show that people rate the risk of poor air quality
from outdoor sources higher than indoor sources.
Homo sapiens evolved a particular gene in the
aryl hydrocarbon receptor that makes us less sensitive to environmental pollutants including
smoke from fire. This gene occurs uniquely in
humans and is not found in closely related species
like Homo neanderthalensis. Researchers believe
that the ability to gather around a fire for cooking
and heating gave Homo sapiens this relative
advantage [7]. Paradoxically, the World Health
Organization (WHO) has determined that nearly
four million people die each year due to indoor air
pollution, largely by pollution from fires used for
cooking and heating [8].
While much research has been done on outdoor
air pollution, indoor air pollution has not received
the same attention; prior to the mid-1970s, the
level of interest was very low. The oil crisis in
the 1970s resulted in buildings becoming better
sealed and insulated to reduce heating expenses,
leading to accumulation of indoor air pollutants.
The term sick building syndrome (SBS) was
coined by the WHO in 1986. At that time, the
WHO estimated that 10–30% of new office buildings had poor indoor air quality. Symptoms of
SBS include headache, eye, nose, and throat irritation, fatigue, dizziness, and nausea. There is
now increasing concern regarding indoor air quality [9]. In the United States, indoor air is often
recirculated to improve energy efficiency; outdoor
air is mixed with indoor air in air handling units
(AHUs). This reduces the energy used to adjust
humidity and heat (or cool) the outside air to
control the indoor air temperature. Consequently,
this leads to a decrease in the air change rates in
buildings, which lowers the indoor air quality
(IAQ).
There are many sources of indoor air pollution.
The materials used in buildings, such as glues,
paint, sealants, carpets, walls, and furniture, give
off volatile organic compounds (VOCs). The concentrations of VOCs and other indoor pollutants
are often higher than outdoor concentrations;
indoor air can be as polluted as outdoor air with
the added burden of the indoor sources
[10]. Indoor air pollution is a complex problem;
one example is that building standards are not
uniform throughout the world. In some cases
they are not enforced, or they may not exist. In
addition, up to 90% of people in developing countries rely on coal and biomass for their domestic
energy. These fuels are typically burned inside,
which means that IAQ is a much bigger concern in
developing countries, as this results in high indoor
concentrations of pollutants [11].
This state-of-the-art review article gives an
overview of different types of indoor air pollutants
as well as their sources and sinks, in situ chemistry, and their health impacts. Remediation strategies are also assessed, as well as sustainable
building practices.
Residential Air Pollution
Exposure to indoor air pollution is especially
problematic in areas that may combine poor ventilation, lack of building standards and enforcement, and indoor pollution sources including fires
for cooking and heating. People in the developing
world rely heavily on in situ generation of energy
for their daily activities. In 2012, the WHO stated
that over 1.6 million people died of causes attributable to household air pollution in South-East
Asia, and around 1.6 million in the Western
Pacific, and around 100,000 people in Europe.
The combustion of fuels like wood and coal in
indoor environments leads to exposure to smoke
including particulate matter (PM) and volatile
organic compounds. PM is often described by
the metrics PM 10 and PM 2.5 , the total particulate
mass per volume of air with an aerodynamic
diameter less than 10 and 2.5 mm, respectively.
PM found in the air is a combination of liquid
droplets and airborne solid particles. Liquids can
include an aqueous phase with dissolved salts and
an organic phase. Solids can include soil minerals
and organic material. Specific chemical components include sodium, potassium, ammonium,
sulfate, nitrate, chloride, bi/carbonate, and black
carbon. Inhalation of PM leads to its deposition in
the respiratory tract. Coarse particles mainly
deposit in the airways of the head, and fine and
ultrafine particles penetrate deep into the lungs
where they introduce foreign chemicals directly
into the bloodstream. Examples of pollutants from
combustion include soot, polycyclic aromatic
Indoor Air Quality: Status and Standards
137
from outdoor sources higher than indoor sources.
Homo sapiens evolved a particular gene in the
aryl hydrocarbon receptor that makes us less sensitive to environmental pollutants including
smoke from fire. This gene occurs uniquely in
humans and is not found in closely related species
like Homo neanderthalensis. Researchers believe
that the ability to gather around a fire for cooking
and heating gave Homo sapiens this relative
advantage [7]. Paradoxically, the World Health
Organization (WHO) has determined that nearly
four million people die each year due to indoor air
pollution, largely by pollution from fires used for
cooking and heating [8].
While much research has been done on outdoor
air pollution, indoor air pollution has not received
the same attention; prior to the mid-1970s, the
level of interest was very low. The oil crisis in
the 1970s resulted in buildings becoming better
sealed and insulated to reduce heating expenses,
leading to accumulation of indoor air pollutants.
The term sick building syndrome (SBS) was
coined by the WHO in 1986. At that time, the
WHO estimated that 10–30% of new office buildings had poor indoor air quality. Symptoms of
SBS include headache, eye, nose, and throat irritation, fatigue, dizziness, and nausea. There is
now increasing concern regarding indoor air quality [9]. In the United States, indoor air is often
recirculated to improve energy efficiency; outdoor
air is mixed with indoor air in air handling units
(AHUs). This reduces the energy used to adjust
humidity and heat (or cool) the outside air to
control the indoor air temperature. Consequently,
this leads to a decrease in the air change rates in
buildings, which lowers the indoor air quality
(IAQ).
There are many sources of indoor air pollution.
The materials used in buildings, such as glues,
paint, sealants, carpets, walls, and furniture, give
off volatile organic compounds (VOCs). The concentrations of VOCs and other indoor pollutants
are often higher than outdoor concentrations;
indoor air can be as polluted as outdoor air with
the added burden of the indoor sources
[10]. Indoor air pollution is a complex problem;
one example is that building standards are not
uniform throughout the world. In some cases
they are not enforced, or they may not exist. In
addition, up to 90% of people in developing countries rely on coal and biomass for their domestic
energy. These fuels are typically burned inside,
which means that IAQ is a much bigger concern in
developing countries, as this results in high indoor
concentrations of pollutants [11].
This state-of-the-art review article gives an
overview of different types of indoor air pollutants
as well as their sources and sinks, in situ chemistry, and their health impacts. Remediation strategies are also assessed, as well as sustainable
building practices.
Residential Air Pollution
Exposure to indoor air pollution is especially
problematic in areas that may combine poor ventilation, lack of building standards and enforcement, and indoor pollution sources including fires
for cooking and heating. People in the developing
world rely heavily on in situ generation of energy
for their daily activities. In 2012, the WHO stated
that over 1.6 million people died of causes attributable to household air pollution in South-East
Asia, and around 1.6 million in the Western
Pacific, and around 100,000 people in Europe.
The combustion of fuels like wood and coal in
indoor environments leads to exposure to smoke
including particulate matter (PM) and volatile
organic compounds. PM is often described by
the metrics PM 10 and PM 2.5 , the total particulate
mass per volume of air with an aerodynamic
diameter less than 10 and 2.5 mm, respectively.
PM found in the air is a combination of liquid
droplets and airborne solid particles. Liquids can
include an aqueous phase with dissolved salts and
an organic phase. Solids can include soil minerals
and organic material. Specific chemical components include sodium, potassium, ammonium,
sulfate, nitrate, chloride, bi/carbonate, and black
carbon. Inhalation of PM leads to its deposition in
the respiratory tract. Coarse particles mainly
deposit in the airways of the head, and fine and
ultrafine particles penetrate deep into the lungs
where they introduce foreign chemicals directly
into the bloodstream. Examples of pollutants from
combustion include soot, polycyclic aromatic
Indoor Air Quality: Status and Standards
137