may not exist; and new

tractor drivers must be taught how to operate tractors.

Common extra rider locations on tractors include persons standing on drawbars, side
links of three-point hitches, rear axle housing, rear wheel fenders, and the area
immediately around the operator’s seat. This latter situation usually happens when
small children ride. A larger person often will have his or her feet, body, and hands
spread out on different parts of the tractor. Extra riders may intend to hang on tightly
to the tractor, but it is difficult to maintain the concentration and the finger/hand
strength needed for more than a few minutes at a time. Older riders tend to lose their
gtip and concentration as they engage in conversation with the operator, or focus their
attention on field equipment operation. Younger riders may simply have wandering
minds, or their hands/fingers may tire quickly. Neither group can foresee all the stops,
starts, bumps, and jerks that may occur during tractor operation, nor can they always
handle the shocks and jarring from rough terrain, even when expected.

Tractors are designed to provide a reasonably safe place for the operator, and that is
the operator’s seat. For a second person to ride safely, tractor operator stations would
have to be significantly redesigned. This would require a substantial investment in
engineering by manufacturers, changes in some international engineering standards
that govern tractor manufacturing, and a change in the federal safety law that rules
farm tractor operation by employees, among other changes. In other words, it would
be an enormous undertaking. The provision of a second seat introduces other risks
that are less problematic when only the operator is in the operator’s station. For eo
example, adequate protection for the passenger during a rollover event may not be
provided, and interference with tractor controls may occur. A major impediment for
mounting such an effort is the real possibility that even with the second seat, the extra
rider hazard on tractors would stil} exist.

Other runover incidents involve the tractor driver either falling off the tractor as it is
operating, or being knocked out of the seat, usually by a low hanging tree branch.
Many of these incidents happen with older mode] tractors that have less shock
absorption capacity in their seat assembly, no back or side arm supports on seats, and
no rollover protection. The operator may also be reaching back to adjust hitched
equipment, or standing on the operator’s platform to stretch his or her legs. Abrupt
movement of the tractor, such as from hitting a hole, may throw an operator off,
especially when the operator is standing or isn’t wearing a seat belt.

Tractors are often operated close to trees. A limb may have dropped lower from the
previous year as it extended out from the tree trunk, a tractor that is slightly higher off
the ground is being used, or the operator's attention is diverted. In any case, the
operator is knocked out of the seat. Lastly, another type of runover incident occurs
when operators attempt to hurriedly remount a tractor because it has unexpectedly
started to drift or roll. This is particularly risky if the person tries to enter the
operator’s station from in front of the rear wheel, or when there is trailing equipment
attached to the tractor.

Persons already on the ground are occasionally runover by tractors and their attached
equipment. Two groups form most of these types of incidents: tractor operators and e@
‘small children. Tractor operators sometimes try to start their tractor from the ground, -
instead of from the operator’s seat. Most of these incidents occur with older tractors

T-4



AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

Coroner and Medical
Examiner Reports

Law Enforcement
Agency Reports

State Motor Vehicle
Accident Reports

Manufacturers’ Records

Court Records

Denominator Sources
and Data

farmers. The typical farm property and casualty insurer may not be the health insurer,
and some farm families may not be insured at all. The result of this variability is that
there is no central source of insurance records. A rural health maintenance organization
(HMO) that can generate data for farmers would be an exception.

Sudden or unexplained deaths require investigation by the local coroner or medical
examiner to determine cause of death. The results of the investigation are used to
establish the cause of death for the death certificate, and in the case of death due to
injury, a brief description of how the injury occurred. In addition to the death
certificate, a report may be filed with county or state agencies. Depending upon the
state, the report may require certain information, the report may be filed in a central
State office, and much of the information on the report may be computer searchable.
Searches may be conducted by occupation (such as farmer) or location (such as a farm).

Medical examiner reporting systems have been used in at least one farm fatality study
(Bernhardt and Langley, 1991). If there is no central reporting requirement, and the
filing and reporting depend upon individual counties, the contents and availability of
the reports will vary. There may be no way of searching for farm-related fatalities, other
than manually or by requesting specific reports. In some cases the report may not
contain details of interest, such as the circumstances surrounding the incident. Even if it
does, the accuracy would depend on the knowledge of the coroner.

Law enforcement officers may also investigate fatalities or serious injuries. They may
be called by the coroner to assist or be called to the scene by another party. They may
also be normally responsible for some investigations, such as when accidents occur on
public roads. The level of detail in such a report will vary by the officer’s
understanding and knowledge of the farm environment, plus the level of detail required
to fulfill reporting requirements. These reports are not likely to be available to the
public, although it may be possible to request specific reports for research purposes. It
is unlikely that report files would be computer searchable; reports would be dispersed
throughout the state by county except for investigations by state police.

Every state has a central database of motor vehicle traffic accident reports. For those
accidents involving farm equipment, the data may be available if “farm equipment” or
something similar is a distinct item on the report form. These data would provide
information only on those accidents involving farm equipment on public roads. Such
reports would include incidents where property damage, but no personal injury,
occurred. Information would also be available on other, non-farm-related parties
involved in the accident.

Manufacturers of farm equipment often receive reports of injuries involving their
machines. These reports may be followed up by investigations. Such records are
proprietary and generally not available to the public. There may be a considerable time
lapse before manufacturers learn of incidents involving their products. Also, incidents
do occur that are never reported.

Because farm accidents sometimes result in litigation, some farm injury information
exists in court records. These records are distributed by jurisdiction, although some
may be published. They will include only cases litigated: many other cases are settled
out of court.

The sources of denominator data are fewer than for numerator data, and the data are
more difficult to obtain. Use of such data requires surveillance of the entire population
to which the numerator belongs. The most realistic denominator value to use in rate
calculations of farm injury is hours of exposure. This is because the working hours of



AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

remember that even power-assisted controls may have to be manually operated in the
event of an emergency power failure and should be designed accordingly. @

There are situations where a compromise design or average is acceptable. Things that
are not adjustable and are used by the general public fall into this category. Examples
are the height of the checkout counter at the supermarket, the height of drinking
fountains, and stair tread height. These are examples of equipment that would be
designed to inconvenience the fewest number of people. Designing these facilities for
the average-size person will be acceptable to more people in general than would be
the case if the equipment were sized for an extremely small or extremely large person.

Because the force that the human body can exert depends upon the position of the
body or limb, as well as the muscle strength, the engineer/designer must consider
what the equipment design requires the operator to do. A repositioned control can be
the difference between a control that is easy to operate and one that is not acceptable.
Biomechanical design data and criteria are given in texts such as The Human Body in
Equipment Design by Damon et al., Biomechanics of Ergonomics by Tichauer, and
Human Engineering Guide to Equipment Design by Van Cott and Kinkade.

It is not unusual to find even new equipment that is designed and marketed with
operating forces that are excessive. An understanding and application of
anthropometrics will correct many of these situations.

Design for the Extremes When an engineer/designer designs equipment, he or she must consider the total
population that will use the item. This involves careful study of the population that
will affect the design. Usually there is some limiting anthropometric dimension
Tequiring a design that will accommodate individuals at this extreme on the
anthropometric scale. The logic follows that if the design will accommodate -the ©
extreme individual, virtually the entire population can be accommodated. For
example, a design requires a minimum dimension, such that the height of a door or
passageway would be based upon the upper percentile sizes. If large individuals (in
the 95th percentile) can pass through the opening, then certainly smaller individuals
will be able to as well. Dimensions requiring a “maximum” specification, such as the
maximum height to reach, need to be designed to accommodate individuals at the
lower percentiles, typically the Sth percentile person. If individuals of this size can
reach the control, the larger person should have no difficulty.

Design for a Range Some equipment requires adjustment in order to accommodate people of varying

Adjustment sizes. Some examples are: the forward and backward seat adjustment in vehicles, the
height of desk chairs, the seat suspension setting for tractors, and steering wheel and
control locations in vehicles.

Usually it is not reasonable or economically feasible to try to accommodate the total
100% of the size range in the design. A decision is made to include a range of the
population that will accommodate the maximum number of individuals with a
reasonable design and cost. This is the designer’s choice and, typically, the cut-off
points on the range of population are at the 5% and 95% points. With this choice the
design will accommodate the middle 90% of the population with only the smallest
(those below 5%) and the largest (those above 95%) outside the design range.

Because there are relatively few persons that fall into the extreme size categories, the

number of people inconvenienced is small. Studies have shown that from the :
perspective of design economics, the range of adjustment needed to accommodate the e
middle 90% is reasonable. To include the first 5% and the last 5% may require a

greater range of adjustment than is required for the middle 90%; the design is much

HI-12



Figures
I-1.
1-2.
1-3.
Il-1.
Ii-2.
II-3.
Ttl-1.
Ill-2a.
TH-2b.
Il-3.
Tll-4.
Ils.
Iil-6.
Il-7.
1-8.
THl-9.
Iv-1.
IV-2.
Iv-3.
Iv-4.
IV-5.
IV-6.
IV-7.
IV-8.
Iv-9,
IV-10.
Iv-11.
IV-12.
V-1.
V-2.

Tables
I-1.

1-2.
I-1.

ILLUSTRATIONS

Average age of operators and percent aged 65 and over ..........-2-0+5+
Non-transport deaths on farms: 10 years, 1979-1988 ............
Tractor accidents are the single most common farm fatal accident .
The “point of no return” during a rear turnover .......-.....++-
APTO driveline ........... 2.00 eee eee +.
A slow-moving vehicle emblem (SMV) .....-...-000 0 eee eeeeeeeeeees
A model of a human-machine system ..... 2.0.0.6 0. eee e cece eee cence
Relationship between stimuli and behavior in objects and systems . -
Relationship between stimuli and human behavior .....-........-2.605
System design and desired system behavior ..............00seeeeeeeee
Behavior can be excluded or included ..............02-000-
A hypothetical distribution of time; system specified tolerance limit .
Equipment should fit the operator . .

Anthropometric dimensions ...........

Body dimensions in vehicular cab design .
Gaussian probability density function ...............2 2 cece cere eens
Typical FMEA form .......... 060 c sce e cence eee ce eect eee eeeeeee
Criteria for selecting SEV value ....
Criteria for selecting OCCF value ...............
Criteria for selecting likelihood of detection value ..
Fault tree analysis symbols and explanations .......
Fault tree analysis of tractor bypass start hazard ..
General scales for hazard elements ............
Typical hazard analysis worksheet . .
An example task analysis format ............0.ceseeeeee .
UPSAT operator actions/decisions with shredder power off ...........-.
UPSAT operator actions/decisions with shredder power on ...........++
UPSAT operator actions/decisions with shredder rotation reversed
The five senses as warning devices ........-....20-000000- -
Dimensions for openings through mesh/grille guards ................--

National Safety Council estimates for accidental work deaths ...........
National Safety Council estimates for accidental work death rates . .
How to compute percentiles from standard deviations ...............+-

vil



AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

The use of tethers and override switches illustrate the trade-offs common to safety
engineering problem solving. On the one hand, these devices reduce risk taking by
allowing workers to achieve work objectives in a relatively safe manner with a e@
minimum of effort and inconvenience. On the other hand, such devices may increase
tisk if workers fail to follow appropriate safe operating procedures.

Use Safety Warnings
There are some hazards that cannot be designed out of a product and cannot be
effectively guarded. A common example is the crop intake area of any harvesting
machine. An attempt to effectively guard this area will interfere with the basic
function of the machine. In such situations, the third-priority safety engineering
strategy is appropriate. Warnings should be strategically placed in close proximity to
the hazard.

Safety messages should not be used indiscriminately or the “billboard effect” may
result. The billboard effect is a confusing array of instructional material displayed on
the machine. The use of safety messages should be limited to those major hazards that
pose the threat of death or disability, or to denote reminders of safety practices. The
temptation to overuse safety messages (the billboard effect), and to overstate hazards,
is strong. Safety message hazard classification refers to the use of the signal words
DANGER, WARNING, and CAUTION. Overclassification occurs when a more
serious signal word, such as DANGER, is used when a lesser one, such as
WARNING, is more appropriate. ASAE Standard $441 (ASAE, 1993) governs hazard
classification for safety messages, but the process is not an exact science. This, and
the nature of product liability case law, encourages overuse and overclassification of
safety messages. That is, to protect themselves from charges of negligence,
manufacturers and dealers may place more numerous and serious warnings on
products than otherwise is needed, based on more objective criteria.

When safety messages are needed, an effective safety engineering strategy is to limit @
the use of the DANGER signal word to the most serious one or two hazards on a
product. This preserves the impact of the DANGER signal word. Both DANGER and
WARNING signal warnings should be located as close as possible to the hazard point.
CAUTION signal warnings, which are usually safety practice reminders, are more
appropriately located at the operator's station as a reference. The use of pictorials as a
part of a safety message is both popular and relatively effective (see Aherin et al.,
1992). The amount of text is minimized, comprehension is faster and may last longer,
and pictorials can be effective for persons with limited reading or language ability.
Train and Instruct
Most equipment sold today is provided with an owner’s manual or operator’s manual.
This manual provides another way that warnings and instructions can be conveyed to
product users. How owner’s manuals are organized with respect to safety messages is
primarily a concern of instructional materials and communications professionals.
However, engineers have a critical role in developing owner’s manuals because they
have the most intimate knowledge of the product, including its actual and potential
hazards. The owner's manual provides opportunity for a fuller explanation of those
hazards, which are identified by warnings on the product. A section on safety at the
beginning of the manual should reproduce warnings on the product, include a diagram
of the product to identify hazard and warning locations, and give full safety- and
health-related precautions and instructions.

Specific safety messages should be repeated in different sections of the manual that
may involve the hazard area. For example, a safety message from the beginning
section may be repeated in the service or maintenance section. This process is
particularly important for products used in environments that render safety messages e}
unreadable over time. Safety and health information in-owner’s manuals also provides

V-14



UNIT H — Agricultural Hazards

Slow Moving Vehicles
(SMV)

is to try to pull away; this action simply results in a tighter, more binding wrap. The
1,000 rpm shaft decreases the opportunity for evasive action by approximately 50%.

There are. many reasons why PTO-powered machinery may be engaged while no one
is on the powering tractor. Some PTO-powered farmstead equipment is operated in a
stationary position; it needs no operator except to start and stop the equipment.
Examples are grain augers and silage blowers. At other times, adjustments or
malfunctions of machine components can only be made or found while the machine is
operating. Additionally, many work practices by machinery operators lead to exposure
to operating PTO shafts. Clearing crop plugs has been mentioned. Other practices
include mounting, dismounting, and reaching for control levers from the rear of the
tractor, and stepping across shafts instead of walking around the machinery. Having
an extra rider while PTO-powered machinery is operating is another exposure
situation.

The wrapping hazard is not the only hazard associated with IID shafts. Serious injury
has occurred when shafts have become separated while the tractor’s PTO was
engaged. The machine’s IID shaft is a telescoping shaft. That is, one part of the shaft
will slide into a second part. This feature of shafts provides a sliding sleeve that
greatly eases the hitching of PTO-powered machines to tractors. If an IID shaft is
coupled to the tractor’s PTO stub but no other hitch is made between the tractor and
the machine, then the tractor may pull the IID shaft apart. If the PTO is engaged, the
shaft on the tractor end will swing wildly and may strike anyone in range. The
swinging force may break a locking pin, allowing the shaft to become a flying missile,
or it may strike and break something that is attached or mounted on the rear of the
tractor. Separation of the driveline shaft does not commonly occur. It is most likely to
happen when three-point mounted equipment is improperly mounted or aligned, or
when the hitch between the tractor and attached machine breaks or accidentally
uncouples.

This topic could have been addressed in the tractor hazards section, but the greater
hazard exists while machines and other equipment, such as wagons, are being towed
by tractors. Tractors and machinery on public roads are called “slow moving vehicles”
because they move slowly in comparison with automobiles, trucks, buses, and
motorcycles normally found traveling public roads. The ASAE Standard $276.3
identifies slow moving vehicles as vehicles designed for and traveling at speeds less
than 25 mph (40 km/h). This definition is supported by most state and federal bodies
that govern or regulate the movement of agricultural machinery on public roads.

There are several hazards associated with the interaction of agricultural machinery
and other vehicles on public roads. Regular vehicular traffic generally moves at a
greater speed than agricultural traffic and is less accustomed to overtaking agricultural
machines than other vehicles. These two factors contribute to closure-time errors by
drivers of other vehicles. Closure time is the time it takes for one moving vehicle to
overtake another moving vehicle. When a closure-time error is made, it usually results.
in the vehicle crashing into the slow moving vehicle, or leaving the road to avoid a
crash. The following example helps to clarify the closure time concept and errors.

If one automobile is traveling at 45 mph (72 km/h) and an overtaking vehicle is 400 ft
(122 m) behind it traveling at 55 mph (89 kmV/h), it will take the second vehicle
27 seconds to reach the first vehicle. This is closure time. Now substitute a tractor
pulling a wagon traveling at S mph (8 knv/h) for the first vehicle. In this case, the
second vehicle, still traveling at 5S mph (89 km/h), will close the 400 ft (122 m) and
reach the tractor and wagon in only 5 seconds. Time for the overtaking vehicle to
react is actually less than 5 seconds because it takes a couple of seconds to recognize

1-9



AGRICULTURAL SAFETY AND HEALTH FOR ENGINEERS

solid manure is converted to a slurry. This is done by mixing water with the manure
and stirring with the help of a powered machine. The mixing and pumping processes
may cause high levels of certain gases to be released. These gases are hydrogen
sulfide (HS), carbon dioxide (CO), ammonia (NH;), and methane (CH,). Hydrogen
sulfide is highly toxic, CO, and CH, are asphyxiant gases, and NH; is a severe
irritant to the throat and lungs. Methane is also extremely flammable. Warm weather
and poor ventilation increase the risks of dangerous accumulations of these gases.
Below ground pits and tanks may hold toxic levels of gases, or lack oxygen, for
months or years after the pit or tank has been emptied. This may occur if a solid lid
covers the empty storage.

Belowground manure pits and tanks have been associated with multiple-victim
fatality events. The usual scenario is similar to the following. One person enters the
storage to inspect or service a pump, or to retrieve a dropped tool or other object. This
person is overcome by gases or a lack of oxygen and collapses. A second person then
tries a rescue and is also overcome. Tragically, as many as four or five people may
enter the storage as would-be rescuers and end up as victims. These are usually family
members and neighbors of the first victim, acting out of panic. Some would-be
rescuers mistakenly think they can hold their breath during the entire rescue attempt
while others feel there won’t be any harm in taking one or two breaths. Experience
strongly suggests otherwise.

‘Three types of silo structures exist on farms: oxygen-limiting silos, conventional silos,
and trench (bunker) silos. Trench silos use earthen or concrete retaining walls as sides,
with no structural component over the top. Respiratory hazards are not normally
identified with this type of silo. Each of the other two silos, also called upright or
tower silos, do contain respiratory hazards, and a person may become exposed.
Hazardous gases, such as CO, and various nitrogen gases (NO,), are by-products of
the fermentation process. Fermentation involves chemical and bacterial changes to
forages that allow them to be preserved for a long time, and it makes the forage a
more valuable feed product. The actual fermenting of the forage takes place in the
absence of oxygen, in the sense that oxygen contained within the mass of the forage
material is used up during the fermenting process. The specific respiratory hazard to
humans depends on the type of silo in use.

Oxygen-limiting silos are built of glass-lined, steel-plated structures or concrete.
These silos have openings at the top and also at the bottom, where silage is unloaded
from the structure by a powered unloader. The majority of these silos are on dairy
farms, but other livestock operations make use of these structures as well, particularly
smaller-sized silos. Most oxygen-limiting silos are for forages, but some are used to
store high moisture grains. Regardless of its use, the hazards are the same. Although it
is a misnomer, an oxygen-limiting silo is sometimes identified as a sealed silo.

As mentioned above, CO, is a by-product of fermenting forages. The oxygen-limiting
silo is designed to hold the CO, inside the structure and prevent oxygen from
entering. Oxygen levels in this type of structure are often near 0%; below 6% is
immediately hazardous to life. Toxic levels of NO, gases may also be produced but,
because of the extreme oxygen deficiency, are not the primary concern. Nitrogen
gases will be discussed in the conventional silo section.

Sometimes called a stave silo, the conventional silo is the most common type of silo
found on farms. Conventional silos are used extensively in dairying operations, and to
a lesser extent in beef operations. Concrete is the most common construction material,
but there are still some wood and porcelain brick silos in use. Conventional silos have
a series of hatch doors up the entire height of the silo. These small doors provide

T-12