NIOSH Education and Information Division
The
National Institute for Occupational Safety and Health (NIOSH)
requests assistance in preventing organic dust toxic syndrome
(ODTS), an acute respiratory illness in agricultural workers
who inhale contaminated organic dust. This Alert describes
four case reports in which a total of 29 agricultural workers
developed ODTS following inhalation of organic dusts contaminated
with microorganisms. Information about ODTS is urgently needed
by agricultural workers and employers, cooperative extension agents, rural veterinarians, physicians, and other health
care providers. NIOSH therefore requests that editors of trade
journals, safety and health officials, labor unions, and agricultural
employers bring this Alert to the attention of all workers
who are at risk. Your assistance in this effort will help
prevent occupational disease among the 3.4 million agricultural
workers in the United States-one of the stated goals of the
1991 Surgeon General's Conference on Agricultural Safety and
Health [DHHS 1992].
Agricultural
workers are at risk for developing respiratory illness from
exposure to inhaled dusts. One of the most common illnesses
is ODTS, a respiratory and systemic illness that may follow
exposures to heavy concentrations of organic dusts contaminated
with microorganisms [doPico 1986; Parker et al. 1992]. An
estimated 30% to 40% of workers exposed to organic dusts will
develop the disease [dopico 1986; Rask-Andersen 1989].
Despite
its common occurrence among agricultural workers, ODTS is
not a widely recognized illness because only serious cases
or clusters of cases are likely to come to a physician's attention.
ODTS is a general term that includes all of the following
conditions:
- Precipitin-negative
farmer's lung disease [Edwards et al. 1974]
- Pulmonary
mycotoxicosis [Emanuel et al. 1975]
- Grain
fever in grain elevator workers [doPico et al. 19821
- Silo
unloader's syndrome [Pratt and May 1984]
- Mill
fever in cotton textile workers [Rylander et al. 1987]
- Inhalation
fever [Rask-Andersen and Pratt 1992]
ODTS
typically occurs where a large amount of organic dust is present
in the air. The syndrome often occurs in small clusters and
affects most individuals who are exposed to heavy concentrations
of organic dust contaminated with microorganisms [Brinton
et al. 1987]. ODTS appears to result from inhaling particles
and toxins produced by microorganisms such as gram-negative
bacteria (Pseudomonas species, Enterobacter agglomerans, and
Klebsiella species), thermophilic organisms (Aspergillus fumi
atus and Micropolyspora faeni), and fungi [Schenker et al.
1991]. Endotoxin is a com-mon component of organic dust in
agriculture [Olenchock et al. 1990; Dutkiewicz 1987] and may
be involved in the development of ODTS.
Although
the focus of this Alert is on ODTS, agricultural workers should
be aware that they are at risk for other important respiratory
illnesses or hazards such as the following:
- Silo
filler's disease, an acute toxic inflammation of the lung
caused by exposure to oxides of nitrogen in freshly filled
silos [Grayson 1956; Horvath et al. 1978]
- Farmer's
lung disease (or hypersensitivity pneumonitis), an immunologic
lung response involving microbial antigens in moldy hay
[Campbell 1932; Parker et al. 1992]
- Bronchitis
- Death
by asphyxiation (suffocation)
- Inhalation
of toxic gases (in manure pits, for example) [NIOSH 1990]
Cotton
dust is the only specific agricultural dust for which the Occupational
Safety and Health Administration (OSHA) has a standard. This
standard protects workers in general industry against byssinosis,
a chronic lung disease [29 CFR 1910.1043]. OSHA also has a standard
for nonspecific dusts: 15 milligrams per cubic meter (mg/m3)
for total dust and 5 mg/m3 for respirable dust [29
CFR 1910.1000].
NIOSH
has recommended exposure limits for cotton dust, grain dust,
and wood dust [NIOSH 1992b], but these limits may not adequately
protect workers exposed to organic dusts contaminated with
microorganisms.
Agricultural
workers may develop ODTS after inhaling dust from contaminated
organic materials. The syndrome is characterized by fever occurring
4 to 12 hours after exposure and flu-like symptoms such as general
weakness, headache, chills, body aches, and cough. Shortness
of breath may also occur.
Listening
to the chest usually reveals normal breathing sounds, and
chest X-rays are usually normal. Pulmonary function may be
impaired, and an increase in the number of white blood cells
is common. Antibodies commonly associated with certain allergic
lung diseases such as farmer's lung are usually not present.
No specific
therapy is needed to treat ODTS. However, the syndrome may
often be misdiagnosed as acute bronchitis, influenza, or farmer's
lung disease, which may lead to unnecessary therapy with antibiotics
or anti-inflammatory medication. ODTS usually disappears within
24 hours to a few days after the worker is removed from exposure.
Repeated episodes of ODTS can occur after reexposure to contaminated
organic dusts. No deaths from ODTS have been reported.
The
following cases highlight examples of ODTS.
Case
No. 1: Nine workers affected Eleven male
workers, aged 15 to 60 years, moved 800 bushels of oats from
a poorly ventilated storage bin in Alabama [Parker et al. 1988].
The oats were reported to contain pockets of powdery white dust.
Work conditions were described as extremely dusty, and all workers
wore single-strap disposable masks while inside the bin. The
workers shoveled the oats for 8 hours in groups of two or three
for shifts of 20 to 30 minutes. Within 4 to 12 hours, all nine
who worked inside the bin became ill with fever and chills,
chest discomfort, weakness, and fatigue. Eight reported shortness
of breath, six had nonproductive coughs, five complained of
body aches, and four developed headaches. The two workers who
remained outside the storage bin developed no symptoms. Six
of the ill workers saw a doctor within the first 2 days of symptoms.
The following abnormal physical signs were reported: body temperature
greater than 100.4øF (38.0øC) in two workers, crackle sounds
in the lungs of two workers, and wheezing sounds in one worker.
Chest X-rays were normal in all six workers. Symptoms disappeared
in all affected workers in 2 to 12 days.
Airborne
dust generated in the laboratory from the bulk oats contained
39.5 mg/m3 of respirable dust. Endotoxin content
in the respirable dust was elevated to 325.7 endotoxin units/mg
of dust.
Despite
an initial diagnosis of farmer's lung disease, the rate of
illness among those who entered the bin (100%, or 9 of 9)
is typical of ODTS.
Case
No. 2: One worker affected A previously
healthy 52-year-old man entered an emergency room with a fever
of 101.8øF, body aches, and marked difficulty in breathing 12
hours after shoveling composted wood chips and leaves [Weber
et al. 1990]. He was treated with oral glucocorticoids and improved
over 3 days. Blood tests did not show that he was suffering
from farmer's lung disease.
Using
respiratory protection, investigators recreated the exposure
and made extensive environmental measurements. Peak exposures
to respirable dust were greater than 80 mg/m3 of
air. Endotoxin concentrations ranged from 244 to 16,300 endotoxin
units/m3-concentrations previously associated with
illness. High concentrations of gram-negative bacteria were
also present [Olenchock et al. 1991].
Case
No. 3: Fourteen workers affected (silo unloader's syndrome)A retrospective
study of hospital visits for farm-associated lung injury in
a rural county in New York over an 11-year period revealed 26
cases of respiratory illness in 23 individuals [Pratt and May
1984]. Fourteen of these individuals suffered fever of short
duration. Illness was most often associated with a 1 - to 3-hour
respiratory exposure that occurred during the preparation of
silos for mechanical unloading. During removal of the moldy
top silage, the workers developed burning in the eyes and throat,
headache, and cough. They attributed these symptoms to the white
powder or "fog" arising from the moldy material. High fever,
chest discomfort, weakness, and nonproductive cough followed
within 4 to 12 hours. Blood tests failed to show that these
workers suffered from farmer's lung disease.
A subsequent
environmental study of five silos [May et al. 1986] revealed
that workers unloading silos encounter total dust concentrations
ranging from 0.2 to 138mg/m with concentrations at the silo
base generally similar to those in the headspace. Respirable
dust concentrations ranged from 0.2 to 24 mg/m3,
and microorganism counts ranged from 105 to 109/M3.
Thermophilic bacteria were the most prevalent organisms of
those cultured.
Case
No. 4: Five workers affected Five workers
at a municipal golf course became ill with an influenza-like
syndrome within hours of manually unloading a trailer truck
filled with wood chips [CDC 1986]. The wood chips were stored
in an enclosed, 40-foot trailer. Eleven workers participated
in the unloading process. Although fresh chips had been ordered,
the vendor included old chips that had been stored in the front
of the trailer for approximately 1 year. Chips unloaded from
the front were visibly contaminated, and growth cultures revealed
a wide variety of bacteria and fungi.
All
five workers who became ill had worked in very dusty conditions
without respiratory protection while unloading the front of
the trailer. The onset of illness ranged from 4 to 16 hours
after beginning work. None of the workers were hospitalized,
but one reported to a local emergency room, and two were too
ill to work the following day. Within 48 hours, symptoms were
greatly improved; within 72 hours, all affected workers had
completely recovered.
The
six workers who did not become ill included three who had
unloaded fresh chips from the back of the trailer, one supervisor
who had briefly checked on the unloading process, and two
workers who finished unloading the front of the trailer the
next morning using air-purifying respirators.
The
cases described in this Alert reveal the seriousness of exposure
to contaminated organic dust among agricultural workers and
others. Because many agricultural workers find it difficult
to seek medical attention and because many physicians fall to
recognize occupational respiratory diseases, ODTS is probably
much more common than documented.
Recommendations
Minimizing
Risk
Agricultural
workers and employers should minimize the risk of exposure to
organic dusts by taking the following precautions:
- Be
aware of the health effects of breathing organic dust. Symptoms
of ODTS occur 4 to 12 hours after exposure and may include
fever, weakness, headache, chills, body aches, cough, and
shortness of breath.
- Inform
your doctor about recent dust exposures when seeking treatment
for respiratory illness.
- Carefully
harvest and store agricultural products to minimize spoilage.
- Use
automated or mechanized equipment to move decayed materials.
- Use
local exhaust ventilation and wet methods of dust suppression
to minimize exposure to organic dusts. For example, adding
a quart of water to the cut side of bedding hay or straw
before chopping is an effective method for reducing dust
levels (but avoid overusing water) [NIOSH 1992c].
- Use
the following engineering controls to reduce the dust exposure
of silo unloaders [Jensen et al. 1993]:
- Design
the silo to provide for product turnover and to provide
unfavorable conditions for microbial growth.
- Design
the conveyor to prevent spills of material and to ventilate
dust effectively.
- Use
ventilated loading spouts when filling trucks and railroad
cars with silage.
- Use
appropriate respirators approved by NIOSH and the Mine Safety
and Health Administration (MSHA) when exposure to organic
dust cannot be avoided (see the following section on respiratory
protection).
- Do
not wear contaminated work clothes inside the home. Prevent
exposure of family members to dusts and other toxic materials
by removing contaminated clothes outside.
Respirators
should not be used as the only means of preventing or minimizing
exposures to airborne contaminants. NIOSH recommends that workers
be protected by controlling dust at its source and by using
controls such as ventilation and wet dust suppression. However,
when exposure to organic dust cannot be avoided, engineering
controls should be supplemented with the use of appropriate
NIOSH/MSHA-approved respirators.
Agricultural
activities may generate a wide range of respirable dust concentrations.
For example, respirable dust concentrations during bedding
chopping have been measured at 1.6 to 2.5 mg/m3
[Olenchock et al. 1990], whereas they may be as high as 24
mg/m3 during silo unloading [May et al. 1986].
Working in confined spaces or enclosed locations can increase
dust concentrations.
Because
of this wide range of potential exposures and because there
are no applicable exposure limits for organic dusts contaminated
with microorganisms, NIOSH recommends that exposed workers
wear the most practical respirator with the highest assigned
protection factor (APF). Table 1 lists NIOSH-recommended respirators
and their APFs. Air-purifying respirators should be worn with
high-efficiency particulate air (HEPA) filters.
Table
1. NIOSH recommended respiratory protection for workers
exposed to organic dust |
Type
of respirator*
| APF**
|
Any
air-purifying respirator with a high-efficiency particulate
air filter |
10 |
Any
powered, air-purifying respirator with a high-efficiency
particulate air filter or, |
25
|
Any
supplied-air respirator equipped with a hood or helmet
and operated in a continuous-flow mode |
25
|
Any
air-purifying, full-facepiece respirator with a high-efficiency
particulate air filter |
50
|
Any
powered, air-purifying respirator with a tight-fitting
facepiece and high-efficiency particulate air filter |
50
|
Any
supplied-air respirator equipped with a half-mask and
operated in a pressure-demand or other positive-pressure
mode |
1,000
|
Any
supplied-air respirator equipped with a full facepiece
and operated in a pressure-demand or other positive-pressure
mode |
2,000
|
Any
self-contained breathing apparatus equipped with a full
facepiece and operated in a pressure demand or other positive-pressure
mode |
10,000
|
Any
supplied-air respirator equipped with a full facepiece
and operated in a pressure-demand or other positive-pressure
mode in combination with an auxiliary self-contained breathing
apparatus operated in a pressure-demand or other positive-pressure
mode |
10,000
|
*
- Only NIOSH/MSHA-certified equipment should be used.
** - Assigned protection factor. The APF is the minimum
anticipated level of protection provided by each type
of respirator [NIOSH 1987b]. For example, an APF of
10 means that the respirator should reduce the air concentration
of dust by a factor of 10 (or to 10% of the concentration
without respiratory protection).
|
Powered,
air-purifying respirators (PAPRs) are the most protective
type of air-purifying respirator. Workers exposed to organic
dusts have been adequately protected by PAPRs [Lenhart and
Reed 1989; Clark 1986; Anderson et al. 1989; van Assendelft
et al. 1985] and less effectively protected by other types
of air-purifying respirators [Lenhart and Cole 1993; M:ller-Wening
and Repp 1989; Dykewicz et al. 1988; Solley and Hyatt 1980].
For
additional information about respirator selection, consult
the NIOSH Respirator Decision Logic [NIOSH 1987b]. Workers
should use respirators certified by NIOSH and MSHA [NIOSH
1992a].
When
respirators are used, the employer must establish a comprehensive
respiratory protection program as outlined in the NIOSH Guide
to Industrial Respiratory Protection [NIOSH 1987a] and as
required in the OSHA respiratory protection standard [29 CFR
1910.134]. Important elements of these programs are as follows:
- An
evaluation of the worker's ability to perform work while
wearing a respirator
- Regular
training of personnel
- Periodic
environmental monitoring
- Respirator
fit testing
- Maintenance,
inspection, cleaning, and storage
- Selection
of appropriate respirators certified by NIOSH and MSHA
- Employers
should evaluate the respiratory protection program regularly.
The
principal contributors to this Alert were Karl J. Musgrave,
D.V.M; John E. Parker, M.D.; Stephen A. Olenchock, Ph.D.;
and Robert M. Castellan, M.D., of the NIOSH Division of Respiratory
Disease Studies. Comments, questions, or requests for additional
information should be directed to
- Dr.
Gregory Wagner
- Director,
Division of Respiratory Disease Studies
- 944
Chestnut Ridge Road
- Morgantown,
WV 26505-2888
- Telephone
(304) 291-4474
For
more information about NIOSH health hazard evaluations, technical
assistance, and other research and support activities concerning
lung diseases in agricultural workers, contact the following:
- Coordinator,
Respiratory Disease Hazard Evaluation and Technical Assistance
Program
- Division
of Respiratory Disease Studies
- NIOSH
- 944
Chestnut Ridge Road
- Morgantown,
WV 26505-2888
- Telephone:
(304) 291-4203
We greatly appreciate your assistance in protecting the health
of U.S. workers.
Richard
A. Lemen, Ph.D.
Acting Director, National Institute for Occupational Safety
and Health Centers for Disease Control and Prevention
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and Reproduction Information: Information in NASD does not
represent NIOSH policy. Information included in NASD appears
by permission of the author and/or copyright holder. More
NASD Review: 04/2002
This
document is NIOSH Publication No.
94-102
.
Publication date: April 1994.
National
Institute of Occupational Safety and Health, Department of
Health and Human Services, 200 Independence Avenue, SW, Washington,
DC, 20201. Phone: (800) 356-4674.
Disclaimer:
Mention of the name of any company or product does not constitute
endorsement by the National Institute for Occupational Safety
and Healt
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