Biological monitoring of asphalt workers by urinary 1-hydroxypyrene: comparison between outdoor and indoor paving

Abstract

Introduzione: Lo studio valuta l’escrezione urinaria di 1-idrossipirene (1-OHP) in 108 lavoratori dell’asfalto che svolgevano la loro attività attenendosi scrupolosamente a criteri di carattere preventivo e protettivo coerenti con le specifiche indicazioni della Regione Lombardia. Obiettivi: Valutare la sensibilità del dosaggio dell’idrossipirene urinario come descrittore dell’esposizione a idrocarburi policiclici aromatici e valutare il contributo del fumo sull’escrezione urinaria dell’1-OHP. Metodi: Sono stati confrontati valori rilevati dopo 2 giorni di asfaltatura con valori dopo 2 giorni di inattività. Sono stati inoltre eseguiti confronti tra fumatori e non fumatori, e tra realizzazioni di pavimentazioni stradali all’aperto e asfaltatura in luoghi confinati. Risultati: Sono state riscontrate differenze non statisticamente significative nel dosaggio dell’1-OHP dopo asfaltatura rispetto all’1-OHP dopo inattività, eseguito nei medesimi soggetti. Tali differenze assumono invece significatività nel gruppo che ha svolto attività in ambiente confinato. Anche il confronto tra fumatori e non fumatori ha rilevato differenze non statisticamente significative. Conclusioni: L’1-OHP urinario è un indicatore che correla meglio con l’esposizione a fumi di bitume quando questa è particolarmente elevata, come avviene durante le operazioni di asfaltatura in luoghi confinati, mentre in caso di esposizioni molto basse, gli incrementi nella escrezione urinaria dell’indicatore, pur presenti, possono non assumere significatività statistica. Il fumo di sigaretta, noto per la sua interferenza con l’indicatore di esposizione esaminato, potrebbe averne limitato la specificità, ma non ha prodotto alterazioni significative nei test eseguiti in assenza di esposizione. Biological monitoring of asphalt workers by urinary 1-hydroxypyrene: comparison between outdoor and indoor paving www.preventionandresearch.com Jan-Mar 2012|P&R Scientific |Volume 2|N°1 82 Introduction Paving using bituminous mixtures involves a work-related exposure which depends on amount of time spent working and on the specific activity done. Variability of exposure is more relevant in terms of quantity than(for)quality of chemical hazards. Substances involved, mostly represented by polycyclic aromatic hydrocarbons (PAH), can be a hazard through different penetration ways (1, 2, 3, 4). Bitumen which is used as glue mixed with aggregate particles to create asphalt concrete, is a non volatile residue of petroleum refining process. Due to low levels of aromatic substances contained, bitumen is not classified by EU as carcinogen, as opposed to tar, a substance with similar uses but produced by coal refinery. Bitumen is useful in paving because it is solid at room temperature but fluid or liquid at higher temperatures, therefore it is used between 150°/180° C. Operating temperatures are much lower than boiling temperatures of each PAH. Melting and boiling temperatures of the most common PAH present in the bitumen are listed below. Molecule Melting (°C) Boiling(°C) Acenaphthene 95 279 Acenaphthylene 91,8 275 Anthracene 217 340 Benzo(a)anthracene 162 436,7 Benzo(a)pyrene 177 495 Benzo(b)fluoranthene 168 481 Benzo(g,h,i)perylene 278 500 Benzo(k)fluoranthene 215 480 Chrysene 254 448 Dibenzo(a,h)anthracene 266 524 Phenanthrene 96 340 Fluoranthene 109 384 Fluorene 116 295 Indeno(1,2,3-c,d)pyrene 164 497 Naphthalene 79 218 Pyrene 145 404 Biological monitoring of asphalt workers by urinary 1-hydroxypyrene: comparison between outdoor and indoor paving www.preventionandresearch.com Jan-Mar 2012|P&R Scientific |Volume 2|N°1 83 As shown in the table, naphthalene, a non carcinogenic PAH, has the lowest boiling temperature which is at least 40° C higher than that bitumen is utilized . This is why during usual paving working a massive phase change from liquid (or in some cases solid) to gas state is not possible. Obviously a little part of these aromatics changes to gas but expected values are so low to be indistinguishable from other molecules coming from other sources like traffic and home heating. Such phenomena are described in the “Vademecum for improving Workers’ Health and Safety in Asphalt Works” released by Regione Lombardia in June 2006 and updated in 2011, which suggests to measure aero disperse dPAHs through an analytic method sensible enough to allow measurements within the order of ng. The increase of bitumen temperature, during its processing, results in an increase of airborne PAHs. The relevance of their presence in air and the correlate deposition of workers are the basis of the possible risk for workers health (5, 6, 7). In base conditions, exposition does not appear to be relevant but there are some particular situations when the PAHs can amass and their concentration in air becomes higher, as it is the case in indoor paving. Respiratory hazard is not the only one because during working activities a skin contact with bitumen may occur in the presence of dirty tools and also from contaminated clothes or individual protective equipment (8, 9). Environmental surveys cannot determine all these kinds of exposition, so a biomarker that better correlates with exposure to fumes of bitumen is needed (10). Urinary1-hydroxypyrene is a metabolite of pyrene, a non carcinogenic PAH, whose presence is constantly correlated to total PAH (11, 12, 13). For this reason, the ACGIH believes that the urinary 1-OHP measured at the end of weekly work shift (at the end of the workweek) is a biological indicator of exposure to polycyclic aromatic hydrocarbons (14). The ACGIH classifies this biomarker as NQ, non quantitative, probably due to the lack of correlation between exposure and excretion of metabolite (15). Objectives To evaluate the sensitivity of the assay of urinary hydroxypyrene as a descriptor of exposure to polycyclic aromatic hydrocarbons in standard conditions and in higher hazard environment as in case of indoor paving. Moreover, several factors interfering with liability of 1-OHP as biomarker are reported in literature; one of the most important is smoke, so its contribution of urinary excretion of 1-OHP has been evaluated and sized. Methods A sample of 108 asphalt workers with different specific tasks, all exposed to bitumen fumes and also to skin contact with bitumen. The tasks were: ground operator, road paver driver, roller compactor operator and service guy. Both outdoor and indoor paving were considered. Workers did their daily activities adhering scrupulously to the preventive and protective policies laid down by "Regione Lombardia" in the “Vademecum for improving Workers’ Health and Safety in Asphalt Works”. The main features of this document are listed below. Norms of personal hygiene and work  Avoid contact with dirty equipment and with the bitumen emulsion, lubricating oil, diesel oil and fats, especially during cleaning and maintenance of vehicles.  Keep the skin clean and dry.  Wash frequently hands and face.  Clean hands after using the toilet.  Take a shower after extraordinary maintenance work. Biological monitoring of asphalt workers by urinary 1-hydroxypyrene: comparison between outdoor and indoor paving www.preventionandresearch.com Jan-Mar 2012|P&R Scientific |Volume 2|N°1 84  Keep cloche clean.  Do not wear dirty or contaminated work clothes: do a periodical washing.  Periodically replace suits and work clothes.  Avoid contact between your clothes and work suit.  Do not eat, drink or smoke during production of asphalt and paving