U. S. Department of Labor

Occupational Safety and Health Administration

Directorate of Science, Technology & Medicine

Office of Occupational Medicine

SHIB 09-24-2007

Safety and Health Information Bulletin

Respiratory Disease Among Employees in

Microwave Popcorn Processing Plants

This Safety and Health Information Bulletin is not

a standard or regulation, and it creates no new

legal obligations. The Bulletin contains both

recommendations and descriptions of relevant

mandatory safety and health standards. The

recommendations are advisory in nature,

informational in content, and are intended to

assist employers in providing a safe and healthful

workplace. Pursuant to the Occupational Safety

and Health Act, employers must comply with

safety and health standards promulgated by OSHA

or by a state with an OSHA-approved state plan.

In addition, pursuant to Section 5(a)(1), the

General Duty Clause of the Act, employers must

provide their employees with a workplace free

from recognized hazards likely to cause death or

serious physical harm. Employers can be cited for

violating the General Duty Clause if there is a

recognized hazard and they do not take reasonable

steps to prevent or abate the hazard. However,

failure to implement any specific recommendation

in this Safety and Health Information Bulletin is

not, in itself, a violation of the General Duty

Clause. Citations can only be based on standards,

regulations, and the General Duty Clause.

Purpose

The purpose of this Safety and Health Information

Bulletin (SHIB) is to:

• Provide employees and employers in the

microwave popcorn industry with

information about the potential health

effects associated with exposure to butter

flavorings.

• Recommend exposure controls that may be

implemented by employers and used by

employees at these facilities to reduce

exposures to butter flavorings.

• Inform employers of applicable mandatory

OSHA standards.

Background

In 2000, the Missouri Department of Health and

Senior Services (MDHSS) and the National

Institute for Occupational Safety and Health

(NIOSH) conducted an investigation of a

microwave popcorn processing facility where eight

former employees had been diagnosed with a rare

lung disease called bronchiolitis obliterans. A ninth

case was discovered later in the same Jasper,

Missouri plant. All nine individuals were employed

at this microwave popcorn production facility for

eight months to 17 years. They first noticed

breathing problems five months to nine years

(median, 1.5 years) after starting work at this

facility. Five of the former employees had worked

in the mixing room where butter flavorings and oil

are mixed. The other four had worked on the

packaging lines where popcorn and the oil/

flavorings mixture are added to microwaveable

bags and packaged for shipment. The employees

reported similar symptoms, including progressive

shortness of breath, persistent cough, and unusual

fatigue. Five of the nine employees were placed on

a lung transplant candidate list [1]. One of the

employees died in April 2006 without receiving a

lung transplant. She had worked for 18 months at

the plant during the mid-1990s.
2

Using information supplied by the employer for the

eight original cases, the initial incidence of disease

for the microwave popcorn mixing and packaging

areas was determined. The four ill employees who

worked in the mixing area represented 31 percent

of the estimated 13 employees who worked in that

area between 1992 and 2000. The other four ill

employees worked on the packaging line (they

never worked as mixers) and represented 1.4

percent of the estimated 272 employees who

worked in this area between 1992 and 2000.

Based on the results of their initial investigation,

NIOSH researchers concluded that the bronchiolitis obliterans identified in the eight former

employees was most likely caused by occupational

exposure to volatile butter-flavoring ingredients.

Diacetyl, a butter-flavoring chemical, was the

predominant chemical isolated from air samples in

the facility and was used as a marker for volatile

organic compounds (VOC) exposure during the

investigation of the Jasper plant [2]. To protect

employees during the initial and subsequent phases

of the investigation, NIOSH and MDHSS recommended the installation and use of exposure

controls in the facility. These controls included

general dilution ventilation, local exhaust ventilation of tanks that contained butter flavorings,

process isolation, and personal protective equipment (respiratory, skin and eye protection).

NIOSH evaluated data from several follow-up

medical and environmental surveys at this facility

to assess the effects of these exposure controls on

employee health. NIOSH’s investi gation and

findings are summarized later in this SHIB.

NIOSH has published an Alert on flavoringsrelated lung disease [3] and has a Safety and

Health Topic page with additional references on

this subject on its Web site [4].

Additional cases of lung disease characterized by

fixed airways obstruction, including bronchiolitis

obliterans, have been recognized among employees

at other microwave popcorn plants as well as

among those who manufacture flavorings for foods

outside the microwave popcorn manufacturing

industry [3, 5]. A survey by NIOSH at five other

microwave popcorn plants with five to 206

employees identified six additional employees with

clinical findings consistent with bronchiolitis

obliterans. These involved one mixer at each of

three plants and three packaging line employees at

a fourth plant [5]. Analysis of air samples for

diacetyl at the plants where these six employees

worked indicated lower mean concentrations than

those found in comparable areas of the Jasper plant

– 0.6 ppm (1.6 percent of the mean in Jasper) or

less in the mixing areas for the three mixers and 0.3

ppm (16 percent of the mean in Jasper) in the

packaging area for the three packagers [5]. These

cases occurred at lower levels of diacetyl than

those initially measured in the Jasper plant.

NIOSH investigators have stated that “[a]t this

time, insufficient data exist on which to base

workplace exposure standards or recommended

exposure limits for butter flavorings”[5].

However, in the same paper, they also cautioned

that, because safe levels of occupational exposure

to butter-flavoring chemicals have not been

determined, “it is important to limit worker

exposures as much as possible”[5].

Fixed Airways Obstruction and Bronchiolitis

Obliterans

The lung disease identified in the NIOSH

investigations is usually characterized by

spirometry (lung or pulmonary function tests, PFT)

findings of fixed airways obstruction although

some employees have also had findings of

restriction, a decreased ability to expand the lungs.

Airways obstruction is diagnosed when the person

tested has difficulty blowing air out of the lungs. A

fixed obstruction means that there is no improvement in lung function even after administration of

asthma medication (i.e., bronchodilators).

Symptoms of fixed airways obstruction include

cough, fatigue, and shortness of breath with

exertion. Symptoms usually have a gradual onset,

but in some cases severe symptoms have occurred

suddenly with rapid progression of lung disease.

Symptoms generally do not improve when employees go home for the weekend or go on

vacation. In some instances, lung function tests
3

have indicated that employees had fixed airways

obstruction even in the absence of respiratory

symptoms [3].

Some employees identified in the NIOSH

investigations have been diagnosed with

bronchiolitis obliterans, a rare, potentially lifethreatening lung disease characterized by cough,

shortness of breath with exertion, and spirometry

findings of fixed airways obstruction [1, 6]. In

constrictive bronchiolitis obliterans, the smallest

airways of the lung become inflamed and scarred,

resulting in thickening and narrowing of the

airways. Established occupational risk factors for

development of bronchiolitis obliterans include

inhalation of toxic fumes, grain dusts, mineral

dusts, and irritant gases [3, 7].

In the NIOSH investigation, employees with severe

fixed airways obstruction, including bronchiolitis

obliterans, have not improved with treatment (e.g.,

corticosteroid medications). Some employees

diagnosed with fixed airways obstruction noticed

gradual improvement in their cough several years

after removal from the flavoring exposure, but their

pulmonary function never improved and their

shortness of breath with exertion persisted. Some

affected employees have developed severe,

disabling lung disease and have been placed on

lung transplant waiting lists [1].

Description of Hazard

Process Description

In August 2000, NIOSH carried out its first

evaluation of a microwave popcorn manufacturing

facility at a plant located in Jasper, Missouri.

Seven additional surveys of the plant were

conducted from April 2001- August 2003 and the

final report was published in January 2006 [8].

The plant has been in operation since 1986 and

packages popcorn (microwave and plain popcorn

kernels) for both national and international

distribution. Whole kernel corn from Missouri and

Nebraska is air cleaned on arrival, treated with an

organophosphate insecticide, and transferred to

silos. From the silo, the corn is processed by

screening and air cleaning on a gravity table. The

corn is then sent to either the polyethylene

packaging area or the microwave production area.

In the polyethylene packaging area, corn is

packaged in polyethylene bags by machine without

the addition of flavorings or additives. After

packaging, the bags are boxed, stacked, wrapped

in plastic, and transported to the warehouse by a

forklift.

In the microwave production area, the corn is

prepared and packaged using a series of steps. In

the flavor mixing area - where five of the ill former

employees worked - salt, butter flavorings, and

coloring agents are mixed by a single person and

manually added to a large tank of heated soybean

oil. This process produces visible dust, aerosols,

and vapors with a strong buttery odor. Following

mixing, the oil/flavoring mixture is piped into

holding tanks in the packaging area and maintained

at a temperature of 140°F to keep the mixture from

solidifying. In the packaging area – where the

other four employees worked – the oil/flavoring

mixture and the kernel popcorn are added to

microwavable bags, and the bags are then wrapped

in plastic and placed into boxes for distribution.

The boxes are stacked on pallets and enclosed in

plastic wrap. The pallets are sent to the

warehouse. Management and clerical staff work in

an office physically removed from the microwave

production area.

NIOSH Investigation

To evaluate the health condition of the employees

in the Jasper plant, NIOSH collected health

information using a questionnaire and performed

pulmonary function testing. Using the pulmonary

function test data, NIOSH found that the number

of employees with airways obstruction on a

spirometry test was 3.3 times higher than expected,

compared to national data. This discrepancy

increased to 10.8 times higher than expected for

current employees who had never smoked. Results

from the health survey indicated that the number of

individuals with physician-diagnosed asthma and
chronic bronchitis was about two times higher than

expected from national data, and the number of

non-smokers with chronic bronchitis was 3.3 times

higher than expected [8].

In November 2000, NIOSH collected air samples

throughout the plant and analyzed them for volatile

organic compounds (VOCs), respirable dusts,

endotoxin, bacteria, and fungi. Results from air

samples collected in the flavor mixing area indicated the presence of over 100 VOCs at various

concentrations [8]. None of the compounds

identified in these samples or those collected in the

rest of the plant were known to cause bronchiolitis

obliterans. Several VOCs were present in

relatively high levels in the flavor mixing area

including: diacetyl, methyl ethyl ketone, 2-

nonanone, acetoin, acetaldehyde, and acetic acid.

With the exception of one sample, which indicated

an acetic acid concentration of 12.4 parts per

million (ppm), all VOCs with established OSHA

PELs as well as respirable particulates (particulates

not otherwise regulated or PNOR), were well

below their respective PELs. OSHA PELs are

expressed as 8-hour time-weighted averages

(TWA). The 8-hour TWA PELs for acetic acid,

acetaldehyde, and methyl ethyl ketone are 10 ppm,

200 ppm, and 200 ppm, respectively (29 CFR

§1910.1000). The 8-hour TWA PEL for respirable

particulates is 5 milligrams per cubic meter (mg/

m3

) (29 CFR §1910.1000).

Diacetyl - a chemical with butter-flavoring

characteristics - was the most predominant VOC

identified in air samples taken in the Jasper plant.

Diacetyl levels were measured and used as an

indicator (marker) for exposure to volatile butter

flavorings during investigations of working areas of

the plant [8, 9]. Area sample results indicated that

diacetyl concentrations ranged from below the limit

of detection to 97.9 ppm. The mean concentration

was the highest in the flavor mixing area and was

calculated as 37.8 ppm [8]. Diacetyl concentrations in the flavor mixing area were about

1,000 times higher than in the office and outdoor

areas; about 100 times higher than in the

polyethylene packaging, warehouse, maintenance

and quality control areas; and about 17 times

higher than in the microwave packaging area [8].

Diacetyl does not have an OSHA PEL or a NIOSH

Recommended Exposure Limit (REL).

NIOSH ranked the employees who provided health

information and completed a pulmonary function

test in four groups according to their cumulative

diacetyl exposure. Cumulative exposure was

estimated using work history and the air sampling

data obtained by NIOSH. NIOSH found that there

was a statistically significant, positive relationship

between cumulative exposure to diacetyl and the

proportion of employees (prevalence) with airways

obstruction – as the cumulative diacetyl exposure

increased, the prevalence of airways obstruction

increased. NIOSH concluded that the investigation

in the Jasper plant “revealed a risk for occupational

lung disease in workers with inhalation exposure to

butter-flavoring chemicals” [3].

NIOSH recommended the installation and use of

engineering controls, work practices, and

respiratory protection. Controls implemented at

the Jasper plant resulted in a marked reduction in

diacetyl levels in the mixing room, from a mean of

38 ppm in November 2000 to 0.46 ppm in July

2003. NIOSH conducted seven additional surveys

while control measures were being implemented in

the facility. Engineering controls such as isolation

of the mixing processes and the heating tanks

appeared to protect most employees that were part

of the follow-up investigations [9]. NIOSH’s

January 2006 final report of the Jasper plant

investigation states that analysis of the data from

these surveys does “provide some indication that

control of exposures to butter-flavoring chemicals

has decreased the risk to most workers” [8].

NIOSH evaluated employee exposure to butter

flavorings in investigations of six microwave

popcorn plants including the Jasper plant. Cases of

fixed airways obstruction with clinical findings

consistent with bronchiolitis obliterans were

identified in five out of the six plants. The mean

airborne concentrations of diacetyl in mixing areas

with affected employees (either personal or area

4
measurements) ranged from 0.02 to 37.8 ppm. In

one plant with an affected employee who worked

as a mixer, the average air concentration of diacetyl

in the mixing area was 0.2 ppm, but air monitoring

in the employee’s breathing zone revealed peak

levels of 80 ppm when the employee was pouring

liquid butter flavor into heated mixing tanks. After

investigations of six microwave popcorn

manufacturing facilities, NIOSH investigators

concluded that employees exposed to butter

flavorings were at risk for development of

occupational lung disease and that brief exposures

to high levels may be hazardous even when

ventilation maintains low average exposures [5].

Based on the evaluation of the Jasper plant,

NIOSH conducted initial animal exposure studies.

Rats were exposed to vapors of one of the

flavoring mixtures used in the Jasper plant,

maintained at 131°F for 6 hours. The average

concentration of diacetyl in the flavoring vapors,

350 ppm, was comparable to the concentration in

the air space above the heated oil/flavoring mixture

in the tanks at the Jasper plant. Necropsy of the

rats showed extensive damage to nasal, tracheal,

and bronchial tissue [10]. In a different preliminary

animal study, rats acutely exposed to pure diacetyl

vapors had similar, but less extensive airway

damage (nasal and tracheal) at concentrations of

198.4 ppm or higher [11]. These studies

demonstrate that inhalation exposure to butter

flavoring and diacetyl vapors can cause airways

injury in laboratory animals exposed to these

vapors at high concentrations.

Flavorings are complex mixtures of chemical

ingredients and the inhalational toxicities of many

of the chemicals found in flavorings have not been

evaluated [5]. Other volatile flavoring chemicals,

in addition to diacetyl, were found in air samples

during NIOSH investigations of microwave

popcorn plants and it is possible that some of these

chemicals may have a role in the development of

the lung disease found in these facilities. NIOSH,

National Jewish Medical Center, the National

Institute for Environmental Health Studies

(NIEHS), and other researchers are currently

investigating the role of flavoring chemicals,

including diacetyl, in the development of fixed

airways obstruction and bronchiolitis obliterans.

OSHA Recommendations

Based on the NIOSH investigation of the Jasper

plant, OSHA conducted an on-site review of the

process modifications and controls that had been

implemented in the Jasper plant. The purpose of

the on-site visit was to determine whether the

engineering controls and personal protective

equipment (PPE) measures that had been instituted

could be enhanced to further reduce exposure to

the butter flavoring. Based on the findings of

OSHA’s on-site review and NIOSH’s investigation,

OSHA is making recommendations in this SHIB to

assist employers in addressing safety and health

concerns regarding employee exposures to butterflavoring chemicals in these facilities. Microwave

popcorn facilities are subject to a wide range of

OSHA mandatory occupational safety and health

standards. Apart from the following

recommendations, this SHIB in later sections also

describes those applicable OSHA standards that are

particularly relevant to protecting employees from

potentially hazardous butter-flavoring chemicals at

microwave popcorn plants.

Several sections of this SHIB present important

information directed at the control and reduction of

exposure to butter-flavoring chemicals, such as

recommendations for engineering controls and

work practices, and standards that address

respiratory protection and PPE. Other sections of

the SHIB covering pulmonary function testing,

environmental monitoring, and training are also key

components in an overall program to protect the

health of employees working at microwave

popcorn facilities that use butter-flavoring

chemicals.

5
OSHA Recommendations: Engineering and

Work Practice Controls

Engineering and work practice controls are the

primary methods for controlling exposures in the

workplace and include: local exhaust and general

dilution ventilation to remove contaminants,

isolation of the process or source, and restricted

access to areas where hazardous materials are used

or stored. Experience has shown that occupational

exposures in most situations can be controlled by

the use of these controls. A risk for occupational

lung disease has been identified in NIOSH

investigations for employees who work as mixers

of butter flavorings and oil and packagers working

in areas near open or nonisolated tanks of oil and

butter flavorings. In the Jasper plant, five of six

employees working in quality control laboratories

where many dozens of bags of product were

heated and opened also had abnormal lung function

(obstruction) [5, 8].

Operations that may expose employees to

intermittent, high concentrations of butter

flavorings, such as opening tanks where butter

flavors are heated or mixed, or pouring butter

flavorings into containers may also pose a health

risk to employees [5]. Employers should pay

particular attention to the need for additional

engineering and work practice controls in the

operations described above, as well as in situations

where employees report respiratory symptoms.

However, the absence of employee symptoms does

not necessarily mean that adequate engineering

controls have been implemented. Employees with

fixed airways obstruction may not have symptoms

early in the course of their disease [3].

Employers should consult with the plant engineers

and may also want to consult with a ventilation

specialist for ways to control employee exposures

to workplace contaminants, particularly in

operations where butter flavorings are heated,

handled, or mixed in open processes. More

information on the topics of ventilation and

engineering controls can be found in the

publications listed in the reference section of this

document [12, 13].

Some engineering and work practice controls that

have been shown to help reduce employee

exposures to flavoring ingredients include:

• Isolating the mixing room from the rest of

the plant using walls, doors, or other

barriers.

• Providing the mixing room with a separate

ventilation system or ensuring that negative

air pressure (relative to the rest of the

plant) is maintained in the mixing room.

Both will control the migration of contaminated air from the mixing room to

adjacent areas of the plant.

• Reducing the operating temperature of the

holding and mixing tanks to the minimum

temperature necessary to prevent

solidification of the flavoring mixture. This

will aid in reducing the volatilization of

components of the butter flavoring and

their release into the workroom air.

• Equipping the head space of the mixing and

holding tanks where flavorings are added to

oil or held in pure form with local exhaust

ventilation directed out of the plant in a

manner compliant with environmental

regulations.

• Automating the mixing process and using

closed processes to transfer flavorings.

• Covering the flavoring and finished oil

tanks and ventilating the headspace to

reduce emissions into the room.

• Eliminating spillage from overfilling tanks,

leaks in seals and fittings, and manual

transfer of materials - all have been

identified as sources of emissions.

Ventilation of finished oil tanks in mixing room.

6
• Installing commercially available bagdumping stations equipped with local

exhaust ventilation (three-sided canopy

hood) and bag disposal. This will reduce

dust exposure during this operation.

• Pumping flavoring from smaller to larger

tanks to avoid manual transfer or putting

lids on the transfer buckets or placing the

buckets in a ventilated area following

transfer to avoid residual vapor release.

• Adding flavorings at room temperature or,

if preheating is necessary, transferring the

heated flavoring to the mixing tank using a

pumping system rather than manual

transfer.

• Providing additional general dilution

ventilation using axial flow wall fans

(requires adequately tempered make-up air

during cold weather). Caution should be

used to assure that general dilution

ventilation does not spread contaminants to

other areas in the facility.

• Establishing standard procedures for

cleaning the workplace, tanks and

containers, and spills. For example, isolate

cleaning areas, rinse tanks or containers

with cold water before sanitizing, and avoid

cleaning powdered butter-flavoring

chemicals with compressed air. When

vessel entry is necessary, ensure compliance

with the confined space entry requirements.

• Maintaining good housekeeping in any

areas where flavorings substances or their

ingredients are handled.

 .

Pulmonary Function Testing

Spirometry, or pulmonary function testing (PFT),

measures the breathing capacity of the lungs and is

the best available test for early detection of

decreasing or abnormal lung function among

exposed employees [3]. Decreased lung function

has been observed in employees exposed to

flavorings before the onset of the symptoms of

bronchiolitis obliterans [3]. For this reason,

diminished breathing capacity, particularly among

younger employees in the plant population, may

indicate potential problems with exposure to

volatile butter flavorings or respirable dust and

should signal the need for further investigation

Since decreased lung function is an important

identifying factor for the presence of the disease,

OSHA recommends that all newly-hired employees

have a baseline PFT and be asked to complete a

health questionnaire before they start work in areas

where butter flavorings are used. This baseline

information is necessary for comparison during

subsequent evaluations. Employers may seek Flavor tank ventilation

Covered/Ventilated flavor tank ventilation.

7
medical expertise to develop their own

questionnaire which should focus on respiratory

symptoms and a history of preexisting lung disease.

Questionnaires used by NIOSH during

investigations of microwave popcorn

manufacturing plants are found in the NIOSH

Health Hazard Evaluations (see http://

www.cdc.gov/niosh/topics/flavorings/). OSHA

recommends that new employees with pre-existing

lung diseases and abnormal PFT results be further

assessed by a physician to evaluate the potential for

adverse health effects from exposure to volatile

flavorings or dust.

OSHA recommends, at a minimum, an annual

evaluation for symptoms (i.e., health questionnaire)

and annual PFT for all employees exposed to

volatile butter flavorings and their ingredients.

More frequent evaluation and pulmonary function

testing may be indicated (i.e., every three to six

months) if employees report symptoms or develop

PFT abnormalities. Testing should follow criteria

established by the American Thoracic Society

(ATS) guidelines for standardization of spirometry

(PFT) (see the ATS Web site: http://

www.thoracic.org/sections/publications/statements/

index.html).

Employers should encourage all employees to

immediately report respiratory symptoms or

symptoms of eye, nose, throat, or skin irritation.

Employers should promptly refer employees with

abnormal PFT findings, accelerated loss of lung

function, respiratory symptoms or evidence of eye,

nose, throat, or skin irritation to a physician for

further medical evaluation. The physician should

advise the employee about any suspected or

confirmed medical conditions that may be caused

or aggravated by work exposures. The physician

can also assist the employer and employee with

recommendations addressing continued workplace

exposures and use of respirators and PPE.

Physician recommendations regarding employee

exposures or use of PPE should be communicated

to both the employer and the employee.

OSHA Recommendations: Environmental

Monitoring

NIOSH identified diacetyl, a ketone with butter

flavor characteristics, as the predominant volatile

organic compound (VOC) present during mixing

room and other related operations. Diacetyl can be

measured as an indicator of butter flavoring

exposure.

Before conducting exposure monitoring,

workplace control measures and work practices

should be reviewed. OSHA recommends that

employers collect full-shift industrial hygiene air

samples (when applicable) to measure the

concentration of diacetyl in the work environment.

Personal full-shift monitoring provides information

about employee exposures during workplace

operations. Short-term personal sampling is

recommended for operations that involve open

handling of flavoring substances (i.e., pouring,

mixing, transfer, and packing operations). Area

sampling is also recommended and can provide

information about the general work environment

and identify processes that may be sources of

butter flavoring exposures. However, area

sampling is not a substitute for personal sampling.

Samples collected before engineering and

administrative controls are implemented can be

used to determine the concentration and location of

diacetyl and other VOCs throughout the work area

and can be compared with exposure monitoring

results reported in NIOSH health hazard

evaluations. Once controls are in place, subsequent

samples should be collected to determine the effect

Sampling pump and sampling tube.

8
of these controls in reducing potential exposure to

diacetyl and other VOCs. OSHA does not have a

PEL for diacetyl.

While OSHA recommends that all areas of the

plant be initially evaluated, it is of particular

importance that samples be collected in the

following plant areas or operations:

• Mixing rooms

• Rooms where flavoring tanks are located

• Production lines

• Quality control laboratory

• During maintenance and cleaning

operations

Since the composition of butter flavorings varies

among manufacturers, consult with the flavoring

manufacturer and an industrial hygiene laboratory

before conducting environmental monitoring.

When applicable, air monitoring should also

include sampling for particulates (total and

respirable dust) and flavoring substances with

OSHA PELs. A list of flavoring substances that

have OSHA PELs is found in the Appendix of

NIOSH’s Alert [3].

Applicable Standards of Special Importance

Microwave popcorn facilities are subject to a wide

range of OSHA occupational safety and health

standards. The following discussion focuses on

applicable OSHA standards that are particularly

relevant to protecting employees from potentially

hazardous chemicals at microwave popcorn plants.

OSHA Applicable Standards: Respiratory

Protection

Engineering controls are the preferred method for

protecting employees from hazardous respiratory

exposures in the workplace. Respirators are the

least preferred method of exposure control because

employees may still be exposed to respiratory

hazards if respirators are improperly used or

incorrectly fitted [5, 29 CFR §1910.134]. When

effective engineering controls are not feasible or

while they are being instituted, OSHA’s

Respiratory Protection standard, 29 CFR

§1910.134(a), requires employers to provide and

require the use of respirators when “necessary to

protect the health of the employee” from exposure

to harmful airborne substances. The employer

must provide respirators that are “applicable and

suitable for the purpose intended.”

The NIOSH finding of severe lung disease in some

employees at several microwave popcorn

manufacturing plants demonstrates that butterflavoring chemicals can pose severe respiratory

hazards in certain circumstances. Different

formulations of butter flavoring (powder, liquids or

pastes) may represent potential respiratory hazards

via inhalation of volatile chemicals or respirable

particles [14]. Accordingly, a microwave popcorn

manufacturing facility using these ingredients must

determine whether respirators are necessary to

protect its employees’ health. Where a substance is

used that may pose a respiratory hazard, the

employer must assess the nature and magnitude of

the hazard in the conditions of use in its workplace,

considering normal operating conditions and

reasonably foreseeable emergencies. See 29 CFR

§1910.134(d)(1)(iii) and 63 Fed. Reg. 1152 1198-

99 (discussion of Paragraph (d) – Selection of

Respirators in the preamble to Respiratory

Protection Final Rule). This assessment will guide

the employer in determining whether respirators

are necessary and in selecting the appropriate

respirator(s).

Employers in microwave popcorn manufacturing

facilities that use butter-flavoring ingredients must

conduct the evaluation required by

§1910.134(d)(1)(iii) of the Respiratory Protection

standard. The hazard evaluation requirement is

performance-oriented, and a variety of estimation

techniques may be used to characterize employee

exposures, depending upon the nature of the

chemical products, processes, operating

environment, and other factors. The preamble to

the Respiratory Protection Final Rule contains

further guidance on the hazard assessment

requirement and outlines several alternative

9
estimation approaches that may be useful (63 Fed.

Reg. 1198-1200, see discussion of Paragraph (d) –

Selection of Respirators).

Employers must ensure that the hazard evaluation

results in a reasonably accurate estimate of the

nature and extent of the respiratory hazards in the

workplace (See 29 CFR §1910.134(d)(1)(iii)).

Because there is no PEL for diacetyl, employers

need to consider a variety of factors when

performing their evaluations. They should consider

the relevant available information from NIOSH and

other sources on the hazards of volatile butterflavoring ingredients, including diacetyl, and use

informed professional judgment in estimating the

nature and magnitude of the hazards to employees

under existing plant conditions. Additional

information is provided below:

• Information on the health effects of

exposure to volatile butter-flavoring

ingredients in microwave popcorn

processing plants is provided in the

sources listed in the references

section of this SHIB. Employers need to

evaluate this and other available relevant

information to determine whether their

processes are similar to those in plants

studied by NIOSH. NIOSH investigations

found that employees working in mixing

rooms and in areas near non-isolated tanks

of oil and butter-flavoring ingredients had a

higher prevalence of respiratory symptoms

and airways obstruction [5]. Employers

should give special attention to these

situations when performing hazard

evaluations. Other production processes

involving employee exposure to flavoring

dusts, aerosols and/or vapors should also

be evaluated.

• Respiratory symptoms or eye, nose, throat,

or skin irritation in exposed employees may

be a significant indication of a hazard

requiring respiratory protection. If

employees develop abnormal PFT findings,

have PFT evidence of accelerated loss of

lung function, or are diagnosed with lung

disease, employers need to take reasonable

steps to determine whether employees are

exposed to volatile butter-flavoring

ingredients and have developed

occupational lung disease. The

recommendations in the Pulmonary

Function Testing section of this SHIB may

assist employers in identifying relevant

health effects. NOTE: Do not rely only on

the presence or absence of symptoms as the

sole consideration for implementation of a

respiratory protection program. Employees

with fixed airways obstruction may not

have symptoms early in the course of their

illness.

• In performing the hazard evaluation,

employers can use a variety of methods to

estimate employee exposures to airborne

concentrations of volatile butter-flavoring

ingredients. As such, OSHA strongly

recommends that employers conduct

exposure monitoring to measure the

concentration of diacetyl in the workplace.

Air sampling results may be used to gauge

the effectiveness of environmental and

work practice controls in reducing

employee exposures to volatile butterflavoring ingredients. Employers may also

compare their exposure monitoring results

with NIOSH Health Hazard Evaluation

(HHE) recommendations for respiratory

protection in other microwave popcorn

manufacturing facilities http://

www.cdc.gov/niosh/topics/flavorings/.

Recommendations for collecting and using

air samples are contained in the

Environmental Monitoring section of this

SHIB.

• Given that lung disease has been found in

some employees exposed to butter

flavorings containing diacetyl and given

that no exposure limits have been

established at this time for butter flavoring

and diacetyl, OSHA recommends that

employers should err on the side of caution

when evaluating when employees need to

wear respirators, especially when

10
employees work in such situations as

flavoring mixing rooms, quality control

laboratories, or near open or nonisolated

tanks of oil and butter flavorings.

If respiratory protection is necessary or if the

employer requires that respirators be used, the

employer must comply with the Respiratory

Protection standard at 29 CFR §1910.134. In

compliance with this standard, the employer must

select a suitable respirator in accordance with the

criteria in 29 CFR §1910.134 (d)(2) and (3).

Based on the NIOSH investigations of microwave

popcorn plants, a NIOSH-certified air-purifying

respirator equipped with organic vapor cartridges

in combination with particulate filters would

provide the minimum level of protection. Supplied

air respirators can also be used in these facilities.

Powered air-purifying respirators (PAPRs) (with

organic vapor cartridges and particulate filters) are

also acceptable alternatives and may be easier for

employees to wear in hot mixing rooms [3]. If airpurifying respirators are provided, employers must

implement a change-out schedule for canisters and

cartridges to ensure that they do not exceed their

operational lifespan. Employers must also develop

and implement a respiratory protection program

outlining how respirators will be selected, used,

and maintained. In addition, employers must

ensure that employees are trained, medically

evaluated, and fit tested before using respiratory

protection. The elements required in the written

program are outlined in 29 CFR §1910.134(c);

medical evaluation is discussed in paragraph (e), fit

testing requirements are provided in paragraph (f),

and training and other employee information

requirements are located in paragraph (k). OSHA

has a number of useful resources related to

respiratory protection on the agency’s Web site at

www.osha.gov.

OSHA Applicable Standards: Eye and Skin

Protection

OSHA’s PPE standards require employers to assess

their workplaces to determine if hazards are

present, or are likely to be present, which

necessitate the use of PPE (29 CFR §1910.132). If

such hazards are present or are likely to be present,

employers must ensure that employees use the

appropriate PPE to protect their eyes, face, hands,

and extremities, depending on the nature of the

hazard (29 CFR §§1910.132, .133, .138). The

employer is accountable both for the quality of the

hazard assessment and for the adequacy of the PPE

selected (59 Fed. Reg. 16336, see preamble

discussion of §1910.132(d)).

NIOSH found that, in addition to inhalation

hazards, butter flavorings also created eye and skin

hazards for employees. NIOSH identified eye

injuries which occurred when employees at one

microwave popcorn plant were exposed to vapors

from a new flavoring mixture. These volatile

organic compounds may affect the eyes and skin

due to their irritant properties. NIOSH also

indicated that many employees at the Jasper plant

reported the development of skin problems, such as

rashes, after they started working there [3]. Skinpatch testing of one of the mixers from the Jasper

plant with various butter-flavoring mixtures used at

that plant indicated the presence of a skin allergy

(dermatitis) in addition to his fixed obstructive

airways disease [1].

Powered air-purifying respirator.

11

Half-mask air-purifying respirator.
Employers should consider a variety of factors

when performing their hazard assessments, including the degree of employee exposure to butter

flavorings, relevant information from NIOSH and

other sources on the eye and skin hazards

associated with butter-flavoring ingredients, and

the presence of eye or skin irritation in exposed

employees. If the results of the hazard assessment

performed by an employer at a facility using butter

flavoring indicate that PPE is necessary to protect

employees from eye or skin hazards, the employer

must ensure that employees use appropriate equipment. Employers must ensure that employees use

chemical goggles or other appropriate eye protection when working with diacetyl and liquid food

flavorings containing diacetyl when exposure to

these chemicals is likely to cause injury to the eye

(29 CFR §1910.133). Goggles that fit over

corrective lenses are available. Chemical-resistant

gloves and sleeves, or other protection for exposed

skin must be used when handling liquid, paste, or

powdered flavoring ingredients that could cause

dermal injury. The employer must also provide

training for exposed employees as indicated in 29

CFR §1910.132. Since butter flavorings vary

among manufacturers, employers should communicate with both their flavoring manufacturer

and glove vendor to select the appropriate glove

material.

OSHA Applicable Standards: Training

The Hazard Communication standard requires

employers to train their employees on the hazards

of chemicals in the workplace. 29 CFR

§1910.1200(h)(3). Employers must ensure that all

Material Safety Data Sheets (MSDS) are available

to employees and provide training to employees

who may be exposed to volatile butter-flavoring

ingredients, including diacetyl. This training must

include information about the potential for

respiratory, eye, and skin problems from workplace

exposure to hazardous butter-flavoring chemicals.

OSHA recommends that this training include the

signs and symptoms of the lung disease discussed

in this document. Employers must also train

employees on when and how to use appropriate

PPE. In addition, employers must provide

information on the value, limitations and

maintenance of this equipment in accordance with

29 CFR §§1910.132 and 134.

Edwin G. Foulke, Jr.

Assistant Secretary

Occupational Safety and Health Administration

12
References

1. Akpinar-Elci, M., et al. Bronchiolitis

obliterans syndrome in popcorn production plant

workers. Eur. Respir. J. 24(2):298-302, 2004.

2. Kreiss, K., et al. Clinical bronchiolitis

obliterans in employees at a microwave-popcorn

plant. New Engl. J. Med. 347(5): 330-338, 2002.

3. NIOSH Alert. Preventing Lung Disease in

Workers Who Use or Make Flavorings. NIOSH

Publication No. 2004-110. http://www.cdc.gov/

niosh/topics/flavorings/.

4. NIOSH Safety and Health Topic:

Flavorings-Related Lung Disease. http://

www.cdc.gov/niosh/topics/flavorings/.

5. Kanwal, R., et al. Evaluation of flavoringsrelated lung disease risk at six microwave popcorn

plants. J. Occup. Environ. Med. 48(2):149-157,

2006.

6. Centers for Disease Control and

Prevention. Fixed obstructive lung disease in

employees at a microwave popcorn factory —

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345-347, 2002.

7. King, T., Jr. Overview of bronchiolitis.

Clinics in Chest Medicine 14(4): 607-610, 1993.

8. Kanwal, R., et al. NIOSH Health Hazard

Evaluation Report, HETA #2000-0401-2991,

Gilster-Mary Lee Corporation, Jasper, Missouri,

January 2006 http://www.cdc.gov/niosh/hhe/

reports/pdfs/2000-0401-2991.pdf..

9. Kreiss, K., Flavoring-related bronchiolitis

obliterans. Curr. Opin. Allergy Clin. Immunol

7:162-167, 2007.

10. Hubbs, A., et al. Necrosis of nasal and

airway epithelium in rats inhaling vapors of

artificial butter flavoring. Toxicol. Appl.

Pharmacol. 185(2): 128-135, 2002.

11. Hubbs, A., et al. Inhalation toxicity of the

flavoring agent, diacetyl (2,3- butanedione), in

the upper respiratory tract of rats [Abstract]

Toxicologist 78(Suppl. 1): 438-439, 2004

(Available from URL http://www.toxicology.org/

AI/Pub/tox/2004tox.pdf) [Accessed February 27,

2007].

12. Industrial Ventilation: A Manual of

Recommended Practice, 25th Edition, ACGIH

Worldwide Signature Publications 2004.

13. Technical Manual (OTM), TED 1-00-015

[TED 1-0.15A], Section III Chapter 3 (Ventilation

Investigation) http://www.osha.gov/dts/osta/otm/

otm_iii/otm_iii_3.html.

14. Boylstein R., et al. Diacetyl emission and

airborne dust from butter flavorings used in

microwave popcorn production. J. Occup.

Environ. Hygiene 3(10): 530- 535, 2006.

13