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Fact Sheet no. 7
Revised and Reprinted August 1999
Farmers are exposed to many respiratory irritants as they perform their work
and therefore are at risk for lung diseases. Damp grains, straw and hay
provide ideal growing conditions for molds and fungi in stored grain and
livestock feeds. Information on molds and fungi may be found under such
terms as mycotoxins, aflatoxins, ochratoxins, thermophilic actinomycetes and
estrogenic compounds. Some effects caused of exposure to the mold or fungi
and some effects are caused by endotoxins (poisons) produced by these
organisms.
Conditions for Growth
Many molds and fungi occur naturally in the soil. Fungal spores can be
carried attached to grain dust along with bacteria, insect parts and wastes,
rodent hair and wastes, and pollen. During harvest these particles may be
picked up and deposited in storage facilities along with the grains. Grain
stored with a moisture content of greater than 14% increases the likelihood
of mold and fungi growth. Mold growth occurs between 20-30°C but fungi can
grow in temperatures as low as 5°C. Large bales create conditions favourable
for mold growth. Molds and fungi typically produce a white, sharp smelling
dust. Heavy concentrations of mold spores have also been described as dry,
white or grey powder or clouds.
Activities
Closed environments, such as bins and barns, may have increased
concentrations of molds and fungi. Activities that take place in these
closed environments may increase the farmer's exposure to mold-laden dusts
potentially resulting in illness. Up to 75% of cases in studies have
developed some symptoms after extreme exposure to dust while handling grain.
Examples of work tasks that have produced symptoms include:
- cleaning moldy grain out of bins
- cleaning out moldy grain to dry it
- exposure to moldy silage
- cleaning out harvest equipment (including grain
dryers) in preparation for the next year's harvest.
Routes of Entry
Most of the information that is available on health effects of molds and
fungi is related to breathing in these organisms carried along with dust.
The extremely small size of mold and fungal spores allows them to enter deep
into the lungs by bypassing the body's normal defenses such as the lining of
those nose, coughing and sneezing. Molds and fungi can be carried
accidentally to the mouth from hands and other exposed skin and be absorbed
through the stomach and intestines.
Health Effects
Inhaling molds and fungi in dust can cause a variety of (immediate) and
(long term health problems. Immediate mold health effects include allergies, skin
irritation, poor appetite, headache, and vomiting, and long term health effects
can include emphysema, chronic bronchitis, lung fibrosis, dermatitis (skin
inflammation), and lung and intestinal cancers.
Medical Conditions
Exposure to molds/fungi in dust may cause a number of medical conditions*.
Following are brief descriptions of some conditions that have been
identified after exposure to these dusts.
Farm's Lung Disease (FLD)
- Symptoms may develop within 4-6 hours after exposure
to moldy hay or grain. Symptoms include weakness, chills, cough, fever,
and a general feeling of unwellness. This disease may also have a more
gradual onset with laboured breathing, weight loss and increasing fatigue.
Blood tests, x-rays, and lung tests will show changes from normal. The
lungs can be permanently damaged. This is an allergic reaction and can be
triggered by increasingly small amounts of dusts. FLD may eventually cause
death from lung fibrosis if individual does not avoid exposure to dusts or
does not wear respiratory protection. Because this is an allergic
reaction, within a small group, one individual will usually become ill.
Organic Dust Toxic Syndrome (ODTS)
- This disease occurs when individuals are exposed to
moldy grains, hay or silage. Initial symptoms include burning in the eyes
and throat, headache and sometimes a cough. Four to twelve hours later an
exposed person may suffer with fever, chest discomfort, weakness, muscle
aching, shortness of breath, and a nonproductive cough. There is usually
no permanent lung damage. Large amounts of dust exposure are usually
necessary to trigger the syndrome. Small groups of exposed individuals may
become ill.
Silo Filler's Disease
- This is an immediate reaction with the individual
experiencing shortness of breath. It is an inflammatory reaction in the
lung caused by nitrogen gas from silos. It may result in problems with
oxygen being absorbed into the body. X-ray shows lung changes.
Asthma
- Many people who have been diagnosed with asthma are
very sensitive to molds and fungi. Exposure to molds and fungi may cause a
worsening of symptoms. These individuals are advised to wear a protective
device such as an airstream helmet or avoid exposure.
Other
- Some illnesses related to molds and fungi appear
less commonly. Examples of this are mycosis and mycotoxicosis.
Mycosis
- It is an effect on the body caused by the fungi
itself. Some fungi can lodge in the airways or in a distant part of the
lung and grow until a "fungus ball" is formed.
Mycotosicosis
- It is a poisoning of the body caused by the
toxins/wastes produced by a fungi. Symptoms include chills; fever; dry
irritating cough; abnormal blood results and x-ray. This illness does not
recur.
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*It is important to note that these illnesses can only be
distinguished by medical examination and testing. |
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ORGANIC DUST TOXIC SYNDROME |
FARMER'S LUNG DISEASE |
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TIME TO ONSET OF ILLNESS |
4-12
hours lasting 24-72 hours |
4-6
hours lasting about 12-24 hours |
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SYMPTOMS |
Burning eyes,throat, headache or cough when exposed followed by: High
fever, chest disconfort, weakness, non-productive cough |
Weakness, chills, cough, fever, malaise, shortness of breath, mucle
aches or Gradual onsed of labored breathing, weight loss, increasing
fatigue |
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EFFECTS |
Not
known to cause permanent damage |
Reaction worsens with each exposure; permanent damage to lungs; death
may result |
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TRIGGERS |
Large
amounts of dust. In small groups more than one individual may become ill
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Increasingly smaller amounts of dust. Allergic reaction; usually within
a small group only one person becomes ill |
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DIAGNOSIS |
White
blood count is raised |
Blood
tests, x-rays and lung testing show abnormal results |
Preventing Mold Growth and Human Contact
- Avoid crop rotations that favour fungal infection
- Prevent initial infection in grain by:
- drying to <13.5% moisture content
- storing at low temperatures
- Work outside when possible if bales and grain appear
moldy
- Use ventilation (fans, exhaust blowers, filters) if
you must work in an enclosed area.
- Wet down moldy materials to reduce dust
- Use mechanized systems to distance yourself while
handling moldy materials
- Use caution when harvesting crops that have
overwintered in the field. They provide ideal conditions for mold growth
- Wear personal protective equipment if you must
handle moldy grain or feeds.
- Use caution when using bale-grinders or feed mixers
Safety Equipment and Measures
- A disposable dust mask with two straps and a
mouldable metal strip or a respirator with dust filter cartridges (NIOSH
approved)
- Wear coveralls over work clothes
- Remove coveralls outside and wash exposed skin
(hands, face, neck) well before meals to remove mold/fungi, preventing
accidental ingestion while eating.
- Change air filters frequently on harvesting
equipment
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Although every care had
been taken in providing this information, the authors accept no
responsibility or liability for any consequences arising from the use
of such information.
Reference list available upon request.
Do not reproduce in whole or in part without written permission.
©Centre for Agricultural
Medicine,
University of Saskatchewan, 1999. |
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