Most people are well aware that outdoor air pollution can damage their health, but many are not aware of the serious harm that indoor air pollution, or contamination, can also cause. In industrialized nations, people now spend over 90% of their time inside. The U.S. Environmental Protection Agency (EPA) found that indoor levels of some pollutants are more than 100 times higher than outdoor levels, ranking indoor air contamination among the top four environmental health risks to the public. This risk is even higher for infants, the elderly, and people with underlying chronic diseases.

In this first installment of a year-long IAQ column, we should begin by surveying the stakes and the enemies.

IAQ and Occupant Health

Indoor air (IA) pollutants, whether from human activities or building materials or HVAC systems, can have acute or long-term effects that vary from mild discomfort from unpleasant odors to lethal cancer or infections. Understandably, the respiratory system is the most common site of injury by indoor air pollutants; however, non-respiratory effects can also occur depending on the toxicity of the substances and on the host. Some illnesses attributed to poor IAQ are:

  • Asthma and allergic reactions from exposure to gases, pollen, organic particulate matter and microorganisms;
  • Infectious diseases: influenza, colds, pneumonia, Tuberculosis, Legionnaire’s Disease, Pontiac Fever, sepsis; 
  • Cancer or other teratogen toxicity;
  • Central nervous system, skin, gastrointes, tinal, respiratory, circulatory, and musculoskeletal symptoms
  • Sick Building Syndrome (SBS) – defined as symptoms that are associated with occupancy of a particular building but not associated with a specific measurable cause.

The Clean Air Act requires the EPA to set National Ambient Air Quality Standards for the six common air pollutants in residential and commercial buildings. While outdoor levels of these substances are generally decreasing, indoor levels are not. These pollutants are:

  • Ozone (ground level)
  • Particulate Matter: infectious micro-organisms, dust, other biological matter
  • Carbon Monoxide
  • Nitrogen Oxides
  • Sulfur oxides
  • Lead

The sources of these compounds are ubiquitous in homes, offices, and hospitals. For example, employees in offices over parking garages may be exposed to carbon monoxide carried through fresh-air-intake vents. Frequently, unvented printers, fax machines, and copiers emit ozone, a powerful oxidant that can irritate the airways, triggering chronic coughing, asthma, and other lung diseases.

Biological building pollutants such as molds, bacteria, viruses, pollen, animal dander, and particles from dust mites and cockroaches can cause respiratory infections, provoke allergic symptoms, or trigger asthma attacks. An estimated 40 million individuals in the United States are affected by allergies, and the prevalence rate of pediatric asthma has increased 72.3%. Asthma is now the sixth-ranking chronic condition and the leading serious chronic illness of children in the U.S. Pediatricians link the high incidence of asthma with inhaled particulate matter in homes and schools.

Secondhand tobacco smoke is still a major indoor air pollutant. In the U.S., an estimated 3,000 lung cancer deaths and up to 50,000 heart disease deaths occur in nonsmokers. In children, especially infants, smoke exposure is responsible for pneumonia, upper respiratory tract infections, ear infections, and asthma.

Combustion pollutants from fuel-burning equipment include colorless and odorless CO and NO2. Along with other IAQ risks like radon and formaldehyde, can cause a host of symptoms ranging from milder symptoms like skin and membrane irritation on to insufficient oxygen delivery to the body and lung cancer.

Into The Fray

With that cast of characters representing many (but not all) of the IAQ risks for occupants, next month we will move on to some common weapons to fight back: building codes, HVAC equipment, and techniques for design, operation, and monitoring.