Setting threshold levels for POPs in marine mammals is not an easy task. Basically because few exposure studies have been made. Also, there are large interspecies differences in the toxicokinetics of POPs in marine mammals, and also the physiology differs between species. This makes is very difficult to extrapolate between species even among marine mammals. However, some years ago a report published by AMAP (Arctic Monitoring Assessment Program) was published in which levels of various POPs in Arctic sea mammals and other top predators were compared with various threshold levels reported in other wildlife and experimental animals and to guideline levels for contaminants in human food. This report can be downloaded for free (http://www.amap.no/documents/doc/amap-assessment-2002-persistent-organic-pollutants-in-the-arctic/96). Some useful info might be found from page 168, and perhaps also in other parts of the report. Sonne 2010 (Environment International 36:461-491) also used this approach in an attempt to assess if polar bears were of risk due to POPs exposure. Of course, the approach used in the AMAP report and the paper by Sonne must be taken for what it is, and it is important to take into consideration that there most likely are large species differences, even among marine mammals. However, I guess this approach still provides some indications as to wether or not levels of POPs are below or above threshold levels shown to cause more or less adverse effects in experimental animals and wildlife, and in relation to guidelines for human exposure. You should also note that some of the human guideline values probably have changed, and that there might be some more recent effect-levels reported in relevant wildlife species.

Well IT us à very common but difficult question. You can look at Fournier et al. But you will get a ld50 for marine mammals. You can look at dnels for human or pnec for marine or bcf or eqs. A make a reasoning on which best values to use.

Perhaps you should pose the question on MARMAM, the Marine Mammal Research and Conservation Discussion list. Go to https://lists.uvic.ca/mailman/listinfo/marmam to sign on and then post your question

Marine mammals cover a very broad group with varying susceptibility to pollution load. Focus on one group such as top predators, e.g. Orcas for which size, age, gender and life history stage are variables. Human values might be comparable.

Try looking into the work by the US NOAA, the Medical University of South Carolina, and the University of South Florida. NOAA has an oceans and human health program that evaluates contaminant effects on marine mammals as indicators of the ways in whiich marine contaminants influence human health. hope this is useful.

Thanks for your answers.

Mathieu, do you co-authored Fournier et al paper? I could not find it in your research gate references. Would you mind giving me the full reference of this paper ?

Jerry, I had no choice on the species, as my work is to analyze data previously gathered by NGOs. I have data about several species of whales (Balaenoptera physalus, Physeter macrocephalus) or dolphins (Stenella coeruleoalba, Tursiops truncatus, Ziphius caviriostris). The aim would be to conclude sth like : "this dolphin population has a mean concentration of X for contaminant Y, so it could be considered it's impacted by pollution, whereas this whale population has a mean concentration of X for contaminant Z, so it is less impacted" ! I admit this is maybe unrealistic !

Setting threshold levels for POPs in marine mammals is not an easy task. Basically because few exposure studies have been made. Also, there are large interspecies differences in the toxicokinetics of POPs in marine mammals, and also the physiology differs between species. This makes is very difficult to extrapolate between species even among marine mammals. However, some years ago a report published by AMAP (Arctic Monitoring Assessment Program) was published in which levels of various POPs in Arctic sea mammals and other top predators were compared with various threshold levels reported in other wildlife and experimental animals and to guideline levels for contaminants in human food. This report can be downloaded for free (http://www.amap.no/documents/doc/amap-assessment-2002-persistent-organic-pollutants-in-the-arctic/96). Some useful info might be found from page 168, and perhaps also in other parts of the report. Sonne 2010 (Environment International 36:461-491) also used this approach in an attempt to assess if polar bears were of risk due to POPs exposure. Of course, the approach used in the AMAP report and the paper by Sonne must be taken for what it is, and it is important to take into consideration that there most likely are large species differences, even among marine mammals. However, I guess this approach still provides some indications as to wether or not levels of POPs are below or above threshold levels shown to cause more or less adverse effects in experimental animals and wildlife, and in relation to guidelines for human exposure. You should also note that some of the human guideline values probably have changed, and that there might be some more recent effect-levels reported in relevant wildlife species.

I am not aware of LD-50 studies on marine mammals. The closest studies are by P. J. Reinders, (1986) Nature 324, 456-457. Sam

Have you tried to find reference TEQ values for PCBs in mammals, instead of LD 50 ?

Pierre, Michel Fournier has published many articles on imminotoxic effects in beluga for instance. There are also some measurements in fat and tissues in polar bears rtc in Amal report as already indicated above.

Maybe you can use data from the ERED database? http://el.erdc.usace.army.mil/ered/

After reading some papers, I found the reference of Kannan et al. 2000 (http://www.usask.ca/toxicology/jgiesy/pdf/publications/JA-224.pdf). In this paper, the authors propose the value of 17 000 ng g−1 lw for PCB concentration in the blubber as a threshold for adverse effect.

Maybe you would be interested in reading this paper ?

Thank you all for your contributions !