Document ID: OSHA-2008-0046-0069
Agency: osha
Document Type: Supporting & Related Material
Title: 
Posted Date: 2009-04-30T04:00Z

Site Visits Related to Diacetyl and Flavorings that Contain Diacetyl:

Food Manufacturing Facility B – 

A Commercial Bakery

Table of Contents

  TOC \o "1-5" \h \z \u    HYPERLINK \l "_Toc199755298"  1.	Introduction
  PAGEREF _Toc199755298 \h  1  

  HYPERLINK \l "_Toc199755299"  1.1.	Project Overview	  PAGEREF
_Toc199755299 \h  1  

  HYPERLINK \l "_Toc199755300"  1.2.	General Site Overview	  PAGEREF
_Toc199755300 \h  1  

  HYPERLINK \l "_Toc199755301"  2.	Process Descriptions	  PAGEREF
_Toc199755301 \h  2  

  HYPERLINK \l "_Toc199755302"  2.1.	Unbaked Dough Product Line	 
PAGEREF _Toc199755302 \h  2  

  HYPERLINK \l "_Toc199755303"  2.2.	Solid Food Product Line	  PAGEREF
_Toc199755303 \h  4  

  HYPERLINK \l "_Toc199755304"  3.	Exposure Assessment	  PAGEREF
_Toc199755304 \h  7  

  HYPERLINK \l "_Toc199755305"  3.1.	Sampling and Analytical Methods	 
PAGEREF _Toc199755305 \h  7  

  HYPERLINK \l "_Toc199755306"  3.1.1.	Equipment	  PAGEREF _Toc199755306
\h  7  

  HYPERLINK \l "_Toc199755307"  3.1.2.	Side-By-Side Sampling	  PAGEREF
_Toc199755307 \h  9  

  HYPERLINK \l "_Toc199755308"  3.1.3.	Other Analytes	  PAGEREF
_Toc199755308 \h  10  

  HYPERLINK \l "_Toc199755309"  3.1.4.	Limit of Quantification	  PAGEREF
_Toc199755309 \h  10  

  HYPERLINK \l "_Toc199755310"  3.1.5.	Blank Samples	  PAGEREF
_Toc199755310 \h  11  

  HYPERLINK \l "_Toc199755311"  3.2.	Air Monitoring Results	  PAGEREF
_Toc199755311 \h  11  

  HYPERLINK \l "_Toc199755312"  3.2.1.	Diacetyl and Acetoin	  PAGEREF
_Toc199755312 \h  11  

  HYPERLINK \l "_Toc199755313"  3.2.1.1.	Unbaked Dough Product
Line—Mixer Operator	  PAGEREF _Toc199755313 \h  13  

  HYPERLINK \l "_Toc199755314"  3.2.1.2.	Unbaked Dough Product
Line—Line Attendant	  PAGEREF _Toc199755314 \h  14  

  HYPERLINK \l "_Toc199755315"  3.2.1.3.	Unbaked Dough Product
Line—Production Relief Worker	  PAGEREF _Toc199755315 \h  14  

  HYPERLINK \l "_Toc199755316"  3.2.1.4.	Unbaked Dough Product
Line—Packing Operator	  PAGEREF _Toc199755316 \h  14  

  HYPERLINK \l "_Toc199755317"  3.2.1.5.	Unbaked Dough Product
Line—Package Sealing Operator	  PAGEREF _Toc199755317 \h  14  

  HYPERLINK \l "_Toc199755318"  3.2.1.6.	Solid Food Product
Line—Blender/Line Operator	  PAGEREF _Toc199755318 \h  15  

  HYPERLINK \l "_Toc199755319"  3.2.1.7.	Solid Food Product
Line—Packaging Operator	  PAGEREF _Toc199755319 \h  16  

  HYPERLINK \l "_Toc199755320"  3.2.1.8.	Solid Food Product Line—Fill
Station Operator	  PAGEREF _Toc199755320 \h  16  

  HYPERLINK \l "_Toc199755321"  3.2.1.9.	Solid Food Product
Line—Sanitation Worker	  PAGEREF _Toc199755321 \h  16  

  HYPERLINK \l "_Toc199755322"  3.2.1.10.	Solid Food Product
Line—Other Area Samples	  PAGEREF _Toc199755322 \h  17  

  HYPERLINK \l "_Toc199755323"  3.2.2.	Other Analytes	  PAGEREF
_Toc199755323 \h  18  

  HYPERLINK \l "_Toc199755324"  4.	EXAMPLES OF CONTROLS IN PLACE	 
PAGEREF _Toc199755324 \h  18  

  HYPERLINK \l "_Toc199755325"  4.1.	Overview	  PAGEREF _Toc199755325 \h
 18  

  HYPERLINK \l "_Toc199755326"  4.2.	Controls Available to Specific Job
Categories	  PAGEREF _Toc199755326 \h  18  

  HYPERLINK \l "_Toc199755327"  4.2.1.	Unbaked Dough Product Line	 
PAGEREF _Toc199755327 \h  18  

  HYPERLINK \l "_Toc199755328"  4.2.1.1.	Engineering Controls	  PAGEREF
_Toc199755328 \h  18  

  HYPERLINK \l "_Toc199755329"  4.2.1.2.	Housekeeping	  PAGEREF
_Toc199755329 \h  19  

  HYPERLINK \l "_Toc199755330"  4.2.1.3.	Room Temperatures	  PAGEREF
_Toc199755330 \h  19  

  HYPERLINK \l "_Toc199755331"  4.2.1.4.	Personal Protective Equipment	 
PAGEREF _Toc199755331 \h  19  

  HYPERLINK \l "_Toc199755332"  4.2.2.	Solid Food Product Line	  PAGEREF
_Toc199755332 \h  19  

  HYPERLINK \l "_Toc199755333"  4.2.2.1.	Engineering Controls	  PAGEREF
_Toc199755333 \h  19  

  HYPERLINK \l "_Toc199755334"  4.2.2.2.	Housekeeping	  PAGEREF
_Toc199755334 \h  20  

  HYPERLINK \l "_Toc199755335"  4.2.2.3.	Personal Protective Equipment	 
PAGEREF _Toc199755335 \h  20  

  HYPERLINK \l "_Toc199755336"  5.	DISCUSSION	  PAGEREF _Toc199755336 \h
 21  

  HYPERLINK \l "_Toc199755337"  5.1.	Relationship Between Results,
Sources of Exposure, and Controls in Use	  PAGEREF _Toc199755337 \h  21 

  HYPERLINK \l "_Toc199755338"  5.2.	Other Opportunities for Exposure
Control	  PAGEREF _Toc199755338 \h  22  

 Introduction

Project Overview 

Eastern Research Group, Inc. (ERG) conducted an industrial hygiene site
visit in January 2008 to Food Manufacturing Facility B, a commercial
bakery (hereafter referred to as Facility B). The purpose of the site
visit was to obtain information regarding the use of flavor products
containing diacetyl and commonly associated flavors (e.g., acetoin) in
the manufacture of food and beverage products; gather information on the
exposures of employees at the facility to diacetyl and acetoin; and
document the controls in place to reduce exposure. In particular, the
site visit was intended to evaluate the exposures of workers who
created, handled, or worked near dough and flavored oil during
production and sanitation/housekeeping activities.

Four ERG industrial hygienists and assistants met with representatives
of Facility B on January 22 to discuss the manufacture of dough and a
related solid food product, the materials used in these processes, and
the job categories with potential for exposure to diacetyl and related
butter flavor components. A walk-through of the facility was conducted
as part of the meeting. That evening and the next day (over two
partial-shifts and one full-shift), ERG sampled two production processes
(associated with the two different products) that use artificial butter
flavorings containing diacetyl. ERG conducted short-term, partial-shift
and full-shift personal breathing-zone (PBZ) and area air monitoring and
observed the work practices of employees identified as having potential
for exposure to diacetyl. ERG also noted airflow patterns and exposure
controls in use at the facility.

General Site Overview

Food Manufacturing Facility B (Facility B) is a commercial bakery
located in United States. The facility was built about 45 years ago and
employs over 100 workers. Approximately 8 percent of the workforce is
directly involved in making food products that contain artificial butter
flavorings. This plant has a mature and relatively stable unionized
workforce working on three staggered shifts. Among the employees that
ERG interacted with, English language proficiency was high. 

Facility B has been using artificial butter flavorings for more than 20
years. According to Facility B representatives, their use of artificial
butter flavorings has increased over time. The facility currently uses
at least three different brands of liquid butter flavoring and stores
less than 1,000 gallons in 5-gallon plastic pails. The amount of
diacetyl in the artificial butter flavorings ranges from about 1 percent
to 15 percent. The percentage of diacetyl in the flavorings is not
necessarily stated on the product material safety data sheet (MSDS).
However, Facility B was able to obtain this information by contacting
the flavoring manufacturers. Facility B does not use liquid butter
flavorings in all of its food products.

Process Descriptions

The two processes that ERG sampled at Facility B include production of
an unbaked dough product and production of a solid food product that
includes artificial butter flavored oil, which is also produced at this
facility. These processes are described below.

Unbaked Dough Product Line

The unbaked dough operation produces a rolled dough product containing
less than 0.01 percent diacetyl in the finished product. It is made on
two shifts and involves 10 to 12 employees per shift. The process takes
place in two different rooms, both with high ceilings (about 25 to 30
feet high). The first room is a very large open space where dough is
mixed, processed, and dropped into containers. In the second room, the
containers are covered and sealed so that they form air-tight packages.
No local exhaust ventilation (LEV) is directly associated with the
manufacture of this particular unbaked dough product.

Dough is supplied to the process by multiple mechanical dough mixers
operating simultaneously. The enclosed dough mixers are controlled by
mixer operators and there are three mixer operators per shift. Each
mixer operator operates two to three dough mixers at a time and a new
batch of dough (about a half-ton) is produced every 20 to 30 minutes.
The mixer operator adds flour and water to the mixers automatically
through sanitary liquid and flour inlets and manually adds additional
pre-measured dry or solid ingredients (e.g., shortening) by dumping the
ingredients into the mixer bowl when the mixer door is opened. In
addition, the mixer operator is responsible for manually measuring small
amounts of liquid ingredients including artificial butter flavoring
(approximately 1 pound of artificial butter flavoring per half-ton of
dough), coloring, and a preservative as a batch mix that this employee
hand pours (using a small plastic pitcher) into the waist-height mixer
bowl. The measuring process takes less than 30 seconds per batch, as
does the addition to the mixer. The operator measured a couple of
batches worth of flavor and associated liquids at a time, then used them
in subsequent batches. For example, during the typical 16-minute period
of a short-term exposure monitoring sample (#11), the mixer operator
performed the following actions: 

Added a pre-measured flavor batch to a mixer, pre-measured flavor to be
added later to two more batches, ran the mixer, emptied a second mixer,
added additional ingredients to the first mixer, refilled the second
mixer and started blending the dough, stepped into the hall to confer
with a supervisor, then returned to add flavor and other ingredients to
the second mixer.

The filled plastic pitchers containing batches of flavor sat uncovered
in the area where they were prepared for the 2 to 10 minutes until they
were added to the mixer. Over the course of the shift ERG estimates that
the mixer operators use a total of between one-third and two pounds of
diacetyl, always as a component (1 to 3 percent) of the artificial
butter flavor obtained premixed from a flavor manufacturing
establishment.

The liquid ingredients and plastic utensils (measuring cups, beakers,
pitcher) are stored on an open-sided portable storage rack in the dough
mixing area. During the site visit, the rack's bottom shelf was used to
store 5-gallon containers of the liquid ingredients; the middle shelf
(waist height) held the plastic utensils and was used as a work surface
to measure out the liquid ingredients; the top shelf was empty. Evidence
of spillage residue was observed on the shelves; a raised rim around the
perimeters kept the spilled material on the shelf. 

Dough mixers are fully enclosed during the physical mixing process.
After the dough is mixed, the mixer operator opens the door to the mixer
and dumps the mixed dough into a portable dough trough lubricated with
oil. By controlling the action of the mixer, the operator ejects the
mixed dough out of the mixer and into the dough trough. On occasion, the
mixer operator was observed manually handling the mixed dough to pull it
out of the mixer and into the trough. 

The mixer operator wheels the filled dough trough to the bottom of a
trough hoist, sprays the dough with oil, and activates the trough hoist.
The hoist lifts the dough trough up and dumps the mixed dough into an
elevated receiving hopper at the beginning of a sheet dough or "sheeter"
line. From the receiving hopper, the dough is openly conveyed for about
150 feet through a process where it is blended (to incorporate
additional ingredients), flattened, sampled, and shaped. The dough
sheet, about 3 feet wide, is systematically processed, then
automatically dropped into packaging material. 

During the site visit, two workers (line attendant and production relief
worker) tended to the sheeter line and performed a variety of tasks
including dispensing additional ingredients from an overhead hopper into
a drum, manually adding ingredients throughout the process line,
sampling the dough to ensure it has the right characteristics, placing
additional ingredients on a conveyor feeding into the sheeter line, and
performing housekeeping duties on and around the conveyor system and
work areas. Relief workers fill in for production workers during breaks,
performing the same process activities as needed. Three line attendants
and three production relief workers typically work each shift. 

The automated packaging operation is overseen by four packing operators
per shift who monitor the supply and filling of the containers, remove
product that is rejected (e.g., product that falls off the conveyor onto
the floor) or requires re-work (e.g., misshapen product), and perform
housekeeping. Two container filling work stations were observed;
however, only one was in operation during the site visit.  

After filling, the still-open packages, each with about 2 to 4 square
inches open area of exposed dough, are conveyed into a smaller room
(about 1,600 square feet) where they are automatically covered and
sealed. The open containers travel over about 25 feet of conveyor before
being sealed and have about 1/10th the amount of exposed dough per foot
of conveyor compared to the dough mixing and processing room. The
sealing process is operated by two to three workers (package sealing
operators) per shift who observe the process, collect quality assurance
samples, monitor the sealing equipment, stock packaging supplies, and
perform housekeeping (e.g., sweeping the floor). The package sealing
room is maintained at a cooler (60°F) temperature than other areas
within the facility to maintain product quality. During the air
monitoring session ERG confirmed this temperature and measured a
relative humidity of 43 percent.

Potential sources of exposure to artificial butter flavoring by job
title for these workers are summarized in Table 1. Mixer operators
appear to have the greatest potential for exposure during the
preparation of liquid butter flavoring batch mixes (i.e., the weigh up
process) and again when the flavoring is poured into the dough mixer
bowl.  

Solid Food Product Line

The solid food product line is operated on one 12-hour shift and
involves three production operators and two sanitation workers. The
operation produces several different solid food products including one
for which Facility B produces a butter flavored oil made with less than
0.5 percent of an artificial butter flavoring, The flavoring itself
contains about 15 percent diacetyl. Thus, the butter flavored oil is not
greater than approximately 0.07 percent diacetyl. The product that
includes the artificial butter flavored oil is typically produced two to
three times per week and the flavored oil is mixed in a heated process
several times per shift on the days it is to be used. During an average
production day, at least 150 pounds or 20 gallons of artificial butter
flavoring is used.

The solid food product operation takes place in a controlled work area
about 2,500 square feet in size (also with 25 to 30 foot high ceilings)
with a large ceiling exhaust fan and several sources of local exhaust
ventilation. Process operators are required to wear half-face air
purifying respirators with combination organic vapor/acid gas
cartridges. 

The process begins with the blender/line operator who first agitates (to
mix settled ingredients), then measures liquid butter flavoring from
5-gallon containers into an open-top 5-gallon transfer container and
manually pours it into closed and ventilated tanks, each containing
approximately 1,000 gallons of heated oil (125°F to 140°F). The
operator pours the liquid flavoring through hatches (about 24 inches in
diameter at chest height) on top of the tanks that are closed when not
in use. This is the procedure that occurred during the 28-minute
short-term sample (#10) obtained for the blender/line operator. The
process typically takes 10 to 15 minutes, but was prolonged that day
because other startup delays meant that the oil tank had not been
completely filled as expected. In this case, the operator used the extra
time to measure a second batch of flavor that was used sometime later.
The operator also peeked into the oil tank several times. Evidence of
spillage was observed on a cardboard mat in the pouring area on the
floor, the hatches, at the base of the tanks, and in the area of the
valves under the mezzanine surrounding the tanks.  

The completed hot flavored oil is then pumped to an automated
proprietary process in the same room (with an estimated 135 square feet
of exposed dilute butter flavored oil) where it is used in production of
a solid food product. Flavored oil of about 100°F is exposed to air at
the beginning of the production process. The ultimate product is quickly
cooled to between 7°F to 15°F , then automatically transferred (at
room temperature) over several dozen feet of open conveyor to a
collection hopper. The butter flavored oil is present on the food
product surface; therefore, the total product surface area (e.g., at the
proprietary process, on the conveyor, spilled on the floor) create an
estimated minimum of about 210 square feet of exposed dilute butter
flavored oil. This area is consistent throughout the shift.

At the base of the collection hopper is the product packaging operation.
A packaging operator (box maker) prepares boxes for the solid food
product by assembling and placing a plastic liner in each box. Lined
boxes travel a short distance on a conveyor to the dispensing chute at
the base of the collection hopper where they are automatically filled
with the solid food product. The dispensing chute is flanked with
horizontal slot ventilation on the left and right sides. A fill station
operator dispenses product into each box, controls the fill rate, folds
in the liner, and sends the box along the conveyer to an automatic box
sealer. Some product and oily residue may contact this employee’s
uniform. Sealed boxes are then palletized and stored elsewhere until
shipped.      

On the day that ERG performed monitoring, ambient conditions in this
room were relatively stable, cooling slightly from 69°F (with relative
humidity of 32 percent) in the morning to 65°F with 36 percent relative
humidity in the afternoon.

At the completion of each work day, one of two sanitation workers
thoroughly cleans the entire process line and the floor of the room. A
combination of compressed air and hand scraping are used to remove waste
solid food product and the oily residue from process equipment
(conveyors, hopper, dispensing chute, etc.) and the floor. The
sanitation worker sampled during the site visit cleaned under and inside
the process equipment in very close proximity to the waste food product.
After all visible waste food product is removed, the process equipment
and floor are rinsed with hot water (160°F to 180°F). 

Normal daily cleaning in the solid food product area takes up to eight
hours. Once a week, a more thorough 12-hour cleaning is performed which
includes scrubbing the floor. The same sanitation workers also clean
other parts of the facility on a rotating schedule. 

Potential sources of exposure to artificial butter flavoring by job
title for the solid food product line workers are also summarized in
Table 1. Blender/line operators appear to have the greatest potential
for exposure during preparation of liquid butter flavoring batch mixes
and again when they are poured into the hot oil tanks.  

Table 1. Potential Diacetyl-Containing Flavoring Exposure Sources for 

Food Manufacturing Facility B - Commercial Baking

January 22-23, 2008

Job Title	

Activities/Potential Sources of Exposure

Unbaked Dough Product line 

Mixer Operator	Operates dough mixers. Adds ingredients (dry, liquid, and
solid) through automatic and manual means. Prepares liquid butter
flavoring batch mixes and hand pours into mixer bowls. Hands-on handling
of liquid butter flavorings and unbaked dough product.

Line Attendant	Monitors sheet dough line (dough blending, flattening,
shaping into individual products). Exposure to large surface area (about
3 feet wide and 150 feet long) of flattened dough containing liquid
butter flavoring. Hands-on handling of unbaked dough product.  

Production Relief Worker	Relieves workers on sheet dough and packing
lines (see other job titles). 

Packing Operator	Monitors package filling operation. Exposure to small
surface area of rolled dough product containing liquid butter flavoring
during packaging and when removing product that is rejected (falls off
conveyor) or requires re-work (misshapen product on conveyor). Hands-on
handling of unbaked dough product.    

Package Sealing Operator	Monitors container sealing operation. Exposure
to open containers filled with dough product containing liquid butter
flavoring. Exposed dough product has about 1/10th the amount of exposed
surface area per foot of conveyor compared to mixing and processing
area. No hands-on handling of unbaked dough product.

Solid Food Product line

Blender/Line Operator	Operates process line. Prepares liquid butter
flavoring batch mixes and hand pours into tanks of hot oil. Monitors
flavored oil when openly processed into solid food product and conveyed
to storage hopper (a minimum of about 210 square feet of exposed dilute
butter flavored oil). Hands-on handling of liquid butter flavorings and
solid food product.   

Packaging Operator

(box maker)	Prepares boxes for product filling. Assembles cardboard
boxes and inserts plastic liners. Works in close proximity (5 to 10
feet) to product filling station. No hands-on handling of liquid butter
flavorings or solid food product, except when relieving other workers on
break.  

Fill Station Operator	Operates the product fill station. Dispenses solid
food product into boxes and closes and seals boxes. Hands-on handling of
solid food product; food product and oily residue can get on work
uniform.

Sanitation Worker	Cleans process equipment and floors. Hands-on exposure
to waste solid food product and oily residue.

          

Exposure Assessment

Sampling and Analytical Methods

Equipment

ERG used SKC Universal Flow Sampling Pumps calibrated at a flow rate of
1.2 to 1.5 liters/minute, combined with SKC adjustable-flow quad sorbent
tube holders drawing a maximum total of 500 ml/minute. The pumps, set up
per manufacturers instructions for use with low flow sampling media, and
each port of the adjustable-flow tube holders were set in advance to the
designated flow rate (see Table 2) and checked for calibration levels
immediately before sampling and again at the end of the period using a
Dry-Cal DC-1 primary air flow meter (flow cell serial number: S2348;
base serial number: B2440) manufactured by BIOS International
Corporation; or a BIOS DC-Lite primary air flow meter (5 ml/min to 5000
ml/min), model 412360.





Table 2.  Sampling and Analytical Methods

Low Flow Tube Holder Port

Analyte	Sampling & Analytical Method	Sample

Media	Sample Air 

Volume	Sample

Air Flow Rate	Sample Duration	Notes/Special Handling

Port A

Diacetyl/Acetoin

(experimental)	Based on

OSHA PV2118, but  with both increased air flow rate and extended
sampling time	Silica gel 

200/400 mg 

SKC 226-10-3

pair in series	Not defined	150 to 200 ml/min

	2 hours

(doubled for extended time)	Two “jumbo” tubes in series

Port B

Diacetyl/Acetoin

(extended)	OSHA PV2118 with extended sampling time	Silica gel 

200/400 mg

SKC 226-10-3

pair in series	6 L	50 ml/min

	2 hours

(doubled for extended time)	Two “jumbo” tubes in series; larger
sample volume acceptable at lower temperature and humidity. Increased
air volume collected with longer sampling times.

Port C

Benzaldehyde

(as vapor)

DISCONTINUED*	OSHA 68	XAD-2 tube

75/150 mg

SKC 226-117 	12L	50 ml/min	4 hours	Acetaldehyde may also be analyzed
upon request. 

Port D (partial-shift)

Total Volatile Organic Compounds (TVOC)

DISCONTINUED*	OSHA 07	Anasorb-CSC 50/100 mg 

SKC 226-01

 	10 L	50 ml/min

	4 hours	Cumulative total of analytical peaks

Port D (short-term)

TVOC

DISCONTINUED*	OSHA 07	Anasorb-CSC 50/100 mg 

SKC 226-01

 	10 L	150 to 200 ml/min

	30 minutes	Cumulative total of analytical peaks

Notes:

L means liters.

ml/min means milliliters per minute.

SKC# indicates the brand and model number of sampling media.

* Monitoring for benzaldehyde, acetaldehyde, and TVOCs was discontinued
after the first two site visits (to Food Manufacturing Facilities A and
B).

Complying with food manufacturing industry policies against exposed
glass in food handling areas, ERG maintained all sampling media enclosed
in appropriate size plastic tube covers (SKC models 222-3-1 L, XL or XD)
attached to the tube holders. To change sorbent tubes the ERG team
removed the entire sampling train (or in some cases just the tube holder
and associated covered media) from the employee and carried the sampling
equipment to a designated area before removing tube covers, replacing
sorbent tubes and covering the new tubes. The sampling train could then
be returned to the employee in the food handling area, while the samples
were sealed and stored under refrigeration. To improve air flow
calibration reliability for later samples, the flow rate through pumps,
holder, and tube sets were individually checked before these were placed
on an employee. All analyses were performed by the OSHA Salt Lake
Technical Center (SLTC) Laboratory using the methods presented in Table
2. 

ERG obtained temperature and humidity readings and, where feasible,
ventilation system air velocity measurements using a VelociCalc model
9545-A thermoanemometer (air velocity meter), manufactured by TSI, Inc.,
Shoreview, Minnesota. Both the flow meters used to calibrate air
sampling pumps and the air velocity meter were factory calibrated within
the previous 12 months.

Side-By-Side Sampling

Use of the SKC quad adjustable-flow tube holders permitted up to four
low-flow samples to be obtained simultaneously using one air sampling
pump. Air sampling ports on the quad tube holders were labeled A through
D. For evaluating diacetyl (CAS 431-03-8) in Port B, ERG used jumbo
silica gel tubes in series following a modified version of the OSHA
provisional sampling method (OSHA PV2118), which allows for an increased
sampling time compared to the unmodified method using standard size
media. In order to maintain a low-as-possible limit of detection, in
several cases ERG extended the sampling period beyond the recommended 2
hours, but maintained the recommended air flow rate of 50 ml/minute.
Anecdotal information suggested that a previous investigator had success
with this extended time method, providing the humidity and temperatures
were relatively low and the sample duration was maintained well below 8
hours. In an attempt to further reduce the diacetyl sample limit of
detection, ERG also used identical media and an informal experimental
procedure to test a higher air flow rate in some samples (Port A, with
air flow rate to between 150 and 200 ml/minute). Therefore, for most
diacetyl samples, a second side-by-side sample was obtained at the
alternate flow rate. These results, which are designated with sample
numbers ending in “A” (for Port A) should be considered
experimental. Sorbent tubes were used as a pair in series to detect
analyte breakthrough if analyte was captured on the second “backup”
tube. None of these backup tubes contained detectable diacetyl or
acetoin. In the range of the results obtained at Facility B, most
samples show generally good correlation between the Port A and Port B
results, so all of the side-by-side results were averaged.

Under the PV2118 method the SLTC laboratory is able to simultaneously
analyze acetoin (acetyl methyl carbinol, CAS 513-86-0) from the same
media as is used for diacetyl, so for each sample ERG obtained a result
for each of these analytes.

Other Analytes

Ports C and D were designated for testing the value of monitoring
airborne benzaldehyde (or benzaldehyde and acetaldehyde) and total
volatile organic compounds (TVOC) in the facility using standard methods
available for typical industrial monitoring through the OSHA SLTC
laboratory, as listed in Table 2. OSHA and ERG originally wondered
whether these and related analytes (such as organic acids) might be used
as alternatives to diacetyl as markers to evaluate beneficial exposure
controls (e.g., engineering, work practice controls). However, the
analytical methods as tested did not add practical value. Furthermore,
food manufacturing facilities were unable to discuss the presence of
these other ingredients in food flavors because this is considered
protected information. Sampling of these analytes was discontinued after
the first two site visits. A brief summary of the aldehyde results is
provided in the section of this report on Air Monitoring Results, Other
Analytes.

Limit of Quantification

The SLT laboratory usually reports sample results that are less than the
limit of quantification (LOQ), as “less than the LOQ” (or < x ppm,
where x is the LOQ). The LOQ is a statistically derived value below
which results are often judged unacceptably imprecise due to limitations
of the analytical process. ERG, however, is interested in quantifying
exposures in the same range as the LOQs for OSHA’s available
analytical method, but anticipated that some results obtained at this
site could be in that range. Therefore, instead of reporting results as
simply “< LOQ”, the laboratory reported the numeric value that the
analytical equipment provided, even if it was below the LOQ. ERG
provides these results in Table 3, believing they offer more information
about the approximate airborne concentration than would a blanket
description of “< LOQ.” ERG acknowledges, however, that the lower
the result, the less precise that value is likely to be. Individual
values surrounding the LOQ might not be reproducible, although together,
they might suggest trends that should be confirmed later using more
precise techniques. With the results in Appendix A (Table A-1), ERG
indicates whether each result is above or below the LOQ and reports the
LOQ as a ppm value for each sample, calculated from the reporting limits
of 0.468 μg per sample for diacetyl and 1.008 μg per sample for
acetoin.

Results for samples in which no analyte was detected are reported as ND
(“none detected”). In calculating averages, ERG takes ND to be equal
to 0 parts per million (ppm), but acknowledges that this practice also
introduces a small but undefined degree of imprecision. The laboratory
did not provide a minimum limit of detection (LOD), since the actual
measured values were reported down to the level at which no analyte was
detected.

Blank Samples

ERG submitted two blank samples for every 10 air samples. The blanks
were handled in the same manner as the air samples, except that air was
not drawn through them. The laboratory reported no measurable background
levels in the diacetyl/acetoin blanks, so the sample results required no
adjustment. All samples and blanks were handled with clean hands in a
designated conference room. 

Air Monitoring Results

Diacetyl and Acetoin

Air sampling results for diacetyl and acetoin are presented in Table A-1
(Appendix A) and Tables 3 through 5. OSHA has not published an exposure
limit for either diacetyl or acetoin. For this reason, all results are
presented relative to each other, rather than relative to a fixed
standard. 

The results show that during the site visit, all of the workers sampled
at Facility B had positive sample results (not reported as ND) for
diacetyl. Only one of the 28 diacetyl results (4 percent), an area
sample, was less than the LOQ. All but one (sanitation worker) had
positive results for acetoin; however 17 of the 28 acetoin results (61
percent) were below the LOQ. 

In general, the highest diacetyl concentrations (personal and area
samples) were associated with tasks or operations where liquid butter
flavorings are openly handled or processed. Of the two processes
investigated, the solid food product line had higher diacetyl
concentrations (both task-based and longer term personal and area
samples) than the unbaked dough line. The highest acetoin concentrations
were associated with the sheet dough line attendant followed by the
mixer operator. In contrast, acetoin concentrations were higher for
unbaked dough line workers than solid food production employees. Most of
the acetoin results above the LOQ are associated with the unbaked dough
product line. 

Table A-1 (in Appendix A) summarizes all of the diacetyl and acetoin air
sampling results for Facility B by process and job title or sample
location. All sample results in Table A-1 are based on the sampling
duration and have not been time-weighted for eight hours. The laboratory
reported results as not detected (ND) when there was no indication of
the analyte in the sample. 

Table 3 summarizes the partial period PBZ results for workers on the
unbaked dough and solid food product lines. Each concentration in the
table represents the average of two simultaneously collected
side-by-side samples in the worker’s breathing zone. Any ND results
were regarded as zero for the purposes of calculating the average
airborne concentration.   

As shown in Table 3, PBZ concentrations for diacetyl on the unbaked
dough product line ranged from 0.183 parts per million (ppm) to 0.396
ppm. The highest concentration (0.396 ppm) was associated with the mixer
operator. Acetoin concentrations ranged from 0.028 ppm to 0.458 ppm. The
highest acetoin concentration (0.458 ppm) was associated with the line
attendant on the sheet dough line. 

On the solid food product line, Table 3 shows that PBZ concentrations
for diacetyl ranged from 0.059 ppm to 1.706 ppm. The highest
concentrations (0.899 ppm and 1.706 ppm) were associated with the
blender/line operator; the lowest concentration was associated with the
sanitation worker (0.059 ppm). Acetoin concentrations ranged from ND to
0.030 ppm. The highest concentration (0.030 ppm) was associated with the
blender/line operator; the lowest acetoin concentration was associated
with the sanitation worker (ND). 

Table 4 presents the estimated full-shift PBZ concentrations for three
production operators on the solid food product line. For each of these
workers, two consecutive sets of air samples were collected over a
significant portion of the 12-hour work shift and combined to estimate
the worker’s full-shift exposure to diacetyl and acetoin. The
estimated full-shift exposures are based on combined sample durations of
476 minutes, 535 minutes, and 552 minutes. ERG notes that the workers’
activities were unchanged throughout the remainder (unsampled portion)
of the work shift; therefore their exposure is also expected to have
been similar and the combined sample results are good estimates of their
full-shift exposure. As shown, estimated full-shift TWA diacetyl
concentrations for the period monitored ranged from 0.425 ppm to 1.282
ppm; acetoin concentrations ranged from 0.004 ppm to 0.029 ppm. For both
analytes, the blender/line operator had the highest diacetyl and acetoin
levels, followed by the fill station operator and the packaging
operator.    

Table 5 presents the short-term (task-based) sample results for the
unbaked dough and solid food product lines. Short-term samples were
collected on two production operators while measuring and pouring liquid
artificial butter flavoring into their respective processes (i.e., into
mixed dough in the mixer bowl and into hot oil through hatches on
tanks). Task-based diacetyl concentrations ranged from 0.309 ppm to
2.702 ppm; acetoin concentrations ranged from 0.044 ppm to 0.232 ppm.
The highest short-term diacetyl concentration (2.702 ppm) was associated
with the blender/line operator on the solid food product line; the
highest acetoin concentration (0.232 ppm) was associated with the mixer
operator on the unbaked dough product line. 

Table 6 summarizes the area sample results for the unbaked dough and
solid food product lines. Each concentration in Table 6 represents the
average of two simultaneously collected side-by-side samples; any ND
results were regarded as zero for the purposes of calculating the
average airborne concentration. Diacetyl concentrations ranged from
0.026 ppm to 0.996 ppm. The highest general area diacetyl concentration
(0.996 ppm) was obtained in the solid food production room along a
walkway employees use to pass through to the next room. The sample
location was about 8 feet from the open process (about 135 square feet
of exposed surface area) where warm flavored oil is used in production
of the solid food product. The lowest diacetyl concentrations (0.026
ppm) were collected in the warehouse immediately outside a doorway to
the solid food production line. This doorway was covered by hanging
plastic strips and most airflow appeared to move from the warehouse into
the solid food product room. Minor foot traffic passed through the
doorway, as did solid food product line employees moving pallets of
sealed boxes with a hand cart (a task typically performed by a different
employee, a forklift operator).

Area acetoin concentrations ranged from ND to 0.177 ppm. The highest
acetoin concentration (0.177 ppm) was obtained in the unbaked dough area
at a work station used for measuring liquid butter flavoring and other
liquid ingredients. Four out of six area samples collected in the solid
food product area were reported as ND for acetoin.    

Diacetyl and acetoin sample results are discussed below by process and
job category.

Unbaked Dough Product Line—Mixer Operator

Two types of PBZ samples were collected on the mixer operator; two
short-term task-based samples (16 and 38 minutes) while the worker was
measuring and pouring liquid butter flavoring into the mixer bowl, and a
longer term (i.e., 4.5 hours) partial-shift sample representative of all
the activities the worker performed during the sampling period
(including measuring and pouring butter flavoring). The mixer
operator’s partial-shift exposure to diacetyl and acetoin was 0.396
ppm and 0.121 ppm, respectively. Task-based exposures while handling
liquid butter flavoring ranged from 0.309 ppm to 0.334 ppm for diacetyl
and 0.044 ppm to 0.232 ppm for acetoin. In addition, an area sample
collected at the mixer operator’s work station for measuring liquid
butter flavoring and other liquid ingredients had diacetyl and acetoin
concentrations of 0.464 ppm and 0.177 ppm, respectively. 

Of the five production workers sampled in the unbaked dough area, the
mixer operator had the highest diacetyl concentration. Evidence of
spillage was observed at the mixer operator’s liquid measure and mix
work station. Liquid butter flavorings prepared for addition to the
dough mixer are left uncovered at the liquid mix work station until hand
poured into the mixer bowl.     

Unbaked Dough Product Line—Line Attendant

The sheet dough line attendant’s exposure to diacetyl and acetoin was
0.250 ppm and 0.458 ppm, respectively. These results represent about 3.5
hours of work time in the unbaked dough area. The line attendant had the
highest acetoin concentration at Facility B; although it is not readily
apparent why. The acetoin level of the three other workers in the
unbaked dough area, including the production relief worker who also
monitored the sheet dough line, was approximately 0.1 ppm (0.076 ppm,
0.098 ppm, and 0.121 ppm). In addition, the acetoin concentration at the
liquid measuring and mixing work station, which presumably should have
the highest acetoin concentration, was approximately 0.2 ppm. The sheet
dough line attendant was not observed handling liquid butter flavorings;
however, line attendants do have exposure to a large surface area of
unbaked dough (approximately 3 feet wide and 150 feet long) containing
liquid artificial butter flavorings.   

Unbaked Dough Product Line—Production Relief Worker

The production relief worker performed activities similar to those of
the sheet dough line attendant; i.e., both the sheet dough line
attendant and the production relief worker monitored the sheet dough
line during the site visit. The production relief worker’s exposure to
diacetyl and acetoin was 0.183 ppm and 0.076 ppm, respectively. These
results represent approximately 2.75 hours of work time and are similar
to those of other employees in the unbaked dough area. The production
relief worker noted that the work rate during the sampling seemed to be
a little greater than normal. 

Unbaked Dough Product Line—Packing Operator

The packing operator’s diacetyl and acetoin sample results were 0.280
ppm and 0.098 ppm, respectively. These results represent approximately 4
hours of work time in the unbaked dough area. Although the packing
operator has hands-on contact with unbaked dough containing artificial
butter flavorings (e.g., picks up product that has fallen off the
conveyor), the exposed surface area during container packaging is
significantly less than at other points on the sheet dough line.   

Unbaked Dough Product Line—Package Sealing Operator

The package sealing operator’s exposure to diacetyl and acetoin was
0.266 ppm and 0.028 ppm, respectively. These results represent about 4
hours of work time in the package sealing room. The package sealing
operation takes place in a smaller room adjacent to the unbaked dough
room. Open-top containers of rolled, unbaked dough product travel into
the room on a conveyor through a small opening in the wall (less than 4
square feet). Due to the conveyer configuration, ERG was not able to
access the wall opening to determine the quantity or direction of
airflow through it. The amount of exposed dough per foot of conveyor is
about 1/10th that of the dough mixing and processing area. Workers in
this area do not have hands-on contact with the unbaked dough. The
package sealing operator stood on an elevated platform in front of the
package sealing machine, usually approximately 5 to 15 feet away from
the exposed dough and 15 feet from the wall opening.     	

Solid Food Product Line—Blender/Line Operator

Two partial-shift (about 4.5 to 4.75 hours each) PBZ samples were
collected on the blender/line operator in addition to a task based
sample while the worker was preparing and adding liquid butter flavoring
to hot oil. The blender/line operator’s partial-shift diacetyl sample
results ranged from 0.899 ppm to 1.706 ppm. The time-weighted average
diacetyl concentration for the combined sampling period (552 minutes)
was 1.282 ppm. The worker’s partial-shift results for acetoin ranged
from 0.028 ppm to 0.030 ppm with a combined time-weighted average
concentration of 0.029 ppm. A short-term PBZ sample (28 minutes)
collected on the blender/line operator while the worker prepared and
then poured liquid butter flavoring into a tank of hot oil resulted in a
diacetyl concentration of 2.702 ppm and an acetoin concentration of
0.094 ppm. 

The blender/line operator had the highest diacetyl concentrations of all
of the workers sampled. This worker prepared batch mixes of artificial
butter flavorings by openly pouring flavoring from closed-top 5-gallon
pails (through a pour spout) into open-top transfer containers. Batch
mixes (of approximately three gallons) were hand-poured into 1,000
gallon tanks of hot oil through hatches. Once prepared, the batch mixes
(in the transfer containers) were generally loosely covered prior to
pouring into the hot oil.

The blender/line operator noted that it was a normal workday and that a
total of six tank additions would be made throughout the work shift.
Evidence of spillage was noted in the batch mixing area. The
blender/line operator was observed accidentally splashing a minor amount
of butter flavoring on his hand and in the work area while the first
partial-shift sample was being collected (290 minutes). During the
collection of the subsequent partial-shift sample (262 minutes), the
blender/line operator splashed a couple of drops of artificial butter
flavoring on the air sampling tube holder. The tube holder was carefully
cleaned before the sample tube was removed at the completion of the
sampling. The diacetyl concentration for this sample was the highest of
all the partial-shift samples (i.e., 1.706 ppm). Because artificial
butter flavoring splashed on the sample tube holder, one cannot rule out
that the sample result was not due in part to the splash of flavoring.
However, under normal working conditions, the splash would have landed
on the employee’s shirtfront where it would have been equally likely
to influence the breathing zone diacetyl concentration.

In addition to PBZ samples, an area sample was collected in the vicinity
of the blender/line operator’s work zone. The sample was mounted on a
wall in a walkway that employees use to gain access to an adjacent work
room and was approximately 8 feet from the open operation where warm
flavored oil is processed into the solid food product. The diacetyl
concentration of this sample was 0.996 ppm, the highest diacetyl
concentration of seven area samples collected in the facility during the
site visit. The acetoin concentration was 0.018 ppm. 

Solid Food Product Line—Packaging Operator

Two partial-shift samples (about 4 hours each) were collected on the
packaging (box maker) operator. The diacetyl concentrations ranged from
0.235 ppm to 0.630 ppm; the time-weighted average diacetyl concentration
for the combined sampling period (476 minutes) was 0.425 ppm. The
packaging operator’s partial-shift acetoin results ranged from 0.002
ppm to 0.006 ppm with a combined time-weighted average concentration of
0.004 ppm. This worker assembled and lined cardboard boxes within ten
feet of the filling station operator.

Solid Food Product Line—Fill Station Operator

The filling station operator filled individual cardboard boxes with
solid food product as the boxes passed underneath the locally exhausted
dispensing chute. During the filling process, the exposed solid food
product drops with some velocity and quickly fills the boxes. Two
partial-shift samples of about 4.5 hours each were collected on the fill
station operator. Diacetyl concentrations ranged from 0.368 ppm to 0.846
ppm with a combined time-weighted average concentration of 0.599 ppm.
Acetoin concentrations ranged from 0.012 ppm to 0.016 ppm; the
time-weighted average acetoin concentration for the combined sampling
period (535 minutes) was 0.014 ppm. The fill station operator had the
next highest diacetyl and acetoin concentrations behind the blender/line
operator. 

In addition to the PBZ samples, two area samples were collected in the
fill station operator’s work zone. These samples were mounted on a
control panel immediately to the right of the fill station (4 to 5 feet
away). Diacetyl concentrations ranged from 0.292 ppm to 0.398 ppm;
acetoin concentrations ranged from ND to 0.004 ppm.      

Solid Food Product Line—Sanitation Worker

One PBZ sample was obtained on a sanitation worker in the solid food
product area during the first 105 minutes of an 8-hour cleaning cycle.
During this time frame, the worker scraped waste food product from
surfaces (process equipment and the floor) and used compressed air for
about 15 minutes to blow waste product out from under the conveyor and
the fill station. The diacetyl concentration of this PBZ sample was
0.059 ppm; acetoin was non-detectable. Sanitation workers clean and hot
rinse process equipment and the floors on a daily basis in the solid
food product area and on a rotating schedule in other process areas at
the completion of the work shift. Unfortunately, due to scheduling
conflicts, ERG was only able to monitor the first portion of the
cleaning process (that involving removing the bulk of the product
residual and spillage using mechanical techniques at room temperature).
The air monitoring results of the sanitation worker were the lowest of
all of the workers evaluated in both the unbaked dough and the solid
food product lines. However, the sampling period was the shortest of the
partial-shift samples and did not represent all of the activities that
sanitation workers typically perform, such as hot rinsing the
pre-cleaned equipment and floors. Therefore, it is possible that, due to
the subsequent heated cleaning process, sanitation workers could
experience higher airborne exposures to diacetyl under typical cleaning
conditions because the evaporation of diacetyl will be greater at higher
temperatures. Diacetyl evaporation from unheated food product is not
rapid so the airborne concentration is not likely to change notably over
time. (Factors influencing the rate of evaporation include, but are not
limited to, temperature, vapor pressure, humidity, air movement, and
surface area.)   

In addition to the PBZ sample, an area sample was collected during the
cleaning at breathing zone height at the base of the elevated platform
holding the oil tanks (in the center of the room's back wall) during the
first 83 minutes of the sanitation worker's cleaning cycle. The diacetyl
concentration of this sample was similar to that experienced by the
sanitation worker, 0.056 ppm; no acetoin was detected.

Solid Food Product Line—Other Area Samples

In addition to the four area samples collected inside the solid food
process area, two consecutive area samples were collected (at breathing
zone height) in one location immediately outside one of the doorways to
the room. This particular doorway is within 10 to 15 feet of the product
filling station. Long, floor-to-ceiling vertical strips of clear plastic
(plastic strip door) are suspended from the doorway and help isolate the
solid food product area from a storage warehouse immediately outside the
room. The diacetyl concentration of both area samples was 0.026 ppm;
acetoin results were non-detectable. These diacetyl results are the
lowest of all the area samples and suggest that the plastic strip door
and room ventilation are effective in containing product emissions.
However, during the sampling period, boxed product was removed from the
room manually by use of a hand cart instead of a fork lift truck, which
is what typically is used. A fork lift truck passing in and out of the
room through the plastic strip door might affect the movement of air
contaminants outside the room to a greater degree. So, it is possible
that these area sample results could be higher under more typical
working conditions.         	

Other Analytes

In addition to diacetyl and acetoin, all of the samples (PBZ and area)
collected inside the solid food product line room and the two area
samples collected immediately outside the room were also analyzed for
acetaldehyde and benzaldehyde (commonly used flavoring chemicals).
However, it was not known if the artificial butter flavorings in use
contained acetaldehyde and/or benzaldehyde (this information is
considered confidential by the flavor manufacturers and is not provided
to the food manufacturer). In all cases, acetaldehyde and benzaldehyde
were not detected. The laboratory reporting limits (limit of
quantification) for acetaldehyde and benzaldehyde are 4.75 micrograms
(μg) and 3.99 μg per sample, respectively.   

EXAMPLES OF CONTROLS IN PLACE

Overview

Facility B uses a combination of controls to minimize employee exposure
to artificial butter flavoring chemicals including engineering controls
(e.g., general dilution and local exhaust ventilation, process
containment), daily housekeeping, and personal protective equipment
(air-purifying respirators).

Controls Available to Specific Job Categories	

Unbaked Dough Product Line

Engineering Controls

The unbaked dough product is produced and packaged in two different
rooms (dough mixing/processing/packing and package sealing), both with
high ceilings (25 to 30 feet high) and general dilution ventilation
systems. Several wall mounted axial fans were observed in the package
sealing room that contributed to good air movement [50 to 75 feet per
minute (fpm)] within the vicinity of the worker that was sampled. Local
exhaust ventilation was not in use in these rooms for the job activities
sampled. However, two other sheet dough lines in the dough
mixing/processing room that were not evaluated during the site visit
(not making product with diacetyl-containing flavorings) were equipped
with a local exhaust hood at one point on each line.  

In addition to ventilation, the doorways and conveyor wall openings to
both rooms have plastic strip doors which are used to control
temperature loss and minimize the movement of air contaminants.  

Housekeeping

Daily cleaning is reportedly conducted in the process areas of the
facility to remove waste food product from process equipment and the
floors. Additionally, line workers are encouraged to clean during their
shifts and were observed sweeping the floor during the site visit. 				

Room Temperatures	

Production rooms were cool, in part to maintain product integrity, but
this could also have had an effect on diacetyl and acetoin vapor
release, which might have been higher if temperatures had been warmer.	

Personal Protective Equipment

Production workers in the unbaked dough production and packaging rooms
were observed wearing work uniforms, hair nets, smocks/aprons (not all
workers), disposable Nitrile gloves, and hearing protection. Several
workers in the dough production area were also observed wearing
disposable half-mask particulate respirators on an intermittent basis
(not related to flavor use). 

Solid Food Product Line

Engineering Controls

The solid food product is produced in a dedicated room (about 2,500
square feet with high ceilings) equipped with both general dilution and
local exhaust ventilation systems. A large ceiling-mounted exhaust fan
is located above the process equipment and reportedly runs whenever the
line is operated.  

Two closed-top 1,000 gallon tanks are consecutively filled with hot oil
that is flavored with artificial butter flavorings. Workers manually add
the liquid flavoring (about 3 gallons per batch) to the hot oil by
opening hinged hatches (about 24 inches in diameter) on the tops of the
tanks. The head space of each tank is exhausted by local exhaust
ventilation. 

Elsewhere in the room, the product dispensing chute (fill station) at
the base of the storage hopper is exhausted with lateral local exhaust
ventilation on both sides. (The ventilation was reportedly installed due
to the strong butter flavor odor at the fill station.) The face velocity
of the exhaust air through the slot opening (about 15 square inches) on
the left side of the dispensing chute ranged from 1,350 fpm to 2,100 fpm
(average 1,836 fpm); the volumetric exhaust flow was estimated to be
about 190 cubic feet per minute (cfm). On the right side of the
dispensing chute, the face velocity ranged from 1,100 fpm to 1,250 fpm
and the exhaust flow was estimated to be about 120 cfm. These slots draw
air from the general area of the chute, but their range of influence
does not cover the chute opening or the zone through which the product
falls into boxes.  

The doorways to the solid food production area also contain plastic
strip doors to control temperature and minimize the spread of air
contaminants. Containers used to transfer batch flavoring mixes to the
hot oil were generally observed to be loosely covered prior to addition.

Housekeeping

Daily housekeeping is performed in the solid food production area to
remove waste food product containing artificial butter flavoring from
process equipment and the floor. Hand scraping, sweeping, and compressed
air are used daily to effectively remove about 99.9 percent of the bulk
waste. Once per week, more in-depth cleaning is performed by scrubbing
the floor with brushes. At the completion of cleaning, the process area
(equipment and floor) is rinsed with hot water (160°F to 180°F) to
remove product residue.   

Personal Protective Equipment

Production workers in the solid food product area wear the standard work
attire worn by workers in the unbaked dough area (i.e., work uniform,
hair net, gloves, and hearing protection). Over the course of the day
the front torso area became stained with oily residue from solid food
product, which could be a possible additional source of exposure for
these workers. In addition, respiratory protection is mandatory for all
production operators in this room. The blender/line, packaging, and fill
station operators were all observed wearing half-mask air-purifying
respirators with combination organic vapor/acid gas cartridges
continuously throughout the work shift. Non-production employees (e.g.,
fork truck driver picking up boxed product, maintenance workers
servicing process equipment) and others briefly passing through to the
adjacent work room did so without wearing respiratory protection. 

Sanitation workers also wear the standard work attire when performing
daily housekeeping at the completion of the production operation.
However, when using compressed air, the sanitation worker evaluated
during the site visit was observed wearing safety glasses and a
half-mask disposable N95 particulate respirator.  

DISCUSSION

Relationship Between Results, Sources of Exposure, and Controls in Use	

Two production operations, unbaked dough product and solid food product,
that use liquid butter flavorings were evaluated at Facility B on
January 22-23, 2008. Both production areas have general dilution
ventilation systems and daily housekeeping is performed to remove waste
(bulk) food product containing artificial butter flavoring from process
equipment and the floors. Local exhaust ventilation is used in the solid
food production area to minimize flavoring emissions in the head space
of closed tanks containing hot flavored oil and at the solid food
product filling station.

Personal breathing zone and area air samples were collected to evaluate
worker exposure to diacetyl and acetoin. Nine different job categories
were evaluated, five in the unbaked dough area and four in the solid
food production area. The air sampling results indicate that nearly all
of the workers evaluated in both production areas have exposure to some
level of diacetyl (0.059 ppm to 1.706 ppm) and acetoin (0.002 ppm to
0.458 ppm) most likely due to the open nature of the processes (i.e.,
exposed product containing artificial butter flavoring). 

In general, diacetyl levels were greater than acetoin levels in both
production areas. However, the highest diacetyl concentrations were not
associated with the highest acetoin concentrations. The highest acetoin
levels were observed in the unbaked dough area and might be associated
with the process temperatures (room temperature or lower) and/or the
particular artificial butter flavoring that is used. The diacetyl
content of the artificial butter flavorings in use at the time of the
site visit ranged from about 1 to 3 percent; information on the acetoin
contents was not available.

Open handling (measuring, mixing, pouring, spilling) of artificial
butter flavoring was associated with the highest diacetyl levels in both
production areas. For the blender/line operator in the solid food
production room, diacetyl levels were about two to nine times greater
than the mixer operator in the unbaked dough area. This finding is
likely due to open handling of greater quantities of artificial butter
flavoring and hot process temperatures which increase the emissions of
volatile chemicals into the air. 

Numerous factors (individually or in combination) may be associated with
the exposure results observed at Facility B.  These factors include: 

A lack of local exhaust ventilation and/or containment when preparing
(measuring, weighing, pouring) artificial butter flavoring batch mixes
and pouring batch mixes into dough mixers and tanks of hot oil.

Spillage when pouring/handling butter flavoring.

Loose-fitting lids or no lids on transfer containers used for artificial
butter flavoring batch mix. 

The effectiveness of the general dilution and local exhaust ventilation
systems. 

The temperature of the hot oil.

The effectiveness of the seals on the tank hatches when closed.

Worker diligence in keeping hatches closed except when making artificial
butter flavoring additions. 

The substantial amount of exposed surface area of the unbaked dough and
solid food products during production operations.  

 

Other Opportunities for Exposure Control

If additional exposure control is desirable for the jobs and situations
observed at Facility B, the following possible options might offer an
additional level of exposure management:

Using local exhaust ventilation and a partial enclosure to prepare and
store artificial butter flavoring batch mixes (among the options are a
floor-mounted or walk-in chemical hood or bench-mounted laboratory
chemical hood).

Managing transfer operations to decrease the frequency of splashes and
spills (in both the unbaked dough area and the solid food product
lines). Pour aids (e.g., spouts, spigots, funnels) might help improve
control without increasing pouring time; however, these will never be a
substitute for careful attentive work practices. 

Using pre-measured quantities of artificial butter flavor for batch
operations that involve multiple identical quantities. These might be
prepared ahead in a partial enclosure with exhaust ventilation as was
noted previously – in which case the empty transfer containers would
also need to be controlled (e.g., by placing in a sealed container) so
they do not become an additional source of exposure. 

Reducing manual flavor handling by using closed or automated processes
to add artificial butter flavoring to dough mixers and hot oil tanks. A
possible method might involve automated dispensing from large bulk
containers (e.g., a two-week or one-month supply). Use of larger
containers would minimize the frequency with which dispensing equipment
would need to be transferred to a new container. In-container stir
equipment would likely eliminate the need to agitate flavors that
require mixing prior to use.

Securely covering containers of artificial butter flavoring batch mix
(after mixing and when moving or handling).

Investigating and ensuring the effectiveness of tank local exhaust
ventilation in minimizing worker exposure to tank emissions during
additions of butter flavoring (e.g., using ventilation smoke tubes
and/or measuring the capture velocity of the tank exhaust when the hatch
is open).

Investigating and ensuring the effectiveness of tank hatch seals
(repairing or replacing if necessary). 

Confirming that hot oil temperatures are being maintained as low as is
practical, to minimize flavoring emissions.

Investigating the feasibility of reducing the amount of exposed solid
food product as it free-falls into boxes in the solid food production
area (e.g., partially enclosing the food product as it drops through the
air or raising the height of the box under the dispensing chute).

Investigating the feasibility of limiting the amount of exposed product
surface area during production (e.g., enclosing and ventilating a
portion of a process line).

Considering options for reducing the surface area (total volume) of
spilled solid food product during the work shift. Examples of solutions
might include adjusting production and conveying equipment to further
reduce spillage, picking up spilled material several times during the
shift; or enclosing (with exhaust ventilation) significant portions of
the process and transfer equipment where spillage typically occurs.

Establishing and enforcing work practices to minimize the release of
emissions into the workplace when flavorings are added to hot oil (e.g.,
monitoring worker diligence in closing hatches as soon as flavoring
additions have been made; adding/checking the function of external
monitoring systems that allow employees to check oil level and
temperature without peeking into the tank; cleaning up spills promptly
while using appropriate personal protective equipment).

Changing work clothing that has absorbed flavoring agents (either as
splashed commercial flavorings or through contact with food product
containing flavoring). Smocks or washable/disposable aprons might help
accomplish this goal. Some industries that control microgram or part per
billion quantities of substance find it helpful to provide uniforms and
enforce policies of changing them frequently – more than once per day
if contamination occurs.

Investigating and ensuring that areas where artificial butter flavorings
are openly handled are maintained under negative air pressure relative
to the rest of the facility. This type of action could help ensure that
one process area is not contributing to another (e.g., is unbaked dough
production room air blowing into the package sealing room?).

Investigating the general dilution ventilation systems in the process
areas and ensuring that the design and operation conform to the
guidelines for general industrial ventilation presented in Industrial
Ventilation—A Manual of Recommended Practice, 26th Edition (American
Conference of Governmental Industrial Hygienists (ACGIH), Cincinnati,
Ohio, 2007).

Defining the purpose of the slot exhaust ventilation at the solid food
product filling station, then checking the function and design to
confirm that it meets those goals (e.g., using a ventilation smoke tube
to examine the location and range of influence of the exhaust
ventilation, which draws air from outside the center point of the
vertical sides of the chute).

Evaluating exposure of nonessential workers (and/or workers that are not
protected) who enter areas where artificial butter flavorings are openly
handled (e.g., fork truck operators, maintenance workers, and others
passing through). For example, modified work schedules on the day of
this air monitoring visit meant no workers who typically pass through
the solid food product area could be identified for monitoring, so this
evaluation was not preformed as part of this site visit.





Table 3. Personal Diacetyl and Acetoin Concentrations for 

Food Manufacturing Facility B – Commercial Baking

January 22-23, 2008

Job Title	Sample Time

(minutes)	Diacetyl

Concentrationa

(ppm)	Acetoin

Concentrationa

(ppm)

UNBAKED DOUGH PRODUCT LINE

Mixer Operator	265	0.396	0.121

Line Attendant	207	0.250	0.458

Production Relief Operator	163	0.183	0.076

Packing Operator	254	0.280	0.098

Package Sealing Operator	248	0.266	0.028

SOLID FOOD PRODUCT LINE

Blender/Line Operator	290	0.899	0.030

	262	1.706	0.028

Packaging Operator (box maker)	247	0.235	0.002

	229	0.630	0.006

Fill Station Operator	276	0.368	0.012

	259	0.846	0.016

Sanitation Worker	105	0.059	ND

a	The average of two simultaneously collected side-by-side samples in
the worker’s breathing zone. ND

 	(not detected) results were regarded as zero for the purposes of
calculating an average concentration.

 	An ND result was reported by the laboratory when there was no
indication of the analyte in the sample.

 	See Appendix A for individual ND sample results. 

ND = not detected

ppm = parts per million parts of air by volume





Table 4. Estimated Full-Shift Personal Diacetyl and Acetoin
Concentrations for 

Food Manufacturing Facility B - Commercial Baking

January 22-23, 2008

Job Title	Sample

Time

(minutes)	Diacetyl

Concentration

for the  Sampling Perioda

(ppm)	Estimated

Full-Shift

Diacetyl Concentration

(ppm)b	Acetoin Concentration for the Sampling Period

(ppm)a	Estimated

Full-Shift

Acetoin Concentration

(ppm)b

solid food product line

Blender/Line Operator	290	0.899	1.282	0.030	0.029

	262	1.706c

0.028

	Packaging Operator	247	0.235	0.425	0.002	0.004

	229	0.630

0.006

	Fill Station Operator	276	0.368	0.599	0.012	0.014

	259	0.846

0.016

	a	The average of two simultaneously collected side-by-side samples in
the worker’s breathing zone. ND

 	(not detected) results were regarded as zero for the purposes of
calculating the average concentration.

 	An ND result was reported by the laboratory when there was no
indication of the analyte in the sample.

 	See Appendix A for individual ND sample results. 

b	Estimated full-shift personal breathing zone concentration based on
the combined results of the two

 	sampling periods. The combined sampling results represent a
significant portion of the workers' 12-hour

 	workshift (i.e., 67 to 75 percent).

c	Worker splashed two drops of butter flavoring on the sample tube
holder during sampling. Tube holder

 	was carefully cleaned before the sorbent tube was removed from the
holder.

ppm = parts per million parts of air by volume.

 



Table 5. Short-Term Personal Diacetyl and Acetoin Concentrations for 

Food Manufacturing Facility B - Commercial Baking

January 22-23, 2008

Job Title	Activity	Sample

Time

(minutes)	

Diacetyl

Concentrationa

(ppm)	

Acetoin

Concentrationa

(ppm)

UNBAKED DOUGH PRODUCT LINE

Mixer Operator	Measuring/pouring butter flavoring into mixer bowl	16
0.309	0.044

38	0.334	0.232

SOLID FOOD PRODUCT LINE

Blender/Line Operator	Measuring/pouring butter flavoring into hot oil
tanks	28	2.702	0.094

a	The average of two simultaneously collected side-by-side samples in
the worker’s breathing zone. ND

 	(not detected) results were regarded as zero for the purposes of
calculating the average concentration.

 	An ND result was reported by the laboratory when there was no
indication of the analyte in the sample.

 	See Appendix A for individual ND sample results. 

ppm = parts per million parts of air by volume.

Table 6. Area Diacetyl and Acetoin Concentrations for 

Food Manufacturing Facility B – Commercial Baking

January 22-23, 2008

Sample

Location	Sample Time

(minutes)	Diacetyl

Concentrationa

(ppm)	Acetoin

Concentrationa

(ppm)

UNBAKED DOUGH PRODUCT LINE

On liquid mixing cart directly above the middle shelf.	111	0.464	0.177

SOLID FOOD PRODUCT LINE

On control panel adjacent to the fill station operator about 4 feet
above the floor.	335	0.292	0.004

	320	0.398	ND

On wall adjacent to glycol drum (employee pass through area) about 5
feet above the floor.	332	0.996	0.018

Outside doorway to room mounted on storage rack about 5 feet above the
floor.	289	0.026	ND

	126	0.026	ND

Bottom left corner of tank platform on back wall (about 5 feet above the
floor).	83	0.056	ND

a	The average of two simultaneously collected side-by-side samples. ND
(not detected) results were

 	regarded as zero for the purposes of calculating the average
concentration. An ND result was reported

 	by the laboratory when there was no indication of the analyte in the
sample. See Appendix A for

 	individual ND sample results. 

ppm = parts per million parts of air by volume



APPENDIX A

Individual Diacetyl and Acetoin Air Sampling Results for Food
Manufacturing Facility B



Table A-1.  Diacetyl and Acetoin Air Sampling Results for Food
Manufacturing Facility B - Commercial Baking 

January 22-23, 2008

Sample No.	

Job Title 

or 

Area Sample and location	

Sample

Duration

(minutes)	

Sample Volume

(liters)	

Diacetyl Results

	

Acetoin Results

Diacetyl 

Conc.

(ppm)A 	LOQ

(ppm)B 	Sample Concentration versus LOQ	Acetoin 

Conc. 

(ppm)A 	LOQ

(ppm)C 	Sample 

Concentration

versus LOQ

UNBAKED DOUGH PRODUCT LINE

B-1A	Package (container) Sealing Operator

	248	38.8	0.425	0.003	> LOQ	0.031	0.007	> LOQ

B-1B

248	17.5	0.106	0.003	> LOQ	0.024	0.016	> LOQ

B-2A	Production Relief Worker

	163	25.9	0.366	0.005	> LOQ	0.057	0.011	> LOQ

B-2B

163	9.5	ND	0.014	< LOQ	0.096	0.029	> LOQ

B-6A	Line Attendant

	207	48.2	0.225	0.003	> LOQ	0.073	0.006	> LOQ

B-6B

207	9.4	0.274	0.014	> LOQ	0.843	0.030	> LOQ

B-8A	Area Sample

(on liquid mixing cart – 5 feet above floor)	111	18.0	0.444	0.007	>
LOQ	0.176	0.016	> LOQ

B-8B

111	6.8	0.483	0.020	> LOQ	0.178	0.041	> LOQ

B-9A	Packing Operator

	254	34.8	0.251	0.004	> LOQ	0.076	0.008	> LOQ

B-9B

254	9.6	0.308	0.014	> LOQ	0.120	0.029	> LOQ

B-11A	Mixer Operator

	16	2.6	0.278	0.051	> LOQ	0.089	0.108	< LOQ

B-11B

16	0.9	0.341	0.148	> LOQ	ND	0.311	< LOQ

B-13A

38	5.8	0.341	0.023	> LOQ	0.121	0.048	> LOQ

B-13B

38	2.0	0.326	0.067	> LOQ	0.344	0.141	> LOQ

B-15A

265	30.8	0.183	0.004	> LOQ	0.053	0.009	> LOQ

B-15B

265	14.5	0.609	0.009	> LOQ	0.188	0.019	> LOQ

SOLID FOOD PRODUCT LINE

B-3A	Fill Station Operator

	276	57.0	0.376	0.002	> LOQ	0.006	0.005	> LOQ

B-3B

276	20.6	0.359	0.007	> LOQ	0.019	0.014	> LOQ

B-14A

259	49.7	0.854	0.003	> LOQ	0.016	0.006	> LOQ

B-14B

259	12.9	0.838	0.010	> LOQ	0.017	0.022	< LOQ

B-4A	Packaging Operator (box maker)

	247	42.8	0.219	0.003	> LOQ	0.005	0.007	< LOQ

B-4B

247	14.0	0.251	0.010	> LOQ	ND	0.020	< LOQ

B-16A

229	36.5	0.624	0.004	> LOQ	0.012	0.008	> LOQ

B-16B

229	11.1	0.636	0.012	> LOQ	ND	0.025	< LOQ

B-5A	Area Sample

(adjacent to fill station operator – 

4 feet above floor)	335	35.7	0.310	0.004	> LOQ	0.008	0.008	= LOQ

B-5B

335	11.5	0.275	0.012	> LOQ	ND	0.024	< LOQ

B-7A	Blender/Line Operator

	290	49.1	0.887	0.003	> LOQ	0.043	0.006	> LOQ

B-7B

290	18.8	0.912	0.007	> LOQ	0.017	0.015	> LOQ

B-12A

262	39.7	1.662	0.003	> LOQ	0.028	0.007	> LOQ

B-12B

262	13.1	1.751	0.010	> LOQ	0.028	0.021	> LOQ

B-10A

28	3.7	2.703	0.036	> LOQ	0.051	0.076	< LOQ

B-10B

28	1.9	2.701	0.070	> LOQ	0.138	0.147	< LOQ

B-17A	Area Sample

(adjacent to fill station operator – 

4 feet above floor)	320	47.9	0.797	0.003	> LOQ	ND	0.006	< LOQ

B-17B

320	17.8	ND	0.008	< LOQ	ND	0.016	< LOQ

B-18A	Area Sample

(on wall adjacent to glycol drum –  5 feet above floor)	332	52.8	0.979
0.003	> LOQ	0.019	0.005	> LOQ

B-18B

332	21.0	1.012	0.006	> LOQ	0.018	0.013	> LOQ

B-19A	Area Sample

(outside solid food product line door – 5 feet above floor)	289	37.1
0.025	0.004	> LOQ	ND	0.008	< LOQ

B-19B

289	16.1	0.028	0.008	> LOQ	ND	0.017	< LOQ



Table A-1.  Air Monitoring Results for Food Manufacturing Facility B -
Commercial Baking 

January 22-23, 2008

Sample No.	

Job Title

 or 

Area Sample and location	

Sample

Duration

(minutes)	

Sample Volume

(liters)	

Diacetyl Results

	

Acetoin Results

Diacetyl 

Conc.

(ppm)A 	LOQ

(ppm)B 	Sample Concentration versus LOQ	Acetoin 

Conc. 

(ppm)A 	LOQ

(ppm) C	Sample 

Concentration

versus LOQ

SOLID FOOD  PRODUCT LINE (continued)

B-21A	Area Sample

(outside solid food product line door – 5 feet above floor)	126	24.4
0.025	0.005	> LOQ	ND	0.012	< LOQ

B-21B

126	6.3	0.027	0.021	> LOQ	ND	0.044	< LOQ

B-22A	Area Sample

(on corner of raised platform on back wall – 5 feet above floor)	83
13.3	0.058	0.010	> LOQ	ND	0.021	< LOQ

B-22B

83	4.3	0.055	0.031	> LOQ	ND	0.066	< LOQ

B-23A	Sanitation Worker

	105	14.9	0.060	0.009	> LOQ	ND	0.019	< LOQ

B-23B

105	5.3	0.059	0.025	> LOQ	ND	0.053	< LOQ

A	Sample concentrations are based on the period monitored (i.e., the
sample duration). Samples were reported (by the laboratory) based on any
amount of analyte that was

	found; reporting limits were not considered. An ND (not detectable)
result was reported when there was no indication of the analyte in the
sample.

B	The analytical reporting limit (limit of quantification) for diacetyl
is 0.468 micrograms (μg) per sample.

C	The analytical reporting limit (limit of quantification) for acetoin
is 1.008 μg per sample.

> LOQ = sample concentration is greater than the limit of quantification
for the specific analyte.

< LOQ = sample concentration is less than the limit of quantification
for the specific analyte.

Abbreviations

BZ = breathing zone

Conc. = concentration

LOQ = limit of quantitation

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sing a mixing bowl that tilts open on its horizontal axis, with internal
mixing blade. (This information is offered as an example for readers
unfamiliar with high-speed mixers. These sources do not necessarily
represent the equipment models and brands used by Firm B)   HYPERLINK
"http://www.thebiscuitdoctor.com/F/3/c/3cc1.htm" 
http://www.thebiscuitdoctor.com/F/3/c/3cc1.htm ;      HYPERLINK
"http://www.bakerperkinsgroup.com/product/244/51/high-speed-mixers.html"
 http://www.bakerperkinsgroup.com/product/244/51/high-speed-mixers.html 

  PAGE  2 

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                                                   PAGE  14 

Site Visits Related to Diacetyl –Food Manufacturing Facility B        
                                                 							       PAGE  31