From the authors of MOLD: The War Within

The Toxic Soup of Indoor Air

07 Nov The Toxic Soup of Indoor Air

Healthy and happy is what we all want to be but sometimes that can be a sizable challenge breathing the air in our complex modern world. Although our bodies are designed to detoxify air pollutants with which we come into contact, sometimes our defense systems get overburdened, which can weaken the immune system, leaving us susceptible to developing more serious health conditions.

Create an Oasis

One of the simplest ways to help ourselves stay well and aid our detoxification systems is to create a healthy oasis inside our own homes by taking the following three steps:

  1. Identify the sources of contaminants from both the outdoors and indoors that are lowering the quality of our indoor air.
  2. Eliminate any sources of contaminants that are within our control to rectify.
  3. Use HEPA air purifiers to reduce the toxins and air particulates that are not within our control to eliminate. Select HEPA air purifiers specifically designed to address the particular type of air contaminants given each individual situation.
Sources of Outdoor Air Pollutants

It is important to take a look at the quality of outside air where we live and work because not only do we breathe it when we are outdoors but the outside air is the source of our indoor air. Common sources of outdoor air pollutants include the following:

  • Elevated levels of pollen and mold
  • Smoke from wood burning stoves or wildfires
  • Debris dislodged from trees, bushes and plants
  • Particulates discharged from factories
  • Car exhaust and road dust
  • Agricultural and aerial spraying
  • Feedlot pollutants
  • Insecticide and pesticide spraying
How Does Your Air Rank?

For daily air quality updates by zip code in the U.S., go to  where area air is ranked as follows:

  1. Good
  2. Moderate
  3. USG-Unhealthy for Sensitive Groups
  4. Unhealthy
  5. Very Unhealthy
  6. Hazardous

People in high-risk groups should pay particular attention to when the air in their area is ranked USG or higher and stay indoors with their windows and doors closed. Even better would be to increase indoor air quality with the use of a HEPA air purifier since the indoor air comes from the outdoors.

Sources of Indoor Air Pollutants

When the outdoor air comes inside it can mix with even more contaminants from indoor sources, such as the following:

  • Pet dander
  • Dust
  • Formaldehyde
  • Radon
  • Natural gas
  • Mold spores and associated toxins
  • Bacteria and associated toxins

These combined contaminants—from both outdoor and indoor sources—become concentrated in indoor living environments. It is no wonder that the EPA reports, “Indoor air pollution is among the top five environmental health risks.” [1. EPA, “Guide to Air Cleaners in the Home.” Available at: (accessed April 2013).]

Invisible Indoor Air Pollutants

Indoor air pollution can come in two forms: particulates and vapors. Particulates can be reduced by capturing them in a HEPA filter. Only the vapors that have absorbed into the particulates will be reduced by the HEPA filter. Other airborne vapors will not be reduced by the HEPA filter itself, which is why many brands of air purifiers are designed with an additional charcoal pre-filter. As the air passes through the charcoal filter, vapors are absorbed before the air passes through the HEPA filter. The effectiveness of charcoal pre-filters varies depending on the design of the charcoal filter as well as the design and scope of the HEPA air purifier.

Published, Peer-reviewed Studies

One of the most common contaminant vapors is smoke—from cigarettes, forest fires, wood burning stoves and fireplaces. There are several published, peer-reviewed studies that have been conducted to investigate the benefits of using HEPA air purifiers to reduce indoor levels of smoke. One study investigated the impact of using HEPA air purifiers on community health when stressed by smoke from wildfires. The researchers reported, “Our study found lessened lower respiratory tract symptoms with longer use of high-efficiency particulate air cleaners.”[2. Joshua A Mott et al., “Wildland forest fire smoke: health effects and intervention evaluation, Hoopa, California, 1999” Western Journal of Medicine. 2002 May; 176(3): 157–162. Available at: (accessed April 2013).]

Cardiovascular Benefits

Most interesting were the studies that reflected a positive effect on cardiovascular health from the use of a HEPA air purifier. One such study reported the potential to reduce the risk of cardiovascular disease associated with exposure to airborne pollutants caused by wood burning stoves by using a HEPA air purifier.

According to study investigators, “Our results support the hypothesis that systemic inflammation and impaired endothelial function, both predictors of cardiovascular morbidity, can be favorably influenced by reducing indoor particle concentrations.”[3. Ryan W. Allen et al., “An Air Filter Intervention Study of Endothelial Function among Healthy Adults in a Woodsmoke-impacted Community” American Journal of Respiratory and Critical Care Medicine, Vol. 183, No. 9 (2011), pp. 1222-1230. Available at: (accessed on April 2013).]

Another such study concluded, “Reduction of particle exposure by filtration of recirculated indoor air for only 48 hours improved MVF [microvascular function] in healthy elderly citizens, suggesting that this may be a feasible way of reducing the risk of cardiovascular disease.”[4. Bräuner EV et al., “Indoor particles affect vascular function in the aged: an air filtration-based intervention study” American Journal of Respiratory and Critical Care Medicine. 2008 Feb 15;177(4):419-25. Available at: (accessed April 2013).]

Asthma Benefits

Other studies examined the effects of environmental interventions, including the use of HEPA air purifiers, on childhood asthma in environments where secondhand smoke was present.[5. Bruce P. Lanphear et al., “Effects of HEPA Air Cleaners on Unscheduled Asthma Visits and Asthma Symptoms for Children Exposed to Secondhand Tobacco Smoke.” Pediatrics, 2011 January; 127(1): 93–101. Published online 2010, December 13. Available at: (accessed April 2013); Herman Mitchell et al., “Implementation of Evidence-based Asthma Interventions in Post-Katrina New Orleans: The Head-off Environmental Asthma in Louisiana (HEAL) Study.” Environmental Health Perspectives, November 2012, vol. 120, no 11, pg. 1607-1612. Available at: (accessed April 2013).] The findings from these various studies revealed the following:

  1. Reductions in the number of unscheduled asthma doctor visits
  2. Significant reductions in asthma symptoms
  3. Reductions in both unscheduled asthma-related doctor visits and symptoms
Reduces Airborne Pet Allergens

Studies have also documented successful reduction of airborne pet allergens in association with the use of HEPA air purifiers.[6. Green R et al., “The effect of air filtration on airborne dog allergen.” Allergy 1999 May; 54(5): 484-8. Available at: (accessed April 2013); van der Heide S et al., “Clinical effects of air cleaners in homes of asthmatic children sensitized to pet allergens,” J Allergy Clin Immunol. 1999 Aug;104 (2 Pt 1):447-51. Available at: (accessed April 2013).]

Influencing Factors

Results of studies can vary based on various factors such as the following:

  • Parameters of each particular study
  • Design and implementation of each study
  • Brand of HEPA air purifier used in each study

Different brands of HEPA air purifiers can provide varying degrees of performance based on each brand’s specifications, including the following:

  • Design
  • Measurement of airflow, e.g. amount of cubic feet per minute (CFMs)
  • HEPA filter media
  • Pre-filter design and effectiveness

HEPA filter life will always depend on the level of airborne contaminants in the environment in which the HEPA air purifier is being used as well as the effectiveness of the pre-filter.

For More Information

To discuss how a HEPA air purifier may benefit your individual health, check with your treating physician. For information on which type of HEPA air purifier would be most appropriate for your specific environment, contact one of the indoor air quality consultants listed in our HEPA Air Purifier directory at .