Health Hazard Evaluation Report 2015-0180-3261 Page 1

Evaluation of Noise and Metal Exposure at a 

Security Portal Manufacturer

HHE Report No. 2015-0180-3261

November 2016

Jessica F. Li, MSPH

Steven Ahrenholz, PhD, MS, CIH

U.S. Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health
Page 2 Health Hazard Evaluation Report 2015-0180-3261

Contents

Highlights...............................................i

Abbreviations ..................................... iii

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

Methods ............................................... 2

Results and Discussion........................ 3

Conclusions.......................................... 7

Recommendations............................... 8

Appendix A ........................................ 10

Appendix B ........................................ 11

References.......................................... 15

Acknowledgements........................... 19

The employer is required to post a copy of this report for 30 days at or near the 

workplace(s) of affected employees. The employer must take steps to ensure 

that the posted report is not altered, defaced, or covered by other material.

The cover photo is a close-up image of sorbent tubes, which are used by the HHE 

Program to measure airborne exposures. This photo is an artistic representation that may 

not be related to this Health Hazard Evaluation. Photo by NIOSH.
Health Hazard Evaluation Report 2015-0180-3261 Page i

We were asked to evaluate 

employees’ exposures to metal 

dust and noise in the fabrication 

areas. Employees were not 

overexposed to aluminum 

or other metals. Sanders and 

the mill/saw operator were 

overexposed to noise over an 

8-hour work shift. However, 

employees typically performed 

these tasks for only 2–3 hours 

per shift. We recommend 

re-evaluating noise exposure 

during a typical work shift and 

whenever production changes.

Highlights of this Evaluation

The Health Hazard Evaluation Program received a request from a security portal 

manufacturing facility. The employer was concerned about employees’ exposure to dust and 

noise when they sanded and sawed aluminum alloy.

What We Did

● We visited the facility in January 2016. 

● We collected bulk dust samples in the fabrication area to screen for metals.

● We collected personal samples for respirable aluminum, total metals, and noise on 

fabrication area employees.

● We measured the size of airborne particles in 

the fabrication and office areas.

● We observed the airflow around the downdraft 

table in the sanding area.

● We observed employees’ personal protective 

equipment use.

What We Found

● Bulk dust samples contained mostly aluminum, 

chromium, manganese, and nickel. 

● Employees sanding, assembling, and operating 

the mill/saw were not overexposed to 

aluminum, chromium, manganese, and nickel.

● Two sanders and the mill/saw operator were 

overexposed to noise. 

● Employees in the electronics and assembly 

areas near the mill/saw were unnecessarily 

exposed to noise.

● The employer did not provide employees with Appendix D of the Occupational Safety 

and Health Administration respiratory protection standard for voluntary respirator use.

● We saw an employee improperly wearing an N95 filtering facepiece respirator.

● One employee stood in an awkward posture when sanding aluminum pieces on a 

downdraft table.

What the Employer Can Do

● Enclose the band saw area and make other changes to reduce noise exposure. 

● Re-evaluate employee’s noise exposures under typical sanding and sawing production 

levels and whenever fabrication processes change.
Page ii Health Hazard Evaluation Report 2015-0180-3261

● Provide employees with Appendix D of the Occupational Safety and Health 

Administration respiratory protection standard for voluntary respirator use.

● Redesign the sanding tasks to lessen employees having to work in awkward positions.

● Create a health and safety committee with employer and employee representatives.

● Ask employees to report any symptoms they consider to be work-related to their 

supervisor and personal physician.

What Employees Can Do

● Use hearing protection when sanding and while the band saw is in operation.

● Participate in the health and safety committee.

● Take breaks from a task if you feel discomfort.

● Report any symptoms you believe to be work-related to your supervisor and 

personal physician.
Health Hazard Evaluation Report 2015-0180-3261 Page iii

Abbreviations

μg/m3 Micrograms per cubic meter of air

AL Action level

ACGIH® American Conference of Governmental Industrial Hygienists

CFR Code of Federal Regulations

dBA Decibels, A-weighted

Hz Hertz

NIHL Noise-induced hearing loss

NIOSH National Institute for Occupational Safety and Health

OEL Occupational exposure limit

OSHA Occupational Safety and Health Administration

PEL Permissible exposure limit

REL Recommended exposure limit

TLV® Threshold limit value

TWA Time-weighted average
Page iv Health Hazard Evaluation Report 2015-0180-3261

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Health Hazard Evaluation Report 2015-0180-3261 Page 1

Introduction

The Health Hazard Evaluation Program received a request for an evaluation from a security 

portal manufacturing company. The employer was concerned that the noise and dust 

produced from sanding aluminum alloy and the noise generated from sawing alloy could be a 

health hazard to employees. We visited the company in January 2016. After the visit, we sent 

letters to the company and employee representative summarizing our activities.

Process Description

The workplace included a fabrication area and an office area with a conference room. At the 

time of the evaluation the employer planned to relocate the company in the next few months. 

Seven fabrication area employees worked 8-hour shifts from 6:30 a.m. to 3:00 p.m. The 

amount of aluminum fabricated depended on the design and size of each custom security 

portal, which are interlocking security door systems that are used in buildings requiring 

increased security including banking institutions, detention centers, and secure government 

buildings. All employees were cross-trained to do different jobs, such as sanding, milling, 

sawing, and assembling. Only one or two jobs were performed at the same time. 

Aluminum fabrication began by sawing 24-foot long hollow aluminum alloy “sticks” with 

an automatic scissor-style band saw into shorter lengths (Figure 1). The width and depth of 

the sticks varied from 1 inch by 0.5 inch to 6 inches by 6 inches. After sawing the sticks, 

employees milled and sanded the surfaces in preparation for painting. Sanding was typically 

done for 2–3 hours per day for no more than 8–10 hours per week. Sanded aluminum pieces 

were sent out for painting by a contractor, then returned to the company for final assembly 

into custom-designed security portals. For large portals some processes such as milling and 

sanding were outsourced before returning to the company for final assembly.

Figure 1. Automated band saw sawing a stick of aluminum alloy. The operating station is to the right 

of the saw. Photo by NIOSH.
Page 2 Health Hazard Evaluation Report 2015-0180-3261

During our visit, two employees sanded aluminum pieces for the entire 8-hour work shift 

(Figure 2), and one employee milled for half of the work shift and operated the band saw for the 

remainder of the work shift. Management adjusted their work practices for an 8-hour work shift 

to set up a worst-case scenario, where sanding occurred for the maximum time of 8 hours.

Figure 2. Employees power-sanding aluminum pieces on a downdraft table. Photo by NIOSH.

Methods

The objectives of this evaluation were to determine (1) if the dust generated during sanding 

presents a potential health hazard, (2) if there are other workplace exposures of concern, such 

as noise, and (3) if the ventilation system and downdraft table is adequate for the industrial 

processes performed at the facility.

Workplace Observations and Ventilation Assessment

We observed fabrication processes, work practices, workplace conditions, and personal 

protective equipment use. We used ventilation smoke tubes to observe airflow at the 

downdraft work table. We measured airborne particle size and number throughout the 

fabrication area and in the office area (for comparison) using an ARTI/Met One HHPC-6 

mobile particle counter.

Bulk Dust and Air Sampling

During the site visit, we reviewed the safety data sheet the employer provided for the 

aluminum alloy. We collected bulk dust samples from inside the vacuum sander filter bag, 

inside the downdraft table bag filter, and settled dust from work surfaces in the sanding 

area and in the electronics area further away from the sanding area. The bulk dust samples 

were analyzed for elements (minerals and metals) using National Institute for Occupational 

Safety and Health (NIOSH) Method 7303 [NIOSH 2016a]. We used the results from the bulk 

sample analyses to select the elements to be analyzed in the air samples.
Health Hazard Evaluation Report 2015-0180-3261 Page 3

We collected personal air samples for respirable aluminum on four employees using NIOSH 

Method 7303 with modification using mixed cellulose ester membrane filters in 3-piece 

cassettes with a BGI Cyclone GK 2.69 [NIOSH 2016a]. The modification was wiping the 

interior of the cassette filter holder with a wet smear tab to collect particles on the inside 

walls. This practice is consistent with the current NIOSH recommendation that all particles 

entering the sampler be included as part of the sample whether they deposit on the filter or 

on the inside surfaces of the sampler [NIOSH 2016b]. We then analyzed the smear tab wipe 

along with the sample filter [NIOSH 2016b]. 

We collected and analyzed personal air samples for selected metals identified from the bulk 

dust samples using NIOSH Method 7303. This method uses a mixed cellulose ester filter with 

Solu-CAP cassette inserts. Use of the inserts eliminated the need for wiping the interior of the 

sample cassette. 

Noise Sampling

We used Larson Davis SparkTM 706RC integrating noise dosimeters to measure timeweighted average (TWA) personal noise exposure on five employees. The dosimeters 

simultaneously collected data on three different settings to compare noise measurements 

with the Occupational Safety and Health Administration (OSHA) permissible exposure limit 

(PEL), the OSHA action level (AL), and the NIOSH recommended exposure limit (REL). 

We also measured real-time, instantaneous noise measurements with a Quest Technologies® 

Model 2400 Type II Sound Level Meter. The instrument was set to measure instantaneous 

noise levels between 70 and 140 decibels, A-weighted (dBA) on a slow response scale. 

The criteria for calculating the OSHA AL include all noise exposure greater than or equal 

to 80 dBA. The criteria for calculating the OSHA PEL include all noise exposure greater 

than or equal to 90 dBA. Both the OSHA AL and the OSHA PEL uses a 5-decibel exchange 

rate. The criteria for calculating the NIOSH REL include all noise exposure greater than or 

equal to 80 dBA, with a more conservative 3-decibel exchange rate. When an employee left 

the workplace during breaks, we stopped the noise dosimeters. We restarted them upon the 

employee’s return.

Results and Discussion

Ventilation Assessment

An employee sanded aluminum pieces using a handheld random orbit electric sander equipped 

with a dust collection bag. The sanding was done on a downdraft ventilated work table. Airflow 

patterns observed using the ventilation smoke tubes showed that the downdraft table was not 

as effective in capturing airborne dust when sanding on either end of the table compared to 

the middle. The capture effectiveness also decreased as the sanding occurred further above the 

surface of the downdraft table, and might not be sufficient if the metal piece is tall.

Employees could not recall the last time the downdraft table filters were changed or 

replaced. The company had just received replacement filters for the downdraft table. When 
Page 4 Health Hazard Evaluation Report 2015-0180-3261

the downdraft table was opened for filter change, we noted a hole in one of the fabric 

filter bags. After the filter bag was replaced the dust capture effectiveness of the table 

appeared to improve on the basis of visual observations using smoke tubes. We contacted 

the manufacturer to inquire about downdraft table and dust types and consulted with the 

downdraft table owner’s manual. According to the manufacturer the downdraft table was 

designed for wood dust; the manufacturer advised against using it for metal dust. Metal 

and wood dust differ in properties such as specific gravity and flammability. The designed 

capture velocity of the downdraft table 6 inches above the table is 673 feet per minute, and 

12 inches above the table is 229 feet per minute. The American Conference of Governmental 

Industrial Hygienists (ACGIH) recommends capture velocities of 500–2,000 feet per minute 

for “grinding” tasks [ACGIH 2016b].

Airborne particle counts, for particles ranging from 0.3 to 10 micrometers in size, were 

consistently higher in the fabrication area than in the conference room (Table A1, Appendix 

A). Particle counts of all sizes increased in the afternoon compared to the morning in the 

fabrication area and the conference room. This could be due to several reasons. At 12:30 

p.m., before the afternoon measurements, milling ceased and sawing began; this shift in 

processes could have changed the amount and size distribution of the dust particles produced. 

The downdraft table filter was changed before the lunch break at 11:30 a.m. It is possible 

that dust dispersed to other fabrication areas during the removal, emptying, and moving 

of the bag filter. Furthermore, the new filter could be less efficient at filtering out dust 

particles without a layer of built-up dust because efficiency increases with dust loading. The 

employer reported the office space was served by two separate heating, ventilating, and airconditioning systems. Because our focus was on aluminum dust and noise exposures in the 

fabrication area we did not evaluate the heating, ventilating, and air-conditioning systems for 

the front administrative offices. If the units’ supply air to offices was drawn from inside the 

building, a potential may exist for introducing dust from fabrication areas into the office. 

Bulk Dust and Air Sampling

We analyzed for 32 elements in the bulk dust samples. From these results, we selected the 

metals that were present in the highest concentrations or have low occupational exposure 

limits (OELs) for analysis in the personal air samples. These included aluminum, arsenic, 

cadmium, chromium, lead, manganese, and nickel. The results of personal air sampling for 

metals are in Table 1. The three metals that were not detected along with their minimum 

detectable concentrations are: arsenic (< 0.6 micrograms per cubic meter [μg/m3

]), cadmium 

(< 0.2 μg/m3

), and lead (< 0.2 μg/m3). For the metals that were detected, air sample results 

were compared to their respective NIOSH RELs, ACGIH threshold limit values (TLVs), and 

OSHA PELs. The personal air sampling results for all metals were well below their most 

protective OELs. Appendix B contains more information on OELs and health effects for 

substances we evaluated.
Health Hazard Evaluation Report 2015-0180-3261 Page 5

Table 1. Personal air sample results for total aluminum, chromium, manganese, and nickel, 

January 2016

Job title Sample

time

(minutes)

Total

aluminum 

(μg/m3

)

Chromium

(μg/m3)

Manganese

(μg/m3)

Nickel

(μg/m3)

Sander 1 501 850 0.50 1.4 0.20

Sander 2 503 930 0.49 0.64 0.12

Assembly 488 31 ND 0.067 [0.046]†

Mill operator/saw operator* 401 25 ND 0.068 ND

NIOSH REL

ACGIH TLV

OSHA PEL

10,000

None

15,000

500

500

1,000

1,000

100

5,000‡

15

1,500

1,000

Minimum detectable concentration

Minimum quantifiable concentration

1

3.2–4.0

0.05–0.06

0.15–0.19

0.01

0.024–0.031

0.02–0.03

0.083–0.11

ND = not detected, below the minimum detectable concentration

*This employee left work during breaks. The sampling pump was stopped when the employee left 

and restarted when the employee returned.

†This value is between the minimum detectable concentration and the minimum quantifiable 

concentration, meaning there is more uncertainty associated with this value.

‡A ceiling limit that should not be exceeded at any time.

The results of the personal air samples for respirable aluminum are presented in Table 2. The 

highest personal exposure was less than 20 μg/m3

, well below the most protective OEL of 

1,000 μg/m3

.

Table 2. Personal air sample results for respirable aluminum, January 2016

Job title Sample time 

(minutes)

Sample volume 

(liters)

Respirable aluminum 

(μg/m3

)

Sander 1 501 2,108 15

Sander 2 503 2,117 20

Assembly 488 2,059 5.3

Mill operator/Saw operator* 401 1,680 5.0

NIOSH REL

ACGIH TLV

OSHA PEL

5,000

1,000

5,000

*This employee left work during breaks. The sampling pump was stopped when the employee left 

and restarted when the employee returned.
Page 6 Health Hazard Evaluation Report 2015-0180-3261

The highest metal exposures were measured on the two sanders. Although results were 

below applicable OELs, improving housekeeping and increasing the frequency of air filter 

replacement may further reduce unnecessary exposure to metal dust.

Noise Exposure and Hearing Conservation

Full-shift TWA personal dosimetry measurements are shown in Table 3. Noise exposures for 

both sanders and the mill/saw operator exceeded the NIOSH REL of 85 dBA for an 8-hour 

TWA. One of the sander’s noise exposure also exceeded the OSHA AL of 85 dBA. During 

our evaluation, employees sanded for the entire work shift; however sawing and sanding is 

typically done for only 2 to 3 hours per day (8 to 10 hours per week). Because employees 

rarely saw and sand for a full work shift, on typical workdays their 8-hour TWA exposures 

would likely be lower than what we measured. However, on the basis of our measurements, 

the mill/band saw operator’s noise exposure would exceed the NIOSH REL after 2.8 hours 

and the sanders’ noise exposures would exceed the NIOSH REL after about 4.5 hours of 

sanding. The sanders’ noise exposure would exceed the OSHA AL after 5.7 hours of sanding. 

Additionally, the band saw was used for the second half of the work shift while sanding 

also occurred. The employer has advised employees not to sand and saw at the same time to 

reduce cumulative noise from both noisy tasks. 

Table 3. Personal noise sampling results, January 2016

Job title Time 

(minutes)

Using NIOSH 

REL criteria 

(dBA)

Using OSHA AL 

criteria 

(dBA)

Using OSHA 

PEL criteria 

(dBA)

Mill operator/saw 

operator*

407 89.5 80.9 79.3

Sander 1 500 87.4 85.2 80.1

Sander 2 501 85.9 83.5 76.7

Electronics/assembly 456 76.2 66.9 56.6

Assembly 486 74.1 66.2 51.7

OELs, as 8-hour TWAs 85 85 90

Noise exposures exceeding the NIOSH REL or the OSHA AL are shown in bold text.

The noise levels reached 115 dBA in the hearing zone of the saw operator during operation 

and 112 dBA in nearby fabrication areas approximately 10 feet away from the band saw. 

When the band saw was not in operation, the noise levels ranged from 68 dBA to 89 dBA in 

the surrounding areas. These measurements show how the sawing operations affects noise 

exposures among nearby employees in the fabrication area. 
Health Hazard Evaluation Report 2015-0180-3261 Page 7

The company did not have a hearing conservation program, but hearing protection was 

available and worn voluntarily. During our evaluation employees sanding wore foam insert 

ear plugs, and the employee operating the band saw wore earmuffs. Hearing protection 

appeared to be worn correctly and consistently throughout the work shift.

Other Observations

We saw two employees of different heights sanding aluminum pieces at the downdraft table 

(Figure 2). The taller employee bent his neck downward while sanding. Awkward work 

postures, such as bending the back or the neck, for prolonged periods can result in muscle 

fatigue, pain, or musculoskeletal disorders [OSHA 2000]. For this employee, a work surface 

that was raised or tilted toward the employee or an adjustable stool could reduce the need for 

awkward work postures. The height of the downdraft table was not adjustable.

Sanding employees voluntarily wore N95 filtering facepiece respirators but had not been 

provided with Appendix D of the OSHA 1910.134 respiratory protection standard. We saw 

some employees incorrectly wearing respirators. For example, an employee wore an N95 

respirator with only the top strap secured. This employee also had facial hair in the area of 

the seal that would interfere with a proper face seal and reduce the protection offered by the 

respirator. Unused N95 respirators were stored in an open box near the sanding area; thus, 

they could become contaminated.

The employer stated that employees had once consumed food and drink in the fabrication 

area, but that this practice had stopped prior to our visit. The formation of a health and safety 

committee would help to facilitate communication about company policies and general 

hygiene practices. At the time of our site visit, the formation of an employee-employer health 

and safety committee was in progress.

Since the conclusion of the site visit, the company relocated its production operations. 

Conclusions

Employees were overexposed to noise when sanding, milling, and sawing over an 8-hour 

work shift. However, because these work tasks are typically performed for only 2–3 hours 

per shift, employee noise exposures should be reevaluated. Fabrication employees near 

the milling/sawing operation were unnecessarily exposed to noise. Employees were not 

overexposed to respirable and total aluminum, or chromium, manganese, and nickel, but 

metal dust exposures may be further reduced by improving housekeeping and other work 

practices, such as frequently maintaining and checking downdraft table filters, using wet 

cleaning methods, and storing respirators away from the contamination source. If voluntary 

respirator use is allowed by the employer, employees should be provided with Appendix D 

of the OSHA respiratory protection standard and receive training on voluntary respirator use. 
Page 8 Health Hazard Evaluation Report 2015-0180-3261

Employees used awkward postures, a risk factor for work-related musculoskeletal disorders. 

These awkward postures should be reduced through engineering or administrative controls.

Recommendations

On the basis of our findings, we recommend the actions listed below. We encourage the 

security portal manufacturer to use an employee-management health and safety committee or 

working group to discuss our recommendations 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 security portal manufacturer. 

Our recommendations are based on an approach known as the hierarchy of controls. 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 personal 

protective equipment may be needed. We recommend the following:

Engineering Controls

Engineering controls reduce employees’ exposures by removing the hazard from the process or by 

placing a barrier between the hazard and the employee. Engineering controls protect employees 

effectively without placing primary responsibility of implementation on the employee. 

1. Enclose the band saw area to prevent unnecessary noise exposure to employees in the 

fabrication area who are not operating the saw.

2. Adjust the downdraft table height to reduce awkward postures by employees when 

sanding. Alternatively, provide height-adjustable stools so employees can be seated 

and adjust their position to avoid awkward postures. 

3. Select and purchase a downdraft table designed for metal dust when it is time to 

replace the current downdraft table.

Administrative Controls

The term administrative controls refers to employer-dictated work practices and policies 

to reduce or prevent hazardous exposures. Their effectiveness depends on employer 

commitment and employee acceptance. Regular monitoring and reinforcement are necessary 

to ensure that policies and procedures are followed consistently.

1. Improve hazard communication training to ensure that all employees are 

knowledgeable about metal dust, noise, and ergonomic hazards, how these exposures 

affect their health, and what protective measures should be used to prevent exposures.

2. Re-evaluate noise exposure during typical working conditions and whenever work 

processes change. If noise exposures exceed the lowest occupational exposure limits, 

implement a hearing conservation program for employees considering that production 

levels may vary. The program should include annual audiometric testing and training. 
Health Hazard Evaluation Report 2015-0180-3261 Page 9

More information on establishing a hearing loss prevention program can be found at 

http://www.cdc.gov/niosh/docs/98-126/pdfs/98-126.pdf, http://www.osha.gov/dts/osta/

otm/noise/hcp/index.html, and http://www.osha.gov/Publications/osha3074.pdf.

3. Until the current downdraft table is replaced, establish a filter inspection and changeout schedule for the downdraft table.

4. Use wet cleaning methods or vacuums equipped with high-efficiency particulate air 

filters to clean floors and surfaces.

5. Require employees to take frequent breaks when doing tasks that are associated with 

awkward positions, or vary tasks between different employees.

6. Encourage good personal hygiene practices such as hand-washing after glove removal 

and before eating, drinking, and smoking to reduce the risk of ingesting metals.

7. Ask employees to report any symptoms they consider to be work-related to their 

supervisor and personal physician.

Personal Protective Equipment

Personal protective equipment is the least effective means for controlling hazardous 

exposures. Proper use of personal protective equipment requires a comprehensive program 

and a high level of employee involvement and commitment. The right personal protective 

equipment must be chosen for each hazard. Supporting programs such as training, changeout schedules, and medical assessment may be needed. Personal protective equipment should 

not be the sole method for controlling hazardous exposures. Rather, personal protective 

equipment should be used until effective engineering and administrative controls are in place.

1. Require employees to use hearing protection when sawing because of high noise levels 

during these tasks.

2. Provide hands-on training for employees on how to insert hearing protectors properly 

and the importance of proper hearing protector fit.

3. Provide employees who voluntarily wear respirators with Appendix D from the 

OSHA respiratory protection standard 1910.134 (Information for Employees Using 

Respirators When Not Required Under the Standard). Employees should be advised on 

the proper donning and use of respirators, and supervisors should monitor the proper 

use and wearing of respirators. If respirators are required in the future, ensure that the 

respiratory protection program meets all required elements in the OSHA respiratory 

protection standard.
Page 10 Health Hazard Evaluation Report 2015-0180-3261

Appendix A: Tables

Table A1. Particle counts by diameter (in micrometers)

Location Time 0.3 0.5 1.0 3.0 5.0 10

Conference room 9:00 a.m.

2:02 p.m.

3,444

31,033

1,268

5,856

861

1,891

138

201

79

91

22

15

Downdraft table 9:25 a.m.

9:40 a.m.

9:47 a.m.

2:10 p.m.

11,591

11,274

11,066

81,529

4,292

3,981

3,942

16,300

2,380

2,167

2,185

4,949

411

413

439

729

328

372

432

626

90

144

167

224

Electronics assembly 10:05 a.m.

2:15 p.m.

8,901

76,903

3,043

14,237

1,517

4,091

222

510

152

365

38

91

Assembly 10:12 a.m. 9,266 3,110 1,543 239 179 41

Mill 10:00 a.m. 13,295 3,774 1,454 187 121 23
Health Hazard Evaluation Report 2015-0180-3261 Page 11

Appendix B: Occupational Exposure Limits and 

Health Effects 

NIOSH investigators refer to mandatory (legally enforceable) and recommended OELs for 

chemical, physical, and biological agents when evaluating workplace hazards. OELs have 

been developed by federal agencies and safety and health organizations to prevent adverse 

health effects from workplace exposures. Generally, OELs suggest levels of exposure that 

most employees may be exposed to for up to 10 hours per day, 40 hours per week, for a 

working lifetime, without experiencing adverse health effects. However, not all employees 

will be protected if their exposures are maintained below these levels. Some may have 

adverse health effects because of individual susceptibility, a pre-existing medical condition, 

or a hypersensitivity (allergy). In addition, some hazardous substances act in combination 

with other exposures, with the general environment, or with medications or personal habits of 

the employee to produce adverse health effects. Most OELs address airborne exposures, but 

some substances can be absorbed directly through the skin and mucous membranes.

Most OELs are expressed as a TWA exposure. A TWA refers to the average exposure during 

a normal 8- to 10-hour workday. Some chemical substances and physical agents have 

recommended short-term exposure limits or ceiling values. Unless otherwise noted, the shortterm exposure limit is a 15-minute TWA exposure. It should not be exceeded at any time 

during a workday. The ceiling limit should not be exceeded at any time.

In the United States, OELs have been established by federal agencies, professional 

organizations, state and local governments, and other entities. Some OELs are legally 

enforceable limits; others are recommendations. 

● The U.S. Department of Labor OSHA PELs (29 CFR 1910 [general industry]; 29 CFR 

1926 [construction industry]; and 29 CFR 1917 [maritime industry]) are legal limits. 

These limits are enforceable in workplaces covered under the Occupational Safety and 

Health Act of 1970. 

● NIOSH RELs are recommendations based on a critical review of the scientific and technical 

information and the adequacy of methods to identify and control the hazard. NIOSH 

RELs are published in the NIOSH Pocket Guide to Chemical Hazards [NIOSH 2010]. 

NIOSH also recommends risk management practices (e.g., engineering controls, safe work 

practices, employee education/training, personal protective equipment, and exposure and 

medical monitoring) to minimize the risk of exposure and adverse health effects.

● Other OELs commonly used and cited in the United States include the TLVs, which 

are recommended by the ACGIH, a professional organization, and the workplace 

environmental exposure levels, which are recommended by the American Industrial 

Hygiene Association, another professional organization. The TLVs and workplace 

environmental exposure levels are developed by committee members of these 

associations from a review of the published, peer-reviewed literature. These OELs are 

not consensus standards. TLVs are considered voluntary exposure guidelines for use 

by industrial hygienists and others trained in this discipline “to assist in the control 

of health hazards” [ACGIH 2016a]. Workplace environmental exposure levels have 
Page 12 Health Hazard Evaluation Report 2015-0180-3261

been established for some chemicals “when no other legal or authoritative limits exist” 

[AIHA 2016].

Outside the United States, OELs have been established by various agencies and organizations 

and include legal and recommended limits. The Institut für Arbeitsschutz der Deutschen 

Gesetzlichen Unfallversicherung (Institute for Occupational Safety and Health of the German 

Social Accident Insurance) maintains a database of international OELs from European Union 

member states, Canada (Québec), Japan, Switzerland, and the United States. The database, 

available at http://www.dguv.de/ifa/gestis/gestis-internationale-grenzwerte-fuer-chemischesubstanzen-limit-values-for-chemical-agents/index-2.jsp, contains international limits for 

more than 2,000 hazardous substances and is updated periodically. 

OSHA requires an employer to furnish employees a place of employment free from 

recognized hazards that cause or are likely to cause death or serious physical harm 

[Occupational Safety and Health Act of 1970 (Public Law 91–596, sec. 5(a)(1))]. This is 

true in the absence of a specific OEL. It also is important to keep in mind that OELs may not 

reflect current health-based information.

When multiple OELs exist for a substance or agent, NIOSH investigators generally 

encourage employers to use the lowest OEL when making risk assessment and risk 

management decisions. NIOSH investigators also encourage use of the hierarchy of controls 

approach to eliminate or minimize workplace hazards. This includes, in order of preference, 

the use of (1) substitution or elimination of the hazardous agent, (2) engineering controls 

(e.g., local exhaust ventilation, process enclosure, dilution ventilation), (3) administrative 

controls (e.g., limiting time of exposure, employee training, work practice changes, medical 

surveillance), and (4) personal protective equipment (e.g., respiratory protection, gloves, 

eye protection, hearing protection). Control banding, a qualitative risk assessment and risk 

management tool, is a complementary approach to protecting employee health. Control 

banding focuses on how broad categories of risk should be managed. Information on control 

banding is available at http://www.cdc.gov/niosh/topics/ctrlbanding/. This approach can be 

applied in situations where OELs have not been established or can be used to supplement 

existing OELs. 

Metal Dust

Fine metal dusts produced from mechanical processes such as sanding, grinding, and milling 

can represent a health and safety hazard. Dusts can enter the body through inhalation, 

ingestion, and skin absorption. Depending on the properties of the metal dust (size, shape, 

and composition), exposure can be associated with health risks ranging from irritation 

to pneumoconiosis or cancer. Exposures to metal dust may be acute, occurring in a short 

time period, or chronic, occurring over months or years. Chronic occupational exposure 

to aluminum dust above the applicable exposure limits may cause pulmonary fibrosis, 

respiratory irritation, cough, and sore throat [Smolkova and Nakladalova 2014].

Metal dust also presents an explosion hazard when it is combustible. For example, airborne 

aluminum powder can explode [Khambekar and Pittenger 2013]. For a combustible dust 

to explode, there must be fuel (the combustible dust), an oxidizer, an ignition source, dust 
Health Hazard Evaluation Report 2015-0180-3261 Page 13

dispersion in a sufficient concentration, and confinement of the dust cloud. 

Aluminum

Wheezing, dyspnea, and impaired lung function have been observed in workers chronically 

exposed to fine aluminum dust at much higher concentrations than were measured in this 

evaluation [Kongerud and Samuelson 1991]. Occupational asthma has also been associated 

with chronic exposure to aluminum [Abramson et al. 1989; Kilburn 1998]. Pulmonary 

fibrosis is the most commonly reported respiratory effect observed in workers exposed to fine 

aluminum dust, although there are conflicting reports on the fibrogenic potential of aluminum 

[ATSDR 2008].

Noise

Noise-induced hearing loss (NIHL) is an irreversible condition that progresses with noise 

exposure. It is caused by damage to the nerve cells of the inner ear and, unlike some other 

types of hearing disorders, cannot be treated medically [Berger et al. 2003]. More than 

22 million U.S. workers are estimated to be exposed to workplace noise levels above 

85 dBA [Tak et al. 2009]. NIOSH estimates that workers exposed to an average daily noise 

level of 85 dBA over a 40-year working lifetime have an 8% excess risk of material hearing 

impairment. This excess risk increases to 25% for an average daily noise exposure of 90 dBA 

[NIOSH 1998]. NIOSH defines material hearing impairment as an average of the hearing 

threshold levels for both ears that exceeds 25 dB at frequencies of 1,000 Hertz (Hz), 2,000 

Hz, 3,000 Hz, and 4,000 Hz.

Although hearing ability commonly declines with age, exposure to excessive noise can 

increase the rate of hearing loss. In most cases, NIHL develops slowly from repeated 

exposure to noise over time, but the progression of hearing loss is typically the greatest 

during the first several years of noise exposure. NIHL can also result from short-duration 

exposures to high noise levels or even from a single exposure to an impulse noise or a 

continuous noise, depending on the intensity of the noise and the individual’s susceptibility 

to NIHL [Berger et al. 2003]. Noise-exposed workers can develop substantial NIHL before 

it is clearly recognized. Even mild hearing losses can impair a person’s ability to understand 

speech and hear many important sounds. In addition, some people with NIHL also develop 

tinnitus. Tinnitus is a condition in which a person perceives sound in one or both ears, but 

no external sound is present. Persons with tinnitus often describe hearing ringing, hissing, 

buzzing, whistling, clicking, or chirping like crickets. Tinnitus can be intermittent or 

continuous and the perceived volume can range from soft to loud. Currently, there is no cure 

for tinnitus. 

The preferred unit for reporting of noise measurements is the dBA. A-weighting is used 

because it approximates the “equal loudness perception characteristics of human hearing for 

pure tones relative to a reference of 40 dB at a frequency of 1,000 Hz” and is considered to 

provide a better estimation of hearing loss risk than using unweighted or other weighting 

measurements [Earshen 2003].
Page 14 Health Hazard Evaluation Report 2015-0180-3261

Employees exposed to noise should have baseline and yearly hearing tests to evaluate 

their hearing thresholds and determine whether their hearing has changed over time. 

Hearing testing should be done in a quiet location, such as an audiometric test booth where 

background noise does not interfere with accurate measurement of hearing thresholds. In 

workplace hearing conservation programs, hearing thresholds must be measured at 500 Hz, 

1,000 Hz, 2,000 Hz, 3,000 Hz, 4,000 Hz, and 6,000 Hz. Additionally, NIOSH recommends 

testing at 8,000 Hz [NIOSH 1998]. The OSHA hearing conservation standard requires 

analysis of changes from baseline hearing thresholds to determine if the changes are 

substantial enough to meet OSHA criteria for a standard threshold shift. OSHA defines a 

standard threshold shift as a change in hearing threshold (relative to the baseline hearing test) 

of an average of 10 dB or more at 2,000 Hz, 3,000 Hz, and 4,000 Hz in either ear [29 CFR 

1910.95]. If a standard threshold shift occurs, the company must determine if the hearing loss 

also meets the requirements to be recorded on the OSHA Form 300 Log of Work-Related 

Injuries and Illnesses [29 CFR 1904.1]. In contrast to OSHA, NIOSH defines a significant 

threshold shift as a change in the hearing threshold level of 15 dB or more (relative to 

the baseline hearing test) at any test frequency in either ear measured twice in succession 

[NIOSH 1998].

NIOSH has an REL for noise of 85 dBA, as an 8-hour TWA. For calculating exposure limits, 

NIOSH uses a 3-dB time/intensity trading relationship, or exchange rate. Using the NIOSH 

criterion, an employee can be exposed to 88 dBA for no more than 4 hours, 91 dBA for 

2 hours, 94 dBA for 1 hour, 97 dBA for 0.5 hours, etc. Exposure to impulsive noise should 

never exceed 140 dBA. For extended work shifts NIOSH adjusts the REL to 84.5 dBA for a 

9-hour shift, 84.0 dBA for a 10-hour shift, 83.6 dBA for an 11-hour shift, and 83.2 dBA for a 

12-hour work shift. NIOSH recommends the use of hearing protection and implementation of 

a hearing loss prevention program when noise exposures exceed the REL [NIOSH 1998]. 

The OSHA noise standard specifies a PEL of 90 dBA and an AL of 85 dBA, both as 8-hour 

TWAs. OSHA uses a less conservative 5-dB exchange rate for calculating the PEL and AL. 

Using the OSHA criterion, an employee may be exposed to noise levels of 95 dBA for no 

more than 4 hours, 100 dBA for 2 hours, 105 dBA for 1 hour, 110 dBA for 0.5 hours, etc. 

Exposure to impulsive or impact noise must not exceed 140 dB peak noise level. OSHA does 

not adjust the PEL for extended work shifts. However, the AL is adjusted to 84.1 dBA for a 

9-hour shift, 83.4 dBA for a 10-hour shift, 82.7 dBA for an 11-hour shift, and 82.1 dBA for a 

12-hour work shift. OSHA requires implementation of a hearing conservation program when 

noise exposures exceed the AL [29 CFR 1910.95]. 
Health Hazard Evaluation Report 2015-0180-3261 Page 15

References

Abramson MJ, Wlodarczyk JH, Saunders NA, Hensley MJ [1989]. Does aluminum smelting 

cause lung disease? Am Rev Respir Dis 139(4):1042–1057, http://dx.doi.org/10.1164/

ajrccm/139.4.1042.

ACGIH [2016a]. 2016 TLVs® and BEIs®: threshold limit values for chemical substances 

and physical agents and biological exposure indices. Cincinnati, OH: American Conference 

of Governmental Industrial Hygienists.

ACGIH [2016b]. Industrial ventilation: a manual of recommended practice for design. 

Cincinnati, OH: ACGIH Signature Publications, American Conference of Governmental 

Industrial Hygienists.

AIHA [2016]. AIHA 2016 emergency response planning guidelines (ERPG) & workplace 

environmental exposure levels (WEEL) handbook. Fairfax, VA: American Industrial 

Hygiene Association.

ATSDR (Agency for Toxic Substances and Disease Registry) [2008]. Toxicological profile 

for aluminum. Atlanta, GA: U.S. Department of Health and Human Services, http://www.

atsdr.cdc.gov/toxprofiles/tp22.pdf.

Berger EH, Royster LH, Royster JD, Driscoll DP, Layne M, eds. [2003]. The noise manual. 

5th rev. ed. Fairfax, VA: American Industrial Hygiene Association.

CFR. Code of Federal Regulations. Washington, DC: U.S. Government Printing Office, 

Office of the Federal Register.

Earshen J [2003]. Sound measurement: instrumentation and noise descriptors. In: Berger EH, 

Royster LH, Royster JD, Driscoll DP, Layne M, eds. The noise manual. 5th rev. ed. Fairfax, 

VA: American Industrial Hygiene Association.

Khambekar J, Pittenger BH [2013]. Understanding and preventing metal-dust hazards. Int J 

Powder Metallurgy 49(4):39–47, http://jenike.com/files/2013/09/IJPM_Article_11.13.pdf.

Kilburn KH [1998]. Pulmonary and neurological effects of aluminum. In: Ron WN, ed. 

Environmental and occupational medicine. Philadelphia, PA: Lippincott-Raven.

Kongerud J, Samuelsen SO [1991]. A longitudinal study of respiratory symptoms in 

aluminum potroom workers. Am Rev Respir Dis 144(1):10–16, http://dx.doi.org/10.1164/

ajrccm/144.1.10.

NIOSH [1998]. Criteria for a recommended standard: occupational noise exposure (revised 

criteria 1998). Cincinnati, OH: U.S. Department of Health and Human Services, Centers for 

Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS 

(NIOSH) Publication No. 98-126, http://www.cdc.gov/niosh/docs/98-126/pdfs/98-126.pdf.
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NIOSH [2010]. NIOSH pocket guide to chemical hazards. Cincinnati, OH: U.S. Department 

of Health and Human Services, Centers for Disease Control and Prevention, National 

Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 2010-168c, 

http://www.cdc.gov/niosh/npg/.

NIOSH [2016a]. NIOSH manual of analytical methods (NMAM®). 5th ed. Ashley K, 

O’Connor PF, eds. Cincinnati, OH: U.S. Department of Health and Human Services, Centers 

for Disease Control and Prevention, National Institute for Occupational Safety and Health, 

DHHS (NIOSH) Publication No. 2014-151, http://www.cdc.gov/niosh/nmam.

NIOSH [2016b]. NIOSH manual of analytical methods, 5th ed. Consideration of sampler 

wall deposits: inclusion of material adhering to internal cassette surfaces during sampling 

and analysis of airborne particles. Cincinnati, OH: U.S. Department of Health and Human 

Services, Centers for Disease Control and Prevention, National Institute for Occupational 

Safety and Health, DHHS (NIOSH) Publication No. 2014-151, http://www.cdc.gov/niosh/

nmam/cassetteguidance.html.

OSHA [2002]. Ergonomics: the study of work. Washington, DC: U.S. Department of 

Labor, Occupational Safety and Health Administration, https://www.osha.gov/Publications/

osha3125.pdf.

Smolkova P, Nakladalova M [2014]. The etiology of occupational pulmonary aluminosis: 

the past and the present. Biomed Pap Med Fac Univ Palacky Olomouc Czech Repub 

158(4):535–538, http://dx.doi.org/10.5507/bp.2014.017.

Tak S, Davis RR, Calvert GM [2009]. Exposure to hazardous workplace noise and use of 

hearing protection devices among U.S. workers—NHANES, 1999–2004. Am J Ind Med 

52(5):358–371, http://dx.doi.org/10.1002/ajim.20690.
Health Hazard Evaluation Report 2015-0180-3261 Page 17

Keywords: North American Industry Classification System 335999 (All Other 

Miscellaneous Electrical Equipment and Component Manufacturing), Colorado, aluminum 

(CAS 7429-90-5), chromium (CAS 7440-47-3), manganese (CAS 1317-35-7), nickel 

(CAS 7440-02-0) metals, sanding, sawing, noise, ventilation
Page 18 Health Hazard Evaluation Report 2015-0180-3261

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Health Hazard Evaluation Report 2015-0180-3261 Page 19

The Health Hazard Evaluation Program investigates possible health hazards in the workplace 

under the authority of the Occupational Safety and Health Act of 1970 (29 U.S.C. § 669(a)

(6)). The Health Hazard Evaluation Program also provides, upon request, technical assistance 

to federal, state, and local agencies to investigate occupational health hazards and to prevent 

occupational disease or injury. Regulations guiding the Program can be found in Title 42, Code 

of Federal Regulations, Part 85; Requests for Health Hazard Evaluations (42 CFR Part 85).

Disclaimer

The recommendations in this report are made on the basis of the findings at the workplace 

evaluated and may not be applicable to other workplaces.

Mention of any company or product in this report does not constitute endorsement by NIOSH.

Citations to Web sites external to NIOSH do not constitute NIOSH endorsement of the 

sponsoring organizations or their programs or products. NIOSH is not responsible for the 

content of these Web sites. All Web addresses referenced in this document were accessible as of 

the publication date.

Acknowledgments

Analytical Support: Bureau Veritas North America

Desktop Publisher: Shawna Watts 

Editor: Ellen Galloway 

Logistics: Donnie Booher and Kevin Moore

Availability of Report

Copies of this report have been sent to the employer and employees at the facility. The state and 

local health department and the Occupational Safety and Health Administration Regional Office 

have also received a copy. This report is not copyrighted and may be freely reproduced. 

Recommended citation for this report:

NIOSH [2016]. Evaluation of noise and metal exposure at a security portal 

manufacturer. By Li JF, Ahrenholz S. Cincinnati, OH: U.S. Department of Health and 

Human Services, Centers for Disease Control and Prevention, National Institute for 

Occupational Safety and Health, NIOSH Health Hazard Evaluation Report 2015-0180-

3261, http://www.cdc.gov/niosh/hhe/reports/pdfs/2015-0180-3261.pdf.
To receive NIOSH documents or more information about 

occupational safety and health topics, please contact NIOSH:

Telephone: 1–800–CDC–INFO (1–800–232–4636)

TTY: 1–888–232–6348

CDC INFO: www.cdc.gov/info

or visit the NIOSH Web site at www.cdc.gov/niosh

For a monthly update on news at NIOSH, subscribe to 

NIOSH eNews by visiting www.cdc.gov/niosh/eNews.

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