Indoor air quality is often much worse than outdoor air. The Environmental Protection
Agency (EPA) estimates that indoor air pollutant levels could be two to five
times higher than pollution levels outdoors. Considering that most Americans spend
an estimated 90 percent of their time inside, indoor air quality has a great impact
on our everyday lives. In addition, indoor air pollutants are one of the foremost
triggers of allergies and asthma.
Why Winter Makes Indoor Air Quality Worse
Homes are built to be energy- (and therefore cost-) efficient by holding heat in
during the winter time and keeping heat out during the summer. Winter weather
prompts homeowners to tightly seal any cracks in insulation that could allow cold
drafts into the home. This, in turn, also seals off the home from any fresh air and
raises the concentrations of both allergens and pollutants in the home.
Pollutant Sources in the Home
Pollutants in the home come from a variety of sources. The first step in making
sure that your family has the cleanest possible air is knowing where the pollutants
come from. Following is a list of common sources of indoor air pollution:
- Combustion sources such as oil, gas, kerosene, coal, wood. Any
household appliances that use any of these fuels can lead to indoor air pollution.
Such appliances include wood-burning stoves, fireplaces, water heaters, dryers, and
stoves. It's crucial to make sure that these appliances are well-maintained and
properly adjusted so that they don't release dangerous levels of pollution into the
home. Heating systems themselves are one type of combustion source. (Another
reason that indoor air pollution can be worse in winter.)
- Building materials and furnishings, ranging from insulation, to
carpeting, to cabinetry or furniture made of pressed wood. The kinds of pollutants
that these items in the home may harbor or release are varied, including VOCs, mold, and dust mites.
- Household cleaning and maintenance products, personal care products; air
fresheners, for example, release pollutants continuously.
- Hobby or home improvement activities including painting, varnishing,
sanding, welding, using adhesives, and more. Basically, if it produces fumes, it's
probably not good for you to be breathing it or filling your home with it,
especially when your home is sealed tight against winter cold - and the healthy
circulation of fresh air.
- Outdoor sources like radon, pollen, lead, and more. Radon occurs in the
soil as the natural decay of uranium occurs and can leak into the home. Pesticides,
pollen, lead, and other outdoor pollutants may be tracked by people or pets into the
home, where their levels become concentrated.
- Pets - animal dander and
other particles from pets with fur or feathers are a major aggravation of allergies
and asthma to sensitive individuals. As people stay indoors more, so do pets that go
outside during less inclement weather.
Common Household Pollutants
The next step in making sure to protect your family from household pollution is
knowing what the pollutants are so that you can know how to deal with them. Here is
a list of the most allergens and pollutants that affect indoor air quality.
- Mold and mildew - when windows are closed tight against cold air,
steam from the bathroom and the kitchen, as well as other kinds of moisture can
build up in the home. Mold and
mildew reproduce through spores, which become airborne and easily inhaled.
- Pet dander - because it is very light and very small, pet dander is one
of the most irritating and difficult-to-remove allergens. Indoor concentrations are
especially high during winter when pets, as well as people, spend more time
- Dust mites - because more time is spent indoors during the winter, the
concentration of dust mite food - shed human skin cells - increases, as do dust mite
populations. Dust mites
are present wherever there is dust, including household surfaces, upholstered
furniture, draperies, carpets, and especially bedding.
- Pollen - though less of a problem in the winter, there are
winter-blooming plants whose pollen can be tracked
indoors. In addition, fluctuations in weather may cause plants to blossom earlier
- Biological pollutants - in addition to molds, pollen, dust mites, and
animal dander, other germs, viruses, and bacteria are present in the home.
- Environmental tobacco smoke (ETS), or secondhand smoke, is also a major
indoor air pollutant.
- Formaldehyde is one of the main volatile organic compounds
(VOCs), and is often found in adhesives or other bonding agents present in
carpets, upholstery, particle board, and plywood paneling.
- Various VOCs -in addition to formaldehyde, many other volatile organic
compounds (VOCs) are present in cleaning products, air fresheners, beauty products,
laundry products, and more. Off-gassing of VOCs from household items (like
dry-cleaned drapes or other clothing, or particle board furniture or cabinets) is
also a source of VOCs.
- Asbestos comes from microscopic mineral fibers that are flexible and
durable and won't burn. They are extremely light and consequently can remain
airborne and therefore easily inhaled. Many home components contain asbestos,
including roofing and flooring materials, insulation, and heating equipment, among
others. These are only a problem if the asbestos is disturbed and becomes airborne,
or when it disintegrates with age.
- Carbon monoxide and nitrogen dioxide are the worst air pollution
components given off by the combustion sources discussed above. Carbon monoxide is
odorless and colorless, and it interferes with the distribution of oxygen in the
body. Symptoms of carbon monoxide poisoning include poor coordination, headache,
nausea, confusion, nausea, dizziness, and fatigue; the gas can also worsen
cardiovascular conditions. High levels can cause death. Nitrogen dioxide is
similarly colorless and odorless, and it irritates the mucous membranes, including
those in the eyes, nose, and throat. Additional effects include shortness of breath,
damaged respiratory tissue, and chronic bronchitis.
- Lead - lead can be present in the home as paint or dust. Older homes
routinely used lead paint, and cracked or chipping paint leads to both paint chips
and paint dust, both dangerous pollutants, especially if there are young children in
Effects of Poor Indoor Air Quality
Immediate effects of poor indoor air quality can show up after just a single
exposure and include headaches, dizziness, fatigue, and itchy eyes, nose, and
throat. Asthma and chemical sensitivities can also be aggravated by exposure to
indoor pollution. Chronic sensitivity may also build up after repeated
Although it remains uncertain what levels or periods of exposure are necessary to
bring on serious health effects from indoor air pollution, long-term effects of
indoor air pollution include respiratory disease, heart disease, and cancer.
Improving Indoor Air Quality
The EPA recommends three basic strategies to improve indoor air quality: source
control, ventilation improvements, and air cleaners or purifiers.
Improving indoor air quality through source control involves removing the sources
of pollution. Gas emissions, like those from a poorly maintained stove, for
instance, can be adjusted in order to lower their emissions; asbestos can be sealed
or enclosed. Often, source control is a more cost-conscious way to remedy poor air
quality than ventilation because increased ventilation can significantly increase
However, increased ventilation is an easy and effective way to control poor
indoor air by bringing fresh indoor air into circulation. Especially because most
heating systems do not bring fresh air into the home, opening windows and doors when
weather permits provides great benefit.
You can easily check to see if your home might have ventilation problems.
Condensation on walls or windows, stuffy air, moldy areas, or dirty heating or
cooling equipment are all indicators. Odors (which are most notable upon entering
the home from outdoors) are also an indication of poor ventilation.
When performing many home improvement or hobbies, it's especially important to be
aware of the need for proper ventilation. Without ventilation, pollutants such those
emitted during painting, welding, sanding, or even cooking, can add toxic elements
into your home environment.
EPA's final recommendation in their three-pronged approach to improving
indoor air quality involves using an air purifier. When investing in an air
purifier, it's important to understand all the factors involved. For instance, most
air purifiers capture particulate matter but do not remove gas and other chemicals.
Activated carbon filters are needed in order to remove gas and chemicals.
Additionally, it's important to get an air purifier that has the
proper capacity to fill the job. This depends on factors such as pollutant levels,
sensitivity, and room size.
Here are a few tips for maintaining healthy indoor air, especially during the
- Clean regularly - dusting safely with proper cleaning equipment like
dust cloths and
masks, and regular and frequent
vacuuming go a long way
in reducing airborne pollutants like mold, pollen, pet dander, and dust mites.
- Replace furnace filters frequently - with your heating unit running
during the cold winter months, your furnace filter is working
hard to keep your air clean. Ensure that airflow is not impeded - or worse, that
contaminants aren't being reissued into the air you breathe - by checking your
filters regularly and replacing them as needed.
- Test for radon - the Surgeon General warns that radon causes lung cancer
and recommends testing your home. The EPA's Web site has more
information about testing for radon.
- Consider purchasing a carbon monoxide detection device to alert you to
the presence of this colorless, odorless, lethal gas.
- Use non-toxic cleaning products.
Especially when cleaning in the winter when ventilation is typically less,
chemicals' fumes stay inside the home and on surfaces cleaned with them.
- Keep bedding clean. Wash bedding frequently (once a week) in hot water or
with a de-mite laundry additive.
Cover mattresses and pillows with dust mite encasings.
- Look for low- or no-VOC products when doing any hobbies or
home-improvement projects. If possible, wait for spring, when you can open the
windows for adequate ventilation.
- Dry cleaning products emit chemicals like formaldehyde from dry-cleaned fabrics.
Consider dry cleaning alternatives or air out dry-cleaned items in the garage
or patio before bringing them indoors or into your closet.
- Air out and clean mold-prone areas of the home. Make sure bathrooms,
kitchens, and basements, which tend to collect extra moisture and may not receive
adequate ventilation, are routinely aired out, and cleaned of any mold.
- Open windows and doors when you can. If you're concerned that outdoor
pollutants may enter your home, use a window filter.
- HEPA air purifiers do an excellent job of filtering particulate contaminants
from the air. Carbon filters are necessary in order to remove gases, odors, and
chemicals from the air. Models like the Austin Air HealthMate and
IQAir HealthPro Plus air purifiers are great
examples of units that feature both types of filtration.
- Many plants are known as
nature's air purifiers because
of their ability to absorb toxins from the air. Just be aware that mold often grows around plants, especially if they're watered often.
Knowing the sources of indoor pollutants, as well as what they are and how to
combat them, is the first step in keeping the air in your home clean. Due to the
combined factors of more time spent indoors and decreased ventilation, winter is a
time to be particularly vigilant about maintaining healthy indoor air quality. But
making sure that your home is as free as possible from indoor pollutants is
important all year round.
Originally published in the
February 2008 issue of
Allergy Consumer Report.
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