Workers
who handle diacetyl or work in areas where diacetyl exposure occurs are at risk
of developing severe lung disease if their exposures are not properly
controlled.
The
National Institute for Occupational Safety and Health (NIOSH) has developed
guidance in a variety of areas to reduce workers’ exposures to diacetyl through
engineering controls, best work prac-tices, and techniques for monitoring
airborne diacetyl exposures.
Although
these guidelines emphasize diacetyl, they can be applied to reduce exposures to
diacetyl substitutes such as 2,3-pentanedione and other alpha-diketones.
DESCRIPTION
OF EXPOSURE AND HEALTH EFFECTS
Flavorings are substances that alter or enhance the
taste of food. They are composed of various natural and manmade chemicals and
may consist of a single chemical, but more often they are complex mixtures.
Workers in the flavorings production industry may be exposed to these
substances in the form of solids, liquids, or vapors.
Although thousands of flavoring ingredients are in
use, little is known about most of these in terms of worker health effects, and
few have occupational exposure guidelines such as recommended exposure limits
(REL), permissible exposure limits (PEL), or threshold limit values (TLV)®.
NIOSH investigations have found that workplace exposure to diacetyl can result
in reduced lung function and also cause a severe lung disease known as
obliterative bronchiolitis.
In obliterative bronchiolitis, inflammation and
scarring occur in the smallest airways of the lung and can lead to severe and
disabling shortness of breath. Symptoms include cough and shortness of breath
on exertion. Obliterative bronchiolitis is an irreversible lung disease whose
symptoms typically do not improve when the worker goes home at the end of the
workday, on weekends, or on vacations. Obliterative bronchiolitis can reduce
lung function enough to cause disability.
Occurrences of obliterative bronchiolitis were
observed in the microwave popcorn indus-try in 2000 when eight workers were
diagnosed with the disease after exposure to vapors from artificial butter
flavoring ingredients including diacetyl [Akpinar-Elci et al. 2004a; Kreiss et
al. 2002]. Several workers in flavoring manufacturing facilities were also
diagnosed with oblitera-tive bronchiolitis or severe fixed obstructive lung
disease [CDC 2007]. Studies in four micro-wave popcorn plants found that a
history of working as a mixer and higher cumulative ex-posure to diacetyl were
associated with decreased lung function [Lockey et al. 2009].
In one flavoring manufacturing plant, nearly one third of workers had
restrictive breathing abnormali-ties [NIOSH 2011a]. This suggests that workers exposed
to diacetyl and other flavoring ingredi-ents could potentially develop a range
of occupational lung diseases. More recently, facilities have begun producing
or working with substitutes for diacetyl, such as 2,3-pentanedione [Day et al.
2011; Boylstein 2012]. 2,3-Pentanedione, a 5-carbon alpha-diketone, is
chemically very similar to diacetyl, a 4-carbon alpha-diketone. Reports on the
toxicity of 2,3-pentanedione were first published in abstract form in 2010
[Hubbs et al. 2010; Morgan et al. 2010].
Acute
inhalation exposures to 2,3-pentanedione cause airway epithelial damage that is
similar to diacetyl in laboratory studies [Hubbs et al. 2012]. In 2-week
inhala-tion studies in rats, 2,3-pentanedione caused proliferation of fibrous
connective tissue in the walls of airways, and projections of fibrous
connective tissue sometimes extended into the air passageways [Morgan et al.
2012a,b]. Preliminary data suggest that repeated exposures to ei-ther
2,3-pentanedione or diacetyl can cause airway fibrosis in rats [Morgan et al.
2012a]. In the acute inhalation study of 2,3-pentanedione, changes in gene
expression were noted in the brain [Hubbs et al. 2012].
As a
group, these results raise concerns that the toxicologic effects of diacetyl
may be shared with other alpha-diketones, which are close structural analogs.
Addi-tional alpha-diketones of interest include but are not limited to those
used in food manufacturing such as2,3-hexanedione and 2,3-heptanedione.
Diacetyl substitutes should not be assumed to be safe until toxicology studies
are performed. It is difficult to quantify the number of employees involved
with flavor manufacturing and, more specifically, those who have diacetyl or
diacetyl substitute exposure in the United States.
According
to the Environmental Protection Agency Non-Confidential Inventory Updating
Re-port, diacetyl had an aggregate production volume between 10,000 and 500,000
pounds in 2002 [EPA 2002]. The North American Industry Classification System
(NAICS) category 311, the most relevant category, includes subcategories
Flavoring Syrup and Concentrate Manufacturing (NAICS Code 311930), Spice and
Extract Manufacturing (NAICS Code 311942) and All Other Miscellaneous Food
Manufacturing (NAICS Code 311999). In 2002, 21,000 workers were em-ployed in
facilities classified under 311930 and 311942 [Department of Commerce 2004].
According
to the Flavor Extract Manufacturers Association, whose members account for approximately
95% of all flavors produced in the United States, a total of 6,520 employees
work directly in the flavor manufacturing or laboratory activities in
membership companies [Hallagan 2010]. In addition to workers who were exposed
to diacetyl during its production or addition to flavored substances, health
effects have also been observed in workers with downstream exposure to diacetyl
from those flavored substances, including workers in areas such as quality
control and packaging products within microwave popcorn facilities [Kanwal et
al. 2006].
In
2010, California promulgated a regulation for occupational exposure to food
flavorings containing diacetyl that requires installation of exposure controls
to reduce exposures to the lowest feasible levels. In 2012, the American
Conference for Governmental Industrial Hygien-ists published a threshold limit
value® of 0.010 parts per million (ppm) 8hr-time weighted aver-age (TWA) with a
short-term exposure limit (STEL) of 0.020 ppm for diacetyl [ACGIH 2012]. NIOSH
published its draft recommended exposure limits for diacetyl (5 parts per
billion [ppb] 8hr-TWA, 25 ppb STEL) and 2,3-pentanedione (9.3 ppb 8-hr TWA, 31
ppb STEL) in August 2011 [NIOSH 2011b].
CONTROLLING
EXPOSURES
Controlling exposures to occupational hazards is
the fundamental method of protecting workers. Traditionally, a hierarchy of controls
has been used as a means of determining how to implement feasible and effective
controls, which typically include: elimination, substitution, engineering
controls, administrative controls and personal protective equipment (PPE). The
idea behind the hierarchy of controls is that the methods at the top of the
list are generally more effective in reducing the risk associated with a hazard
than those at the bottom.
Following the hierarchy normally leads to the
implementation of inherently safer systems, ones where the risk of illness or
injury has been substantially reduced. To the extent possible, flavors should
be compounded using the ingredients of lowest toxic-ity. For example, if a
diacetyl substitute of lower toxicity that satisfies the requirements of the
job is available, then this substitute should be used. Substitution of
ingredients is often difficult, however, because of the many factors that
determine suitability of a substitute as well as the dearth of knowledge on
relative toxicity of potential substitutes. Diacetyl substitutes should not be
assumed to be safe in the absence of toxicological data.
The potential for workers’ exposure and disease
from these substitutes still remains largely unstudied. When applied and
operating properly, engineering controls can reduce airborne contaminant
concentrations, thereby mitigating worker exposures. NIOSH has identified
control measures includ-ing engineering controls, administrative controls, and
PPE to reduce worker exposure to hazardous substances during the production of
powder and liquid flavorings [NIOSH 2004, 2008a,b,c; Dunn 2007].
While much of this work emphasized the reduction of
exposure to diacetyl, adoption of these control recommendations is anticipated
to also reduce exposure to 2,3-pentanedione and other potentially harmful
substances in the work environment. Many industries have implemented
engineering controls to reduce exposure and risk of disease among their
workers.
Pharmaceutical companies have developed general
design concepts and controls for common unit operations in manufacturing. These
concepts provide a selection of approaches for working with hazardous materials
including the specification of general ventilation; local exhaust ventilation
(LEV); maintenance, cleaning, and disposal procedures; PPE; exposure
monitoring, and; medical surveillance [Naumann et al. 1996].
The primary means for reducing exposures should be
to implement process changes and engi-neering controls (e.g., LEV). Use of PPE
should be the approach of last resort. Production processes differ among
companies, so the approaches discussed below may not apply to all facilities. A
site-specific safety and health plan should be developed and should include
guidance for recognizing haz-ardous exposures and strategies to control them.
Special attention should be given to manual
handling of flavoring ingredients, particularly in heated processes, and when
spraying flavoring ingredients. The food and flavoring production industries
have several primary processes that may result in the potential for worker
exposure to diacetyl, 2,3-pentanedione, and other flavoring ingredients.
These
may be grouped, from an exposure standpoint, into a few general categories
including produc-tion operations, packaging operations, cleaning, and
maintenance operations [ERG 2008].
Table 1 displays a list of job categories and major
activities associated with these categories. For each major activity, the table
indexes the figure(s) showing relevant engineering control systems. These
process-es include blending, mixing, and handling of flavoring ingredients in
liquid and powder form. Bag emptying, bag filling, charging tanks, benchtop
weighing and handling, and drum filling and empty-ing are a few of the
production tasks of concern.
The following sections discuss engineering
controls that can be used to reduce workers’ exposures to diacetyl,
2,3-pentanedione, and other potential airborne hazards in the primary
production processes used in the food and flavoring industries.
Engineering controls are the preferred methods for reducing occupational exposures. Administrative
controls such as medical
surveillance programs and work
practice changes are the next steps. Safe work practices, incorporated into standard production procedures, can pro- mote a safe and healthy workplace as well as improve efficiency and increase production.
Following are recommended administrative and work practice controls:
· Establish, implement, and maintain a medical
surveillance program for all exposed em- ployees.
Medical monitoring of exposed workers can identify early work-related health effects in workers so that steps can be taken to prevent disease
progression.
· Ensure workers do not
eat, drink, or
use tobacco products in the work area.
· Establish a hazard communication program that meets the requirements
of the OSHA hazard communication standard [29 CFR 1910.1200] and the Globally Harmonized System of Classification and Labeling of Chemicals [OSHA 2006].
· Use a closed
process wherever possible to transfer flavoring ingredients instead of manual pouring. When poured, liquids should be added through
a funnel into a covered mixing vessel to limit spills. The work area should be kept clean and spills dealt with promptly.
· Develop procedures for assessing and maintaining ventilation systems, and document them in a written plan. Periodic
monitoring of system performance may include mea- surement of hood static pressure and face/duct velocity as well as smoke tube testing.
· Restrict access to all areas where flavorings are being handled openly to properly protect workers (see section
on PPE).
· Establish standard procedures for cleaning containers and mixing tanks. When possible, use an initial cold water rinse followed by warm water cleaning to reduce volatilization.
· Establish standard procedures for cleaning up spills small and large, wet and dry.
· Use a vacuum with a high efficiency particulate air filter or a wet cleaning technique. Do not use compressed air and dry sweeping for cleaning, as these will re-entrain airborne particulate into the environment.
· Cover containers used to mix and store flavoring ingredients when not in use. Keep empty containers sealed as they may contain residual flavorings.
· Use cold storage for flavoring ingredients to reduce evaporation of chemicals into the air. Volatile ingredients should be added while cold to mixtures. Do not use heat when mixing flavoring ingredients.
·
Wait until the pressure is at or below ambient to open pressurized vessels.
Source: NIOSH [2015]. Best practices: engineering controls, work practices and exposure monitoring for occupational exposures to diacetyl and 2,3-
pentanedione. By Dunn KH, McKernan LT, Garcia A. Cincinnati, OH: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS
(NIOSH) Publication 2015-197.
pentanedione. By Dunn KH, McKernan LT, Garcia A. Cincinnati, OH: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS
(NIOSH) Publication 2015-197.
DHHS (NIOSH) Publication No. 2015-197
July 2015