"Indoor air pollutant levels are 25-62% greater than outside [pollutant] levels," according to
California Air Resources Board. "...levels of about a dozen common organic pollutants [were found] to be 2 to 5 times higher inside homes than outside, regardless of whether the homes were located in rural or highly industrial areas"
EPA - Total Exposure Assessment Methodology (TEAM) study
What? There's more pollution inside our homes than outside? How can that be?
For one, our building codes tend to be reactive and just haven't caught up with this problem.
Let's start with explaining the HOW. To maintain healthy indoor air quality, the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) recommends a ventilation rate of 0.35 air changes per hour for new homes. That means over eight complete air changes of the interior volume of air in your home every day.
However, our codes have given builders a free ride on this requirement for years, assuming that homes will achieve this ventilation standard either via "drafty" construction and the high infiltration of outside air or for newer homes with somewhat tighter construction by the opening and closing of windows. Its no surprise then that during all or part of the year, either category of home (tight or drafty) can experience sub-standard ventilation and increased levels of indoor air pollution.
Where does all this pollution come from? Basically it comes from three primary sources:
- The material's used to build our homes
- By products of combustion given off by our homes heaters, fireplaces, wood stoves, and appliances
- The stuff we bring into our homes
Many of the materials commonly used in construction contain VOC's or volatile organic compounds that can out gas over time and pollute our home's air. These can be found in range of products including:
- Sealants and caulk
- Glues and adhesives
- Paints, primers, and sealers
- Certain kinds of insulation
- Certain kinds of Carpet
- Engineered wood products like particleboard, OSB, or plywood that are bonded together with Urea Formaldehyde (UF) or Phenol Formaldehyde (PF). Many of these products can be found in furniture, kitchen cabinets, and floor systems like cork or artificial wood laminate floor systems.
Many of our homes use gas or propane in forced air furnaces, water heaters, and stoves and ovens. In addition, many homes use wood fireplaces or stoves for supplemental heat. What most of us are unaware of is that combustion gases, including carbon monoxide, and particles can be back-drafted from the chimney or flue into the living space if a combustion appliance is not properly vented or does not receive enough supply air. Back-drafting can be a particular problem in tightly constructed homes.
And then there is the stuff we bring in or let into the home either knowingly or unknowingly. Here are just a few examples:
- Biological contaminants include bacteria, molds, mildew, viruses, animal dander and cat saliva, house dust mites, cockroaches, and pollen.
- Formaldehyde from tobacco smoking, household products, and the use of unvented fuel-burning appliances, like gas stoves or kerosene space heaters.
- Organic chemicals are widely used as ingredients in household products. Paints, varnishes, and wax all contain organic solvents, as do many cleaning, disinfecting, cosmetic, degreasing, and hobby products. Fuels are made up of organic chemicals. All of these products can release organic compounds (VOC's) while you are using them, and, to some degree, even when they are stored.
- Methylene Chloride is included in many paint strippers, adhesive removers, and aerosol spray paints. Methylene chloride is known to cause cancer in animals. Also, methylene chloride is converted to carbon monoxide in the body and can cause symptoms associated with exposure to carbon monoxide.
- Benzene is a known human carcinogen. The main indoor sources of this chemical are environmental tobacco smoke, stored fuels and paint supplies, and automobile emissions in attached garages.
- Perchloroethylene is the chemical most widely used in dry cleaning. In laboratory studies, it has been shown to cause cancer in animals. Recent studies indicate that people breathe low levels of this chemical both in homes where dry-cleaned goods are stored and as they wear dry-cleaned clothing. If dry-cleaned goods have a strong chemical odor when you pick them up, do not accept them until they have been properly dried.
- According to a recent EPA survey, 75 percent of U.S. households used at least one pesticide product indoors during the past year. Products used most often are insecticides and disinfectants. It is important to remember that the "-cide" in pesticides means "to kill."
- Paradichlorobenzene is a commonly used active ingredient in moth repellents. This chemical is known to cause cancer in animals. The EPA requires that products containing paradichlorobenzene bear warnings such as "avoid breathing vapors" to warn users of potential short-term toxic effects. Where possible, paradichlorobenzene, and items to be protected against moths, should be placed in trunks or other containers that can be stored in areas that are separately ventilated from the home, such as attics and detached garages. Paradichlorobenzene is also the key active ingredient in many air fresheners (in fact, some labels for moth repellents recommend that these same products be used as air fresheners or deodorants)!
All of these sources of indoor air pollution can be eliminated or at least mitigated by taking a few simple steps.
- Specify VOC free construction materials
- Provide outside air for combustion appliances, and outside ventilation for gas stoves
- Wire bathroom exhaust fans to humidistat controls so that they actually get used to mitigate a major source of mold and mildew
- Read labels and understand what you bring in the home may be a source of pollution (for non-toxic alternatives see http://www.cleanair.org/CEH/CEHCleaners.html)
- Install an energy efficient whole house ventilator to provide out of sight, out of mind 7/24 fresh air to your home at all times.