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Differentiation and measurement of polycyclic aromatic hydrocarbons in hard coal dust

A pilot study was carried out to determine the polycyclic aromatic hydrocarbons (PAH) content of coal dust and identify the resulting cancer risk. PAHs are condensed aromatic ring systems. The PAHs benzo(a)anthracene (BaA), benzo(b)fluoranthene (BbF), benzo(a)pyrene (BaP), indeno(1,2,3)pyrene and dibenz(a,h)anthracene are classified as carcinogenic. As a result of their low vapour pressure, PAHs in vapour form are found only in extremely low concentrations. Airborne PAHs are mainly in particulate or particle-bound form. Nine coal samples were used for the study: three anthracites, two steam coals, three coking coals and one gas-flame coal.

The highest level of carcinogenic BaP is found in gas-flame coal at a level of 3.7 parts per million (ppm). BaP is not identifiable in anthracite (ie its level is <0.04 ppm). The BaP content of coking coal is between 0.5 and 2 ppm, whereas steam coal contains between 2.2 and 2.7 ppm BaP. According to the German regulations on hazardous substances, a mixture is classified as carcinogenic if it contains >50 ppm BaP. The types of coal investigated here contain substantially less and are therefore not classified as carcinogenic. A point to note is the close correlation between the BaP and BaA contents of the types of coal investigated; BaP concentrations are 2-3 times lower than BaA concentrations. The report on the project on the specific toxicity of mine dusts states that the investigation of a relatively large group of hard coals from various seam horizons showed that BaA levels did not exceed 9 ppm. BaP contents were not investigated. Taking the factor of 2-3, BaP concentrations would not exceed 5 ppm. In other words, hard coal should not be classified as carcinogenic.

Reported by

Institut für Gefahrstoff-Forschung der Bergbau-Berufsgenossenschaft
Waldring 97
44789 Bochum
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