Technical Note Environmental use of diVusive samplers: evaluation of reliable diVusive uptake rates for benzene, toluene and xylene† Richard H. Brown Health and Safety Laboratory, Broad Lane, SheYeld, UK S37HQ Received 2nd October 1998, Accepted 16th November 1998 The measurement of workplace air quality is a key part of an firm limit values (LVs) been set. However, measurements in identified sick buildings are about two orders ofmagnitude below exposure assessment in relation to legislative requirements such as, for Europe, the Chemical Agents Directive (98/24/EC).1 workplace LVs.Usually, such concentrations are measured in relation to outside air, which is considered relatively innocuous. For volatile organic compounds (VOCs), diVusive sampling methods based on a thermally desorbable tube design2 have The concentration range of interest for indoor air is, therefore, well within the capability of diVusive samplers, which, for ambi- been used by the Health and Safety Laboratory (HSL) for many years as the primary measurement technique and the ent air, can measure two further orders of magnitude lower.This is done by the simple expedient of exposing the samplers for a procedure is well established in Health and Safety Executive (HSE)3 and international4 standards.longer time: typically, samplers are exposed for a few hours for workplace measurements, a few days for indoor air and a few The assessment of outdoor air quality is just as important. Research at HSL,5 and corroborated elsewhere,6–14 has demon- weeks for outdoor air.It is well known, however, that the diVusive uptake rate of strated that tube-type thermally desorbable diVusive samplers, such as the Perkin-Elmer sampler, can be used eVectively for samplers can be dependent both on the time of exposure and the concentration to be measured.16 This is particularly the case monitoring VOCs, particularly benzene, toluene and xylene, in outdoor air.These pollutants arise primarily from vehicle for tube-type samplers with sorbents designed for thermal desorption. Uptake rates for workplace applications (i.e., for exhaust, and so are of greater concern in the urban environment. Of the three, benzene is the most emotive, because of its carcino- exposures in the 1–100 ppm range for 1–8 h) have been published3 for a wide range of VOCs.A shorter list for environ- genic potential. In most European states, these three pollutants are measured by fixed monitoring stations. However, diVusive mental applications (i.e., for exposures in the 1–10 ppb range for 1–4 weeks) has also been published,17 but from a limited sampling can be implemented at a fraction of the cost of fixed monitoring stations, and can cover a larger number of typical number of sources.Tables 1–3 document known data for three commonly measured environmental pollutants: benzene, tolu- sites. Moreover, they give long-term averages, which are more consistent with the proposed European limit value which is likely ene and xylene (not distinguishing between isomers). These data demonstrate good agreement between the independent to be set on a yearly basis. DiVusive sampling can also be used for monitoring indoor air estimates of uptake rate, bearing in mind that the practical uptake rates will be influenced by the experimental conditions quality,15 where VOCs are implicated, along with formaldehyde and many other factors, in ‘sick building syndrome’.There is no of temperature and concentration.The magnitude of this error can be estimated from the mean of the standard deviations, consensus, as yet, as to whether ‘total VOCs’ (however they are defined) or specific individual VOCs are to blame, nor have any which is about 10%. Table 1 DiVusive uptake rates for benzene for the Perkin-Elmer diVusive sampler Uptake rate/ng ppm-1 min-1 Benzene HSLa NMI 1 NMI 2 ERLAPc BRE 1b NMI 3 BPc LUA 1 LUA 2 LUA 3 BRE 2b Ref. 5 6 6 7 8 9 10 11 12 13 14 Mean s Tenax TA— 1 week — — — — — 1.45 — — — — — 1.45 — 2 weeks — — — 0.96 — 1.06 — — — — 0.86 0.96 0.1 4 weeks — — — 0.67 0.64 0.8 — — — — 0.64 0.62 0.2 Carbograph TD-1 or Carbopack B— 1 week 1.99 2.28 — — — — — — — — — 2.14 0.21 2 weeks 2.00 2.22 2.13 1.75 — — — — — — — 2.03 0.2 4 weeks 2.00 1.89 1.84 1.68 — — — — — — — 1.85 0.13 Chromosorb 106— 1 week 1.46 1.58 — — — — — — — — — 1.52 0.08 2 weeks 1.45 1.2 — 1.34 — — 1.6 1.42 1.62 2.25d — 1.43 0.16 4 weeks 1.47 0.96 — 1.22 — — — 1.2 1.33 1.86 — 1.34 0.3 aHSL, Health and Safety Laboratory, SheYeld, UK; NMI, Nederlands Meetinstituut, Delft, The Netherlands; ERLAP, European Reference Laboratory for Air Pollution, EC Joint Research Centre, Ispra, Italy; BRE, Building Research Establishment, Garston, UK; BP, BP International Ltd, Sunbury Research Centre, UK; LUA, Landesumweltamt Nordrhein-Westfalen, Essen, Germany.bIndoor air monitoring. cSampler with membrane in the diVusive end-cap. dOutlier excluded. † © Crown copyright. J. Environ. Monit., 1999, 1, 115–116 115Table 2 DiVusive uptake rates for toluene for the Perkin-Elmer diVusive sampler Uptake rate/ng ppm-1 min-1 Toluene HSLa NMI 1 NMI 2 ERLAPc BRE 1b BPc LUA 1 LUA 2 LUA 3 BRE 2b Ref. 5 6 6 7 8 10 11 12 13 14 Mean s Tenax TA— 1 week — — — — — — — — — — 2 weeks — — — 1.18 — — — — — 1.43 1.31 0.18 4 weeks — — — 0.87 1.22 — — — 1.2 1.1 0.2 Carbograph TD-1 or Carbopack B— 1 week 1.75 2.57 — — — — — — — — 2.16 0.58 2 weeks 2.11 2.38 2.21 1.86 — — — — — — 2.14 0.22 4 weeks 2.39 1.98 2.14 1.83 — — — — — — 2.09 0.24 Chromosorb 106— 1 week 1.64 2.45 — — — — — — — — 2.05 0.57 2 weeks 1.89 2.05 — 1.7 — 1.9 1.95 2.12 2.2 — 1.97 0.17 4 weeks 2.10 1.67 — 1.64 — — 1.80 1.97 2.03 — 1.87 0.19 aFor laboratory identifications, see Table 1.bIndoor air monitoring. cSampler with membrane in the diVusive end-cap. Table 3 DiVusive uptake rates for xylene for the Perkin-Elmer diVusive sampler Uptake rate/ng ppm-1 min-1 Xylene HSLa NMI 1 NMI 2 ERLAPc BRE 1b BPc LUA 1 LUA 2 LUA 3 BRE 2b Ref. 5 6 6 7 8 10 11 12 13 14 Mean s Tenax TA— 1 week — — — — — — — — — — 2 weeks — — — 1.96 — — — — — 2.19 2.08 0.16 4 weeks — — — 1.28 1.67 — — — — 1.93 1.63 0.33 Carbograph TD-1 or Carbopack B— 1 week 2.16 2.58 — — — — — — — — 2.37 0.3 2 weeks 2.19 2.08 2.24 2.27 — — — — — — 2.2 0.08 4 weeks 2.18 1.66 2.2 2.21 — — — — — — 2.06 0.27 Chromosorb 106— 1 week 2.2 2.63 — — — — — — — — 2.41 0.3 2 weeks 2.08 2.13 — 2.14 — 2.1 2.25 2.51 2.65 — 2.27 0.28 4 weeks 2.07 1.62 — 2.11 — — 2.17 2.36 2.46 — 2.13 0.29 aFor laboratory identifications, see Table 1.bIndoor air monitoring. cSampler with membrane in the diVusive end-cap. 6 NMI data cited in ref. 5. In most cases, ambient uptake rates have been determined at 7 P. P. Ballesta, R. A. Field and E. De Saeger, Field intercomparison concentrations typical of urban background levels, i.e., a of VOC measurements, JRC Environment Institute Report EUR few mg m-3 of benzene, toluene or xylene. Rates have been 18085 EN, 1998. determined either (NMI 1 and BRE) in the laboratory with 8 V.M. Brown, D. R Crump, D. Gardiner and C. W. F. Yu, test atmospheres themselves checked with an independent Environ. Technol., 1993, 14, 771. 9 R. Peters and T. Hafkenscheid, DiVusive Monit., 1995, 7, 8. method (usually a pumped sorbent tube) or (other data) 10 BP data in C. E. H. Downing, G. W. Campbell and J. C. Bailey, directly against one or more samplers of an independent A survey of sulphur dioxide, ammonia and hydrocarbon concen- method under field conditions.The BRE data give uptake rates trations in the United Kingdom, using diVusion tubes: July to for indoor air, where the total VOC concentration level of the December 1992, UK Environmental Technology Executive generated test atmosphere was 2 mg m-3, which is typical of Agency, Report LR 964, Contract No.PECD/7/12/76, 1994. the mean 4 week concentrations found in urban homes after 11 Landesumweltamt, Validierung von Passivsammlern fur Immissionsmessungen von KohlenwasserstoVen, Materialen Nr. 46, recent painting and decorating activities. Landesumweltamt Nordrhein-Westfalen, Essen, 1998, Table 7, DD40 station. References 12 Landesumweltamt, Validierung von Passivsammlern fur Immissionsmessungen von KohlenwasserstoVen, Materialen Nr. 46, 1 Council Directive 98/24/EC on the protection of the health and Landesumweltamt Nordrhein-Westfalen, Essen, 1998, Table 7, safety of workers from the risks related to chemical agents at VHAG station. work, 1998. 13 Landesumweltamt, Validierung von Passivsammlern fur Immis- 2 R. H. Brown, J.Charlton and K. J. Saunders, Am. Ind. Hyg. sionsmessungen von KohlenwasserstoVen, Materialen Nr. 46, Assoc. J., 1981, 42, 865. Landesumweltamt Nordrhein-Westfalen, Essen, 1998, Table 7, 3 Health and Safety Executive, Volatile organic compounds in air: LISE station. laboratory method using diVusive solid sorbent tubes, thermal 14 D. Crump, DiVusive Monit., 1998, 10, 5. desorption and gas chromatography, MHDS 80, HM Stationery 15 P.WolkoV, Indoor Air, Suppl. 3/95, 1995. OYce, London, 1995. 16 N. Van den Hoed and M. T. H. Halmans, in DiVusive Sampling, 4 International Standards Organisation, Indoor, ambient and work- ed. A. Berlin, R. H. Brown and K. J. Saunders, CEC Publication place air—sampling and analysis of volatile organic compounds by 10555 EN, Royal Society of Chemistry, London, 1987, sorbent tube/thermal desorption/capillary gas chromatography— pp. 131–142. Part 2: DiVusive sampling, ISO DIS 16017–2, 1998. 17 DiVusive Monit., 1995, 7, 9. 5 N. T. Plant and M. D. Wright, European diVusive sampling initiative: project report with status at March 1998, HSL Internal Report IACS 98/01, 1998. Paper 8/07686C 116 J. Environ. Monit., 1999, 1, 115–116