David
E. Baker, Brooke Ballenger and Rusty Lee
University of Minnesota Extension Service
Many
farming situations present respiratory health hazards to farm
workers. In fact, high percentages of farm workers may risk
this type of health problem. For example, exposure to various
respiratory hazards has been linked to coughs and the presence
of sputum (with or without airflow obstructions) in 20 to
90 percent of farm workers and families, depending on the
type of exposure. Symptoms of chronic bronchitis have been
observed in as many as 50 percent of swine confinement workers
and grain handlers.
Yet
with a few precautions and an understanding of respiratory
dangers, these hazards can be minimized or even eliminated.
This publication discusses some respiratory hazards common
to farming and the equipment that can reduce the threat to
farm workers.
FARMER'S
LUNG. Farmer's Lung is an allergic reaction caused by inhaling
dust from moldy hay, straw and grain. Dairy and grain farmers
are the most common victims. Working outdoors with these materials
poses minimal danger because the dust is quickly dispersed.
The months when moldy crops are handled indoors are the most
dangerous.
Because
the dust is so fine, it gets past defense systems in the nose
and throat. When the dust reaches the inner parts of the lungs,
the lung's internal defense system usually takes over and
removes it without damage. But a few people will develop an
allergy. The first exposure creates the allergy in sensitive
individuals, and subsequent exposures trigger an allergic
reaction. Symptoms may resemble anything from a cold to pneumonia.
Scar tissue forms in the lungs. The cold-like symptoms may
c ear up, but the scarring is permanent.
Lung
damage may be too slight to notice during the early stages
of Farmer's Lung. Repeated exposure increases tissue damage,
causing victims to begin experiencing shortness of breath.
This makes strenuous work more difficult, and victims eventually
may find it a struggle to even get out of a chair.
TOXIC
ORGANIC DUST SYNDROME. Dust from moldy hay, grain and
silage also can cause Toxic Organic Dust Syndrome (TODS),
which has symptoms resembling Farmer's Lung. However, TODS
does not produce long-term illness or cause permanent lung
damage. Even if TODS occurs several times in the same person,
it will behave similarly each time, with severity depending
on the individual and the dose of inhaled dusts. Farmers will
not contract TODS unless they inhale large amounts of moldy
dust.
NUISANCE
DUSTS. Suspended dust particles encountered during farm
operations that do not contain spores from moldy organic matter
are considered "nuisance dusts." While inhaling them usually
will not cause an allergic reaction, repeated exposure can
turn portions of the lung into hardened, non-functioning tissue.
As a result, the lung's capacity to take in oxygen will be
reduced, and the victim will become more vulnerable to respiratory
diseases like pneumonia, tuberculosis and bronchitis.
GASES.
A variety of worker-disabling gases, including nitrogen dioxide
(NO2), hydrogen sulfide (H2S), ammonia (NH3), carbon dioxide
(C02) and methane (CH4), are produced during many routine
farm operations. These gases are commonly produced in areas
such as silos and manure pits. Exposure to low levels of these
gases will produce lung and eye irritations, dizziness, drowsiness
and headaches. High levels will quickly render a worker unconscious,
and death will follow (see MU publication 01931, Animal Handling
Safety Considerations).
FARM
CHEMICALS. Pesticides (herbicides, insecticides and fungicides),
fertilizers (ammonium nitrate), sanitizers (calcium hypochlorite)
and battery acid are common farm chemicals which produce harmful
fumes. Always follow label directions when handling these
chemicals. Labels will list potential hazards to workers and
identify the personal protective equipment necessary during
handling (see MU publication G01917, Personal Protective Equipment
for Working With Pesticides).
Table
1. Comparison of air-purifying respirators.
None of these should be used in oxygen-limiting
environments. |
Disposable
mechanical filter respirators
- Uses:
Dusts. Not recommended for gases.
- Fit:
Good fit hard to obtain. Adjustable and two-strap
models available.
- Amount
of maintenance: low
- Breathing
resistance: High (unless has exhalation value)
- Remarks:
Easy to see over. Lightweight. Clog with moisture
from wearer's breath in humid air. Cause glasses
to fog in cold weather.
|
Mechanical
filter respirators
- Uses:
Dusts. Not recommended for gases
- Fit:
Moderately good for half-mask models.
- Amount
of maintenance: Moderate (unless disposable)
- Breathing
resistance: moderate
- Remarks:
Reusable mask with replaceable dust filter
|
Chemical
cartridge respirators
- Uses:
Dusts, gases.
- Fit:
Good
- Amount
of maintenance: Moderate
- Breathing
resistance: Moderate
- Remarks:
Some "disposables" available that are discarded
when cartridge is spent. Selecting the correct
type of particulate or gas cartridge is mandatory.
Particulate prefilters available.
|
Gas
masks
- Uses:
Dusts, gases
- Fit:
Good
- Amount
of maintenance: Moderate
- Breathing
resistance: Moderate
- Remarks:
Larger capacity canisters rather than cartridges.
Correct type of canister must be selected.
|
Powered
air purifiers
- Uses:
Dusts, gases
- Fit:
Good
- Amount
of maintenance: Moderate to high
- Breathing
resistance: Low
- Remarks:
Add noticeable weight. Not recommended for protection
against gases unless specified. Will be expensive
to repair. Possible lengthy repair period.
|
|
Table
2. Respirator types that should be used against
common agricultural airborne contaminants. |
Respiratory
hazard |
Required
type of respiratory protection |
Pesticides |
Chemical
cartridge approved1 pesticide respirator;
gas mask or self-contained breathing apparatus,
depending on concentration, oxygen level and type
of application (refer to Precaution note on product
label). |
Fumigants
(for buildings) |
Gas
mask, supplied-air or self-contained breathing apparatus,
depending on type of application. |
Fumigants
(for soil) |
Chemical
cartridge, full-face organic vapor respirator. |
Carbon
monoxide |
Self-contained
breathing apparatus. |
Nitrogen
dioxide (silage gas) |
Self-contained
breathing apparatus. |
Hydrogen
sulfide |
Supplied-air
respirator with full face piece, helmet or hood,
or self-contained breathing apparatus. |
Ammonia |
Chemical
cartridge respirator approved for ammonia and methylamines. |
Chemical
additives (powder or solids) |
An
approved toxic dust respirator. |
Grain
dust |
An
approved toxic dust respirator. |
Paint |
An
approved spray paint respirator. |
Welding |
An
approved fume respirator. |
Fungal
spores |
An
approved toxic dust respirator. |
1
- Approved refers to respirators with NIOSH/MSHA
approval. This will be clearly designated on the
package, and an approval number will appear on the
respirator. The approval ensures that the equipment
has been tested and meets a minimum standard of
performance. |
|
Selection
of specific types of protective equipment depends on the hazards
present and the amount of filtering necessary (see Table 1 and
Table 2). Regardless of the type that is chosen, however, all
respiratory protection must be approved by NIOSH.
AIR-PURIFYING
RESPIRATORS. Air-purifying respirators remove contaminants
from the air but can be used only in an environment that has
enough oxygen to sustain life. Do not use air purifiers to
provide protection from the dangers of oxygen-limited environments.
Respirators are effective only up to their specified concentration
limits.
The
composition of a respirator's filter depends on the contaminant
to be filtered. Various chemicals are used to remove gases
and vapors. The useful life of the respirator is determined
by the contaminant concentration, breathing volume of the
wearer and capacity of the air purifying medium.
There
are several styles of air-purifying respirators, but only
two general types: the mechanical filter and the chemical
cartridge.
MECHANICAL
FILTERS provide protection against particulates such as
dusts, mists or metal fumes. A fibrous material in the filter
traps the particles.
A mechanical
filter respirator with toxic dust approval should be used
to protect against grain dusts and mold spores. It should
seal tightly around the nose and mouth. A fume-approved respirator
of this type also should be worn when welding. Do not use
a mechanical filter for protection from chemicals or toxic
gases.
As the
filtering capacity is exhausted, the filter will become plugged
with the trapped particles. This becomes apparent when more
effort is required to draw air. At this point, the filter
should be replaced.
CHEMICAL
CARTRIDGES protect against certain gases and all but the
most toxic organic vapors. The filtering medium is activated
carbon, which retains the contaminant. Its primary function
is to remove organic vapors, but filters also can be added
for protection from a variety of specific gases. The correct
cartridge for the material to be filtered must be in place.
Do not use chemical cartridge filters when working with gases
or vapors that cannot be effectively filtered out by the cartridge, regardless of concentration.
Cartridges
should be replaced regularly with heavy use, or the carbon's
capacity will be exhausted and contaminants will pass through
the filter and be inhaled.
For
protection during spray painting or pesticide application,
chemical cartridges that work in conjunction with a specific
mechanical filter should be used.
POWERED
AIR PURIFIERS. The powered air purifier can be a mechanical
filter, a chemical cartridge respirator, or a combination
of both. These devices have a motor blower assembly that forces
air through the filter and into the breathing zone of the
wearer. Breathing is much easier because no effort is required
to draw air through the filter.
Powered
air purifiers may be preferred for excessively high concentrations
of dusts or pesticides, but they cannot be used in oxygen-limited
environments.
Common
headgear for powered air purifiers consists of a hard helmet
and a rigid visor. Non-rigid head and face covers also are
available.
Powered
air purifiers are powered by a battery pack strapped onto
the user's waist or back. The batteries may be of the rechargeable
or disposable type. Another option is an adapter that allows
the unit to be powered by the 12V or 24V DC available from
a vehicle battery, such as that in a tractor or skid-steer
loader.
Since
most powered air purifiers provide constant positive pressure,
they do not require a tight face seal, so beards, sideburns
and different sized faces or heads do not hinder a good fit.
GAS
MASKS. Gas masks are more effective than chemical cartridge
respirators against high concentrations of toxic gases. The
chemical filter in the gas mask removes toxic vapors and particles
from the air, such as fumigants for buildings. Like all air-purifying
devices, gas masks also should not be used in oxygen-limited
environments.
Gas
masks have replaceable canisters that are larger than the
cartridges used in chemical cartridge respirators and are
more effective than chemical cartridges against high concentrations
of toxic gases and vapors. The canisters also contain a larger
volume of chemical sorbent and may be used for longer periods
of time than the chemical cartridges before breakthrough occurs.
For
canisters and cartridges, the fit of the mask to the individual
is equally important to the degree of protection as is the
volume of chemical sorbent. Gas masks usually have a full
face piece with an attached hose leading to a canister mounted
on the wearer's belt. Chin-type canisters also are available,
but they have somewhat smaller capacities.
SUPPLIED-AIR
RESPIRATORS. Because none of the air-purifying respirators
or powered air
purifiers
supply oxygen, they should never be used in oxygen-deficient
areas. Instead, a supplied-air respirator that brings in uncontaminated
air from an outside source should be used.
Two
types of supplied-air respirators are approved for use in
oxygen-deficient areas, such as manure pits, silos containing
silo gas, airtight silos, or bins containing high-moisture
grain. They are the hose mask with blower and emergency air
supply (not to be confused with powered air purifiers) and
the self-contained breathing apparatus (SCBA). When using
a SCBA, the wearer carries a portable supply of air that is
independent of the environment.
This
equipment is expensive to buy and maintain. Its high cost
often makes it impractical to have on the farm. Take precautions
entering oxygen-deficient environments, especially if you
do not have a SCBA. If you must enter these settings, all
panels and doors should be open and all ventilation systems
should be on for at least 30 minutes before entry.
Always
secure a lifeline to yourself when entering areas that may
be deficient in oxygen. Without a SCBA, this lifeline is the
only means others have to rescue you if you become unconscious.
Regardless
of the type of equipment selected, it must fit properly to ensure
complete protection. OSHA requires fit testing for all respiratory
protection used by employees.
A device
must have a tight seal around the nose and mouth or contaminated
air will leak through the seal. Facial hair can prevent a
good seal, even if it is only one day's stubble.
For
best results, have equipment fitted to the wearer by qualified
personnel and follow the manufacturer's instructions. An easy
way to check the seal is to conduct a positive or negative
fit check. For a positive check, cover the exhalation valve
with the palm of the hand and exhale so that air builds up
inside the respirator. If there is a leak, you will feel it
against the skin of your face. For a negative fit check, cover
the cartridge(s) with your hands and inhale. If there is no
leakage, the mask will be drawn tightly to your face.
Respiratory
protective equipment should be stored in a clean, dry place
away from work and chemical storage areas.
Regular
cleaning, repairing and changing of cartridges is required
when using respirators more than once. The prefilter should
be changed after each day of spraying, and the pesticide cartridge
should be changed as soon as the wearer detects the odor of
the pesticide. It is important to always have a spare set
of cartridges available.
Dust
filters should be replaced when they become difficult to breath
through. For respirators with rubber face pieces, make sure
the valves are intact. The face piece may be washed with warm
water and mild soap.
The
most convenient, maintenance-free device is the disposable
air-purifying respirator. When the filter is used up, it may
be replaced with a new one.
Partial
funding for this guide was provided by the University of Missouri-Columbia/National
Institute for Occupational Safety and Health Cooperative Agricultural
Promotions Agreement.
Disclaimer
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
GO1935
,
published by the University Extension, the University of Columbia-Missouri,
Columbia, MO 65211. Publication date: October 1993.
David
E. Baker, Brooke Ballenger and Rusty Lee, Department of Agricultural
Engineering, University Extension, the University of Missouri-Columbia,
Columbia, MO 65211 .
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