* Corresponding author. Tel.: #358-17-201393; fax: #358- 17-201265. E-mail address: pasi.penttinen@ktl." (P. Penttinen) Atmospheric Environment 34 (2000) 2581}2586 Measuring re#ectance of TSP-"lters for retrospective health studies Pasi Penttinen*, Sari Alm, Juhani Ruuskanen, Juha Pekkanen Division of Environmental Health, National Public Health Institute, P.O.Box 95, FIN-70701 Kuopio, Finland Department of Environmental Sciences, University of Kuopio, P.O.Box 1627, FIN-70211 Kuopio, Finland Received 8 September 1998; received in revised form 19 October 1999; accepted 29 October 1999 Abstract We measured the re#ectance of 174 TSP "lters from an air quality study to determine whether the blackness of the "lters (an indication of incomplete combustion) could be used as an additional measure of particulate air pollution in retrospective health studies. It is important in health studies to di!erentiate soil-derived coarse particles from combus- tion-derived particles. Re#ectance was measured with a monochromatic re#ectometer and absorption coe$cients were derived from the re#ectance values using the ISO formula for black smoke absorption coe$cients. In the urban setting, the absorption coe$cients for TSP "lters were associated with black carbon (r"0.89), black smoke absorption coe$cients (r"0.9), and gaseous, tra$c-related pollutants (r for NO  "0.84), which were measured recently at the same location. Measuring the re#ectance of TSP "lters is a useful method to estimate the relative concentration of combus- tion-derived particulate matter in a subarctic winter climate. This method could be useful in retrospective health studies.  2000 Elsevier Science Ltd. All rights reserved. Keywords: Air pollution; Black smoke; Particles; PM  ; Respiratory health; TSP 1. Introduction A growing amount of evidence is being published on the adverse health e!ects of airborne particles. Day-to- day variations in total suspended particles (TSP), partic- ulate matter sized 10 m or less (PM  ) and black smoke (BS) have been shown to be associated with daily mor- tality, and daily variation of acute respiratory health e!ects (Schwartz and Dockery, 1992; Peters et al., 1997; Timonen and Pekkanen, 1997). The possibility to assess and characterize past expo- sures to airborne particulate matter could be of signi"- cant use in epidemiological studies. Of speci"c interest for health studies is the ability to di!erentiate emissions from combustion processes and other sources. This would give further insight into the mechanisms behind the health e!ects. In Finland, as in most other countries, a large amount of particulate matter concentration data measured by the TSP method has been collected at ambient air monitor- ing sites during the last decades. The TSP method col- lects all particles above 0.03 m with a 50% cuto! point at 30}50 m aerodynamic particle diameter (AD) that is dependent on wind speed and direction (Chow, 1995). In the Finnish subarctic winter climate TSP mass corre- lates highly (r"0.86}0.94) with PM  measurements (Reponen et al., 1996). In Britain, measuring black smoke (British Smoke, BS) has been used to measure airborne particulates since the 1920s (Chow, 1995). In this method particles smaller than 5 m AD are collected on a white "lter material and the blackness of the "lter is measured with a re#ectometer, based on the use of monochromatic light. In a recent discussion it has been suggested that the staining capa- city of ambient air, measured by the BS method might be a better indicator for health e!ect studies than TSP or PM  (Muir and Laxen, 1995). The reason for this is that BS is an indicator of the black carbon content of particles derived from combustion processes. One important AEA=2767=Durai=Venkatachala=BG 1352-2310/00/$ - see front matter  2000 Elsevier Science Ltd. All rights reserved. PII: S 1 3 5 2 - 2 3 1 0 ( 9 9 ) 0 0 4 9 1 - 4