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Health & Nutrition
Indoor Air Quality for Health
Causes
of Indoor Air Problems?
• Ventilation
• Your Health
• Air Quality Problems
• Indoor Pollutants
• Radon
• Tobacco Smoke
• Biological Contaminants
• Stoves, Heaters, Fireplaces, and Chimneys
• Household Products
• Exposure to Household Chemicals
• Formaldehyde
• Pesticides
• Asbestos
• Lead
• References
Most people are aware of the potential health hazards of outdoor
air pollution but may not know of the significant dangers that indoor air
pollution can pose. E-P-A studies of human exposure to air pollutants indicate
that indoor air levels of many pollutants may be 2-5 times, and occasionally,
more than 100 times higher than outdoor levels. These levels of indoor air
pollutants are of particular concern because it is estimated that most people
spend as much as 90% of their time indoors.
What causes Indoor Air
Problems?
Over the past several decades, our exposure to indoor air
pollutants has increased due to a variety of factors, including the construction
of more tightly sealed buildings, reduced ventilation rates to save energy, the
use of synthetic building materials and furnishings, and the use of personal
care products, pesticides, and housekeeping supplies. In addition, our
activities and decisions, such as deferring maintenance to "save" money, can lead to problems from sources and ventilation.
The indoor environment in any building is a result of the
interactions among the site, climate, building structure and mechanical systems,
construction techniques, contaminant sources (outside and inside, and part of
the building), and building occupants.
Pollutant Sources
Indoor air pollutants can originate within the building or be
drawn in from outdoors. If pollutant sources are not controlled, indoor air
quality problems can arise even if heating, ventilation and air conditioning
system is properly designed, operated, and maintained. Air contaminants consist
of particles, dust, fibers, bioaerosols, and gases or vapors.
In addition to the number of potential pollutants, another
complicating factor is that indoor air pollutant concentration levels can vary
by time and location within the building, or even a single room. Pollutants can
be emitted from point sources, such as from storerooms, or from area sources,
such as newly painted surfaces. Also, pollutants can vary with time, such as
only when floor stripping is done, or continuously such as mold growing in the
heat, ventilation, and air conditioning system.
There are many sources of indoor air pollution in any home.
These include combustion sources such as oil, gas, kerosene, coal, wood, and
tobacco products; building materials and furnishings as diverse as deteriorated,
asbestos-containing insulation, wet or damp carpet, and cabinetry or furniture
made of certain pressed wood products; products for household cleaning and
maintenance, personal care, or hobbies; central heating and cooling systems and
humidification devices; and outdoor sources such as radon, pesticides, and
outdoor air pollution.
Ventilation
If too little outdoor air enters a home, pollutants can
accumulate to levels that can pose health and comfort problems. Unless they are
built with special mechanical means of ventilation, homes that are designed and
constructed to minimize the amount of outdoor air that can "leak" into
and out of the home may have higher pollutant levels than other homes. However,
because some weather conditions can drastically reduce the amount of outdoor air
that enters a home, pollutants can build up even in homes that are normally
considered "leaky".
Outdoor air enters and leaves a house by: infiltration, natural
ventilation, and mechanical ventilation. In a process known as infiltration,
outdoor air flows into the house through openings, joints, and cracks in walls,
floors, and ceilings, and around windows and doors. In natural ventilation, air
moves through opened windows and doors. Air movement associated with
infiltration and natural ventilation is caused by air temperature differences
between indoors and outdoors and by wind. Finally, there a number of mechanical
ventilation devices, from outdoor-vented fans that intermittently remove air
from a single room, such as bathrooms and kitchen, to air handling systems that
use fans and duct work to continuously remove indoor air and distribute filtered
and conditioned outdoor air to strategic points throughout the house.
Apartments can have the same indoor air problems as
single-family homes because many of the pollution sources, such as the interior
building materials, furnishings, and household products are similar. Indoor air
problems similar to those in offices are caused by such sources as contaminated
ventilation systems, improperly placed outdoor air intakes, or maintenance
activities.
Indoor Air and Your Health
Immediate effects from indoor air pollution may show up after a
single exposure or repeated exposures. These include irritation of the eyes,
nose, and throat, headaches, dizziness, and fatigue. Such immediate effects are
usually short-term and treatable. Sometimes the treatment is simply eliminating
the person's exposure to the source of the pollution, if it can be identified.
Symptoms of some diseases, including asthma, hypersensitivity pneumonitis, and
humidifier fever, may also show up soon after exposure to some indoor air
pollutants.
Indoor air often contains a variety of contaminants at
concentrations that are well below any standards or guidelines for occupational
exposure. It is often difficult to relate complaints of specific pollutant
concentrations, especially since the significant exposures may be to lower levels
of pollutant mixtures. Some individuals may be particularly susceptible to the
effects of indoor air contaminants:
- individuals with allergies or asthma
- individuals who may be sensitive to chemicals
- children exposed to secondhand tobacco smoke are at
higher risk for respiratory illnesses
- children exposed to significant levels of nitrogen
dioxide are at higher risk for respiratory infections
Because of varying sensitivity to airborne chemicals and
irritants, individuals with heightened sensitivities may react to a particular
indoor air quality problem while others display no ill effects. Symptoms that
are limited to only one or a individuals can also occur when only their area
contains the airborne pollutant. In other cases, complaints may be widespread.
In addition to different degrees of reaction, an indoor air pollutant or problem
can trigger different reactions in different people.
Other health effects may show up either years after exposure has
occurred or only after long or repeated periods of exposure. These effects,
which include some respiratory diseases, heart disease, and cancer, can be
severely debilitating or fatal.
Identification of Air Quality Problems
Some health effects can be useful indicators of an indoor air
quality problem, especially if they appear after a person moves to a new
residence, remodels or refurbishes a home, or treats a home with pesticides. If
you think that you have symptoms that may be related to your home environment,
discuss them with your doctor or your local health department to see if they
could be caused by indoor air pollution. You may also want to consult a
board-certified allergist or an occupational medicine specialist for answers to
your questions.
Another way to judge whether your home has or could develop
indoor air problems is to identify potential sources of indoor air pollution.
Although the presence of such sources does not necessarily mean that you have an
indoor air quality problem, being aware of the type and number of potential
sources is an important step toward assessing the air quality in your home.
A third way to decide whether your home may have poor indoor air
quality is to look at your lifestyle and activities. Human activities can be
significant sources of indoor air pollution. Finally, look for signs of problems
with the ventilation in your home. Signs that can indicate you home may not have
enough ventilation include moisture condensation on windows or walls, smelly or
stuffy air, dirty central heating and air conditioning equipment, and areas
where books, shoes, or other items become moldy. To detect odors in your home,
step outside for a few minutes, and then upon reentering your home, note whether
odors are noticeable.
Specific Indoor Pollutants
Radon
The most common source of indoor radon is uranium in the soil or
rock on which homes are built. As uranium naturally breaks down, it releases
radon gas which is a colorless, odorless, radioactive gas. Radon enters the home
through dirt floors, cracks in concrete walls and floors, floor drains, and
sumps. When radon becomes trapped in buildings and concentrations build up
indoors, exposure to radon becomes a concern. Radon can also enter homes through
well water.
Any home may have a radon problem. This means new and old homes,
well-sealed and drafty homes, and homes with or without basements.
The predominant health effect associated with exposure to
elevated levels of radon is lung cancer. Research suggests that swallowing water
with high radon levels may pose risks, too, although these are believed to be
much lower than those from breathing air containing radon.
You can't see radon, but it's not hard to find out if you have a
radon problem in your home. Testing is easy and should only take a little of
your time. There are many kinds of inexpensive, do-it-yourself radon test kits
you can get through the mail and in hardware stores and other retail outlets.
E-P-A recommends that consumers use test kits that are state-certified or have met
the requirements of some national radon proficiency program.
Environmental Tobacco Smoke
Environmental tobacco smoke (E-T-S) is the mixture of smoke that
comes from the burning end of a cigarette, pipe, or cigar, and smoke exhaled by
the smoker. It is a complex mixture of over 4,000 compounds, more than 40 of
which are known to cause cancer in humans or animals and many of which are
strong irritants. E-T-S is often referred to as "secondhand smoke" and
exposure to E-T-S is often called "passive smoking."
A 1992 EPA assessment concluded that exposure to EPS is
responsible for approximately 3,000 lung cancer deaths each year in nonsmoking
adults and impairs the respiratory health of hundreds of thousands of children.
Asthmatic children are especially at risk. EPA estimates that exposure to
secondhand smoke increases the number of episodes and severity of symptoms in
hundreds of thousands of asthmatic children, and may cause thousands of
non-asthmatic children to develop the disease each year.
Reducing Exposure to E-T-S
- Don't smoke at home or permit others to do so. Ask smokers to
smoke outdoors.
- If smoking indoors cannot be avoided, increase ventilation in
the area where smoking takes place.
- Do not smoke if children are present, particularly infants and
toddlers.
Biological Contaminants
Biological contaminants include bacteria, molds, mildew,
viruses, animal dander and cat saliva, house dust mites, cockroaches, and
pollen. There are many sources of these pollutants. Pollens originate from
plants; viruses are transmitted by people and animals; bacteria are carried by
people, animals, and soil and plant debris; and household pets are sources of
saliva and animal dander. The protein in urine from rats and mice is a potent
allergen. When it dries, it can become airborne. Contaminated central air
handling systems can become breeding grounds for mold, mildew, and other sources
of biological contaminants and can then distribute these contaminants through
the home.
By controlling the relative humidity level in a home, the growth
of some sources of biologicals can be minimized. A relative humidity of 30 - 50
percent is generally recommended for homes. Standing water, water-damaged
materials, or wet surfaces also serve as a breeding ground for molds, mildews,
bacteria, and insects. House dust mites, the source of one of the most powerful
biological allergens, grow in damp, warm environments.
Some biological contaminants trigger allergic reactions,
including hypersensitivity pneumonitis, allergic rhinitis, and some types of
asthma. Infectious illnesses, such as influenza, measles, and chicken pox are
transmitted through the air. Molds and mildews release disease-causing toxins.
Symptoms of health problems caused by biological pollutants include sneezing,
watery eyes, coughing, shortness of breath, dizziness, lethargy, fever, and
digestive problems.
Children, elderly people, and people with breathing problems,
allergies, and lung diseases are particularly susceptible to disease-causing
biological agents in the indoor air.
Reducing Exposure to Biological Contaminants
- Install and use exhaust fans that are vented to the outdoors in
kitchens and bathrooms and vent clothes dryers outdoors.
- Ventilate the attic and crawl spaces to prevent moisture
build-up.
- If using cool mist or ultrasonic humidifiers, clean appliances
according to manufacturer's instructions and refill with fresh water daily.
- Thoroughly clean and dry water-damaged carpets and building
materials (within 24 hours if possible) or consider removal and replacement.
- Keep the house clean. House dust mites, pollens, animal dander,
and other allergy-causing agents can be reduced, although not eliminated,
through regular cleaning.
- Clean and disinfect the basement floor drain regularly. Operate
a dehumidifier in basement if needed to keep relative humidity levels between
30-50 percent.
Stoves, Heaters, Fireplaces, and Chimneys
In addition to environmental tobacco smoke, other sources of
combustion products are unvented kerosene and gas space heaters, woodstoves,
fireplaces, and gas stoves. The major pollutants released are carbon monoxide,
nitrogen dioxide, and particles. Unvented kerosene heaters may also generate
acid aerosols.
Combustion gases and particles also come from chimneys and flues
that are improperly installed or maintained and cracked furnace heat exchangers.
Pollutants from fireplaces and woodstoves with no dedicated outdoor air supply
can be "back-drafted" from the chimney into the living room,
particularly in weatherized homes.
Carbon monoxide is a colorless, odorless gas that interferes
with the delivery of oxygen throughout the body. At high concentrations it can
cause unconsciousness and death. Lower concentrations can cause a range of
symptoms from headaches, dizziness, weakness, nausea, confusion, and
disorientation, to fatigue in healthy people and episodes of increased chest
pain in people with heart disease. The symptoms of carbon monoxide poisoning are
sometimes confused with the flu or food poisoning. Fetuses, infants, elderly
people, and people with anemia or with a history of heart or respiratory disease
can be especially sensitive to carbon monoxide exposures.
Nitrogen dioxide is a colorless, odorless gas that irritates the
mucous membranes in the eye, nose, and throat and causes shortness of breath
after exposure to high concentrations. There is evidence that high
concentrations or continued exposure to low levels of nitrogen dioxide increases
the risk of respiratory infection; there is also evidence from animal studies
that repeated exposures to elevated nitrogen dioxide levels may lead, or
contribute, to the development of lung disease such as emphysema. People at
particular risk from exposure to nitrogen dioxide include children and
individuals with asthma and other respiratory diseases.
Particles, released when fuels are incompletely burned, can
lodge in the lungs and irritate or damage lung tissue. A number of pollutants,
including radon and benzo pyrene, both of which can cause cancer, attach to
small particles that are inhaled and then carried deep into the lung.
Reducing Exposure to Combustion Products in Homes
Take special precautions when operating fuel-burning unvented
space heaters. Keep heater properly adjusted. A persistent yellow-tipped flame
is generally an indicator of maladjustment and increased pollutant emissions.
While a space heater is in use, open a door from the room where the heater is
located to the rest of the house and open a window slightly.
Install and use exhaust fans over gas cooking stoves and ranges
and keep the burners properly adjusted.
Keep woodstove emissions to a minimum. Choose properly sized new
stoves that are certified as meeting EPA emission standards. Make certain that
doors in old woodstoves are tight-fitting. Use aged or cured wood only and
follow manufacturers directions for starting, stoking, and putting out the fire
in woodstoves. Never burn pressure treated wood indoors.
Have central air handling systems, including furnaces, flues,
and chimneys, inspected annually and promptly repair cracks or damaged parts.
Household Products
Organic chemicals are widely used as ingredients in household
products. Paints, varnishes, and wax all contain organic solvents, as do many
cleaning, disinfecting, cosmetic, degreasing, and hobby products. Fuels are made
up of organic chemicals. All of these products can release organic compounds
while you are using them, and, to some degree, when they are stored.
The ability of organic chemicals to cause health effects varies
greatly, from those that are highly toxic, to those with no known health effect.
As with other pollutants, the extent and nature of the health effect will depend
on many factors including level of exposure and length of time exposed. Eye and
respiratory irritation, headaches, dizziness, visual disorders, and memory
impairment are among the immediate symptoms that some people have experienced
soon after exposure to some organics. Many organic compounds are known to cause
cancer in animals; some are suspected of causing, or are known to cause, cancer
in humans.
Reducing Exposure to Household Chemicals
Follow label instructions carefully. Potentially hazardous
products often have warnings aimed at reducing exposure of the user.
Throw away partially full containers of old or unneeded chemical
safely. Because gases can leak even from closed containers, this single step
could help lower concentrations of organic chemicals in your home. (Be sure that
materials you decide to keep are stored not only in a well-ventilated area but
are also safely out of reach of children.) Do not simply toss these unwanted
products in the garbage can. Find out if your local government or any
organization in your community sponsors special days for the collection of toxic
household wastes.
Buy only quantities that you will use right away.
Keep exposure to emissions from products containing methylene
chloride to a minimum. Consumer products that contain methylene chloride include
paint strippers, adhesive removers, and aerosol spray paints. Methylene chloride
is known to cause cancer in animals.
Keep exposure to benzene to a minimum. Benzene is a known human
carcinogen. The main indoor sources of this chemical are environmental tobacco
smoke, stored fuels and paint supplies, and automobile emissions in attached
garages.
Keep exposure to perchloroethylene emissions from newly
dry-cleaned materials to a minimum. Perchloroethylene is the chemical most
widely used in dry cleaning and has been shown to cause cancer in animals. Dry
cleaners recapture the perchloroethylene during the dry-cleaning process so that
they can save money by re-using it, and they remove more of the chemical during
the pressing and finishing processes. Some dry cleaners, however, do not remove
as much perchloroethylene as possible all of the time. If dry-cleaned goods have
a strong chemical odor when you pick them up, do not accept them until they have
been properly dried.
Formaldehyde
Formaldehyde is an important chemical used widely by industry to
manufacture building materials and numerous household products. It is also a
by-product of combustion and certain other natural processes. Thus, it may be
present in substantial concentrations both indoors and outdoors.
Sources of formaldehyde in the home include building materials,
smoking, household products, and the use of unvented, fuel-burning appliances,
like gas stoves or kerosene space heaters. Formaldehyde, by itself or in
combination with other chemicals, serves a number of purposes in manufactured
products.
In homes, the most significant sources of formaldehyde are
likely to be pressed wood products made using adhesives that contain
urea-formaldehyde (U-F) resins. Pressed wood products made for indoor use
include: Particle board (used as subflooring and shelving and in cabinetry and
furniture); hardwood plywood paneling; and medium density fiberboard (used for
drawer fronts, cabinets, and furniture tops). Medium density fiberboard contains
a higher resin-to-wood ratio than any other formaldehyde-emitting pressed wood
product.
Formaldehyde, a colorless, pungent-smelling gas, can cause
watery eyes, burning sensations in the eyes and throat, nausea, and difficulty
in breathing in some humans exposed at elevated levels. High concentrations may
trigger asthma attacks in people with asthma. It has been shown to cause cancer
in animals and may cause cancer in humans.
Reducing Exposure to Formaldehyde in Homes
Ask about the formaldehyde content of pressed wood products,
including building materials, cabinetry, and furniture before you purchase them.
Pesticides
Pesticides used in and around the home include products to
control insects (insecticides), termites (termiticides), rodents (rodenticides),
fungi (fungicides), and microbes (disinfectants). They are sold as sprays,
liquids, sticks, powders, crystals, balls, and foggers.
EPA registers pesticides for use and requires manufacturers to
put information on the label about when and how to use the pesticide. It is
important to remember that the "-cide" in pesticides means "to
kill." These products can be dangerous if not used properly.
In addition to the active ingredient, pesticides are also made
up of ingredients that are used to carry the active ingredient. These carrier
agents are called "inerts" in pesticides because they are not toxic to
the targeted pest; nevertheless, some inerts are capable of causing health
problems.
Both the active and inert ingredients in pesticides can be
organic compounds; therefore, both could add to the levels of airborne organics
inside homes.
Reducing Exposure to Pesticides in Homes
- Read the label and follow the directions. It is illegal to use
any pesticide in any manner inconsistent with the directions on its label.
- Ventilate the area well after pesticide use.
- Use non-chemical methods of pest control when possible.
- Dispose of unwanted pesticides safely. Dispose of unused or
partially used pesticide containers by following label directions.
- Keep exposure to moth repellants to a minimum. One pesticide
often found in the home is paradichlorobenzene, a commonly used active
ingredient in moth repellants. This chemical is known to cause cancer in animals
but substantial uncertainty exists as to the effects of long-term exposure to
humans.
Asbestos
Asbestos is a mineral fiber that has been used commonly in a
variety of building construction materials for insulation and as a
fire-retardant. Elevated concentrations of airborne asbestos can occur after
asbestos-containing materials are disturbed by cutting, sanding or other
remodeling activities. Improper attempts to remove these materials can release
asbestos fibers into the air in homes, increasing asbestos levels and
endangering people living in those homes.
The most dangerous asbestos fibers are too small to be visible.
After they are inhaled, they can remain and accumulate in the lungs. Asbestos
can cause lung cancer, mesothelioma (a cancer of the chest and abdominal
linings), and asbestosis (irreversible lung scarring that can be fatal).
Reducing Exposure to Asbestos in Homes
Usually it is best to leave asbestos material that is in good
condition alone. Generally, material in good condition will not release asbestos
fiber and there is no danger unless fibers are released and inhaled into the
lungs.
Do not cut, rip, or sand asbestos-containing materials.
When you need to remove or clean up asbestos, use a
professionally trained contractor.
Lead
Lead has long been recognized as a harmful environmental
pollutant. Humans are exposed to lead through air, drinking water, food,
contaminated soil, deteriorating paint, and dust. Airborne lead enters the body
when an individual breathes or swallows lead particles or dust once it has
settled. Before it was known how harmful lead could be, it was used in paint,
gasoline, water pipes, and many other products.
Old lead-based paint is the most significant source of lead
exposure in the U.S. today. Harmful exposures to lead can be created when
lead-based paint is improperly removed from surfaces by dry scraping, sanding,
or open-flame burning. High concentrations of airborne lead particles in homes
can also result from lead dust from outdoor sources, including contaminated soil
tracked inside, and use of lead in certain indoor activities such as soldering
and stained-glass making.
Lead affects practically all systems within the body. At high
levels it can cause convulsions, coma, and even death. Lower levels of lead can
adversely affect the brain, central nervous system, blood cells, and kidneys.
The effects of lead exposure on fetuses and young children can be severe. They
include delays in physical and mental development, lower IQ levels, shortened
attention spans, and increased behavioral problems.
Ways to Reduce Exposure to Lead
- Keep areas where children play as dust-free and clean as
possible.
- Leave lead-based paint undisturbed if it is in good condition -
do not sand or burn off paint that may contain lead.
- Do not remove lead paint yourself. Hire a person with special
training for correcting lead problems to remove lead-based paint. Occupants,
especially children and pregnant women, should leave the building until all work
is finished and clean-up is done.
- Do not bring lead dust into the home. If you work in
construction, demolition, painting, with batteries, in a radiator repair shop or
lead factory, or your hobby involves lead, you may unknowingly bring lead into
your home on your hands or clothes. You may also be tracking in lead from soil
around your home
- Find out about lead in drinking water. Most well and city water
does not usually contain lead. Water usually picks up lead inside the home from
household plumbing that is made with lead materials. Contact your local health
department or the water supplier to find out how to get the water tested.
References:
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