1、DEUTSCHE NORM Januarv 1996 Air quality Particle size fraction definitions for health-related sampling (IS0 7708 : 1995) DIN IS0 7708 - ICs 13.040.30 Luftbeschaffenheit - Festlegung von Partikelgrenverteilungen fr die gesundheitsbezogene Schwebstaubprobenahme (IS0 7708 : 1995) This standard incorpora
2、tes International Standard IS0 7708 Air quality - Particle size fraction definitions for health-related sampling. A comma is used as the decimal marker. National foreword This standard has been prepared by ISO/TC 146. The responsible German body involved in its preparation was the Kommission Reinhal
3、tung der Luft (DIN Commission on Air Quality). IS0 Standard comprises 1 O pages. No pari of this standard may be reproduced without the prior permission of Y Deutsches Institut frNonunge. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany, s the exclusive right of sale for German Standards (DIN-No
4、rmen). Ref. No. DIN IS0 7708 : 1996-0 English price group 07 Sales No. 0407 09.00 Page 1 IS0 7708 : 1995 Air quality Particle size fraction definitions for health-related Sam pli ng Contents Page Scope 3 Definitions . 3 Principle . 4 Assumptions and approximations . . 4 Inhalable convention 5 Thorac
5、ic convention 5 Respirable conventions 5 Extrathoracic and tracheobronchial conventions . 5 Performance of instruments . 6 Annexes A Nomenclature of inhalable and respirable fractions 6 B Numerical approximations to cumulative log-normal distributions 7 C Bibliography 10 Foreword IS0 (the Internatio
6、nal Organization for Standardization) is a worldwide federation of national standards bodies (IS0 member bodies). The work of preparing International Standards is normally carried out through IS0 technical committees. Each member body interested in a subject for which a technical committee has been
7、established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. IS0 collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standar
8、dization. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 YO of the member bodies casting a vote. International Standard IS0 7708 was prepared by Technical Comm
9、ittee I SOPC 146, Air quality. This first edition cancels and replaces the Technical Report ISO/TR 7708:1983, of which it constitutes a technical revision. Annexes A, B and C of this International Standard are for information only. Page 2 IS0 7708 : 1995 Introduction The fraction of airborne particl
10、es which is inhaled into a human body de- pends on the properties of the particles, the speed and direction of air movement near the body, the rate of breathing, and whether breathing is through the nose or mouth. Inhaled particles can then deposit somewhere in the respiratory tract, or can be exhal
11、ed. The site of deposition, or prob- ability of exhalation, depends on the properties of the particles, respiratory tract, breathing pattern and other factors. Liquid particles or soluble components of solid particles can be absorbed by the tissues wherever they deposit. Particles can cause damage c
12、lose to the deposition site if they are corrosive, radioactive, or capable of in- itiating some other type of damage. Insoluble particles can be transported to another part of the respiratory tract or body, where they can be ab- sorbed or cause a biological effect. There is a wide variation from one
13、 person to another in the probability of particle inhalation, deposition, reaction to deposition, and clearance. Nevertheless, it is possible to define conventions for size-selective sam- pling of airborne particles when the purpose of sampling is health-related. These are relationships between the
14、aerodynamic diameter and the frac- tions to be collected or measured, which approximate to the fractions penetrating to regions of the respiratory tract under average conditions. Measurement conducted according to these conventions will probably yield a better relationship between measured concentra
15、tion and risk of disease. For further information on the factors affecting inhalation and deposition and their application in standards, see Stuart et al. LIZ, Phalen et al. 91, Lippmann et al. SI, Heyder et al. 31, Miller et al. 71, Rudolph et al. lo, Vincent 1131, Ogden and Birkett 81 and Soderhol
16、m 111. Page 3 IS0 7708 : 1995 1 Scope This International Standard defines sampling con- ventions for particle size fractions for use in assessing possible health effects of airborne particles in the workplace and ambient environment. Conventions are defined for the inhalable, thoracic and respirable
17、 frac- tions; extrathoracic and tracheobronchial conventions may be calculated from the defined conventions. (The inhalable fraction is sometimes called inspirable -the terms are equivalent. The nomenclature of the frac- tions is discussed in annex A.) Assumptions are given in clause 4. The conventi
18、on chosen will depend on the region of effect of the component of interest in the airborne particles (see clause 3). In this Inter- national Standard, conventions are expressed in terms of mass fractions, but they may also be used when the intention is to evaluate the total surface area or the numbe
19、r of particles in the collected material. The conventions should not be used in association with limit values defined in other terms, for example for limit values of fibres defined in terms of their length and diameter. 2 Definitions For the purposes of this International Standard, the following def
20、initions apply. 2.1 sampling convention: Target specification for sampling instruments which approximates to, for each particle aerodynamic diameter, - in the case of the inhalable convention, the ratio of the mass concentration of particles entering the respiratory tract to the corresponding mass c
21、on- centration in the air before the particles are af- fected by the presence of the exposed individual and by inhalation; - in the case of other conventions, the ratio of the mass concentration of particles entering the spec- ified region of the respiratory tract to the mass concentration of partic
22、les entering the respiratory tract. (These other conventions can also be ex- pressed as ratios to the mass of total airborne particles.) 2.2 particle aerodynamic diameter: Diameter of a sphere of density 1 g/cm3 with the same terminal velocity due to gravitational force in calm air as the particle,
23、under the prevailing conditions of ternper- ature, pressure and relative humidity (see clause 4). NOTE 1 For particles of aerodynamic diameter less than 0.5 Frn. the particle diffusion diameter should be used in- stead of the aerodynamic diameter. The particle diffusion diameter means the diameter o
24、f a sphere with the same diffusion coefficient as the particle, under the prevailing conditions of temperature, pressure and relative humidity. 2.3 inhalable fraction: Mass fraction of total air- borne particles which is inhaled through the nose and mouth. NOTE 2 The inhalable fraction depends on th
25、e speed and direction of the air movement, on the rate of breathing and other factors. 2.4 inhalable convention: Target specification for sampling instruments when the inhalable fraction is the fraction of interest. 2.5 extrathoracic fraction: Mass fraction of inhaled particles which fail to penetra
26、te beyond the larynx. 2.6 extrathoracic convention: Target specification for sampling instruments when the extrathoracic fraction is of interest. 2.7 ticles which penetrate beyond the larynx. thoracic fraction: Mass fraction of inhaled par- Page 4 IS0 7708 : 1995 2.8 thoracic convention: Target spec
27、ification for sampling instruments when the thoracic fraction is of interest. 2.9 tracheobronchial fraction: Mass fraction of inhaled particles which penetrate beyond the larynx, but which fail to penetrate to the unciliated airways. 2.10 tracheobronchial convention: Target specifi- cation for sampl
28、ing instruments when the tracheo- bronchial fraction is of interest. 2.11 particles which penetrate to the unciliated airways. respirable fraction: Mass fraction of inhaled 2.12 respirable convention: Target specification for sampling instruments when the respirable fraction is of interest. 2.13 tot
29、al airborne particles: All particles sur- rounded by air in a given volume of air. NOTE 3 Because all measuring instruments are size- selective to some extent, it is often impossible to measure the total airborne particle concentration. lecting particles of small aerodynamic diameter than it is in h
30、ealthy adults. This is accounted for in the conventions by a second respirable convention, cen- tred at smaller aerodynamic diameters, which gives a coresponding tracheobronchial convention extended to smaller aerodynamic diameters. This tracheo- bronchial convention should be used when the ex- pose
31、d population includes these “ high-risk“ groups, and the “high-risk“ respirable convention may be used in these circumstances Instruments can be used to collect individual fractions according to the conventions, or to collect several fractions simultaneously. For example, an instrument could collect
32、 particles from the air according to the inhalable convention, and then separate this material into portions according to the thoracic, tracheo- bronchial and respirable conventions. Alternatively, an instrument might just collect the respirable fraction from the air. In this case, the design would
33、have to ensure that selection at the entry due to aerodynamic effects, and subsequently within the instrument, was such that the overall selection was in accordance with the conventions. (The performance requirements of instruments are summarized in clause 9.) 3 Principle 4 Assumptions and approxima
34、tions The sampling conventions recognize that only a frac- tion of the airborne particles which are near to the nose and mouth is inhaled. This fraction is called the inhalable fraction (2.3). For some substances, the subfractions of this which penetrate beyond the larynx, or to the unciliated airwa
35、ys, are of special Sig- nificance for health. This International Standard presents conventionalized curves approximating to the fraction inhaled and the subfractions penetrating beyond the larynx or to the unciliated airways. These curves are called the inhalable convention (2.4). the thoracic conve
36、ntion (2.8) and the respirable convention 12.12). The extrathoracic (2.6) and tracheobronchial (2.10) con- ventions may be calculated from these. Instruments used for sampling should conform with the sampling convention appropriate to the region of the respiratory tract where deposition of the subst
37、ance being meas- ured might lead to a biological effect. For example, the inhalable convention would be chosen if the sub- stance might lead to an affection wherever it is de- posited, the thoracic convention would be chosen if the region was the lung conductive airways (bronchi), and the respirable
38、 convention if the region was the gas exchange region extending from the respiratory bronchioles to the alveoli. In children and in adults with certain chest diseases, the tracheobronchial region is more effective at col- Approximations and assumptions are unavoidable when simulating, by sampling co
39、nventions, the very complex interaction of variables that governs respir- atory tract entry and penetration. The conventions are necessarily only approximations to respiratory tract behaviour, and the following as- sumptions should be noted. a) The inhalable fraction depends on air movement - speed
40、and direction - on the rate of breathing, and on whether breathing is through the nose or mouth The values given in the inhalable conven- tion are for representative values of the rate of breathing, and are averaged for all wind directions This is appropriate for an individual uniformly ex- posed to
41、 all wind directions or predominantly ex- posed to wind from the side or from behind, but the convention would usually underestimate the inhalable fraction of larger particles for an individ- ual who usually faced the wind. b) The respirable and thoracic fractions vary from in- dividual to individua
42、l and with the breathing pat- tern, and the conventions are necessarily approximations to the average case. c) Each convention approximates to the fraction penetrating to a region, and not to the fraction Page 5 IS0 7708 : 1995 depositing there. In general, particles must de- posit to have a biologi
43、cal effect. In this respect, the conventions will lead to an overestimate of the potential biological effect. The most important example is that the respirable convention overes- timates the fraction of very small particles which are deposited in the unciliated airways, because a fraction of these p
44、articles is exhaled without being deposited. In many workplaces, these very small particles do not contribute much to the sampled mass. The thoracic convention approximates to the thoracic fraction during breathing through the mouth, which is greater than the thoracic fraction during breathing throu
45、gh the nose The extrathoracic convention may therefore underes- timate the “worst case“ extrathoracic fraction, which occurs during breathing through the nose. Inhalable convention The target sampling curve for instruments collecting the inhalable fraction, when averaged over all wind directions, sh
46、all be as follows for windspeeds u 1 O0 pm, and the convention should not be applied to larger particles For windspeeds u 4 mis, equation (2) is tentatively suggested Equation (2) should not be applied for D 90 pm or u 9 m/s, which are the limits of the experimental data Ei = 50 (1 + exp - 0,06 DI)
47、+ 10-3 u2.75 exp 0,055 O . . . (2) 6 Thoracic convention The target sampling curve for instruments collecting the thoracic fraction shall be as follows. The percent- age ET of the inhalable convention which is to be col- lected at an aerodynamic diameter D (pm) is given by a cumulative log-normal di
48、stribution with a median of 11,64 pm and a geometric standard deviation of 1,5. A numerical approximation for ease of calculation is given in annex B. Note that ET is calculated from the inhalable convention. The fraction of the total airborne particles (2.13) at an aerodynamic diameter D is ob- tai
49、ned by multiplying ET by 0,Ol Ei from equation (1). The values obtained are given in tables B.l and B.2 and illustrated in figure B.1. It will be seen from the tables that 50 % of total airborne particles with D = 10 pm are in the thoracic fraction. 7 Respirable conventions 7.1 Target population: sick and infirm, or children When the population that it is desired to protect are children, or the sick or infirm (the “high risk“ group), the target sampling curve for instruments used for collecting the respirable fraction is as follows. The percentage E, of the inhalable conventio
