The online reference, Indoor Air Pollution: An Introduction for Health Professionals, offers a Diagnostic Quick Reference for assessing symptoms and possible causal factors from
indoor air.


















See links:
American Lung Association’s "Tips For Using Your Wood-Burning Stove And Fireplace"

National Safety Council Fact Sheet Library, "Combustion Appliances"

























Exposures of Concern

Respiratory health is influenced by exposure to a variety of environmental factors that exists both indoors and outside.

Indoor Air

Globally, scientific experts (representing bodies such as the US EPA, WHO and NATO) have proclaimed that poor indoor air quality is a significant environmental health issue. The indoor environment is a particularly important determinant of children’s respiratory health, since children (especially those in temperate climates) spend more than 80% of their time indoors.7 This includes time spent not only in the home environment but also other indoor locations, such as school, day-care and recreational facilities (i.e., swimming pools and hockey arenas). These all represent areas where children may potentially encounter environmental pollutants.

There are a number of indoor air pollutants that are associated with significant effects on health including:

  • Environmental tobacco smoke
  • Combustion products
  • Volatile organic compounds
  • Biological compounds, allergens

Environmental tobacco smoke (ETS) is unquestionably the most significant indoor air pollutant affecting people’s and especially children’s respiratory health. The smoke exhaled by smokers or released from cigarettes, cigars or pipes is a complex mix of many thousands of different chemicals. ETS includes the compounds carbon monoxide, nitric oxide, nitrogen oxides, benzene, formaldehyde, acetaldehyde, acrolein, and nicotine.8 ETS also contains significant amounts of suspended particles that are small enough (< 2.5 µm in diameter) to reach the lower airways.

Children exposed to ETS may exhibit upper and lower respiratory tract effects as well as impaired hematopoietic system functioning. There is an enormous body of literature examining the health effects from exposure (both prenatally and postnatally) to ETS. It is clear that children who are exposed to secondhand smoke are at an increased risk of suffering from a variety of health conditions including:

  • Frequent upper and lower respiratory tract illness, infections9
  • Frequent episodes of otitis media; persistent middle ear effusions10
  • Asthma initiation and/or exacerbation11
  • Recurrent pneumonia
  • Sudden Infant Death Syndrome12
  • Increased risk of developing cancer as adults13 and may have developmental and learning delays.14
Several important Internet resources outline in greater detail the data that link ETS with respiratory health effects in people, especially children. Health Canada’s Web site summarizes issues surrounding indoor air quality.

Combustion products: Pollutants from combustion sources include the gases, carbon monoxide (CO), nitrogen dioxide (NO2), and sulfur dioxide (SO2). It may also include particulate matter. Combustion-type pollution primarily arises indoors when there is faulty heating equipment or when these devices are inappropriately used. For example, if wood stoves, space heaters, gas ranges, furnaces and fireplaces are not properly vented and used in an enclosed space, they may all contribute to indoor pollution. It may also stem from motor vehicle exhaust emissions if a car garage is in close proximity to indoor living space. Effects from these pollutants are generally greater during seasons when heating equipment is used and air flow inside decreases to reduce heat loss.

  • NO2 and SO2 irritate mucous membranes of the eyes, nose, throat, and respiratory tract. Because of differences in solubility, these gases affect different sites. NO2 tends to affect the lower respiratory tract, whereas SO2 affects the eyes and upper respiratory tract more often. Both can produce respiratory effects even at low levels of exposure, asthmatics being particularly susceptible to bronchial effects. Chronic exposure to NO2 is associated with increased risk of respiratory infections in young children; with chronic SO2 exposure, there is increased respiratory symptoms and impaired lung function.
  • CO is an invisible, odorless and tasteless gas that is highly toxic to humans because it prevents delivery of oxygen by the blood to the body’s tissues. It is associated with a spectrum of signs and symptoms, including fatigue, weakness, headache, dizziness, confusion, nausea and vomiting, and prolonged exposure at higher levels can cause death. At lower levels, symptoms of carbon monoxide may often be mistaken for common illnesses, such as the flu.
  • Particulates are small particles that are also physical irritants of the eyes, nose, throat and lungs. If small enough, they can be inhaled deep into respiratory tissues and can exacerbate pre-existing medical conditions, such as asthma. They will increase respiratory symptoms such as coughing and wheezing in most people. Particles may also transfer chemicals that are attached to their surfaces.

Volatile organic compounds (VOCs): VOCs are chemicals that are emitted at room temperature as gases or vapours from liquids or solids. They are generally in higher concentration indoors compared to outdoors. They include chemicals such as formaldehyde, benzene and perchloroethylene. Their sources in the home are generally from building materials, furnishings and a variety of consumer products, including cleaning products, deodorizers, paints and lacquers, solvents such as paint strippers, nail polish remover and pesticides. VOCs are mainly inhaled and therefore affect mucous membranes as well. VOC exposure may manifest as eye and upper respiratory irritation, rhinitis, nasal congestion, rash, pruritus, headache, nausea, vomiting or dyspnea.

  • Formaldehyde – This is a very common indoor air contaminant. It is found in many products and materials and has many uses. For instance, formaldehyde binds wood chips in particleboard, it is a solvent in dyes for cloth or paper, and it is used in wrinkle-resistant material and as a water-repellent in floor coverings. Among VOCs and their health effects, most is known concerning exposure to formaldehyde. Formaldehyde may cause a burning or tingling sensation in the eyes, nose and throat that goes away when the exposure is removed. It may trigger asthmatic symptoms in susceptible infants and children.

Biological compounds, allergens – Pets, cockroaches, mould and dust mites are all sources of biological compounds found in high concentrations in indoor air that are responsible for allergic or toxic effects in children. They are most often inhaled, but some are also absorbed through dermal exposure. Biologicals cause hypersensitivity reactions and toxic reactions. Non-specific effects, such as "sick building syndrome," may be related to microbial contamination in buildings.15

  • Pets – Fur and feather-bearing pets are sources of allergens. The allergens are from the skin of the animal (dander) and are also found in certain secretions (saliva, urine, sebaceous gland secretions). In the case of birds, feathers are reservoirs for dust mites that produce the primary allergens (see below), although people may also be allergic to substances in their droppings.
  • Cockroaches – The feces and body parts of cockroaches are allergens and the main triggers of allergic rhinitis and asthma. Cockroach allergens likely play a significant role in causing asthma. Studies have shown that the majority of asthmatics living in urban areas test positive for allergy to cockroaches.
  • House dust mites – Mite fecal particles are also important allergens that likely play a major role in causing asthma and/or triggering asthmatic attacks. Mites proliferate in or on surfaces that accumulate human dander, the main food source of dust mites. They also thrive in conditions of high humidity and temperature. They accumulate in bedding, pillows, mattresses, carpets and furniture. People are exposed by inhalation.
  • Moulds - People frequently can have toxic or allergic reactions to mould depending on the species of mould. Mould grows in humid, damp areas of the home such as bathrooms or basements that are prone to leaks and flooding. Respiratory symptoms in children exposed to moulds include persistent sneezing, eye irritation, rhinitis, coughing and wheezing. Mycotoxin-producing moulds, such as Stachybotrys atra, have been associated with acute pulmonary hemorrhage in infants.16
Copyright © 2000 Canadian Association of Physicians for the Environment
Credits. Web site designed and maintained by J.Hewak