towards an integrative approach of improving indoor air quality

Please cite this article as: Bluyssen PM. Towards an integrative approach of improving indoor
air quality, Building and Environment (2009), doi: 10.1016/j.buildenv.2009.01.012
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Accepted Manuscript
Title: Towards an integrative approach of improving indoor air quality
Authors: Philomena M. Bluyssen
PII: S0360-1323(09)00022-5
DOI: 10.1016/j.buildenv.2009.01.012
Reference: BAE 2270
To appear in: Building and Environment
Received Date:
7 November 2008
Revised Date:
15 January 2009
Accepted Date:
27 January 2009
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Towards an integrative approach of improving indoor air quality
Dr Philomena M. Bluyssen
TNO Built Environment and geosciences
P.O. Box 49, 2600 AA Delft, The Netherlands
Tlf +31 6 51806610


ABSTRACT
There seems to be a discrepancy between current Indoor Air Quality standards and end-users
wishes and demands. Indoor air quality can be approached from three points of view: the
human, the indoor air of the space and the sources contributing to indoor air pollution.
Standards currently in use mainly address the indoor air of the space. “Other or additional”
recommendations and guidelines are required to improve indoor air quality. Even though we
do not fully understand the mechanisms behind the physical, chemical, physiological and
psychological processes, it is still possible to identify the different ways to be taken
regulatory, politically-socially (awareness), technically (process and product) and
scientifically. Besides the fact that there is an urgent need to involve medicine and neuro-
psychology in research to investigate the mechanisms behind dose-response, health effects
and interactions between and with the other factors and parameters of the indoor environment
and the human body and mind, a holistic approach is required including the sources, the air
and last but not least the human beings (occupants) themselves. This paper mainly focuses on
the European situation.

KEYWORDS
Indoor air quality, source control, labelling, exposure and effect, risk assessment
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INTRODUCTION
Defining indoor air quality can be approached from three points of views: the human, the
indoor air of the space and the sources contributing to indoor air pollution. From the human
point of view, indoor air quality of a space is the physical effect of exposures of people to
indoor air of the space they are visiting or occupying, as experienced by those people. Indoor
air quality at a certain point in time can for example by expressed in an odorous unit, while
indoor air quality over time can for example be related to the number of people developing a
certain illness. From the indoor air point view, indoor air quality is often expressed in a
certain ventilation rate (in L/s per person and/or L/s per m

2
floor area) or in concentrations for
specific compounds. These concentrations are influenced by the sources present in (indoor
sources) or outside the space (outdoor sources and sources present in HVAC systems or
surrounding spaces). So, also from the source point of view indoor air quality can be
approached. Emission rates per source unit for certain pollutants (used for labelling products
in some countries) is then often the result.

For mainly the second point of view (indoor air), standards and guidelines are in use for
evaluating the indoor air quality (based on WHO air quality guidelines [50], ASHRAE [54],
in some cases CEN [55] or nationally determined minimum guidelines based on the presence
of people only (CO
2
concentration)). Even though those standards and guidelines are met, the
quality of the indoor air, as experienced by the occupants, is still not acceptable and even
unhealthy, causing health and comfort problems. There seems to be a discrepancy between
current standards with end-users wishes and demands [1], [2]. Therefore, “other or additional”
recommendations and guidelines are required to improve indoor air quality.

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At European level, several initiatives are being taking ranging from exposure threshold values
of pollutants to labelling of products and even buildings, such as:
- The development of harmonized test methods for release or emission of dangerous
substances to satisfy the requirements of Essential requirement 3 (ER 3) of the
Construction Product Directive (CPD) (see Figure 1) [3].
- A standardised voluntary approach for the delivery of environmental information on
construction products, and to assess the environmental performance of buildings [4].
- Harmonisation of several national labelling schemes for construction and furnishing
products [5].
- REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals) [6].
- Several currently running European funded projects: EnVIE [7], BUMA [8], HealthyAir
[9], etc.

This paper describes and discusses the problem(s) encountered with indoor air quality and
possible ways to get to “other or additional” recommendations, based on examples and
initiatives from mainly European origin.

FACTS AND PROBLEMS
Basically the following process is taking place in the indoor environment. A source (or
sources) emits pollutants that come into the indoor air of a space, directly or indirectly. Those
pollutants can react with each other or with pollutants from other sources, creating new
pollutants (indoor air chemistry). And pollutants from other sources can react with the source.
A person entering or occupying that space, is exposed to those pollutants present in the air of

the space, which possibly creates a response (immediate or after some time), depending most
likely also on previous and future exposures in the same or other spaces. From this latter step
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can be concluded that relating a response to a pollutant or source is very difficult, unless lab
controlled exposures using specific pollutants focused on specific responses is performed. But
even then, since people can response differently and do have a history, this is a complex
matter.

The following facts and problems can be identified.

The emission behaviour of sources is complex.
This complexity is partly related to the fact that the mechanisms (diffusion, desorption,
evaporation [10]) occurring in and on the sources are not well understood. There are sources

in the indoor environment that emit compounds which are absorbed on indoor surfaces, for
example occurring during cooking, cleaning or other user activities. Those compounds can be
desorbed, react with compounds on the new source, and re-emit (secondary emission). This
re-emission, but also the primary emission of sources is a complex phenomenon. For example
the mass transfer coefficient for a compound in a building material differs for each of the
mechanism mentioned but also for each combination compound (caused by polarity, volatility,
vapour pressure) and source (caused by porosity, roughness and specific area) and for different
conditions (such as temperature, humidity, air velocity). For the determination of these
coefficients, for example for the diffusion coefficient of a pair chemical compound – building
material, several experimental techniques are available, each having their pros and cons [11].
Another important issue is the emission over time (see Figure 2). Depending on the
compound emitted, a different pattern of emission over time can occur. Emission patterns
from more compounds emitted from a source can look quit complex. Nevertheless, a better
understanding can possibly result in predictions and explanation on the emission behaviour to
be expected (level and time frame of emissions).
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Indoor and source surface chemistry create “new” fairly unknown compounds, not (yet)
accounted for in current standards and guidelines.
A source can also emit compounds that are caused by coming into contact with other products
such as Ozone with organic compounds transforming to more highly oxidized species [14] or
water facilitating the disproportionation of NO
2
in aqueous surface films, leading to increased
levels of nitrous acid (HONO) in indoor air [15] (see also [16], [17], 18]). And a source can
emit compounds that arise/develop during the in use phase of the source itself, such as ageing,
cleaning or microbiological growth. Additionally, the mix of pollutants in indoor
environments can be transformed due to chemical reactions resulting in a much broader
analytical window of organic compounds that the classic window (as defined by the World
Health Organisation (WHO)) used to explain the effects [19]. Ozone reactions, hydroxyl
radicals reactions, but also other radical reactions (for example nitrate radical NO
3
·) occur in
the indoor environment. Secondary products formed comprise of formaldehyde, aldehydes
and NO
2
. The concentrations of free radicals are not well known and are needed to advance
indoor chemistry modelling [15].

The material constituents and moisture retention characteristics of a product determine the
risk for microbial growth.
Secondary emissions can also comprise of emissions of spores, mycotoxins, synergizers and
VOCs from microbial growth on the surface of the product. It is known that moulds grow on

practically any organic material provided there is enough water (not necessarily liquid). The
availability of water in the indoor environment and on or in construction products is influenced
by several factors: thermal performance of a building envelope, ventilation, occupant behaviour
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(cleaning for example) and material characteristics. Studies have shown that the latter is the
primary reason for microbial growth [20], [21].
Additionally, if a product comprises of organic materials, the risk for growth is higher than
for completely inert materials. The trend towards eco-friendlier products has thus increased
the potential growth risks (for example the use of water-based paints instead of oil-based).
Organic dirt on inert material can also increase the risk, making the cleanability of a product
an important characteristic.
At present, an increased resistance against microbial attack, and therefore the prevention of
mould growth, requires addition of biocides, with paints being the main application area.

Because the actual period of time of biocides activity is short (max. 1-2 year), research is
being performed to incapsulate the biocides and when moulds are present, the encapsulation
breaks and slow release of the biocide occurs. An additional problem is that most traditional
biocides, e.g. mercury compounds, are under prohibitive rules (European Union Biocidal
Product Directive (BPD) [22]) or will be. Eco-friendlier, less toxic alternatives are needed.

The HVAC systems can be a source of pollution as well, which is not always acknowledged.
Research [23] has indicated that main sources and reasons for pollution in a ventilation
system may vary considerable depending on the type of construction, use and maintenance of
the system. In normal comfort ventilation systems the filters and the ducts seem to be the
most common sources of pollution, especially odours. Oil residuals are the dominating source
of pollution in new ducts, while growth of microorganisms, dust/debris accumulated in the
ducts during the construction at the work site (mostly inorganic substances) and organic dust
accumulated during the operation period in the ducts can be sources of pollution as well. If
humidifiers and rotating heat exchangers (RHEs) are used, they are also reasonable to be
suspected as remarkable pollution sources especially if not constructed and maintained
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properly. Micro-organisms are the main source of air pollution if the air humidifier is not used
in the manufacturer-recommended way and/or if they are not properly maintained.
Desalinisation and demineralization devices/agents can also contribute to pollution of the
passing air. In general, RHEs are not pollutant sources in themselves, except when the wheels
are dirty. RHEs may transport contaminants from the supply to the exhaust in three ways:
through air caught by the wheel, by leakage between wheel and gasket, and by adsorption-
desorption on the surface area of the wheel. The pollution load caused by the heating and
cooling coils seems to be less notable, except for cooling coils with condense water in the
pans, which can be microbiological reservoirs and amplification sites that may be a major
sources of pollution in the inlet air.
What should be mentioned is that a positive effect of HVAC systems (i.e. mostly the filters) is
perhaps the removal of ozone, reducing the indoor ozone concentration and levels of potentially
harmful oxidation products [24].

To truly evaluate an exposure, all routes of exposure (physiological and psychologocial)
should be taken into account jointly. And different humans will react differently to the same
exposure.
Human exposure to environmental factors (such as indoor air compounds) occurs mainly
through the senses. Receptors in our nervous system receive sensory information as sensations
via the eyes, ears, nose and skin, enhanced by bodily processes such as inhalation, ingestion
and skin contacts. In addition to the stimuli that can be processed by our sensory system, the
environment affects us in other ways, which are not recognisable to us. The latter stimuli can
cause changes in our psychological state, of which we apparently do not know the cause (no
conscious experience), but can also be harmful to our physical state of well-being (for
example gases, chemical compounds, radiation etc.) [25]. So it seems that the received
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information (sensations) can be looked upon from the physiology of the body and/or from the
psychological point of view. Interactions may occur between stimuli in complex, real-life
mixtures as well as between various body responses to exposure. Some stimuli cause only
nuisance, others can give serious health problems. Some have short term effects, others long
term. Our senses perceive individually, but interpretation occurs together.
The bodily responses (physiologically and/or psychologically) are produced, regulated and
sometimes “killed” by several systems in the body: the nervous system, the immune system
and the endocrine system. The health effects of our human body to stimuli from the
environment are controlled (or better fought against) by the immune system, while our
emotions and evaluations are controlled by our limbic system and other parts of the brain
(Figure 3). Additionally, the endocrine system provides boundary conditions for “control” of
environmental stimuli by our immune as well as our limbic system. So they are pretty much
intertwined.

External stress factors such as indoor air compounds, influence all three systems of the human
body (the nervous system, the immune system and the endocrine system) and can result in
both mental and physical effects.

Not being able to cope with a certain situation (consciously or unconsciously) can cause a
whole range of different diseases and disorders, mostly indirectly related the environmental
factors and affected by psycho-social and personal factors as well. Too much stress can cause
short-term illness and long-term health problems both physical and mental. Hormones play an
important role in the response [26].
Besides the effects of external stress factors, the performance of the human senses (internal
stress factor) can also have a major influence on the first category of complaints. Degradation
of the eyes, ears, olfactory bulb etc., usually occurring with age, are examples of this.
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Degradation of the immune system functions also increases with age. Also here genetics can
be of influence as well, such as being anosmic (not being able to smell normally).
The way we evaluate our environment (perception) and the way we respond to our
environment (behaviour) are two different processes. According to Vroon [27] this can be
explained by the fact that the part of the brain that evaluates the environment is not the same
as the part of the brain that controls the behaviour of a human being. This might explain why
there is often a discrepancy between what people tell us what they need or want and what
their behaviour tells us, or what they tell us what the cause is of certain complaints and what
the real problem is.

There are diverse techniques available to indicate the IAQ people are/were exposed to.
An indication of the environmental quality the persons were exposed to can be given in the
form of prevalence of symptoms, acceptability, measurable pollutants in the body fluids,
prevalence of exposure to specific sources, or even investigating the brain. Questionnaires given
to occupants of the investigated buildings [28] [29], interviews per telephone [30], medical
examination and biological monitoring of body fluids of exposed people [31] [32], and the
response of visitors of the investigated buildings, all belong to this group of techniques. There
are no absolute tests for lethargy, headache and dry throat available. Objective measurements
have been used to validate dry eyes, blocked nose and asthma symptoms. A diagnosis of
allergy and hyper-reactivity can be established by several tests [33]. The same can be said of
eye irritation [34] [35] [36] and for sensory irritation of the nose [37].
Sensory evaluation techniques are available to evaluate the indoor air quality with the human
nose or to evaluate the emission of certain sources (construction and furnishing products,
HVAC system components) [38]. And animals have been used to investigate problems related
to irritation of the respiratory tract in humans [35].
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And last but not least, non-invasive brain imaging techniques are used to investigate people’s
behaviour [25].

It is difficult to relate symptoms with IAQ evaluations
While field studies show every time that it is difficult to relate symptoms with IAQ
evaluations, combined exposures in laboratory settings (such as [73] [74] [75]) give
promising results. As Andersson [76] states: “Controlled experimental studies in climate
chambers and animal studies will increase the possibilities to test hypothesis and minimise the
usual conclusions of many studies finding significant results “indicating potential health
effects”.

From the BASE (Building Assessment Survey and Evaluation) study, a study in 100 offices in
the US, it appeared that human occupants are still the most sophisticated “sensors” [77]. The
most statistically significant parameters found were occupants perception of odour and
relative humidity, while the biological contaminants exhibited lower statistical associations
with the examined health outcomes (upper and lower respiratory sick building syndrome
symptoms, asthma and mould/dust allergies).

Research is required though to fully understand why people react the way they do [76].
Neuroscience could supply insights in how the brain interprets and responds to IAQ. Von
Kempski [78] emphasizes the need for focussing on the understanding of the feelings and
emotions of people, applying methods used in psychology. According to Lan and Lian [79]
behaviour origins from three functional systems: cognition (concerns the information
handling), emotion (feeling and motivation) and executive functions (how behaviour is
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expressed). These neuro-behavioural factors can be tested by so-called psychometric tests
such as the profile of mood status (POMS) to measure individuals emotion [80].
To overcome biased self-reported symptoms (as a result of personal situation and job-related
factors for example), objective clinical methods can be useful as well [81]. Also long term
storage of human body specimen under stable freezing conditions for later retrospective

analyses provides new aspects in indoor air research [82].

Some compounds may have adverse effects on their own while others, seemingly harmless,
become harmful when they interact with each other or over time. Some compounds behave
differently in a mixture than single.
In general, non-specific effects or symptoms have been observed after exposures to low level
indoor air pollution with particulate matter, gases or vapours, etc. This means that a symptom
does not have a specific cause and may even be related to other type of exposures (for
example light or thermal exposure) or to other biological mechanisms (e.g. mental stress)
[39]. On the other hand these relations may be seen at higher prolonged exposure levels, i.e.
our senses are more sensitive than our measuring instruments. The perception of odour and
sensory irritation of the mucous membranes in eyes, are good example of this. The latter is
probably one of the most important symptoms in the SBS, nevertheless no strong and
reproducible association between exposures and responses have been found in the field
studies. In laboratory environments, however, it has been shown that several VOCs in
combination will cause chemosensory irritation of eyes and nasal passages, even when each
individual compound is substantially below its threshold (Cometto-Muniz in [40]). This effect
increases with number of compounds and with compounds that have a high number of
carbons. The latter off-gas longer due to lower vapour pressure, therefore, substituting by
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longer-chained hydrocarbons to reduce VOC emissions in the short term can have the
contrary effect than envisaged.
For odour, it is also well-known that our senses (the human nose) are in general much better
in detecting compounds than the measuring instruments used. The development of
instruments, an artificial nose or an electronic nose, that can evaluate the air quality as the
human nose does, is an ongoing activity (i.e. de European project SysPAQ [41]). Many
attempts have been made, some successful for the purpose they are designed for, others not.
The reason is not only related to the still incomplete knowledge of the perception mechanism
(information processes in brain), but also to the fact that the nose is able to detect very low
concentrations. The human nose is able to detect certain compounds at parts per trillion (ppt)
level. Furthermore, not every nose has the same sensitivity, i.e. the same compound can be
detected by some persons at a much lower level than others. Using human panels to simulate
the behaviour of any person is therefore not easy, even though many methods exist [38]. And,
last but not least, it seems very difficult to develop sensors (and arrays of sensors) that are
able to and detect low levels and at the same time show a stable performance over time and
under influence of changing environmental conditions.
Although available evidence on VOCs causing health effects is assumed inconclusive for now
[42], recently several studies indicate associations between health, asthma or allergy effects
and phthalates [43] [44] [45], dampness and mould [47] [48] and normal office dust [40].
Many compounds which are generated in the indoor environment are semi volatiles such as
phthalates, flame retardants, PAHs, chlorophenols, pesticides, organotins and metals, which
may adsorb to particulate matter present in the indoor air and to house dust. These particles
may be inhaled or ingested, depending on their size. Particulate air pollutants have very

diverse chemical compositions that are highly dependent on their source, and they are also
diverse in terms of particle size. Even though, the penetration factor from outdoors to indoors
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lies between 0.5 and 0.9, being greatest for fine particles (PM
2.5
) and lowest for coarse (PM
10
)
and UFP (Ultra Fine Particles) [49], the composition of particles of outdoor origin can be very
different from that of particles from indoor sources [50].

Problems with IAQ are not only source related, but also process related
The dynamic process of managing the indoor environment and thus the indoor air quality,

involves many stakeholders, such as the owner, the end-user, the contractor, but also the
persons that maintain the indoor environment. If those stakeholders do not understand each
other, problems can occur. It all begins with a definition of the end-users requirements and
the translation of those end-users requirements in the appropriate way. In the traditional
process, the decision process often used is called the ‘over the bench’ methodology, in which
a real team is not formed and communication between the stakeholders does not really occur.
Parties do not understand each other’s stakes or products and end-users wishes and demands
are only incorporated on an individual basis, causing discrepancies between end-users
requirements and the end-products. Thus, providing another reason for problems with the
indoor environment and its parameters (i.e. indoor air quality, thermal comfort, lighting and
sound quality).

DISCUSSION
For ‘indoor air quality’, for most of the 20
th
century, appropriate ventilation was considered to
be enough. Discussions on how much ventilation is sufficient to prevent noxious odour and
spread of disease are originating from the beginning of the 19
th
century [51] and are still going
on (see Figure 4). It was not until the 1990s, that a different approach then ventilation was
considered: source control. It was finally acknowledged that occupants are not the only
polluters in indoor environments [28] and therefore a ventilation rate based on carbon dioxide
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production of occupants was no longer valid in buildings where occupants were not the
dominant source of pollution.
Considering, however, the status of our knowledge with respect to the processes taking place in
and at the emitting side (the sources), the indoor air and also on the perceiving side, it is not
strange that we have a hard time in defining standards and guidelines for a good indoor air
quality. All these facts make the definition of a good indoor air quality not easy. Additionally, it
can be observed that even though scientists, but also regulators, are convinced of the importance
of creating and maintaining a good indoor air quality, for most stakeholders (and specifically
the occupant of a building) are not aware at all that indoor air influences their comfort and
health status. This makes our task even more difficult.
From the practical point of view it is clear that source control (what is not emitted, one cannot
be exposed to) is still the best option we have: preventing rather than curing. But this should not
stop us in developing additional ways to improve indoor air quality. This can be and should be
encountered at different levels.

Regulation
From the regulatory point of view, several ways to control the effect or possible effect on
indoor air quality (exposure to indoor air compounds) are available:
- Minimum allowable emission rates of pollutants from a source (resulting in labelling or

not).
- Ban of use of certain pollutants in products or in general (for example asbestos,
smoking,…).
- A minimum required ventilation rate.
- A maximum allowable concentration level (exposure level) (for example for
formaldehyde).
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- Preventive measures such as design approaches, maintenance activities to prevent growth
of Legionella or strict procedures of intended use of a space or product.
The first two measures are focussed on the source (source control) while the third and fourth are
dealing with the indoor air. The latter can be a combination of source, indoor air and human
activities.

Regulation is the most powerful tool to force people to create a good indoor air quality. From
the regulator point of view, one needs a simple way to test whether a building or future
building, fulfils certain rules to reach a good indoor air quality. REACH [6] as well as the
initiative under the CPD to develop a horizontal method to test potential sources on their
emissions [3], is a good way, since they both start with the source (see Textbox 1 and 2).
However, understanding of the emission behaviour of dangerous substances from
construction products is crucial for making choices on test conditions for a horizontal standard
to assess impacts to indoor air quality. Purpose of emission evaluation testing is identifying
short and long-term emission from a construction product under its intended conditions of use
- those emissions that the user of the building will face after the construction phase has been
completed. Depending on the substance emitted, a different pattern of emission over time can
occur. Therefore, a proper understanding of the emission of substances from construction
products can not be obtained from one or two measurements.

Nevertheless, even though knowledge is lacking about the type of compounds emitted, the
mechanisms behind and more importantly the potential secondary emission that those sources
can cause, this initiative under the CPD stimulates regulation on the emission side (which is not
common at the moment) and possibly also labelling of products. The use of the Finnish M1
system [62] over more than 15 years has shown that it is possible to reduce primary emissions
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from building products. The down-side being the fact that in the last decades VOC were
substituted with longer-chained hydrocarbons (SVOC) to reduce emissions. It is therefore
important to measure SVOCs from construction products as well, even though this most likely
has implications for the procedure of testing (28 days might not be long enough).

Since the relation of growth of microorganism on materials in buildings with health effects is
pretty clear, it is also strongly recommended to consider testing on the sensitivity to growth of
microorganism. Microbial growth in buildings is a threat to occupants’ health as well as the
sustainability of construction products and the building itself. It could well be that this
characteristic has a much larger effect on health than the primary emissions of VOC, VVOC
and/or SVOC altogether.

For HVAC systems, procedures for testing emissions cannot be the same as for construction
and finishing products. Therefore, a different approach has to be considered including specific
attention to compounds transferred and emitted in the in-use phase. Procedures for testing
components of HVAC-systems have been developed [63], but they require pre-normative work
to become usable for standardisation purposes.

Regulations on maximum allowable concentrations are only valid if a clear relation has been
established between the compound regulated and health. In practice these regulations are very
difficult to comply with (measurement in homes cannot be performed on a regular base and the
concentration as well as the types of indoor air pollutants may vary widely as a function of both
time and space). They originate from ambient (outdoor) air regulations, which is a different

problem all together. Regulations for products that possibly emit those regulated compounds is
a much better way to go, specially when it concerns compounds that are (potentially)
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carcinogenic. In fact, when a compound has been clearly identified as being carcinogenic it
should be banned and not allowed to be used at all (asbestos is a good example, but
formaldehyde is a candidate as well, especially originating from ureaformaldehyde resin used in
many wood based products).

Nevertheless, a minimum ventilation rate to dilute pollutant concentrations is always required.
This minimum ventilation rate should not be based on presence of occupants only, but include a
certain rate per square meter of surface area of a space [54] [55]. Even though materials are
selected based on their minimum emission rates, still some emission will take place, whether it
is primary or desorbed secondary emissions. But it should be noted that only regulating on

ventilation is not enough!

Awareness
Awareness of the problem is of utmost importance. We see that for example with architects
and housing corporations, but also product producers and the end-users (occupants)
themselves, this awareness with respect to IAQ in general is not present. Indoor air is thought
to be the same as indoor climate, and therefore related to thermal comfort aspects such as too
warm and too cold. We have a long way to go in that perspective.

In the European project HealthyAir interviews are performed with three target groups
(product producers, architects and housing corporations) to inventory the awareness and the
ways to improve awareness, and moreover to identify ways, strategies, tools, methods to
make them to improve indoor air quality [9]. So far can be concluded that education is of
utmost importance. Education via press releases, television spots, leaflets, internet, courses for
professionals, introduction at elementary schools (with kids from 6-8 years and older for
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example), in high school programmes linked to sustainability; specific courses at universities;
involvement of professional organizations (stakeholders), etc.

In the European coordination project EnVIE [7], the starting point is health effects and how to
reduce those via policy making (see textbox 3) at European level mainly. A green paper is
expected to be written as a follow-up.

Another way of raising awareness is to make it commercially attractive for stakeholders to
include indoor air quality in their daily business. The introduction of labeling is a way of
doing that.
On the one hand there is an European initiative to establish a harmonised labelling system for
building products and components [5] and on the other hand labelling of buildings linked to
sustainability is promoted (see Textbox 4 and 5). At European level, the technical commission
of European standardisation organ CEN TC 351 could form the base for a building product
label, while the CEN TC 350 is more focused on the building label linked to sustainability.

Now the question is: Would both labels have a reason for existence? In other words: will the
labels be used by the target groups for which they are intended? When it is mandatory, of
course, the labels will have to be used. But, eventually it all comes down to the fact whether
they fit the purpose: improve indoor air quality for its occupants.
A label on product level, will at least ascertain that the total emissions of products are reduced
and therefore the total amount of substances emitted to the air, will decrease. The Finnish
experience with the M1 has proven that this can work to a certain extent. Since a “complete
picture” of the effects of substances on each other and on people is missing, the best that can
be done is to reduce exposure and therefore reduce the sources of emissions in the first place.
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The labels linked to sustainability as they exist today do not include the detailed information
required to identify sources of pollutants encountered in the indoor air. Those type of labels
provide generalisations of a building and do make it possible to remediate of even destroy
buildings that are without a doubt dangerous to the indoor air quality (for example when
containing asbestos). They also make it possible for regulators to inventory trends on national
level, but for the individual end-user it will never be possible to guarantee a healthy building
based on those kind of generalisations. The human factor and the changing indoor and
outdoor conditions have too much influence to make a “static tool” as a building label ever
applicable on an individual level, unless the complete picture is available and simplifications
have been made.

Risk assessment
Both for the establishment of end-users wishes and demands (requirements and needs), and,
the communication process required to facilitate the design, construction, maintenance and

occupation of an indoor environment, another approach is required. For example the so-called
interactive top-down approach [2]), in which two things are essential: setting the basic
requirements at the start and good communications between all the stakeholders. Risk
assessment forms the starting point for setting the basic requirements.

Because it is so difficult to directly relate single measurable physical and/or chemical
parameters with health and comfort effects in the indoor environment, methods using some
sort of a risk assessment have been developed. These methods consider and list whether a
certain source or action can cause a health or comfort effect in a certain situation. Clearly
identifiable relations have been found between certain building characteristics/user patterns
and self-reported (health) complaints. The relationship between “to fulfil recommendations
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for design, operation and maintenance of HVAC systems” from the European AIRLESS

project [63], and the number of self-reported complaints in the HOPE project, is an example
[68]. When relations between certain building characteristics / activity patterns and (health)
complaints are known, it is possible to set new/different guidelines (performance indicators
and performance criteria) and evaluation methods, based on which new building concepts can
be realised.

In the design and construction of a new building, a risk-assessment procedure for health and
comfort of people in the indoor environment, could for example comprise the following steps
(inspired by [69]):
1. Identify the end-users wishes and demands, their profile (if possible the mental and
physical status of the end-users of concern including the context and attributes discussed
above) and try to translate those to boundary conditions and criteria for the indoor
environment.
2. Identify the possible risks involved, with assistance of all stakeholders involved (including
the end-users), related to the defined environmental criteria and the end-users profile(s).
3. For simple or known risk problems with few uncertainties the classical quantitative
statistics can be used. For example using existing standards on formaldehyde, PM, etc.
Additionally, known patterns of risks in relation to certain building characteristics should
be applied. (Available field study data could for example be used to create a knowledge
based system for thus purpose).
4. For comfort related risks (those with the possibility that they could become a health risk),
the end-user needs to be involved directly. A prototype of the object of concern or a
reconstruction of the intended activity could be applied. If necessary, (scientific) experts
need to be consulted. Please do not assume that there is a standard responding person.
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5. For health related risks related to more than one factor and for which no acceptable
standards or guidelines are available, the balance between efficiency and fairness needs to
be discussed. For example the risk of getting sick from growth of micro-organisms on a
certain material that is known to be favourable for such growth, is not easily evaluated
even if one knows it can happen. It is a matter for discussion whether it would be
reasonable to use this material in places favourable for growth such as bathrooms.
Another example is the use of HVAC systems in the light of energy use versus health.
6. If controversy regarding risk aspects occurs (other than the probability and extent of
health damage), or a new risk previously unknown is identified then the stakeholders
should be involved in subsequent discussion. For example in the risks of new design
concepts using new materials and configuration, it is perhaps necessary to perform
behavioural observations, interviews, etc.
7. If uncertainties increase in seriousness and extent (for example climate change effects or
(fine) dust from outdoors), a scientific analysis or even a political societal debate is
required. This will result in a definition of the widely accepted risk problem, a strategy to
measure the problem or to keep it ‘on the table’ and eventually to design a decision
framework.

At European level several initiatives focused on indoor air quality are working with risk
assessment (see textbox 6 and 7). Unfortunately, they merely focus on indoor air and do not
consider interactions with other parameters of the indoor environment.


CONCLUSIONS AND RECOMMENDATIONS
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Minimum ventilation rates based mainly on body odour (with CO
2
as an indicator) and to
some extent on primary emissions of some building materials, are not preventing occupants
and visitors of a space to develop health symptoms (cancer, asthma, etc) and/or comfort
complaints (odour, irritation). The indoor air comprises a complex mixture of compounds of

which the source and effects are hardly known for all, and threshold levels for all seem
unrealistic considering the numerous compounds. A clear knowledge gap exists on health and
comfort impacts of contaminants and differences in these impacts among individuals. But also
knowledge gaps exists on the mechanisms between the different pollutants, interactions with
other pollutants in the air but also the surfaces of the sources.
From current research outcomes it seems that there is an urgent need to involve medicine and
neuro-psychology in research to investigate the mechanisms behind dose-response, health
effects and interactions between and with the other factors and parameters of the indoor
environment and the human body and mind. The use of humans as sensors is herewith of
utmost importance.

Even though several initiatives are being undertaken at different levels from different point of
views to improve the ways to get to a better indoor air quality, it should be emphasized that, a
holistic approach is required including the sources, the air and last but not least the human
beings (occupants) themselves, in which more than one way is applied. Even though we do
not fully understand the mechanisms behind the physical, chemical, physiological and
psychological processes, it is still possible to identify the different ways to be taken
regulatory, politically-socially (awareness), technically (process and product) and
scientifically. Several ways have been suggested in the above and summarised in textbox 8. It
is important to realise that those ways should not be undertaken separately, but integrative and
holistically.
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