Inhalation

Inhalation exposure can take place if volatile compounds evaporate during the mixing process. The inhalation – exposure to vapour – evaporation – release area mode: constant model may apply here, where release from a constant area is considered. This model is selected as the default to describe the inhalation exposure from mixing and loading two-component DIY products.

Room volume and ventilation rate

Since the release of volatile substances from the mixing and loading activity occurs in the personal breathing zone, only this small area is relevant to inhalation. ‘Room volume’ is therefore interpreted here as personal breathing zone: a small area of 1 m³ around the user, relevant to the inhalation exposure for the short use duration in which the mixing takes place. A Q-factor of 1 is assigned because this is an assumption based solely on expert judgement.

A ventilation rate of 0.6 h^-1 (te Biesebeek et al., 2014) for an unspecified room is used. This value reflects the default value for air exchange between the room and the outside environment, while the air exchange between the personal breathing zone and the rest of the room is not accounted for, mainly because of the briefness of the mixing effort. A Q-factor of 1 is assigned.

Mass transfer coefficient (MTC)

A generic default value for the mass transfer coefficient of 10 m/h is proposed. This generic default is usable for a situation where specific properties of the substance, the product and the indoor environment are not considered. The Q-factor is set to 2, because of the generic and conservative character of the calculation from which the default is derived.

For further explanations regarding the derivation of the default, please check the overarching issues document provided by RIVM (RIVM, 2018).

Release area

Evaporation of volatile substances is expected from the surface of the mixture in the used mixing vessel.

According to the total product amount that has to be mixed, the vessel may differ. For smaller tasks (total mixed product amount < 5 kg) a bucket with a 12-l capacity seems sufficient. Commonly used buckets in this dimension provide a constant release surface area of 800 cm² (diameter = 32 cm), which is supported by information acquired in a short screening of the available products on the German market (see Table 121). For larger tasks (total mixed product amount > 5 kg) the vessel should provide enough capacity for 20 l product, which results in a release surface area of 1100 cm² (diameter = 37.5 cm) (see Annex II A.5). Both release area values will be set as the defaults in the mixing and loading processes with the related dimension of product amount. Because mixing buckets with these specifications are commonly offered by most DIY retailers, the Q-factor for the default is set to 2.

Molecular weight matrix

The products available on the DIY market are mainly mixtures containing several constituents with different physicochemical properties. Because the evaporation process is not only determined by the substance of interest but by all compounds, the molecular weight matrix parameter is necessary. It is used to correct the evaporation rate since it describes the average molecular weight of the rest of the total product (product minus substance of interest). When the product only consists of substance, with a purity of 100%, this value can be left blank. However, in most cases the exact composition of a product is not exactly known. For this issue, a conservative default value of 3000 g/mol will be set, which is adapted from the Paint Fact Sheet where this value is used for solvent-rich paint. In this case, the main solvent is also the substance of interest, and its vapour pressure is not excessively influenced by other compounds in the paint because their concentration is expected to be rather low, or their molecular weight is very high. Further explanations regarding the molecular weight matrix are available in subsection 2.1.3 of the Paint Products Fact Sheet (Bremmer & van Engelen, 2007) and in the ConsExpo Web Manual (Delmaar & Schuur, 2016).

Dermal

Dermal exposure occurs when the two components are mixed together with some kind of tool. It is assumed that the surface area of two fingertips (small tasks; small mixing vessel, e.g., a cup) or of five fingers (larger tasks; bigger mixing vessels, e.g., a bucket) will be exposed from holding the tool or splattering. The dermal – direct product contact – instant application model is used to calculate the dermal exposure.

Exposed area

The fingertip is defined here as the top phalanx of one finger. According to the General Fact Sheet, the surface area of one hand (both sides) is 450 cm² (te Biesebeek et al., 2014). Half this area is assumed to belong to the fingers, which equals 225 cm². Consequently, the surface area of one finger is 45 cm² divided into 3 phalanges (15 cm² per phalanx). Therefore, the area of two fingertips, or rather top phalanges, is set at 30 cm² (default). Some products have to be mixed in much larger quantities (> 1 kg). In those cases, the dermal contact area is much larger, and it is assumed that the surface area of all 5 fingers will be exposed (=225 cm², see above) (te Biesebeek et al., 2014). An exception here is the mixing and loading of adhesive putty where extensive dermal exposure occurs while using just a small product amount (see subsection 6.5.2).

Inhalation

To calculate the inhalation exposure during mixing and loading within ConsExpo Web, the inhalation – exposure to vapour – evaporation – release area mode: constant model is used.

Room volume and ventilation rate

The defaults for the room volume and the ventilation rate are set according to the considerations made in subsection 4.1.1. The room volume is set to 1 mm³ (personal breathing zone), and the ventilation rate is 0.6 h^-1. The latter value reflects the default value for air exchange between the room and the outside environment, while the air exchange between the personal breathing zone and the rest of the room is not accounted for.

Release area

Evaporation of volatile substances is expected from the open bottle and the surface of the mixture in the vessel. The surface of any measuring cup is neglected at this point because the substance will not remain in the cup for long. Therefore, this potential exposure source will be covered by taking into account the evaporation from the bottle opening, too.

It is assumed that the product is contained in a one-litre bottle that has a circular opening of 5 cm diameter and a surface area of 20 cm².

According to the total product amount that has to be mixed, the vessel used may differ. For smaller tasks (total mixed product amount < 5 kg) a bucket with a 12 l capacity seems sufficient. Commonly used buckets in this dimension provide a constant release surface area of 800 cm² (diameter = 32 cm) which is supported by information acquired in a short internet and on site (2 DIY markets) screening of the available products on the German market conducted by the authors of this report. For larger tasks (total mixed product amount > 5 kg), the vessel should provide enough capacity for 20 l product which results in a release surface area of 1100 cm² (diameter = 37.5 cm) (see Annex II A.5). As the opening of the bottle (20 cm²) has to be considered too, the default release area for mixing and loading liquids amounts to 820 cm² for smaller tasks and to 1120 cm² for larger tasks. Because mixing buckets with these specifications are commonly offered by most DIY retailers, the Q-factor for these defaults is set to 2.

Dermal

To estimate the dermal exposure within ConsExpo Web, the dermal – direct product contact – instant application model is used for both direct pouring and loading with measuring cups.

Exposed area

It is assumed that direct pouring of liquids leads to dermal exposure on the side of the hand directing the bottle to the bowl or bucket. The default for the exposed area is set to be equal to one side of the hand, 225 cm², which is in accordance with the General Fact Sheet (te Biesebeek et al., 2014). Since the assumption that one side of the hand is exposed is based solely on expert judgement (although the default for hand surface area is derived from a data-rich source), the Q-factor is set to 1.

Product amount – dermal

The Biocides Human Health Exposure Methodology Document (ECHA, 2015a) human dermal exposure to biocides during the process of dispersing a concentrate from a container and diluting it with water in a vessel. The 75^th percentile for dermal exposure during this mixing and loading event is 0.01 ml, irrespective of the amount poured (ECHA, 2015a). Assuming a liquid density of 1 g/cm³, the default for the product amount landing on the skin during direct pouring is set to 0.01 g. Because of the availability of quantitative but specific (non-generic) and limited data (i.e., 4 measurements), the Q-factor is set to 2.

Inhalation

In the general mixing and loading scenario of a powder product, the powder is poured either directly from the package or with the help of a measuring cup into a mixing bucket. In the following considerations, no distinction is made between the two variations of pouring because they are not expected to result in exposure differences.

This Fact Sheet follows a different approach from the 2007 version (ter Burg, 2007) to describe the inhalation exposure while mixing and loading powders. The ConsExpo inhalation – exposure to spray – instantaneous release model (Delmaar & Schuur, 2016) is now recommended to estimate the exposure caused by inhalation of product particles. The physicochemical properties of solid aerosols emitted by sprays have much in common with the ones from powders, e.g., the very low volatility and their similar particle shapes. Although a powder is obviously not a spray, the instantaneous release of the spray model is thus best suited to approximate the exposure during the loading of powder. The release is expected to be very short-lived and therefore, the instantaneous release is preferred over the spray model. Default values are provided for the following model parameters for simulation of the generic scenario of exposure to powders (Meesters et al., 2018).

Frequency

In some cases, the amount of powder and water that needs to be mixed is too much to handle in one mixing effort. It is expected that the common DIY user will not have the equipment (automatic mixing device, sufficiently big mixing vessel) nor the physical properties (strength, endurance) in order to mix powder amounts that exceed 5 kg. Furthermore, it might become problematic to mix higher amounts because it is possible that the mixture will harden before it can be completely used.

Therefore, if the amount of 5 kg powder is exceeded, it is assumed that more than one mixing effort has to be conducted. The frequency of the mixing and loading scenario will then be set to be equal to the mixing repetitions that are required. If, for example, 30 kg powder have to be mixed with 7.5 l water, the frequency would be 6 times per event (event = use of tile glue, for instance).

Exposure duration

Specific data regarding the duration of mixing and loading filler products was recently gathered in a feasibility study. In total, there were 83 data points with a minimum of 0.5 minutes and a maximum of 20 minutes. The 75^th percentile equals 3 minutes (Schneider et al., 2018). As there is no further data available for other DIY products, this value will be used as a default for the exposure duration taking into account the assumption that the mixing person is exposed during the whole mixing and loading process. The Q-factor is set to 2 because the parameter is based on only one source.

Released mass

Little information is available about the fraction of powder that is released to indoor air during mixing and loading powder products. Information on dust formation of washing powder is provided in the Cleaning Products Fact Sheet (Meesters et al., 2018; van de Plassche et al., 1999). The original experiments and home observation studies were performed by Hendricks (1970). The author found “that there is on average 0.27 µg detergent dust exposure per cup of product used”. Here, the detergent dust exposure refers to the amount of laundry detergent inhaled while “pouring the product from the carton into a measuring aid and then to the washing machine” (Burg et al., 1977; Hendricks, 1970; van de Plassche et al., 1999). It is possible to recalculate the supposed released mass in the experiments of Hendricks (1970) based on the laboratory conditions described (sampling time of 2 minutes, distance to dust source within personal breathing zone, inhalation rate of 16.3 l/min), by assuming that Cons Expo’s inhalation – exposure to spray – instantaneous release model (Delmaar & Schuur, 2016) is suitable for such a calculation and that the duration of the experiments is too short for the ventilation rate to be effective. The supposed released amount per cup (8.3 µg) is calculated as follows:

8.3 µg released mass per 200 g powder used will be used as the default value. The following assumptions are made in the calculation of the released mass: an instant release model is suitable for the calculation above, ventilation and gravitational settling of the dust is negligible for the exposure time considered and the short distance of the analytical device to the loaded powder directly leads to a release into the personal breathing zone of 1 m³. Because of these limitations, the Q-factor for this default is set to 1.

Room volume and ventilation rate

Room volume is interpreted here as the personal breathing zone, a small area of 1 mm³ around the user. Only this small area is relevant for the inhalation exposure during the brief time period that mixing and loading takes. The Q-factor is considered to be 1, because the interpretation of the personal breathing zone is based on expert judgement.

A ventilation rate of 0.6 h^-1 (te Biesebeek et al., 2014) for an unspecified room is used. This value reflects the default value for air exchange between the room and the outside environment, while the air exchange between the personal breathing zone and the rest of the room is not accounted for. A Q-factor of 1 is assigned.

Dermal

Dermal exposure to powders can be taken into consideration for mixing the powder with water. Within ConsExpo Web, the dermal – direct product contact – constant rate model is suggested to estimate dermal exposure to powder during loading.

Exposed area

It is assumed that both palms will be dermally exposed during mixing and loading through dust falling on hands or direct contact with the powder. According to the General Fact Sheet, 50% of two hands (=two palms) have a surface of 450 cm², which will be used as a default here (te Biesebeek et al., 2014). The Q-factor is set to 2 because the underpinning data for the size of the hands is quantitatively rich but the final determination which body parts will be affected during the task is based on expert judgement (see also subsection 4.5).

Contact rate

In the Guidance on the EU Biocidal Products Regulation (BPR), a dermal exposure study for the use of sprinkling/dusting powders to control dust mites has been described (ECHA, 2015a). The subjects in the study applied crack and crevice powders in a kitchen treating skirting boards, shelves and laminate surfaces. The dermal exposure on hands and forearms ranges from 0.4 to 4.18 mg/min with a 75^th percentile of 2.83 mg/min. The contact rate for dermal exposure for legs, feet and face ranges from 0.22 to 6.56 mg/min with a 75^th percentile of 2.15 mg/min. It is assumed that the values can be adapted for the mixing and loading of DIY powder products. The value for the contact rate of approximately 5.0 mg/min (2.83 + 2.15) is set as a default. The Q-factor is considered to be 1, because the underlying data is rich but collected for the application (not mixing and loading) of biocides in the form of powder.

Release duration

The release duration is assumed to be similar to the exposure duration for inhalation exposure. 3 minutes is set as the default with a Q-factor of 2 because underpinning data is limited.

Inhalation

A major pathway of exposure to spray applications is the inhalation of respirable aerosols generated during the use of aerosol spray cans, trigger sprays and pneumatically/airlessly distributed sprays. Inhalation exposure to these aerosols is driven by a variety of exposure parameters, such as the ventilation rate of the room, the duration of presence of the exposed person in the room during or after spraying, and the way the product is used. Additionally, product-specific characteristics such as the composition, the pressure or the used container (nozzle), are highly relevant to the resulting exposure.

The general exposure scenario for inhalation of substances from spray applications provides interpretations and/or defaults for parameters referring to spray duration, density of non-volatile substances and mass generation rate (i.e., the released mass per unit of time during spraying) for aerosol spray cans, trigger sprays and pneumatically/airlessly distributed sprays.

The exposure to vapour – evaporation – instantaneous release model is used to estimate the exposure to volatile substances from DIY products available on the market as sprays. The Exposure to spray – spraying model is used to estimate inhalation exposure to non-volatile substances when using DIY products as sprays. The parameters of this spray module within ConsExpo Web have been experimentally evaluated in the report by Delmaar & Bremmer (2009). Exposure duration, room volume and ventilation rate are parameters that are not generic. Instead, defaults are specifically derived for each scenario of consumer exposure. The other parameters in the exposure to spray – spraying model are discussed below, describing either the derivation of a generic default value or at least a generic approach to do so. These generic defaults and approaches are consistent with the ConsExpo Web manual (Delmaar & Schuur, 2016), the set of experiments evaluating the critical parameters of the model (Delmaar & Bremmer, 2009), and the General Fact Sheet (te Biesebeek et al., 2014). All consumer exposure scenarios described in the current Fact Sheet to substances in DIY sprays do not consider the ‘spraying toward person’ option, because the intended use is to spray towards surfaces that are to be treated.

Spray duration

‘Spray duration’ is defined here as the net spraying time between start and finish of spraying during the whole event, not counting the time between sprays (Delmaar & Schuur, 2016). A clear definition of ‘spray duration’ is important, because the amount of spray available for inhalation is simulated in ConsExpo Web from the mass generation rate of the spray, the spray duration and ventilation (Delmaar & Schuur, 2016). Default values for spray durations are derived per specific scenario for consumer exposure.

Room height

The default of room height is based on a standard room height of 2.5 m as explained in the General Fact Sheet (te Biesebeek et al., 2014) with a Q-factor of 4 because the underpinning data is quantitatively rich.

Inhalation rate

Spray tasks are considered to be light exercise in the DIY sector. The inhalation rate is therefore set to 1.49 m³/h by default for adults (te Biesebeek et al., 2014).

Mass generation rate of aerosol spray cans

The definition of mass generation rate of sprays is in contrast to that of the Cleaning Product Fact Sheet published in 2006 (Prud’homme de Lodder et al., 2006) where mass generation rate is defined as the average mass released per unit of time over the entire duration of the cleaning task. In the current Cleaning Product Fact Sheet, and consistently in the DIY Products Fact Sheet, the mass generation rate of a spray product is defined as the mass released per unit time of spraying. In the study by Delmaar & Bremmer (2009) such mass generation rates were determined for aerosol spray cans by spraying for 10 seconds and determining the weight loss in the spray can afterwards. To get more insight into the variation of the mass generation rate during the lifetime of the product, the weight loss was measured when the spray container was still full and also when the container was nearly empty (Delmaar & Bremmer, 2009). In these experiments, performed on 17 aerosol spray cans, the mass generation rate ranged between 0.29 and 2.2 g/s. This is consistent with the data from a comparable series of experiments by Tuinman, which show a 75^th percentile of 1.2 g/s (Tuinman, 2004; Tuinman, 2007). The default mass generation rate for aerosol spray cans is therefore set at 1.2 g/s. The Q-factor is set to 3, because the underpinning data is quantitatively rich but in a specific exposure scenario, a specific mass generation rate is still preferred over a generic one.

Mass generation rate of trigger sprays

In addition to the aerosol spray cans, Delmaar & Bremmer (2009) experimentally determined mass generation rates for trigger sprays by squeezing 10 times (which approximately takes 6 seconds) and determining the weight loss in the spray can afterwards. The obtained mass generation rates of 6 different trigger sprays ranged between 1.0 and 1.5 g/s. This is consistent with the data from the comparable series of experiments by Tuinman, which show a 75^th percentile of 1.6 g/s for trigger sprays (Tuinman, 2004; Tuinman, 2007). The default mass generation rate for trigger sprays is therefore set at 1.6 g/s. The Q-factor is set to 3, because the underpinning data is quantitatively rich but in a specific exposure scenario a specific mass generation rate is still preferred over a generic one.

Please note that the above data on mass generation rates is based on pest control products, cleaning products, cosmetics, paints, lubricants, polishes and cockpit sprays, but not on DIY products. At present, there is no other data available to derive the mass generation rate for DIY products in spray form. The compositions and volume distributions may be significantly different for DIY products; nevertheless, the data will be used as a preliminary source and indication for the dimensions of the values.

Airborne fraction

The airborne fraction is defined as the fraction of the non-volatile material that becomes airborne after spraying as droplets. Default values for the airborne fraction depend on the way in which the product is being used, as well as on the aerosol diameter distribution that has been specified. DIY sprays (glue, putty, plaster, several types of removers) are used to treat surfaces and therefore, are sprayed away from the user onto the surface. Delmaar & Bremmer (2009) have derived a default airborne fraction of 0.2 for such surface spraying activities. This default airborne fraction for surface spraying is derived from data collected for all purpose cleaner spray and flea spray. A specific airborne fraction for DIY sprays, however, was not included the series of experiments by Delmaar & Bremmer (2009). The default surface spraying airborne fraction of 0.2 is included in the calculation of an airborne fraction of DIY sprays that is scaled for the aerosol droplets < 22.5 µm.

Delmaar & Bremmer (2009) state that spray droplet sizes fitted from experimental data to lognormal distributions across the entire range generally proved to be poor. As the smaller aerosols in the distribution are the most critical with respect to inhalation exposure, Delmaar & Bremmer (2009) chose to fit the size distributions in the region of diameters up to 22.5 μm, realising that the fit of the distribution for larger aerosol sizes may not be valid. The airborne fraction for surface spraying is therefore multiplied by a scaling factor that refers to the mass fraction of sprayed droplets < 22.5 µm.

The default aerosol diameter for DYI sprays (see aerosol diameter below) actually refers to aerosol diameter distributions with a median diameter of 15.1 µm and a c.v. of 1.2 for pneumatic sprays and 7.7 µm and a c.v. of 1.9 for trigger sprays. These aerosol diameter distribution parameters are actually fitted to best represent the mass fraction of spray droplets, which are < 22.5 µm in series of experiments performed on spray paints and sprays against crawling insects. In addition, Delmaar & Bremmer (2009) derived a scaling factor of 0.7 for the spray paints and a scaling factor of 0.04 for sprays against crawling insects. The airborne fraction is to be multiplied by these scaling factors (Delmaar & Bremmer, 2009), so that the airborne fractions in this Fact Sheet are: 0.2 × 0.7 = 0.14 for the pneumatic DIY sprays and 0.2 × 0.04 = 0.008 for DIY trigger sprays (See Table 3 below).

The Q-factors are set to 2, because the surface sprays that are evaluated in the experiments of Delmaar & Bremmer (2009) include only a small number of samples and none of them belonged to the DIY sector.

Inhalation cut-off diameter

The inhalation cut-off diameter is defined as the diameter below which the sprayed aerosols can be inhaled and reach the lower areas of the lungs, i.e., the alveolar region (Delmaar & Schuur, 2016). It is only an approximation of the complicated process of deposition of aerosols in the lungs, but in practice, its value is suggested to be set at 10–15 μm (Delmaar & Schuur, 2016). In order to be conservative, the default for inhalation cut-off diameter is set here at 15 µm. The Q-factor is considered to be 3, because the value is specifically but qualitatively derived for the parameter inhalation cut-off diameter.

Density non-volatile

The density of the non-volatile fraction is one of the parameters included in the spray model and is defined here as the density of the aerosol droplets that become airborne. Together with the droplet diameter, the aerosol density determines the time that the aerosol droplet is airborne and therefore available for inhalation. Many non-volatile ingredients in DIY products are made of (very) large organic substances with densities between 1.0 and 1.5 g/cm³. The density of salts generally varies between 1.5 and 3.0 g/cm³. For a complex mixture of (organic) substances, the default density is set at 1.8 g/cm³. The Q-factor is set to 3, because density is a physicochemical property that is evident for most substances, but it is presented here on a generic level (Table 4).

Table 4

Default values for density non-volatile substances (Prud’homme de Lodder et al., 2006a).

Aerosol diameter

The aerosol diameter of the sprayed droplets is an important parameter when estimating the exposure. Smaller drops fall at a lower speed and stay in the air longer. Large droplets will quickly disappear from the air after being formed. As an indication, the falling time of droplets with a diameter of 100 µm from a height of 3 metres is calculated to be 11 sec, and for droplets of 10 µm it is calculated to be 17 minutes (Biocides Steering Group, 1998). If a larger droplet is sprayed, part of the aerosol cloud will consist of finer droplets, which will stay in the air longer, as a result of edge effects around the nozzle and the ‘bounce back’ effect due to spraying onto a surface.

Measurements provided by Delmaar & Bremmer (2009) and Tuinman (2007) regarding the aerosol diameter distribution of various spray products lead to the default values listed in Table 5.

At present, there is no information available on the aerosol diameter distributions of DIY products. Nevertheless, as DIY sprays are exclusively used for surface spraying, it is assumed that results referring to similarly used spray products can be considered to be reasonable estimates for the DIY sector, too. Following this paradigm, the default for aerosol spray cans is set at a lognormal distribution with a 15.1 µm mass median diameter and c.v. of 1.2 (default for paint containing spray cans fitted to best represent the mass fraction of droplets < 22.5 µm). Furthermore, the default aerosol diameter distribution for the use of trigger sprays is a lognormal distribution with a mass median diameter of 7.7 µm and a c.v. of 1.9 that was originally fitted to best represent the mass fraction of droplets < 22.5 µm in sprays against crawling insects. The Q-factors are set to 1.

Table 5

Defaults for aerosol diameter distribution (median [µm] and coefficient of variation) (Delmaar & Bremmer, 2009).

Oral non-respirable material exposure

Non-respirable oral exposure is expected from material in aerosols with a diameter larger than the inhalation cut-off diameter. Aerosols of this size are deposited in the higher regions of the respiratory tract, so that they are taken up orally. ConsExpo offers the option ‘include oral non-respirable material exposure’. If this option is checked, ConsExpo adds an oral route model to the exposure scenario and accounts for the non-respirable fraction of the inhaled spray. By default, the option is not ‘included’ for DIY sprays, because the larger aerosols are mostly prone to deposit on the surface at which the spray is directed.

Inhalation of volatiles

The inhalation exposure to volatile substances in cleaning sprays is estimated using the inhalation – exposure to vapour – instantaneous release model. The defaults for the parameters exposure duration, room volume, ventilation and inhalation rate described for non-volatiles in sprays (see above) also apply to volatile substances.

Inhalation

The evaporation pattern of adhesives is different from that of most other DIY products. In contrast to paints, for instance, the surface from which chemicals from adhesives can evaporate is not constantly ‘open’. Adhesives are implicitly used to connect parts. This means that the adhesive is covered with the part that is to be connected. The time during which there actually is a surface–air situation is described as the ‘open time’ of glue. This open time may range from a few seconds to several minutes. The duration of this open time depends on the hardening process and thus on the type of glue. Solvent-based adhesives have relatively short open times, in contrast to (most) water-based adhesives, due to a relatively higher evaporation rate. Polyurethane-based glues are covered after application to prevent reaction with moisture, which is not desirable for a good end result.

The evaporation pattern of adhesives starts with a relatively high temporal evaporation rate (during open time), which is then followed by a relatively slow constant evaporation rate (when the surface is covered). Experimental data from solvent-based glue products shows that the starting emission rate is of the magnitude of 0.4 g/m² per second. After covering the applied product, the vapour concentration will rapidly drop below the odour (smell) detection limit (in the order of 10–20 ppm for solvents) (personal communication with Vereniging Nederlandse Lijmindustrie (VNL) conducted by RIVM during the preparation phase for the 2007 DIY Products Fact Sheet).

Currently, there is no evaporation model in ConsExpo which can describe this two-phased evaporation pattern of adhesives. For this reason, the exposure to vapour – evaporation – release area mode: increasing model is used for relatively small tasks (and amounts). The time during which evaporation takes place is set to be equal to the exposure duration, which is in fact a conservative approach.

Relevant parameters for the exposure to vapour – evaporation – release area mode: increasing model besides the general parameters (exposure duration, product amount, weight fraction of the substance, room volume and ventilation rate) are:

• Release area: The total surface area the product is applied to.
• Application duration: The time period during which the product is applied.
• Temperature: The room temperature prevailing during exposure.
• Molecular weight and vapour pressure: The physicochemical properties of the substance in question.
• Mass transfer coefficient: The rate that describes the transfer of the substance in question between the product’s surface and the air. For further explanations, see subsection 4.1.1.

However, this approach is not considered appropriate when larger gluing tasks are considered. A large task must be divided into segments when the total time required to apply the glue and connect the parts exceeds the open time of glue (see above). This will result in repeated ‘peak’ exposures during the task. Examples of such large tasks are gluing parquet, tiles and carpets. The exposure to vapour –evaporation – release area mode: constant model is used for repeated ‘peak’ exposures within a task. The relevant parameters for this model are largely similar to those mentioned above. One exception is the emission duration, which is necessary instead of the application duration.

• Emission duration: The time period during which the substance is released from the product.

Because (simultaneous) evaporation from the total surface area during a large project is not realistic (laying carpet, gluing parquet etc.), an alternative description of exposure is required to integrate the repeated exposures during these large tasks. The release area is set to be equal to the surface area one can treat per segment. It is assumed that an individual treats 1 m² per segment (4 m² for carpet gluing). After that, the surface is covered, and the exposure is considered negligible compared with the surface to be treated next. These steps are repeated until the task is completed. It is assumed that the inhalation exposure is described by evaporation of the total amount, rather than the adjusted amount, from a constant surface area, i.e., 1 m². The exposure to vapour – evaporation – release area mode: constant model is used. This simplification of the model is necessary, to overcome the problem of depletion of the source. The emission duration and the exposure duration are set to be equal during these tasks because considering the interval approach, a source depletion of the segments is not expected.

Dermal – direct product contact – instant application

Dermal – direct product contact – constant rate

Inhalation

Inhalation of water-diluted products is calculated using the ConsExpo inhalation –exposure to vapour – evaporation model (Delmaar & Schuur, 2016). In order to follow the generic exposure scenario for product dilution with water, some interpretation and defaults are required for the parameters product amount (dermal) and dilution times.

Dermal

If the dermal – direct product contact – instant application model is used to calculate dermal exposure from diluted products, the following considerations for the product amount should be taken into account (mainly for smaller applications).