Contamination of Baikal seals with potentially toxic PFCs
PFCs (perfluorochemicals) are man-made compounds used in many industrial processes. They are commonly used in fire extinguishers and as CFC replacements in refrigerators, as well as being essential in computing, cosmetic and medical industries. They are also used to make non-stick pots & pans and stain-proof fabrics. PFCs have been shown to be particularly persistent in the environment, resisting oxidative decay. Consequently these compounds bio-accumulate in living organisms, and their toxicity to animals especially high up in food chains, is becoming increasingly apparent.
Two studies have recently been published in Environmental Science & Technology which explore concentrations and possible effects of PFCs on Baikal’s freshwater seal, Pusa sibirica (nerpa) (Ishibashi et al. 2008a, 2008b). Because nerpa are at the top of the Baikal food-chain, they too bio-accumulate toxins such as POPs (persistent organic pollutants) (Nakata et al. 1995). In this pair of papers, Ishibashi et al. initially provide evidence for bio-accumulation of PFCs in Baikal seals, especially in their livers. Ishibashi et al. (2008a) found that bio-accumulation tends to be higher in seal pups than in adult seals, which led them to conclude that significant transfer of PFCs occurs between the pups and their mothers (Fig 1). Moreover, concentrations of PFCs in Baikal seal livers increased between 1992 and 2005. This highlights a worrying trend that these globally distributed contaminants are increasingly impacting on remote ecosystems.
Having demonstrated that since the early 1990s PFCs have increasingly accumulated in the livers of Baikal seals, especially young pups, the focus of the second paper was to determine if these man-made, persistent compounds were having a determinable impact on this unique freshwater mammal (Ishibashi et al. 2008b). In order to do this, they relied to previous research which showed that certain metabolic processes in the Baikal seal can be modulated by PFCs. Although they have not as yet determined any toxic, biological impacts of PFCs on the Baikal seal, they have identified specific metabolic responses to these compounds, which they suggest could be useful biomarkers for monitoring future impacts and trends.
Ishibashi, H., Iwata, H., Kim, E.-Y., Tao, L., Kannan, K., Amano, M., Miyazaki, N., Tanabe, S., Batoev, V.B., Petrov, E.A. 2008a. Contamination and Effects of Perfluorochemicals in Baikal Seal (Pusa sibirica). 1. Residue Level, Tissue Distribution, and Temporal Trend. Environmental Science & Technology, 42, 2295 - 2301. doi: 10.1021/es072054f
Ishibashi, H., Iwata, H., Kim, E.-Y., Tao, L., Kannan, K., Tanabe, S., Batoev, V.B., Petrov, E.A. 2008b. Contamination and Effects of Perfluorochemicals in Baikal Seal (Pusa sibirica). 2. Molecular Characterization, Expression Level, and Transcriptional Activation of Peroxisome Proliferator-Activated Receptor α. Environmental Science & Technology, 42, 2302 - 2308. doi: 10.1021/es072055
Nakata, H. Tanabe, S., Tatsukawa, R., Amano, M., Miyazaki, N. and Petrov, E.A. 1995. Persistent organic chlorine residues and their accumulation kinetics in Baikal seal (Phoca sibirica) from Lake Baikal, Russia. Environmental Science & Technology, 29, 2877-2885.