Ergonomic Evaluation 

of Automatic Flat 

Sorting Machines – 

Colorado

Jessica G. Ramsey, MS, CPE

Anthony Almazan, MD

Health Hazard Evaluation Report

HETA 2008-0293-3132

June 2011 

DEPARTMENT OF HEALTH AND HUMAN SERVICES

Centers for Disease Control and Prevention

Workplace

Safety and Health

 National Institute for Occupational 

Safety and Health

This Health Hazard Evaluation (HHE) report and any recommendations made herein are for the specific 

facility evaluated and may not be universally applicable. Any recommendations made are not to be 

considered as final statements of NIOSH policy or of any agency or individual involved. Additional HHE 

reports are available at http://www.cdc.gov/niosh/hhe/
The employer shall post a copy of this report 

for a period of 30 calendar days at or near 

the workplace(s) of affected employees. The 

employer shall take steps to insure that the 

posted determinations are not altered, defaced, 

or covered by other material during such 

period. [37 FR 23640, November 7, 1972, as 

amended at 45 FR 2653, January 14, 1980].
Report Abbreviations................................................................................................ii

Highlights of the NIOSH Health Hazard Evaluation........................iii

Summary .........................................................................................................v

Introduction ...................................................................................................1

Assessment.....................................................................................................2

Results and Discusion.................................................................................3

Conclusions....................................................................................................6

Recommendations.......................................................................................6

References.................................................................................................... 10

Contents

Acknowledgments

Appendix Methods........................................................................................................ 11

Acknowledgments and Availability of Report................................ 12

Health Hazard Evaluation Report 2008-0293-3132 Page i
Abbreviations

′′ Inches

ACT Automation compatible tray

AFSM Automatic flat sorting machine

ATHS Automatic tray handling system

ERMC Eastern regional mail container

ERRP Ergonomic risk reduction process

FMT Flat mail tray

FTS Flat tray sorter

GPMC General purpose mail container

HHE Health hazard evaluation

MSD Musculoskeletal disorder

NAICS North American Industry Classification System

NIOSH National Institute for Occupational Safety and Health

OSHA Occupational Safety and Health Administration

PPE Personal protective equipment

WMSD Work-related musculoskeletal disorder

Page ii Health Hazard Evaluation Report 2008-0293-3132
The National Institute 

for Occupational Safety 

and Health (NIOSH) 

received a request for a 

health hazard evaluation 

(HHE) at a postal facility 

in Colorado. Employees 

submitted the request 

because of ergonomic 

concerns with the 

automatic flat sorting 

machines (AFSMs).

Highlights of the

NIOSH Health

Hazard Evaluation

What NIOSH Did

● We evaluated the facility in April 2009.

● We observed employees working on the AFSM machines. 

We also videotaped employees working at the machines so 

we could examine their work postures.

● We measured workstation heights and reach distances.

● We asked employees about their work and medical history.

● We reviewed occupational safety and health injury and 

illness logs.

What NIOSH Found

● Employees are at risk for work-related shoulder, arm, wrist, 

and hand injuries. This risk is due to awkward postures, 

forceful exertions, and repetitive motions.

● Employees are at risk for work-related back injuries. This 

risk is due to lifting, twisting movements of the trunk, and 

bending at the waist.

● Employees reported injuries in their back, shoulders, arms, 

wrists, and hands.

● Employee rotation patterns were inconsistent between tours, 

machines, and supervisors.

What Managers Can Do

● Design all work areas to be 27–62 inches high. Moving the 

working height toward the middle of the range should reduce 

the risk for back and shoulder injuries.

● Design all lifts to be less than or equal to 27 pounds; this is 

the maximum acceptable weight for lifts that occur two or 

more times a minute in optimal conditions.

● Incorporate job tasks that do not require lifting or repetitive 

grip into current work rotations. Scheduling rotations 

where employees are not required to repeat the same type 

of task will reduce the stress on limbs and body regions. All 

employees should participate in the same rotation patterns.

● Implement an active routine maintenance schedule for 

knives and cutters used in the prepping area. Dull or broken 

tools should be replaced immediately.

● Allow employees to provide input on scheduling, pacing, and 

how jobs are designed and performed.

Health Hazard Evaluation Report 2008-0293-3132 Page iii
Highlights of the

NIOSH Health

Hazard Evaluation

 (continued)

What Employees Can Do

● Work safely and lift properly to reduce your risk of injury.

● Become active in safety and ergonomic committees.

● Report injuries and unsafe work conditions to supervisors, 

union representatives, and management.

Page iv Health Hazard Evaluation Report 2008-0293-3132
NIOSH evaluated 

ergonomic hazards 

among employees who 

work on AFSM 100 

machines. We found that 

employees are exposed to 

risk factors for WMSDs in 

the upper extremities and 

back. Recommendations 

for reducing the risk 

of WMSDs include 

designing work heights 

27′′–62′′ high; designing 

all lifts to be less than or 

equal to 27 pounds; and 

incorporating job tasks 

that do not require lifting 

or repetitive gripping into 

current work rotations.

Summary

On September 16, 2008, NIOSH received an HHE request 

from employees at a postal facility in Colorado. The request was 

submitted because of potential ergonomic hazards among workers 

using the AFSM 100 machines.

During April 1–3, 2009, NIOSH investigators evaluated the postal 

facility. We observed work processes, practices, and workplace 

conditions. We measured workstation design parameters and 

collected video of loading, prepping, and sweeping tasks. We also 

reviewed medical records related to work injuries and talked with 

employees privately about their health and workplace concerns.

We found that employees were exposed to risk factors for 

developing upper extremity WMSDs (including awkward postures, 

forceful exertions, and repetitive motions), and back injuries 

(including lifting, twisting movements of the trunk, and bending 

at the waist). Interviews with employees and review of OSHA Form 

300 Log of Work-Related Injuries and Illnesses for 2005–2009 

confirmed that the most common WMSD injuries were to the 

upper extremities and back. Recommendations for reducing the 

risk of WMSDs, including improved workplace design and rotation 

patterns are included in this report.

Keywords: NAICS 491110 (Postal Service), AFSM 100, postal 

workers, rotation, ergonomics, musculoskeletal disorders 

Health Hazard Evaluation Report 2008-0293-3132 Page v
Page 1 Health Hazard Evaluation Report 2008-0293-3132

Introduction

On September 16, 2008, NIOSH received an HHE request 

from employees at a postal facility in Colorado to evaluate 

potential ergonomic hazards among workers using the AFSM 

100 machines.

During April 1–3, 2009, we conducted a site visit at the 

facility. On April 1, 2009, we held an opening conference with 

management, employees, and union officials from the National 

Postal Mail Handlers. We observed work processes, practices, and 

workplace conditions. We collected video of loading, prepping, 

and sweeping tasks and measured workstation design parameters. 

We also privately interviewed employees to discuss their health 

and workplace concerns, and reviewed medical records related 

to work injuries. On April 3, 2009, we held a closing conference 

and provided preliminary recommendations to management and 

union officials. Preliminary findings and recommendations were 

provided in a letter dated April 24, 2009.

Process Description

Each of the seven AFSM 100 machines had six stations. 

Employee rotation patterns through the stations varied 

depending on the tour (time of day), machine, number of 

employees working on a machine, and supervisor. Employees 

were supposed to rotate stations every 30 minutes, but several 

stated that did not regularly occur. Flat mail includes items that 

are larger than letter size envelopes with a flat profile such as 

an envelope containing a flat sheet of paper or a magazine. The 

following tasks associated with the AFSM 100 were observed.

Loading

Employees manually lifted mail that arrived in FMTs from 

GPMCs or ERMCs and placed the FMTs on an approximately 

waist-level take-away conveyor. Some mail arriving in FMTs was 

removed from larger containers and inducted into the system 

via the “half-prep” station adjacent to the take-away conveyor. 

This process was the same as the ACT process during prepping.

Prepping

Loose mail and bundles were handled on a table surface where 

outer bundle straps and wrappings were cut, removed, and 

placed into a trash receptacle. The mail was then placed into 

an ACT. When the ACT was filled, the employee passed a 
Health Hazard Evaluation Report 2008-0293-3132 Page 2

Introduction

 (continued) finger by an optical switch, and the filled ACT lowered and 

passed into the machine, and an empty ACT moved into the 

working tray position.

Sweeping

After the mail was inducted into the machine, the machine read 

the address information and sorted it into destination FMT bin 

positions along the length of the machine. With the ATHS, 

the system could tell when to remove a full tray and replace the 

location with an empty one. Full trays were directed to the end 

of the AFSM 100 machine. On some lines, trays were manually 

transferred to GPMC and ERMC at the end of the machine, while 

on other lines the trays were automatically sent by conveyor from 

the machine to the FTS. Final sweeping was the removal of all 

FMTs from the machine at the end of a sort run for movement to 

the next processing step.

Flat Tray Sorter

FMTs were manually loaded and unloaded from the FTS conveyor. 

The FTS sorted the FMTs to different areas for additional sorting 

or when ready for delivery.

Assessment

We observed the process of loading, prepping, feeding, sweeping, and 

FTS loading/unloading. We took digital videos to document the tasks 

performed by the employees and measured workstation heights. A full 

description of the ergonomic evaluation criteria we used to determine 

risk factors for WMSDs is provided in Appendix A.

We interviewed employees who worked on the AFSM privately, in 

a separate room. The interviews included questions on work type 

and duration, work-related injuries or illnesses, past or current 

health conditions, medications, smoking status, possible workplace 

exposures, and use of personal protective equipment. We reviewed 

medical records for injured employees and the OSHA Form 300 

Log of Work-Related Injuries and Illnesses for 2005–2009.
Page 3 Health Hazard Evaluation Report 2008-0293-3132

Results and Discussion

Loading

One employee was responsible for transferring mail from GPMCs 

or ERMCs to the conveyor line. We observed that some GPMCs or 

ERMCs were only half full and that in those cases the bottom half 

of the cart was used, eliminating overhead reaches but requiring 

bending at the back. The measured heights for FMT handles in 

a GPMC starting at the top were 59′′ maximum height, 30′′–50′′

middle, and 18′′ bottom row. There was a 33′′ reach distance to 

the back row of FMTs in a GPMC. This reach distance resulted 

in repetitive bending over at the back to perform the lifts for 

the middle and bottom rows of FMTs. It also required extended 

reaches and awkward back postures for reaches from the back of 

the cart. Also, an employee was observed using the “half prep” 

station from an FMT that was close to the floor; this required 

excessive bending at the back.

Prepping

Each machine had four prepping stations; however, during our 

visit we did not always see all four being used. Mail was received at 

each prep station either in an FMT or in bundles. Mail in an FMT 

had to be sorted and placed into the ACT. This required gripping 

of bundles of mail and sometimes awkward wrist postures when 

rotating mail to place in the ACT. Mail bundles had either plastic 

wrapping or bundling straps, or sometimes both. This required 

cutting the wrapping and bundling with a knife, then sorting and 

placing into the ACT. Use of the knife also caused awkward wrist 

postures. The prep table heights were approximately 35′′; when an 

FMT was in the holding position at the prep station hand working 

heights were 39′′–43′′. The ACT working heights were 29′′–40′′. 

These working heights required bent neck postures for some taller 

workers when prepping mail.

Sweeping

Full FMTs were discharged from the system and traveled to the 

end of a conveyor system. We observed employees lifting FMTs 

from a roller conveyor into a wire container. The lift origin was 

approximately 30′′ at the handhold of the FMT. The destination 

of the lifts varied greatly depending on the location that the 

employee chose to place the FMT in the container. Employees 

had to twist at the trunk to perform lifts from the conveyor to the 

wire container. During final sweeps the lift frequency was much 

higher than during a normal sweep. The weights of the FMTs also 
Health Hazard Evaluation Report 2008-0293-3132 Page 4

seemed to vary greatly. The information that we received stated 

that weight depended upon the density and volume of the mail in 

the tray; generally trays weighed less than 35 pounds but they could 

weigh more. Employees expressed concerns that recently the ATHS 

settings had been changed and that more pieces of mail were in 

each tray before it was discharged from the system, resulting in 

heavier FMTs.

Flat Tray Sorter

We observed employees loading the FTS conveyor from “84c” 

wire containers and dollies. Lifts from these wire containers could 

originate from 16′′–37′′, while lifts from dollies could originate 

from 24′′–48′′. The loading jobs varied between very repetitive 

lifting and more sporadic lifting depending on how many FMTs 

were already on the FTS. Occasionally, employees had to hold an 

FMT until a spot became available on the FTS. Loading the FTS 

involved twisting movements of the trunk because of the location 

of the containers in relation to the FTS conveyor. We also observed 

employees removing FMTs from the FTS conveyor lines into 

GPMCs, ERMCs, or dollies. These lifting jobs did not appear to be 

as frequent as loading. These lifts had destination heights at FMT 

handles in a GPMC at 18′′ bottom row; 30′′–50′′ middle; and 59′′

maximum height at the top. The reach distance to the back row of 

FMTs in a GPMC was 33′′.

Medical Interviews

We interviewed a convenience sample of 27 of approximately 

175 employees who worked on the AFSMs. The average age was 

47 years (range: 32–61). The average duration of employment 

as mail handlers was 12 years (range: 2–31). Twenty employees 

reported having a work-related injury (some had more than one) 

and seven reported no work-related injury. Employees reported 

seven shoulder injuries; four back; two each of carpal tunnel 

syndrome, elbow, neck, toe, and wrist injury; and one each of 

abdomen, cubital tunnel syndrome, eye, finger laceration, stiff 

fingers, inhalation, and knee injury. Employees also reported 

understaffing, intimidation by management, fear of discipline or 

warning for unsafe work practices, hazard reports getting lost, not 

being able to take a break until packing was done, having to pay for 

footwear, and feeling guilty about an injury.

Results and Discussion

 (continued)
Page 5 Health Hazard Evaluation Report 2008-0293-3132

OSHA Logs

We reviewed OSHA Logs for 2005–2009. Forty-six reported 

recordable injuries involved mail handlers and clerks, including 

28 WMSDs (61%). The most common WMSDs recorded 

were shoulder sprains/strains, followed by wrist sprain/pain/

tenosynovitis, then back strain.

Rotation Patterns

Prior to the site visit, we reviewed detailed information on work 

rotation patterns developed by the ERRP team for AFSM 100 

employees. Employees were supposed to rotate every 30–45 

minutes between lifting tasks (FTS, loader, sweep) and repetitive 

hand tasks (various prep stations). During interviews with 

management, union, and employees we found the rotation pattern 

varied depending on the tour/shift, machine, and supervisor. 

During one tour/shift, employees moved to different machines 

from week to week; for another tour the same crews stayed on the 

same machines. This can cause unequal work distribution because 

particular zones are assigned to particular machines, and some 

machines did not have conveyors to the FTS.

A recent laboratory-based study looked at the effect of task rotation 

on forearm and back muscle activity, the two muscle groups that 

are utilized during AFSM 100 tasks. In the study, four rotations 

were evaluated: lift-lift, lift-grip, grip-lift, and grip-grip. The 

researchers found that two consecutive segments of either grip or 

lift alone resulted in the greatest muscle effects. They also found 

that the forearm muscles did not benefit as much as hoped by 

rotating between a gripping and lifting task. This occurred because 

even though the handle grip differed between the tasks, the 

forearm muscles used during gripping were also used during lifting 

[Keir et al., in press].

Results and Discussion

 (continued)
Health Hazard Evaluation Report 2008-0293-3132 Page 6

Conclusions

Employees are exposed to a combination of risk factors for upper 

extremity WMSDs (including awkward postures, forceful exertions, 

and repetitive motions) and risk factors for back injuries (including 

lifting, twisting movements of the trunk, and bending at the waist). 

The interviews and OSHA logs confirmed that the most common 

WMSD injuries were upper extremity and back. Recommendations 

for reducing the risk of WMSDs are included in this report.

Because of concerns voiced by employees during our interviews 

and our observations that certain work organization factors might 

play an important role in the MSDs at this facility, we offered to 

return to gather information regarding work organization factors. 

Work organization refers to the way work is organized, supervised, 

and conducted. Examples of work organization variables include 

scheduling, job design, management style, and organizational 

characteristics. The organization of work affects employees’ 

experiences (physical, psychological, and social). Psychological 

and social factors such as job satisfaction and perceived job stress 

levels have been strongly related to WMSDs. Increasing employee 

influence on decisions made about work organization may not 

only reduce the physical demand of the job but also create feelings 

of improved job control [Marras and Karwowski 2006]. As this 

concern was not part of the original request, the headquarters for 

the facility opted not to allow further evaluation.

Recommendations

On the basis of our findings, we recommend the actions listed 

below to create a more healthful workplace. We encourage the 

facility to use a labor-management health and safety committee 

or working group to discuss the recommendations in this report 

and develop an action plan. Those involved in the work can best 

set priorities and assess the feasibility of our recommendations 

for the specific situation at the facility. Our recommendations 

are based on the hierarchy of controls approach. This approach 

groups actions by their likely effectiveness in reducing or removing 

hazards. In most cases, the preferred approach is to eliminate 

hazardous materials or processes and install engineering controls 

to reduce exposure or shield employees. Until such controls are 

in place, or if they are not effective or feasible, administrative 

measures and/or personal protective equipment may be needed.
Engineering Controls

Engineering controls reduce exposures to employees by removing 

the hazard from the process or placing a barrier between the hazard 

and the employee. Engineering controls can be very effective at 

protecting employees without placing primary responsibility of 

implementation on the employee.

● Design all work areas within a working range of 27′′–62′′

[Humantech 2009]. Moving the working height toward the 

middle of the range should reduce the risk for back and 

shoulder WMSDs.

● Design all lifts to be ≤ 27 pounds. This is the maximum 

acceptable lift weight for frequent lifts (≥ 2/minute) for 

optimal reach heights and distances, to reduce the risk of low 

back injury [Humantech 2009]. As reach distances increase, 

the acceptable lift weights decrease. For extended reaches 

with a bent back, the acceptable lift weight is only 8 pounds.

● Design a frequent reach zone (lifts >2/minute) ≤ 16′′ from 

the edge of the container or dolly. If necessary, place tubs 

closer to the edge of the container or dolly and then rotate 

them, rather than reaching to place tubs in the back of the 

container or dolly. This distance is also preferable when 

handling mail during prepping. Every 6′′ of additional 

horizontal reach distance creates 0.2 seconds of wasted 

time [Humantech 2009].

Administrative Controls

Administrative controls are management-dictated work practices and 

policies to reduce or prevent exposures to workplace hazards. The 

effectiveness of administrative changes in work practices for controlling 

workplace hazards is dependent on management commitment and 

employee acceptance. Regular monitoring and reinforcement are 

necessary to ensure that control policies and procedures are not 

circumvented in the name of convenience or production.

● Rotate employees through several jobs with different physical 

demands to reduce the stress on limbs and body regions. 

Incorporate job tasks that do not require lifting or repetitive 

grip into the current rotation. Do not schedule rotations 

where employees are required to repeat the same type of task, 

i.e., grip-grip or lift-lift.

Recommendations

 (continued)

Page 7 Health Hazard Evaluation Report 2008-0293-3132
● Require all tours and all employees to participate in the same 

rotation patterns. Management and union representatives 

should work together with employees to jointly address 

rotation and other ergonomic issues.

● Ensure that knives/cutters are well maintained and in 

good repair. Implement an active routine maintenance and 

replacement schedule for knives/cutters used in the prepping 

area.

● Routinely evaluate the effectiveness of engineering and 

administrative controls.

● Schedule more breaks to allow for rest and recovery. Taking 

short breaks for 3–5 minutes every hour can give the body a 

rest and reduce discomfort.

● Increase employee participation and influence in work 

organization (i.e., the way jobs are designed and performed, 

work scheduling, and pacing). Targeting these factors can 

bring about changes that reduce the risk of WMSDs.

Personal Protective Equipment

PPE is the least effective means for controlling employee exposures. 

Proper use of PPE requires a comprehensive program and calls for a 

high level of employee involvement and commitment to be effective. 

The use of PPE requires the choice of the appropriate equipment to 

reduce the hazard and the development of supporting programs such 

as training, change-out schedules, and medical assessment if needed. 

PPE should not be relied upon as the sole method for limiting 

employee exposures. Rather, PPE should be used until engineering 

and administrative controls can be demonstrated to be effective in 

limiting exposures to acceptable levels.

● Provide industrial antifatigue mats for employees who stand 

for 90% or more of their working hours. Mats should be 

≥ 0.5′′ thick, have an optimal compressibility of 3%–4%, 

have beveled edges to minimize trip hazards, and be placed 

at least 8′′ under a workstation to prevent uneven standing 

surfaces. Mats can be ordered to meet specific electrical/

static requirements [Humantech 2009].

● Implement a routine replacement schedule for mats.

Recommendations

 (continued)

Health Hazard Evaluation Report 2008-0293-3132 Page 8
Healthcare Management

Healthcare management emphasizes the prevention of impairment 

and disability through early detection, prompt treatment, and 

timely recovery. Healthcare management recommendations include 

the following:

● Encourage employees to report musculoskeletal symptoms to 

their supervisors, the union, and management and to seek 

a prompt referral to a healthcare provider experienced in 

the evaluation and treatment of WMSDs. If symptoms are 

identified and treated early, it is less likely that a more serious 

disorder will develop.

● Consistently record cases of WMSDs on OSHA Logs and 

other incident reporting systems to analyze trends and 

understand the magnitude and seriousness of WMSDs. 

These records may also offer leads to jobs or operations that 

can cause or contribute to WMSDs.

Health and Safety Committee 

Managers and employees working together to identify work 

hazards and propose ergonomic solutions is a key component 

to a successful health and safety committee. The following 

recommendation should improve the responsiveness of the 

committee to the ergonomic needs of the employees.

● Encourage employees to participate in health and safety 

committees. Health and safety committee meetings should 

be held regularly to evaluate progress, assign responsibilities, 

and identify potential problem areas. However, if employees 

have immediate health and safety concerns, they should be 

raised and addressed at any time between meetings.

Recommendations

 (continued)

Page 9 Health Hazard Evaluation Report 2008-0293-3132
References

Humantech [2009]. The handbook of ergonomic design guidelines 

– Version 2.0. Ann Arbor, MI: Humantech, Inc.

Keir P, Sanei K, Holmes M [in press]. Task rotation effects on upper 

extremity and back muscle activity. Appl Ergon. [http://dx.doi.

org/10.1016/j.apergo.2011.01.006]. Date accessed: June 2011.

Marras WS, Karwowski W, eds [2006]. Interventions, controls, and 

applications in occupational ergonomics. Boca Raton, FL: CRC Press.

Health Hazard Evaluation Report 2008-0293-3132 Page 10
Appendix: Methods

Musculoskeletal disorders are those conditions that involve the nerves, tendons, muscles, and supporting 

structures of the body. They can be characterized by chronic pain and limited mobility. WMSD refers to 

(1) musculoskeletal disorders to which the work environment and the performance of work contribute 

significantly, or (2) MSDs that are made worse or longer lasting by work conditions. A substantial body 

of data provides strong evidence of an association between MSDs and certain work-related factors 

(physical, work organizational, psychosocial, individual, and sociocultural). The multifactorial nature 

of MSDs requires a discussion of individual factors and how they are associated with WMSDs. Strong 

evidence shows that working groups with high levels of static contraction, prolonged static loads, or 

extreme working postures involving the neck/shoulder muscles are at increased risk for neck/shoulder 

MSDs [NIOSH 1997]. Further strong evidence shows job tasks that require a combination of risk factors 

(highly repetitious, forceful hand/wrist exertions) increase risk for hand/wrist tendonitis [NIOSH 1997]. 

Lastly, strong evidence shows that low-back disorders are associated with work-related lifting and forceful 

movements [NIOSH 1997].

A number of personal factors can also influence the response to risk factors for MSDs: age, sex, smoking, 

physical activity, strength, and anthropometry. Although personal factors may affect an individual's 

susceptibility to overexertion injuries/disorders, studies conducted in high-risk industries show that the 

risk associated with personal factors is small compared to that associated with occupational exposures 

[NIOSH 1997].

In all cases, the preferred method for preventing and controlling WMSDs is to design jobs, workstations, 

tools, and other equipment to match the physiological, anatomical, and psychological characteristics and 

capabilities of the employee. Under these conditions, exposures to risk factors considered potentially 

hazardous are reduced or eliminated.

Workstation design should directly relate to the anatomical characteristics of the employee. Because a 

variety of employees may use a specific workstation, a range of work heights should be considered. Based 

upon functional anthropometry, working heights should be within a range of 27" to no higher than 62" 

[Humantech 2009]. These heights correspond to hand height dimensions for the 5th percentile female and 

shoulder dimensions for the 95th percentile male.

References

Humantech [2009]. The handbook of ergonomic design guidelines – Version 2.0. Ann Arbor, MI: 

Humantech, Inc.

NIOSH [1997]. Musculoskeletal disorders and workplace factors: a critical review of epidemiologic 

evidence for work-related musculoskeletal disorders of the neck, upper extremity, and low back. 

Cincinnati, OH: U.S. Department of Health and Human Services, Centers for Disease Control and 

Prevention, National Institute for Occupational Safety and Health, (DHHS) Publication No. 97–141. 

[http://www.cdc.gov/niosh/docs/97-141/]. Date accessed: June 2011.

Page 11 Health Hazard Evaluation Report 2008-0293-3132
Acknowledgments and

Availability of Report The Hazard Evaluations and Technical Assistance Branch 

(HETAB) of the National Institute for Occupational Safety and 

Health (NIOSH) conducts field investigations of possible health 

hazards in the workplace. These investigations are conducted 

under the authority of Section 20(a)(6) of the Occupational Safety 

and Health Act of 1970, 29 U.S.C. 669(a)(6) which authorizes 

the Secretary of Health and Human Services, following a written 

request from any employer or authorized representative of 

employees, to determine whether any substance normally found 

in the place of employment has potentially toxic effects in such 

concentrations as used or found. HETAB also provides, upon 

request, technical and consultative assistance to federal, state, and 

local agencies; labor; industry; and other groups or individuals to 

control occupational health hazards and to prevent related trauma 

and disease.

The findings and conclusions in this report are those of the 

authors and do not necessarily represent the views of NIOSH. 

Mention of any company or product does not constitute 

endorsement by NIOSH. In addition, citations to websites 

external to NIOSH do not constitute NIOSH endorsement of 

the sponsoring organizations or their programs or products. 

Furthermore, NIOSH is not responsible for the content of these 

websites. All Web addresses referenced in this document were 

accessible as of the publication date.

This report was prepared by Jessica G. Ramsey and Anthony 

Almazan of HETAB, Division of Surveillance, Hazard Evaluations 

and Field Studies. Health communication assistance was provided 

by Stefanie Evans. Editorial assistance was provided by Ellen 

Galloway. Desktop publishing was performed by Greg Hartle.

Copies of this report have been sent to employee and management 

representatives at the postal facility, the state health department, 

and the Occupational Safety and Health Administration 

Regional Office. This report is not copyrighted and may be freely 

reproduced. The report may be viewed and printed at http://

www.cdc.gov/niosh/hhe/. Copies may be purchased from the 

National Technical Information Service at 5825 Port Royal Road, 

Springfield, Virginia 22161.

Health Hazard Evaluation Report 2008-0293-3132 Page 12
Below is a recommended citation for this report:

NIOSH [2011]. Health hazard evaluation report: ergonomic evaluation of 

automatic flat sorting machines – Colorado. By Ramsey J, Almazan A. 

Cincinnati, OH: U.S. Department of Health and Human Services, Centers for 

Disease Control and Prevention, National Institute for Occupational Safety and 

Health, NIOSH HETA No. 2008-0293-3132

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TTY: 1-888-232-6348

E-mail: cdcinfo@cdc.gov

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For a monthly update on news at NIOSH, subscribe to 

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