Oil shale processing as a source of aquatic pollution: monitoring of the biologic effects in caged and feral freshwater fish.

Abstract

The biologic effects of the oil shale industry on caged rainbow trout (Oncorhynchus mykiss) as well as on feral perch (Perca fluviatilis) and roach (Rutilus rutilus) were studied in the River Narva in northeast Estonia. The River Narva passes the oil shale mining and processing area and thus receives elevated amounts of polycyclic aromatic hydrocarbons (PAHs), heavy metals, and sulfates. The effects of the chemical load were monitored by measuring cytochrome P4501A (CYP1A)-dependent monooxygenase (MO) activities [7-ethoxyresorufin O-deethylase and aryl hydrocarbon hydroxylase (AHH)] as well as conjugation enzyme activities [glutathione S-transferase (GST) and UDP-glucuronosyltransferase] in the liver of fish. CYP1A induction was further studied by detecting the amount and occurrence of the CYP1A protein. Histopathology of tissues (liver, kidney, spleen, and intestine) and the percentage of micronuclei in fish erythrocytes were also determined. Selected PAHs and heavy metals (Cd, Cu, Hg, and Pb) were measured from fish muscle and liver. In spite of the significant accumulation of PAHs, there was no induction of MO activities in any studied fish species. When compared to reference samples, AHH activities were even decreased in feral fish at some of the exposed sites. Detection of CYP1A protein content and the distribution of the CYP1A enzyme by immunohistochemistry also did not show extensive CYP1A induction. Instead, GST activities were significantly increased at exposed sites. Detection of histopathology did not reveal major changes in the morphology of tissues. The micronucleus test also did not show any evidence of genotoxicity. Thus, from the parameters studied, GST activity was most affected. The lack of catalytic CYP1A induction in spite of the heavy loading of PAHs was not studied but has been attributed to the elevated content of other compounds such as heavy metals, some of which can act as inhibitors for MOs. Another possible explanation of this lack of induction is that through adaptation processes the fish could have lost some of their sensitivity to PAHs. Either complex pollution caused by oil shale processing masked part of the harmful effects measured in this study, or oil shale industry did not have any severe effects on fish in the River Narva. Our study illustrates the difficulties in estimating risk in cases where there are numerous various contaminants affecting the biota.ImagesFigure 1Figure 2

Transcriptional and post-transcriptional response of drug-metabolizing enzymes to PAHs contamination in red mullet (Mullus barbatus, Linnaeus, 1758): A field study

“…Concerning phase II, our results seem in line with previous field studies that failed to observe any alteration in GST and UDPGT activities in fish resident in PAH-contaminated sites (for a review see van der Oost et al, 2003;Martínez-Gómez et al, 2009) although some evidence of inhibition of GST activity has been reported in fish from PAH-contaminated sites (Bagnasco et al, 1991;Tuvikene et al, 1999). The different trends observed for GST and UDPGT activities with respect to other parameters is somehow unexpected as GST and UDPGT are actively involved in cell detoxification and glutathione conjugates in particular are the preferential substrates of MRP2 (Leslie et al, 2005).…”

The effect of long-term depuration on phase I and phase II biotransformation in mullets (Mugil cephalus) chronically exposed to pollutants in River Douro Estuary, Portugal

“…SigniWcant decreases in GST activity were reported in rainbow trout exposed to TCDD (Hektoen, Bernloft, Ingebrigtsen, Skaare, & Goksøyr, 1994), sea bass and sunWsh exposed to PAH (Lemaire, Förlin, & Livingstone, 1996;Oikari & Jimenez, 1992); and also in Wsh species from polluted environments (Tuvikene et al, 1999;Otto et al, 1996). The GST liver activity did not show a clear correlation with levels of PAHs metabolites in bile.…”

“…Glutathionation is a step within the detoxiWcation of pollutants catalysed by GSTs. However, the data available are not consistent, with some reports indicating an increase in the enzyme activity in contrast with others that do not observe changes or even reported signiWcant decreases (Otto, Buttner, Arquette, & Moon, 1996;Tuvikene et al, 1999;Van der Oost et al, 2003). Mullet was chosen because it possesses several characteristics required in an estuarine bioindicator species, such as the extreme salinity tolerance, and also because it is very common in southern European estuarine systems, and therefore may be a good tool for monitoring programs (Ferreira et al, 2004, Ferreira, Moradas-Ferreira, & Reis-Henriques, 2005.…”

Baltic Countries at the Turning Point

“…Although recent research indicates oil shale wastes may cause little harm to fish (10), any water that washes off oil shale waste piles is now collected and purified, Aarna says. Electrostatic precipitation can cut the fly ash waste by more than 99%, but the country has only been able to install the technology on half of its 20 electricity-producing units, Aarna says.…”