Indoor Air Quality
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Indoor Air Quality January 1999 Primer Environmental Health Programs Office of Toxic Substances he purpose of this document is to give As a result of the energy crisis of the early T the reader a brief overview of possible seventies, the cost of energy increased by a residential indoor air quality (IAQ) problems factor of almost ten. During that time, the and provide a basic understanding of problem U.S. Government, private industry, and the identification, control methodologies, some commercial sector all developed ways to specific pollutants, their sources, potential better design new buildings and homes, as health effects, and indoor air monitoring well as retrofit existing buildings and homes methodology. with better insulation and energy conservation devices. This resulted in energy savings by IAQ in our homes, schools, and office decreasing ventilation, thus reducing or buildings has received increasing attention in eliminating the amount of outside air that the past few years from scientists, engineers, needs to be heated or conditioned. However, regulatory groups, and the public. There is the efforts to conserve energy, along with the growing concern and mounting evidence that increasing use of synthetic building materials, our indoor environment may be responsible contributes to an indoor air environment that for persistent, irritating health effects. is a possible cause of increasing adverse Traditionally, it has been assumed that people health effects. In certain circumstances, were protected from air pollution when reduced ventilation alone has resulted in indoors, particularly near industrialized areas. adverse health effects to occupants due to However, recent research has shown, that this increased levels of indoor air pollutants. is not necessarily true. Current research indicates that our indoor air may be more Several indoor air pollutants have received polluted than outside air, even in special public health attention. These include industrialized areas. This increased concern is formaldehyde, asbestos, radon, and tobacco accompanied by the realization that most smoke. Other indoor pollutants that can be people spend 80-90 percent of their time associated with health or irritating effects are indoors and that the young, aged, and health- carbon monoxide, nitrogen oxides, household compromised may be at greater risk. and personal care products, microorganisms, and allergens. during cold winter days when air infiltration is Although standards for work place exposure high and humidity is low. to many toxic compounds have been established in the United States and other The first appearance of symptoms are countries, almost no regulatory standards or commonly associated with: guidelines have been established in the U.S. for residential indoor air. Several other Q Moving into a recently purchased home or countries have established residential IAQ new mobile home. standards for several pollutants, particularly Q Recent remodeling. formaldehyde. Our ability to accurately Q Homes with urea-formaldehyde foam assess the health risks associated with insulation. exposure to these compounds is limited. Q Implementing energy conservation There is insufficient data on the number of measures that significantly reduce heat people exposed, the susceptibility of loss and ventilation rates. individuals, the patterns and degree of Q Purchase of new furnishings. exposure, and the actual health effects from Q Installation of new kitchen or bathroom exposure to low levels and mixtures of cabinets. pollutants typically found in the residential Q Installation of new carpeting or cleaning environment. of carpeting. Q Use of some recreational vehicles. Problem Identification IAQ related illnesses are usually characterized Office building workers have often been by one or more of the following symptoms: victims of indoor air pollution commonly irritation of the eyes, nose and/or throat; referred to as "Sick Building Syndrome” headache; cough; runny nose; lethargy; and (SBS). SBS events are characterized by a difficulty sleeping. Other less common significant number of building occupants with symptoms reported include dizziness, nausea, specific health complaints. Investigations diarrhea, dry skin, and rash. Symptoms usually reveal several indoor pollutants, more appear unrelated to any identifiable common often than not in extremely low illness. However, because these symptoms concentrations. Usually no one indoor air are common to many different ailments, a pollutant can be identified as the likely cause physician, allergist, or dermatologist should of health complaints. It is often thought that be consulted to determine any physical the many pollutants in combination are condition that may account for the symptoms responsible for reported health effects. experienced. The symptoms are often most Investigations have indicated that SBS occurs severe during the winter months. Symptoms most often in buildings where ventilation rates may affect only selected individuals in the are maintained near minimum requirements. home and usually are most severe in family Often improved ventilation alleviates the members who spend the greatest amount of problem. Nonresidential IAQ is discussed in time at home, such as mothers and their young a separate fact sheet distributed by the children. Symptoms become less severe when Washington State Department of Labor and away from the indoor environment in question Industries. Copies can be obtained by calling and often disappear with extended absences (360) 902-5436. (e.g., during vacations). Symptoms will often become less severe or disappear when the home is ventilated by opening windows or 2 Control of Indoor Air energy efficient and non-energy efficient homes, results in a 43 percent increase in Pollutants indoor air contaminants. This increase is also Three general methods are used for dependent upon the contaminant, its source controlling indoor air pollutants: source strength, and rate of emission. removal or modification, ventilation, and air cleaning. For homes with very low ACH and those with certain pollutant producing sources, an active Source Removal/Source Modification mechanical ventilation system may be Source removal and source modification (or necessary. This may be either a system for the substitution) are generally considered before entire home or to control a specific pollutant other alternatives because the pollutant produced from an activity or appliance. For sources and their rates of emission are the instance, it is recommended that gas ranges most important factors in determining the have a mechanical exhaust hood located overall IAQ. Source removal is the most directly above the cooking surface to exhaust desirable since it permanently removes the combustion by-products directly to the pollutant source. In practice, source outside. Because of the additional heating or modification and substitution are the more cooling costs associated with whole house common forms of control. Source ventilation systems, such ventilation is not modification involves measures to reduce recommended without heat recovery. An pollutant emissions, such as restricting efficient, economical mechanical ventilation smoking. Substitution usually involves system for the entire home is an air-to-air heat replacement with a less toxic alternative, such exchanger. These systems, when properly as water based prodiucts versus solvent based. sized and installed, can provide an average of 60-85 percent heat recovery from exhaust air Dilution Ventilation and substantially reduce the energy penalty Ventilation can be used to reduce pollutant associated with forced ventilation. In general, concentrations to levels below which no the higher the forced ventilation rate the adverse health effects are experienced. By greater the reduction in pollutants. increasing the ventilation rate in a building, pollutants are rapidly dissipated by providing While ventilation is frequently helpful in less contaminated air from the outside to mix reducing indoor air contaminant with and dilute higher indoor contaminant concentrations, it is more efficient to reduce or levels. This is generally accomplished eliminate pollutants at the source. through non-mechanical means such as infiltration or by opening windows and doors. Air Cleaning Air cleaners operate by mechanical filtration, In older homes and new homes that are not absorption, adsorption, or electrostatic well sealed, the air exchange rate is usually precipitation of pollutants. Extended surface between 0.8 and 1.5 air changes per hour pleated filters serve the most effectively and (ACH). Newer, well-constructed houses and will be the most useful over the widest range older, weatherized houses generally have of pollutant types. These filters are available between .5 and 1.0 ACH. Apartments often as stand-alone units, as add-ons, or as in-lines have even lower ACH. One researcher for most home systems. Filter size and reports that each 30 percent reduction in the efficiency vary. Contact your home system ventilation rate, as can be expected between contractor for specific applications. 3 tissue changes, immune system dysfunction Negative ion generators can be effective air and asthma severity and attack rates the cleaners. Negative ion generators emit Department of Health recommends against the negative charged ions which attach to airborne use of ozone generating devices in an particles, which then attach themselves to occupied space. room surfaces removing them from the