Indoor Pollutants
An Overview of Different Types of Indoor Pollutants
The primary sources of indoor air pollutants in residences are those that release particles or gases into the air. Often these come from the burning of natural gas in appliances such as gas stoves and dryers, as well as other fuels burned in fireplaces and furnaces. These pollutants can build up inside the home if there is not enough fresh air coming in through the ventilation system. Another major source of pollutants in the home is high humidity. This can lead to the build-up of mold and allergens such as dust mites, and increase the rate at which building materials, furnishings and furniture emit volatile organic compounds (VOCs). These indoor pollutants can lead to health problems such as headaches, fatigue, eye/nose/throat irritation, breathing problems, allergic reactions, asthma attacks, and skin rashes.
The following briefly describes the types and sources of pollutants that can be found in homes and residential buildings. Articles on specific indoor pollutants can be accessed via the navigation menu on the right side of this page.
Volatile Organic Compounds
Microbial Volatile Organic Compounds
Some molds can emit VOCs known as microbial VOCs (MVOCs), which are responsible for the characteristic "musty, earthy and moldy" odors associated with indoor mold growth. Microbial VOCs can be easily measured in the air at very low levels, and their presence is an indication of indoor mold contamination. Microbial VOCs are unique and include certain aldehydes, alcohols, and ketones that are not typically found to emit from building materials. Frequently found MVOCs also include geosmin, hexanone and octanols. Some MVOCs are irritants and may be a contributing cause of building-related symptoms, including allergy and asthma symptoms.
Microorganisms
Humidity Levels
Uncontrolled moisture in homes can cause major indoor health problems. These include the growth of mold/fungi and dust mites since they need moisture to survive. Mold and fungus begin to grow at humidity levels of 60 percent and dust mites at 50 percent. In addition to biological pollutants, off gassing of certain chemicals, such as formaldehyde, increases as humidity goes up; although ozone, which is produced by some electrical appliances, is at its highest at low levels of humidity.
Combustion Products
Cooking is a primary activity in all homes. The burning of fuel for these purposes produces smoke and fumes, and the irritant and toxic properties of these emissions require their exhaust from the indoor environment. The lack of not venting or poorly venting combustion products represents one of the major sources of indoor air pollution. Combustion products also can infiltrate buildings and other structures via air intakes. Combustion products also can infiltrate buildings and other structures via air intakes.
Smoke is the most obvious and visible product of the combustion process. Other primary products that are always present as a result of burning organic fuels are water and carbon dioxide. Water vapor can increase indoor humidity levels, which can lead to indoor mold growth and create better living conditions for dust mites. Other combustion products that can cause adverse health effects include carbon monoxide; oxides of nitrogen; sulfur dioxide; and coal, smoke, oil and wood smoke. Environmental tobacco smoke from cigarettes, cigars and pipes also are a major source of combustion byproducts and can be very damaging to children.
Particulates
"Particulate" is a general term used for a type of indoor air pollution that consists of various types of particles suspended in the air. They are comprised of bacteria, viruses, dust mites feces, cockroaches body parts, pet dander, fungal spores, pollen, particles in environmental tobacco smoke and from combustible appliances, and asbestos fibers to name a few examples. Particulates that are small enough to be breathed in come in a variety of sizes, shapes, and levels of toxicity. Some building occupants are susceptible to health problems caused by breathing particulates, which can either be acute or chronic.