1 Indoor Air Pollution Thomas G. Robins, MD, MPH

2 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: 1.The levels of some pollutants are higher indoors than outdoors, in some cases exceeding the national standards set for exposure outdoors. 2.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. 3.It is the most susceptible groups—the young, the elderly, and the infirm—who spend the greatest amount of time indoors.

3 Time Spent in Locations: Indoors & Outdoors

4 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

5 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

6 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

7 Hazards of Energy Efficient Buildings  The worldwide energy crisis in 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

8 Fresh Air Exchange Rates

9 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

10 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

11 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

12 Common Indoor Air Pollution Sources

13 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

14 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/m 3 inside homes without kerosene space heaters, but 60 to 150 µg/m 3 in homes where such heaters were operated

15 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/m 3

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

17 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