ASTM D6669 – 01

Designation: D 6669 – 01a Standard Practice for Selecting and Constructing Exposure Scenarios for Assessment of Exposures to Alkyd and Latex Interior Paints1 This standard is issued under the fixed designation D 6669; the number immediately following the designation indicates the year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript epsilon (e) indicates an editorial change since the last revision or reapproval. 1. Scope 1.1 This practice provides procedures for constructing sce- narios for assessment of inhalation exposure to airborne emissions of chemicals released from alkyd or latex paints that are used indoors. 1.2 The indoor environments covered in this practice, in terms of considerations for developing exposure scenarios, are residences and office buildings. 1.3 Elements of the exposure scenarios include the product and chemical(s) to be assessed, the indoor environment where the product is applied, application of the product, chemical emissions during and after product application, and location/ activity patterns of individuals who may be exposed to the airborne chemical emissions. 1.4 Steps to be performed after developing exposure sce- narios, such as monitoring, modeling and exposure/risk assess- ment, also are described. 1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appro- priate safety and health practices and determine the applica- bility of regulatory limitations prior to use. 2. Referenced Documents 2.1 ASTM Standards: D 1005 Test Method for Measurement of Dry-Film Thick- ness of Organic Coatings Using Micrometers2 D 1212 Test Methods for Measurement of Wet-Film Thick- ness of Organic Coatings2 D 1356 Terminology Relating to Sampling and Analysis of Atmospheres3 D 5116 Guide for Small-Scale Environmental Chamber De- terminations of Organic Emissions from Indoor Materials/ Products3 D 6178 Practice for Estimation of Short-Term Inhalation Exposure to Volatile Organic Chemicals Emitted from Bedding Sets3 D 6485 Guide for Risk Characterization of Acute and Irri- tant Effects of Short-Term Exposure to Volatile Organic Chemicals Emitted from Bedding Sets3 E 741 Test Method for Determining Air Change in a Single Zone by Means of a Tracer Gas Dilution4 3. Terminology 3.1 Definitions—For definitions of terms used in this prac- tice refer to Terminology D 1356. 3.2 Definitions of Terms Specific to This Standard: 3.2.1 emission profile, n—a time-series of emission rates of one or more compounds. 3.2.2 exposure scenario, n—a description of how and where an estimated exposure occurs, including (1) the location and emission profile of the product or material that causes expo- sure, (2) the indoor environment where the individual is exposed to airborne emissions from the product or material, and (3) the location and activity patterns of the exposed individual. 3.2.3 potential inhaled dose, n—the product of air concen- tration to which an individual is exposed times breathing rate times duration of exposure. 3.2.4 short-term exposure, n—an exposure of one week or less in duration. 4. Summary of Practice 4.1 This practice documents the items that need to be described when developing an exposure scenario for assess- ment of exposures to chemicals released indoors from alkyd or latex paints. Important considerations are discussed for each item, along with examples or alternatives where appropriate. 4.2 An exposure scenario—a description of how and where an estimated exposure occurs—includes the following ele- ments for paints used indoors (that is, interior paints): 4.2.1 The product and chemical(s) to be assessed. 4.2.2 The indoor environment where the product is applied, including properties such as volume and airflow rate. 1 This practice is under the jurisdiction of ASTM Committee D22 on Sampling and Analysis of Atmospheres and is the direct responsibility of Subcommittee D22.05 on Indoor Air. Current edition approved October 10, 2001. Published August 2002. 2 Annual Book of ASTM Standards,Vol 06.01. 3 Annual Book of ASTM Standards,Vol 11.03. 4 Annual Book of ASTM Standards,Vol 04.11. 1 Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States. 4.2.3 The amount and rate of product use. 4.2.4 Chemical emissions during and after paint application. 4.2.5 Locations and breathing rates of an individual, or individuals, who may be exposed to the airborne chemical emissions. 4.3 Further considerations discussed in this practice include typical versus conservative assumptions, short-term versus long-term exposure perspectives, alkyd versus latex paints, and residential versus office settings. 4.4 More than one exposure scenario can be constructed. The practice also provides a list of elements to be included when comparing multiple scenarios. 5. Significance and Use 5.1 Increasing attention is being paid to human exposure to airborne chemicals from products or materials used indoors, for two reasons: 5.1.1 Individuals spend substantial fractions of their time indoors. 5.1.2 Such exposures can occur repeatedly throughout one’s lifetime. 5.2 The primary objectives of this practice are as follows: 5.2.1 To list the elements that need to be considered in developing a scenario to describe how exposure occurs to chemicals emitted from alkyd or latex interior paints. 5.2.2 To discuss procedures and alternatives for choosing and describing these elements. 5.3 Elements of an exposure scenario, in turn, are used to practice a subsequent step of estimating exposures through monitoring studies or computer modeling exercises. 5.4 Once exposures have been estimated, the results can be used to assess the potential impacts of a specific paint formulation on the health of exposed individuals, or to com- pare the relative impacts of alternative formulations. 5.5 Estimation of exposures, or comparisons of estimated exposures across alternative paint formulations, can lead to development of environmentally preferable products by mini- mizing adverse health effects for exposed individuals. 6. Procedures for Developing Exposure Scenarios 6.1 Describing the Product and Chemical(s): 6.1.1 Chemical emissions can vary according to the type of paint and painted substrate. Describe the following: 6.1.1.1 Alkyd or latex paint. 6.1.1.2 Flat, gloss, or semi-gloss paint. 6.1.1.3 Physical properties such as paint density (for ex- ample, in pounds per gallon or grams per cm3). 6.1.1.4 Typical applications of the paint, in terms of (1) type of substrate to which it is applied (for example, gypsum wallboard vs. wood/trim vs. metal) and (2) type of room (for example, bedroom vs. bathroom or kitchen). 6.1.1.5 Typical warnings or advice on the paint container (for example, “Use in a well-ventilated area”). 6.1.2 The pattern and potential impact of chemical emis- sions over time can vary by chemical. Describe the following: 6.1.2.1 Physical/chemical properties of the chemical(s) un- der investigation, such as molecular weight and vapor pressure. 6.1.2.2 Role of the chemical(s) in the paint (for example, solvent). 6.1.2.3 Weight fraction of the chemical(s) in the paint. 6.1.2.4 Toxicity information, such as that commonly re- ported in Material Safety Data Sheets. 6.1.3 Chemical emissions can be affected by environmental factors such as temperature and humidity. These factors are discussed in 6.2. The pattern of chemical emissions also can depend on factors such as the paint application method, the amount of paint applied, and the rate of application. These factors are discussed in 6.3. 6.2 Describing the Indoor Environment Where the Product Is Applied: 6.2.1 Describe the size/volume and general configuration of the environment (for example, a two-story residence consisting of eight rooms with a volume of 15 000 ft3 or 425 m3). Specific considerations for residential versus office buildings are dis- cussed under 6.6. Distributions for volumes of U.S. residences are presented in the Exposure Factors Handbook (1).5 6.2.2 Describe the indoor-outdoor air change rate (for ex- ample, in h-1 or air changes per hour, ACH) and associated conditions such as opening of doors/windows and use of exhaust/circulation fans. Distributions for air change rates of U.S. residences are presented in the Exposure Factors Hand- book (1). Persily (2) has measured air change rates in a limited set of office buildings. 6.2.3 Discussion—When conducting an actual exposure assessment, as opposed to constructing an exposure scenario to guide the assessment, it may be preferable to replace assump- tions regarding air change rates with actual measurements, using methods such as those described in Test Method E 741. 6.2.4 Describe the fraction of the building (or building volume) that is being painted. It usually is convenient to conceptualize the building as consisting of two indoor air spaces—a painted space and an unpainted space, with commu- nicating air flows between the two spaces—as illustrated in Fig. 1. 6.2.5 Describe the airflow rates between the painted and unpainted spaces. The flows in the two directions are not necessarily equal, but it is often convenient to assume so. More than two indoor spaces can be specified, but the number of airflow rates will increase rapidly (for example, 2 rates for 2 spaces, 6 rates for 3 spaces, 12 rates for 4 spaces). 6.2.6 Discussion—In specifying air flows it is important to maintain a flow balance; that is, for any air space or zone, the sum of air flows entering the zone should equal the sum of exiting air flows. One relatively simple means of accomplish- ing this is to assume that the airflow rates to/from outdoors are proportional to the air change rate (for example, if the zone 5 The boldface numbers in parentheses refer to the list of references at the end of this practice. FIG. 1 Conceptualization of a Painted Building D 6669 – 01a 2 volume is 100 m3 and the air change rate is 0.5 h-1, then the airflow rate to/from outdoors is 50 m3/h) and that the airflow rates between the two zones are the same in both directions. As with other elements describing an exposure scenario, assump- tions here ultimately should be replaced by measurements where possible. However, airflow measurements (typically involving the use of multiple tracer gases) are not simple to perform. A possible alternative is to use an indoor-air model that can model air flows, such as CONTAM (3) or COMIS (4). The MCCEM model (5) has a built-in library of airflow rates for a variety of residences. 6.2.7 Describe the outdoor concentration for the chemi- cals(s) of concern assumed to prevail during and following the painting event. Often the outdoor concentration of the chemi- cal(s) being assessed is low relative to that indoors, such that an assumption of zero concentration outdoors is not unreason- able. Even if a non-zero-concentration is assumed, the estima- tion process can be simplified by assuming that the outdoor concentration is constant over time. 6.2.8 Describe the environmental conditions of the indoor space where paint is to be applied. Conditions such as temperature and relative humidity are particularly important, as these can affect the rate of chemical emissions. 6.2.9 Indoor-air concentrations of chemicals released from paint can be affected by certain types of materials that absorb (and sometimes desorb) emitted chemicals. Describe wall, ceiling and floor materials as well as furnishings such as upholstered furniture or draperies. The preferred method for documenting the presence of such materials is to note their loading rates (that is, ratio of surface area to indoor volume, in units of ft2/ft3 or m2/m3). 6.3 Describing the Product Application: 6.3.1 Describe the substrate that is being painted—gypsum wallboard, wood, metal, etc.—and indicate whether it ever has been painted before. 6.3.2 Indicate whether the substrate is being painted with primer only, paint only, or primer plus paint. 6.3.3 Indicate the number of coats of primer/paint being applied. 6.3.4 Indicate the drying time(s) between successive coats of primer/paint. 6.3.5 Indicate the total amount of primer/paint being used. This quantity, commonly expressed in gallons, can be indicated or calculated in any of the following ways: 6.3.5.1 If the actual quantity used is known, then indicate that quantity. 6.3.5.2 If the painted surface area is known, then the amount applied (A) can be estimated as follows: A ’ surface area/~coverage per coat! 3 number of coats~for example, 1,000 ft2/~400 ft2/gal! 3 2 coats 5 5 gal, (1) or 92.8 m2/~37.12 m2 /gal! 3 2 coats 5 5 gal!. 6.3.5.3 If film thickness is known (see Test Methods D 1005 and D 1212), it can be converted to total coverage using the following formula: Coverage per coat ~ft2/gal! 5 1600/film thickness ~mil!, or (2) Coverage per coat ~m2/gal! 5 148.5/film thickness ~mil!, where: 1 mil = 1/1000 in. The amount applied can then be calculated as in 6.3.5.2. 6.3.5.4 If the volume of the painted space is known and if walls or ceilings are being painted, then the painted surface area can be estimated from the following relationships given in the Exposure Factors Handbook (1) for residences: Wall area ~ft2! ’ volume ~ft3! 3 0.29 ~or m2 ’ m3 3 0.95! (3) Ceiling area ~ft2! ’ volume ~ft3! 3 0.13 ~or m2 ’ m3 3 0.43! The amount applied can then be calculated as in 6.3.5.2. 6.3.6 Indicate the product application rate (for example, gal per h). This rate can depend on factors such as application method (roller, brush, spray) and the number of painters. Indicate the application method and number of painters along with the rate. 6.3.7 Indicate the total duration of the painting event. The duration can be calculated by dividing the total amount of primer or paint, or both used (in gallons) by the application rate (in gal per h), assuming a constant application rate. The drying time(s) between successive coats needs to be added to the painting time to obtain the total duration. In cases where the duration is relatively long (for example, > 8 h), indicate the number of painting hours per day and the resultant number of painting days. 6.4 Describing the Chemical Emissions from the Paint: 6.4.1 General Nature of Emissions Profile. When primer or paint is applied quickly to a small specimen (as when conduct- ing a small-chamber test to characterize emissions), the chemi- cal emissions tend to be higher at first and then to decline over time. Studies of airborne chemical concentrations in chambers (6, 7), following instantaneous application of paint to a substrate such as gypsum wallboard, indicate that the declining emission rate tends to follow a single-exponential model for chemicals released from alkyd paint and a double-exponential model for chemicals released from latex paint. 6.4.2 Direct Estimation of Emissions Profile. An emission profile for the chemical(s) of concern released from primer or paint can be estimated using a small-chamber facility (see Guide D 5116) by (1) applying the primer/paint to the substrate of interest and determining the mass applied through before/ after weight differentials, (2) inserting the painted substrate in the chamber immediately after applying the paint and then measuring the airborne chemical concentrations over time, and (3) using non-linear regression to fit a single- or double- exponential emission model to the concentration data. 6.4.3 Indirect Estimation of Emission Profile. Studies have been conducted to investigate the dependence of an emissions profile on physical/chemical properties. These include empiri- cal models relating the rate of exponential decline to molecular weight and vapor pressure (6), for chemicals in latex paints, and semi-empirical models relating the emission profile to total vapor pressure, wet film thickness, and chemical diffusivity (7), for chemicals in alkyd paints. 6.4.4 Combining Emission Profile with Paint Application Profile. For the above estimation methods, the application of primer or paint is nearly instantaneous. A painting event involves continuous paint application, which can be viewed as D 6669 – 01a 3 a contiguous series of instantaneous applications. Appropriate formulas for combining an exponential model for emissions from near-instantaneous application with a constant application rate over time, to develop a total emissions profile, have been developed and described by Evans (8). These formulas have been incorporated in the MCCEM (5) and WPEM (9) models. 6.4.5 Modeling Versus Monitoring. Estimation of an emis- sions profile is required only when modeling indoor-air con- centrations to estimate resultant exposure. If monitoring is conducted rather than modeling, then exposure can be esti- mated from the measured indoor concentration profile. 6.5 Describing Location/Activity Patterns: 6.5.1 Exposure during and after a painting event is deter- mined by an individual’s location patterns in relation to the time-varying airborne chemical concentrations at those loca- tions. The activity patterns affect the individual’s breathing rate, which determines the potential inhaled dose over the period of interest. 6.5.2 Location During/After Painting Event. Consistent with the building partition given in 6.2.4, an individual’s location patterns can be described using the matrix below (see Fig. 2). Concentrations to which an individual is exposed while in the building are determined through modeling or monitor- ing, as described in 6.4.5. Concentrations to which an indi- vidual is exposed while outside the building are governed by external air quality, as described in 6.2.7. 6.5.3 Breathing Rate. An individual’s breathing rate, com- monly expressed in units of m3/h or m3/day, depends on the type of activity and the associated level of physical/mental exertion, in addition to individual characteristics such as age and gender. 6.5.3.1 Recommended values for breathing rates for differ- ent activity levels and age/gender groups are given in the Exposure Factors Handbook (1). 6.5.3.2 If the individual is involved in the painting event, then exposure will tend to be higher because (1) the individual will be in the painted space, where airborne chemical concen- trations are highest, and (2) the breathing rate will be higher due to the physical exertion associated with painting. 6.5.4 Time Perspective. Describe location/activity patterns over a sufficient duration to allow for indoor chemical concen- trations to decline to a low level. This duration can be determined through modeling or monitoring, as described in 6.4.5. 6.6 Further Considerations: 6.6.1 Typical vs. Conservative Assumptions. In describing the factors listed above in 6.2-6.5, either typical or conserva- tive values can be assigned. It is often customary, when assigning these values, to develop an exposure estimate that will tend to err on the conservative side, by choosing combi- nations that result in a high exposure estimate. Examples of conservative assumptions are choosing a low air change rate or choosing a high breathing rate or a high paint application rate (the latter choice will tend to over-estimate peak rather than average exposure). Choosing too many conservative values, however, can lead to an unreasonable scenario that may never in fact occur. 6.6.2 Short-term vs. Long-term Perspectives. An exposure scenario provides the basis for estimating exposure during and immediately following a painting event. The short-term per- spective for exposure assessment is concerned primarily with acute health effects that may be related to the peak concentra- tion or dose rate. The long-term perspective is concerned with cancer or other chronic hea