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