Indoor Air Pollution Thomas G. Robins, MD, MPH

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Indoor Air Pollution Thomas G. Robins, MD, MPH
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Why the Emphasis on Indoor Air?

• In recent years, the problem of indoor air
  pollution in residential, office, and public
  buildings has come into sharp focus. Concerns
  about the potential health effects of indoor air
  pollution stem from the following three
  observations
• The levels of some pollutants are higher indoors
  than outdoors, in some cases exceeding the
  national standards set for exposure outdoors.
• Urban populations typically spend more than 90
  of their time indoors the single most important
  indoor location is the home, where individuals
  spend about 70 of their time.
• It is the most susceptible groupsthe young, the
  elderly, and the infirmwho spend the greatest
  amount of time indoors.

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Time Spent in Locations Indoors Outdoors
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Indoor Air Versus Outdoor Ambient Air

• There are several factors that differentiate
  indoor air from outdoor ambient air
• enclosed air has less dilution, which may be
  variable over time
• population affected is usually in proximity to
  the source or sources
• multiple contaminants complicate methods to
  analyze and mitigate the hazards of indoor air
  pollution

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Sources of Indoor Air Contaminants

• Types of sources of indoor pollutants include
• infiltration from the outdoor air
• release from the building and its contents
• generation by human activity
• The indoor concentration of any given air
  pollutant depends on
• the type of source
• The strength of the source (rate of generation)
• rate of removal or accumulation in the enclosure

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Sources of Indoor Air Contaminants

• A variety of construction materials, furnishings,
  and consumer products containing volatile
  chemicals provide sources of indoor contaminants
• Synthetic organic materials are associated with
  emissions from walls, ceilings, carpets,
  draperies, plastics, paints, pesticides, cleaning
  materials, and personal and household products
• Use of cheap fuels in home fireplaces, wood
  burning stoves, and unvented kerosene space
  heaters has increased the indoor concentration of
  volatile organic compounds and such combustion
  products as carbon monoxide, sulfur dioxide, and
  nitrogen dioxide

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Hazards of Energy Efficient Buildings

• The worldwide energy crisis in 1973-1974
  contributed to the problem of indoor air
  pollution through efforts made to conserve fuel
  in commercial and residential buildings
• As older buildings became better insulated and
  newer buildings were built with a thermal
  envelope, less fresh air was allowed to
  infiltrate into the structures.
• The natural ventilation provided by opening
  windows was replaced by mechanical ventilation in
  most new office buildings to further conserve
  energy, ventilation systems were often operated
  conservatively
• homes were caulked, weatherstripped, and sealed
• The old-fashioned "leaky" home or office building
  with open windows, having a complete exchange of
  air every few hours, was replaced by
  energy-efficient buildings and homes having
  greatly reduced ventilation rates

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Fresh Air Exchange Rates
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Lack of Regulation

• In contrast with situation for ambient (outdoor)
  air quality standards, to date, no national
  government strategy exists to provide a
  coordinated approach to ensure adequate indoor
  air quality
• In part this reflects the inherent differences in
  the problems of ambient versus indoor air
  pollution
• all members of a community are provided with the
  same ambient air
• in indoor environments, the situation varies
  considerably, especially in private residences,
  where the costs and benefits of both pollution
  control and pollution prevention are internalized
  within individual households

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Lack of Regulation

• There is a lack of general indoor air quality
  standards in the workplace and in the service
  sector
• manufacturing sector is governed by occupational
  regulations, such as source control, ventilation
  requirements, and personal protective equipment
• nonmanufacturing office environment is not
  governed by any standards, as occupational
  standards are neither applicable, relevant, nor
  appropriate
• no standards in place covering exposure to the
  general public in the service sector, such as
  theaters, hotels, transportation facilities,
  recreational facilities, businesses, hospitals,
  or schools
• only exceptions are a few product-specific
  prohibitions such as urea foam formaldehyde and
  cigarette smoke

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Types and Sources of Indoor Air Pollutants

• Indoor air pollutants can be categorized by type
  of source, such as combustion, and by pollutant
  group, such as volatile organic compounds (VOCs)
  and fibers
• Sources can be further characterized by
  pollutants emitted, by locations, and by rate and
  pattern of emissions
• The following discussion of indoor air pollutant
  sources and effects is based on the following
  classification (1) combustion products (2)
  volatile organic compounds (VOCs) and
  formaldehyde (3) microbiologic agents (4)
  environmental tobacco smoke (ETS) and (5) radon

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Common Indoor Air Pollution Sources
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Combustion Sources

• The principal combustion sources indoors include
  tobacco smoking, which generates environmental
  tobacco smoke (ETS) unvented combustion
  appliances and wood stoves and fireplaces
• combustion sources emit inorganic gases (NO, NO2,
  CO, CO2) and particulates
• depending on fuel type and pyrolysis conditions,
  combustion sources can also emit hydrocarbon
  gases, vapors, and organic particles
• most liquid and solid fuels contain impurities or
  additives that may result in emissions of metals,
  mercaptans, sulfur oxides, or particles as the
  fuels burn
• gas appliances may emit very small particles, in
  the sub-micron range, as may burning tobacco
  products

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Combustion Sources

• Unvented gas combustion is a ubiquitous source of
  nitrogen dioxide and carbon monoxide in
  residences
• almost half the homes in the United States have
  gas stoves
• many studies indicate that gas ranges can raise
  indoor nitrogen dioxide concentrations above
  ambient levels
• gas ranges emit carbon monoxide at about 10 times
  the rate of nitrogen dioxide, but under typical
  conditions, concentrations do not exceed 10 ppm
• about 11 of the US population potentially are
  exposed to gas or kerosene space heater emissions
• emissions include particles, carbon monoxide, and
  nitrogen dioxide, plus sulfur dioxide if
  sulfur-containing fuel is burned
• in one survey of homes in Connecticut, the sulfur
  dioxide levels were less than 2 µg/m3 inside
  homes without kerosene space heaters, but 60 to
  150 µg/m3 in homes where such heaters were
  operated

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Environmental Tobacco Smoke (ETS)

• The burning of tobacco products is a ubiquitous
  source of a large number of indoor contaminants
• tobacco burning produces a complex mixture of
  gases, vapors, and particulate matter more than
  4,500 compounds have been identified, about 50
  being known or suspected carcinogens
• the number of smokers and the pattern of smoking
  determine the source strength for generation of
  ETS
• the concentrations of ETS components to which
  nonsmokers are exposed depend further on the
  degree of dilution of the smoke
• in smoky bars, waiting areas, restaurants,
  automobiles, airplanes, or even in the home,
  short-term concentrations of ETS can be high
  concentrations of particles of respirable size in
  rooms contaminated by ETS can range from 100 to
  more than 1,000 µg/m3

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Comparison of PM10 and PM2.5 Levels (ug/m3) in
Homes with Versus without Cigarette Smokers
Detroit
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Volatile Organic Compounds

• Modern furnishings, construction materials, and
  consumer products contaminate indoor air with
  numerous volatile organic compounds (VOCs)
• sources include home-care and building
  maintenance materials such as disinfectants, room
  deodorizers, carpet shampoos, cleaning solutions,
  furniture polish, and floor waxes, moth crystals,
  fabric care products, and cosmetics
• hobbies that call for the use of volatile
  hydrocarbons may at times increase exposures far
  beyond industrial guidelines
• Studies of VOCs found indoors reveal a vast array
  of aliphatic, halogenated, and aromatic
  hydrocarbons, alcohols, ketones, and aldehydes
  in a recent Environmental Protection Agency (EPA)
  study of air quality in 10 public access
  buildings, more than 500 VOCs were identified.
• Many VOCs have been found to have levels higher
  indoors than outdoors