towards an integrative approach of improving indoor air quality

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.. Besides the fact that there

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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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 philo.bluyssen@tno.nl

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 m2 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 (CO2 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 NO2 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 NO3·) occur in the indoor environment Secondary products formed comprise of formaldehyde, aldehydes and NO2 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 (PM2.5) and lowest for coarse (PM10) 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 20th 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 19th 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

- 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

T PI R C S U N A M

D E T P E C C A

Minimum ventilation rates based mainly on body odour (with CO2 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