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1 BG BAU–Berufsgenossenschaft der Bauwirtschaft, An der Festeburg 27–29, D-60389 Frankfurt am Main, Germany
2 Berufsgenossenschaftliches Institut für Arbeitsschutz, Alte Heerstraße 111, D-53757 Sankt Augustin, Germany
3 Justus-Liebig-Universität Gießen, Aulweg 129/III, D-35392 Gießen, Germany
We are pleased to reply to the comments on our paper concerning the Bitumen Forum exposure data (Rühl et al., 2006).
Sampling strategy
Our article summarizes the results of the German Bitumen Forum's extensive database of exposure measurements at typical German workplaces, based on standardized sampling and analytical procedures. It was not our goal to derive exposure–response relationships, rather a database covering typical work conditions. Therefore, in order to give a concise general overview on the German measurement data, we tried to avoid extensive tables with detailed information on every particular job location and task.
We presented the collected data in accordance with the existing guidelines of the German Hazardous Substances Committee, whose guidelines are based on the 95th percentiles of exposure, and accordingly for this a fuller description of the sampling methodology in the paper itself was patently unnecessary.
In no case is it a ‘fatal flaw’ to assume for the exposure over a shift that there are no exposure-free times. This assumption is taken as normal practice, not only in Germany, and indeed it also includes exposure durations >8 h in practice. Therefore, the suggested need for validation of our measurements does not arise, and in any case this approach had been validated by previous investigations. Moreover, the procedure to evaluate an 8-h shift by a 2-h measurement is explicitly permitted by the European Standard EN 689.
It was not the purpose of our paper to evaluate the exposure data in comparison with the data obtained in other countries. This important ongoing evaluation is being carried out by various scientists, including those responsible for the International Agency for Research on Cancer monograph concerning vapours and aerosols of bitumen.
We pointed out the generality that emissions of bitumen do not have the same composition as bitumen. Hence, we more correctly described the exposures in relation to vapours and aerosols of bitumen, not as ‘bitumen fumes and vapours’.
BGIA methods
It was not appropriate, we believe, to describe in detail in our paper the measurement procedure and the detection limits, since the associated literature is long in the public domain. For analytical methods, our paper refers to established Berufsgenossenschaftliches Institut für Arbeitsschutz (BGIA) methods which are described in the BGIA Working Folder (BGIA, 1997): this reference also contains all the required validation data including the limit of quantification. This procedure is German standard practice, just as papers of other nationalities often refer to their respective national methods. In addition, we referred to the paper of Ekström et al. (2001) to provide an overview of international measurement methods for vapour and aerosols of bitumen.
Concerning the number of measurements below detection limit, we can say that overall for the sum of vapours and aerosols of bitumen, only 6% of these were below detection limit. For the aerosol values alone, this occurred more frequently but we mentioned this in context with the associated figures.
Bitumen and tar
It is generally agreed that there is a considerable difference between bitumen and tar composition, as also between the PAH exposure concerning working with bitumen or with tar. Among other studies (Bjorseth, 1983; Bjorseth and Becher, 1986), the Progress Report of the Bitumen Forum fully explained this fact (Rühl, 2006).
We transparently highlighted the one documented case where an increased occurrence of PAH apparently came from bitumen. During the ‘Human Bitumen Study’ (where on some of the examined construction sites Professor Kromhout analysed the dermal exposure), we detected that urine samples from seven mastic asphalt workers after a work shift had significantly higher concentrations of PAH metabolites compared to the other mastic asphalt workers (Schott et al., 2003). The reason was determined to be a pre-existing sublayer of coal tar, on which the hot mastic asphalt was being poured. In the layer of coal tar, a benzo[a]pyrene (BaP) concentration of 768 mg kg–1 was determined, whereas in the mastic asphalt layer itself this was <0.3 mg kg–1. This group of the seven mastic asphalt workers was consequently removed from further evaluations (Raulf-Heimsoth et al., 2006), because of the enhanced PAH exposure received due to the coal tar plates and not due to the bitumen.
The paper of Knecht and Woitowitz (1989) responds to the question of the PAH (and in particular the BaP content) in tar bitumen (Carbobitumen) as a binder in road works. In the case of BaP, the tar bitumen showed an average BaP content which was 
900–1000 times higher than in pure bitumen. The Bitumen Forum has also been studying the PAH emissions from bitumens from various commercial sources. Some of this work has already been published (Knecht et al., 1999), and another more definitive paper is nearing completion for separate inclusion in the annals.
Emissions from the recycling of bitumen contaminated with pre-existing tar are not at all comparable with emissions from modern-day bitumen and were not the subject of our paper.
Received November 28, 2006; in final form March 18, 2007
REFERENCES
BGIA. Measurement of hazardous substances. BIA-working folder: determination of exposure to chemical and biological agents. (1997) Berlin, Germany: Erich Schmidt Verlag.
Bjorseth A. Handbook of polycyclic aromatic hydrocarbons (1983) New York: Marcel Dekker, Inc.
Bjorseth A, Becher G. PAH in work atmospheres: occurrence and determination (1986) Boca Raton, FL: CRC Press, Inc.
Ekström LG, Kriech A, Bowen C, et al. International studies to compare methods for personal sampling of bitumen vapours. J Environ Monit (2001) 3:439–45.[CrossRef][Web of Science][Medline]
Knecht U, Stahl S, Woitowitz HJ. Handelsübliche Bitumensorten: PAH-Massengehalte und temperaturabhängiges Emissionsverhalten unter standardisierten Bedingungen. Gefahrstoffe—Reinhaltung der Luft (1999) 59:429–34.
Knecht U, Woitowitz HJ. Risk of cancer from the use of tar bitumen in road works. Br J Ind Med (1989) 46:24–30.[Web of Science][Medline]
Raulf-Heimsoth M, Pesch B, Schott K, et al. Irritative effects of fumes and aerosols of bitumen on the airways: results of a cross-shift study. Arch Toxicol (2006) 80.
Rühl R. Progress report bitumen (2006) Available at http://www.gisbau.de/bitumen.html.
Rühl R, Musanke U, Kolmsee K, et al. Vapours and aerosols of bitumen: exposure data obtained by the German Bitumen Forum. Ann Occup Hyg (2006) 50:459–68.
Schott K, Raulf-Heimsoth M, Angerer J. Auffälligkeiten bei einer Gussasphaltkolonne—Ursachenklärung einer erhöhten PAK-Belastung. Arbeitsmedizin Sozialmedizin Umweltmedizin ASU (2003) 38:594–7.
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