Assessment of Bile Fluorescence Patterns in a Tropical Fish, Nile Tilapia (Oreochromis niloticus) Exposed to Naphthalene, Phenanthrene, Pyrene and Chrysene Using Fixed Wavelength Fluorescence and Synchronous Fluorescence Spectrometry A. Pathiratne • C. K. Hemachandra • K. A. S. Pathiratne Received: 26 June 2009 / Accepted: 7 April 2010 / Published online: 22 April 2010 Ó Springer Science+Business Media, LLC 2010 Abstract Bile fluorescence patterns in Nile tilapia, a potential fish for biomonitoring tropical water pollution were assessed following exposure to selected polycyclic aromatic hydrocarbons (PAHs): naphthalene, phenan- threne, pyrene and chrysene. Non-normalized fixed wave- length fluorescence signals in the fish exposed to these PAHs reflected dose and/or time response relationships of their metabolism. Normalizing signals to biliverdin intro- duced deviations to these response patterns. The optimal wavelength pairs (excitation/emission) for synchronous fluorescence scanning measurements of bile metabolites of naphthalene, phenanthrene, pyrene and chrysene were identified as 284/326, 252/357, 340/382 and 273/382 respectively. This study supports the use of bile fluores- cence in Nile tilapia by fixed wavelength fluorescence and synchronous fluorescence spectrometry with non-normal- ized data as a simple method for screening bioavailability of these PAHs. Keywords Tilapia Á PAH Á Biomarker Á Bile fluorescence PAHs are a group of ubiquitous organic pollutants in aquatic ecosystems. PAHs are mainly derived from petro- genic and pyrogenic sources. PAHs have received increased attention recently in pollution studies as some PAHs are highly carcinogenic and mutagenic (Srogi 2007). Sixteen PAHs have been categorized under the group ‘‘priority pollutants’’ which include naphthalene, phenan- threne, pyrene and chrysene. Thus exposure assessments of PAHs in the aquatic ecosystems are important especially in the developing world as the presence of these pollutants poses a serious threat to aquatic resources including fish. In fish, PAHs are biotransformed by mainly liver through oxidation and conjugation reactions to hydrophilic metab- olites that are excreted through bile. During the biotrans- formation process highly reactive intermediate products may be produced which can bind with DNA inducing cancers and mutations. Measurement of biliary fluorescent metabolites is a valid fish biomarker for environmental risk assessment process concerning PAH-contaminant sites (van der Oost et al. 2003). PAH metabolite measurements in bile can be carried out using analytical techniques such as high pressure liquid chromatography, gas chromatogra- phy-mass spectrometry (Leonard and Hellou 2001), fixed excitation/emission wavelength fluorescence and synchro- nous fluorescence spectrometry (Ariese et al. 1993; Aas et al. 2000). Simplicity of the fixed wavelength fluores- cence and synchronous fluorescence spectrometry methods makes them suitable for screening recent exposure to PAH on large number of fish rapidly at relatively low cost per sample. Little information is available concerning respon- ses of tropical fish to PAHs. Nile tilapia (Oreochromis niloticus) which is a widespread food fish species in trop- ical countries has been suggested as a test species for biomonitoring of aquatic pollution in tropical environments (Pathiratne et al. 2009). The objective of the present study was to assess the bile fluorescence patterns in Nile tilapia exposed in the laboratory to four commonly occurring PAHs namely naphthalene, phenanthrene, pyrene and chrysene using fixed wavelength fluorescence and syn- chronous fluorescence spectrometry techniques and to A. Pathiratne (&) Á C. K. Hemachandra Department of Zoology, Faculty of Science, University of Kelaniya, Kelaniya, Sri Lanka e-mail: asoka@kln.ac.lk K. A. S. Pathiratne Department of Chemistry, Faculty of Science, University of Kelaniya, Kelaniya, Sri Lanka 123 Bull Environ Contam Toxicol (2010) 84:554–558 DOI 10.1007/s00128-010-9987-y