Indoor Air
Pollution
Ch 17
Indoor air pollution
• Indoor air contains higher concentrations of pollutants
than outdoor air (up to 70x)
– Synthetic materials not comprehensively tested
– To reduce heat loss & improve energy efficiency:
• ventilation systems are sealed off & recirculate air
• windows do not open
• This traps pollutants inside.
• Indoor air pollution usually is a greater threat to human
health than outdoor air pollution.
– Avg. U.S. citizen spends 90% of time indoors
– 6,000 people die per day from indoor air pollution
• Pollution levels inside cars in traffic clogged urban
areas can be up to 18 times higher.
Indoor Air Pollution--Developing World
• From burning wood, charcoal, dung, crop waste
– With little to no ventilation
– Soot and carbon monoxide
– Causes pneumonia, bronchitis, allergies, cataracts,
asthma, heart disease, cancer & death
• ~1.6 million deaths/year
Indoor Air Pollution--Developed World
• According to the EPA, the 4 most dangerous
indoor air pollutants in developed countries are:
– Tobacco smoke
– Formaldehyde
– Radioactive radon-222 gas
– Very small fine & ultrafine particles
• Other Important
Indoor Air pollutants
– Nitrogen dioxide
– Carbon monoxide
– Volatile Organic
Compounds (VOCs)
– House dust mites (&
other allergens… from
pets)
– Chlorinated organic
compounds (ex.
pesticides)
– Asbestos & manmade mineral fibers
• Sources
– Building materials
– Furnishings & fabrics
– Glues
– Cleaning products
– Combustion
appliances (cooking &
heating)
– Open fires
– Smoking
– Living organisms
– Outdoor air
Tobacco Smoke
• The most dangerous indoor pollutants in
the developed world
– Secondhand smoke from cigarettes is
especially dangerous
• Containing over 4000 dangerous chemicals
• Causes eye, nose, and throat irritation
• Smoking has declined in developed nations
Volatile Organic Compounds (VOCs)
• The most diverse group of indoor air pollutants
– Released by everything from plastics and oils to
perfumes and paints
• Ex. formaldehyde, which leaks from pressed wood and
insulation, irritates mucous membranes and induces skin
allergies
• Ex. pesticides, which are found indoors more often than
outdoors due to seepage
• Most VOCs are released in very small amounts
– Unclear health effects due to low concentrations
Radon-222
• colorless, tasteless, odorless, radioactive gas from
decay of U-238 found in some soils & rocks
• can seep into some houses
– Most homes are now radon resistant
• 55% of our exposure to radiation comes from radon
– May harm lungs from long term exposure.
• increases the risk of lung cancer
– Chance increase more if a smoker (synergistic effect)
– causes 20,000 deaths a year in the U.S.
• Reducing the risk
– Sealing cracks in floors and walls
– Simple systems using pipes and fans
Sources & paths of entry for indoor radon-222 gas
Radon risk across the U.S.
Living organisms can pollute indoors
• Dust mites
– feed on human skin & dust
• live in materials such as bedding & furniture fabrics
– can cause asthma attacks & allergic reactions
• Fungi, mold, mildew, airborne bacteria
– cause severe allergies, asthma,
& other respiratory ailments
• Animal dander
– worsen asthma
Major Indoor Pollutants
Pollutant
Source
Health Effects
1, 1, 1Trichloroethane
Aerosol sprays
Dizziness, breathing
irregularities
Asbestos
Pipe insulation,
ceilings, floor
tiles, oven mitts
Lung Cancer and
asbestosis
Benzo-a-pyrene Tobacco smoke,
woodstoves
Lung Cancer
Carbon
Monoxide
Headache, heartbeat
irregularities, death,
CO has 250x affinity
for hemoglobin than O2
Faulty furnaces,
cigarette smoke
http://www.metricmind.com/ac_honda/main.htm
Chloroform
Pulp and paper mills, Cancer
water and
wastewater plants
Formaldehyde
Paneling, particle
board, furniture,
carpeting, adhesives
Nausea, dizziness,
irritation of throat,
eyes, and lungs
Methylene
chloride
Paint strippers and
thinner – persistent
Nerve disorders,
diabetes
Nitrogen oxides
Furnaces, stoves,
fireplaces and vents
ParaAir fresheners,
dichlorobenzene mothballs
http://www.metricmind.com/ac_honda/main.htm
Headaches, irritated
lungs
Cancer
Radon – 222
Soil and rock near
house foundation,
concrete
Carpets, plastics,
Lung cancer
Tetrachlorethylene
Dry-cleaning fluid
Nerve disorders,
damage to liver and
kidneys, cancer
Tobacco
Smoke
Cigarettes and other
smoking sources
Lung cancer and
heart disease
Styrene
Organic
Dust mites, fungal and
Material (Living algal spores, dust
Organisms)
(human skin), animal
dander, hair, carpet
fibers, fur
http://www.metricmind.com/ac_honda/main.htm
Kidney & liver
damage
Allergies, coughs,
sneezing, eye
irritation, sore
throats, difficulty
breathing
Sick Building Syndrome
• A sickness produced by indoor pollution w/
general & nonspecific symptoms
– Ex. dizziness, headaches, coughing, sneezing,
nausea, burning eyes, chronic fatigue, irritability,
eye/nose/throat irritation, dry skin, nasal congestion,
difficulty breathing, nose bleeds, flu-like symptoms
• persistent set of symptoms in >20% population
• complaints/Symptoms relieved after exiting building
• causes(s) not known or recognizable
• New buildings are more commonly “sick” than
old ones because of reduced air exchange.
– Can be solved with low-toxicity building materials &
good ventilation
Building Related Illness
• Also due to exposure to indoor air pollutants
• Recognizable Causes
• Clinically Recognized Disease
–Examples
•
•
•
•
•
•
•
Pontiac Fever – Legionella spp.
Legionnaire's Disease
Hypersensitivity Pneumonitis
Humidifier Fever
Asthma
Allergy
Respiratory Disease
– Chronic Obstructive Pulmonary Disease
Reducing Indoor Air Pollution
•Little effort has been devoted to reducing indoor
air pollution even though it is more harmful to
human health than outdoor air pollution
•Environmental & health scientists call for us to
focus on preventing air pollution (especially
indoor) in developing countries.
Solutions
Indoor Air Pollution
Prevention
Cover ceiling tiles & lining of AC
ducts to prevent release of mineral
fibers
Ban smoking or limit it to well
ventilated areas
Set stricter formaldehyde
emissions standards for carpet,
furniture, and building materials
Prevent radon infiltration
Use office machines in well
ventilated areas
Use less polluting substitutes for
harmful cleaning agents, paints,
and other products
Cleanup or
Dilution
Use adjustable fresh air
vents for work spaces
Increase intake of outside air
Change air more frequently
Circulate a building’s air
through rooftop green houses
Use exhaust hoods for stoves
and appliances burning
natural gas
Install efficient chimneys for
wood-burning stoves
Fig. 19-20, p. 461
We can reduce indoor air pollution
• In developed countries:
– Use low-toxicity material
– Monitor air quality
– Keep rooms clean
– Limit exposure to chemicals
– Allow for better mixing of indoor & outdoor air
• In developing countries:
– Dry wood before burning
– Cook outside
– Use less-polluting fuels (natural gas)
We can reduce indoor air pollution
• The amount of air available (for mixing of indoor
& outdoor air) to dilute pollutants is an important
indicator of the likely contaminant concentration
– Indoor air can mix with outside air by 3 mechanisms
• infiltration
• natural ventilation
• forced ventilation
Mixing of Indoor & Outdoor Air
• Infiltration
– natural air exchange that occurs between a
building & its environment when doors &
windows are closed
• leakage through holes or openings in the building
– Influenced by:
» pressure differentials inside & outside the building
» temperature differentials inside & outside of bldg
~in winter, warm air inside wants to rise  exits
through cracks in ceiling & draws in outside air
» how fast wind is blowing
Mixing of Indoor & Outdoor Air
• Natural ventilation
– air exchange that occurs when windows or
doors are opened to increase air circulation
• Forced ventilation
– mechanical air handling systems used to
induce air exchange using fans & blowers
What Can You Do?
Indoor Air Pollution
• Test for radon and formaldehyde inside your home and take
corrective measures as needed.
• Do not buy furniture and other products containing formaldehyde.
• Remove your shoes before entering your house to reduce inputs
of dust, lead, and pesticides.
• Test your house or workplace for asbestos fiber levels and for
any crumbling asbestos materials if it was built before 1980.
• Don't live in a pre-1980 house without having its indoor air
tested for asbestos and lead.
• Do not store gasoline, solvents, or other volatile hazardous
chemicals inside a home or attached garage.
• If you smoke, do it outside or in a closed room vented to the outside.
• Make sure that wood-burning stoves, fireplaces, and keroseneand gas-burning heaters are properly installed, vented, and
maintained.
• Install carbon monoxide detectors in all sleeping areas.
Fig. 19-21, p. 461