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Indoor Air Quality


Most people spend about 90 percent of their time indoors and are unaware that air pollution levels inside buildings may be higher than outdoor pollution levels; U.S. Environmental Protection Agency (EPA), studies of human exposure to air pollutants indicate that indoor levels of pollutants may be 2 to 5 times—and occasionally more than 100 times—higher than outdoor levels.

What causes indoor air pollution?

Many people are aware that smoking, fuel-burning appliances, radon and nearby power plants, industrial and manufacturing plants, together with automobile and truck emissions, may be significant sources of air pollution found indoors. However, most are unaware that home building materials, such as new flooring, upholstery or carpet and even new cabinetry or furniture, are also primary sources of air pollution in the home.

Equally important, the products we choose for household cleaning and maintenance, personal care, candles and our hobbies can be significant sources of air pollution. Inadequate ventilation and humidity can increase the pollution levels in our home.

Some surprising facts:

    1. Scented candles can be toxic: Most candles are made of paraffin wax, which creates highly toxic carcinogenic benzene and toluene when burned. Solution: Choose beeswax candles, and if you want to freshen your home, open the windows, bake cookies or boil a bit of cinnamon water.
    2. Your shower curtain could harm your health: Polyvinylchloride (PVC) shower curtains contain many harmful chemicals, including volatile organic compounds (VOCs), phthalates and organotins. PVC that is not off-gassed may contribute to respiratory irritation, damage to the central nervous system, liver and kidney damage, nausea, headaches and loss of coordination. Solution: Choose a Low-Emitting shower curtain such as curtains that are verified to be phthalate-free or laboratory tested and certified to be Low-emitting of VOCs and SVOCs.
    3. Renovating? Your new cabinets and floors could emit toxic chemicals. Pressed wood products can emit formaldehyde into your home and some products are worse than others. Solution: Choose real wood or formaldehyde-free plywood. Exterior-grade plywood has the least amount of formaldehyde. Look for formaldehyde-free resins.
    4. Using pesticides or cleaning agents? These chemicals can deposit particles on surfaces that can become gasses depending on temperature and other conditions. Our bodies absorb them through inhalation and through skin contact.
How do building materials increase poor indoor air quality?
Since about the 1980s, buildings have been constructed as tightly sealed structures, to conserve energy. At home, we often shut windows year round, to keep our houses cool in summertime and warm in winter. In addition, we work in buildings with windows that do not open. This traps air pollution inside.

Certain materials including paints, varnishes, lacquers and cleaning and disinfecting compounds emit volatile chemicals into the air. The glues used in engineered wood, carpet backing and to install flooring all emit formaldehyde. Because pollutants cannot escape tightly sealed buildings with closed windows, they build up in indoor air and circulate through the heating and cooling systems, causing a variety of acute and sometimes chronic health effects.

Poor indoor air quality can aggravate the following conditions:

  • Asthma
  • Allergic reactions
  • Bronchitis
  • Ear and upper respiratory infections in children

Making Your Home “Green”

If you are building a new home or remodeling your existing home, consider using nontoxic, durable, efficient products such as those listed below.

  • Structural materials, such as cork or bamboo flooring and engineered stone countertops rather than vinyl or laminate wood flooring
  • Insulate walls with recycled blue jean (cotton) insulation and finish with wall board made from waste wheat straw fiber rather than spray foam.
  • Design options include the use of natural lighting and ventilation.
  • Finishes and fillers that are non-toxic, such as low- or no-VOC paints, or that do not require toxic chemicals to maintain
  • Heating, ventilation and air conditioning (HVAC) systems that are energy efficient

“Green” Does Not Always Mean Nontoxic.

Products that are energy-efficient or recycled are not necessarily healthy. For example, products often  recommended to insulate can be toxic (such as spray foam). Using shredded tire products or refashioning something that is vinyl is not a good idea for inside the home. Always read labels and look for Low- to No-VOC. Try to get products with the lowest emissions. If it is a petroleum product, avoid it. If you are repurposing an old door or window check for lead in the paint. Remember that caulks and glues can have significant emissions, so we recommend checking labels on even these smaller household building supplies.

How do I reduce pollution from these materials?
These two simple steps can have a huge impact: (1) Regularly open doors and windows for good ventilation and (2) Get houseplants that reduce VOCs in the air. Click here for information on choosing the best plants to detoxify your home’s indoor air. Remove and replace toxic building materials when you are able to do so. Click here for information on choosing types of air cleaners to install in your home.
How do home cleaning products impact the air?
Keeping your home clean is one of the most important things you can do to assure healthy indoor air quality, as chemicals can build up in dust. Certain chemicals in cleaning products have been linked to fertility problems, birth defects, increased risk of breast cancer, asthma and respiratory disorders, and hormone disruption. However, there is no federal law requiring companies to list all the ingredients in their products on the label. It is also important to note that “green” does not always mean non-toxic. Please see Dr. Davis video on cleaning here. Vinegar, water and baking soda can be used for most home cleaning needs.

Furthermore, the indoor use of certain common cleaning products and air fresheners when ozone is present may cause a further increase in indoor concentrations of some pollutants.

The case of the plug-in air freshener.

Research has found that chemicals directly emitted from these products, such as terpenes and glycol ethers, generally were below levels of concern, but that they could create indoor chemical reactions which produced some other pollutants at levels of health concern. Specifically, using products that contained terpenes (components of pine and citrus oils) in rooms where elevated levels of ozone were present resulted in the production of formaldehyde and ultrafine particles, both of which can potentially harm human health. Formaldehyde is a known human carcinogen with no level of exposure that poses zero risk, and it is a strong irritant to eyes, noses, throats and lungs.

What can I do?

Choose fragrance-free and easily make your own cleaning products. We recommend Women’s Voices for the Earth for more information on Cleaning Products and Fact Sheets to learn more about what you can do. Read NRDC’s Factsheet on Air Fresheners, and follow the Campaign for Safe Cosmetics.

What other pollutants are in our homes?

Improvements in airtight building technologies have enhanced energy efficiency. Yet, interior areas can sometimes trap moisture due to poor ventilation systems, creating the perfect condition to spur mold growth. Mold spores can emit volatile organic compounds (VOCs) and mycotoxins, which are natural organic compounds capable of instigating a toxic response in both animals and humans. The response to molds can be allergic and include eye irritation, fatigue, headaches and dizziness. Molds can sometimes cause more serious respiratory distress and immune dysfunction.

Health agencies have failed to set adequate exposure limits as people are affected differently when exposed to molds. However, the best safety measure is to prevent mold growth from the start by undertaking basic hygiene and structural change.

How do I prevent mold?

Keep humidity levels as low as you can—no higher than 50%—all day long. Use an air conditioner or a dehumidifier during humid months. Be sure your home has adequate ventilation, including exhaust fans. Do not carpet bathrooms and basements. Remove or replace previously soaked carpets and upholstery. If you have a water drip or leak, deal with the source of the problem as soon as possible, even a small bathroom leak. Get in the habit of always using a window squeegee to wipe down shower walls after use to remove water from tile surfaces and crevices that can grow mold.

Sick Building Syndrome

Sometimes people experience health effects that seem to be linked to time spent in a building. Sick building syndrome (SBS) refers to a variety of symptoms related to the indoor environment. An individual suffering from SBS may only notice symptoms while in a particular room or area, or may notice symptoms throughout the building. According to the World Health Organization and EPA, the poor indoor air quality that causes SBS often results from buildings not being maintained in accordance with the original design and prescribed operating procedures.

Typical symptoms of sick building syndrome include:

  • headaches
  • dizziness
  • irritation of eyes, nose or throat
  • dry cough
  • sensitivity to smells
  • poor concentration

Read more about Sick Building Syndrome.

Building-Related Illness

Unlike sick building syndrome, building-related illness (BRI) is less common and can be linked to a specific source or contaminant in a building. A person suffering from BRI may not have any symptoms at the time of exposure, but the long term effects can be quite serious. A well-known example of a building-related illness is mesothelioma, a form of crippling cancer of the lining of the lungs or abdominal cavity due to long-term asbestos exposure. Check out this YouTube clip where Dr. Davis talks about Asbestos.


Radon is a naturally occurring radioactive gas that comes from deep within the Earth and can enter homes through openings or cracks in the foundation. Radon is the second leading cause of lung cancer after tobacco smoke and accounts for about 20 percent of all lung cancers.

If you live in an area with high levels of background radon, you should have your home tested. If testing shows that radon levels are high (greater than 4 picocuries/liter), radon remediation companies can mitigate radon seepage into your home. In the United States, States provide kits for testing. Following are links to some helpful guides on home testing and radon remediation:


U.S. Consumer Product Safety Commission: Indoor Air Pollution: Introduction for Health Professionals

California Environmental Protection Agency: Reducing Indoor Air Pollution

A Serious Public Health Problem

EPA’s Indoor Air Quality

Air Quality Problems Caused by Floods