I have here a series of slides that review some of the issues we've been seeing since the 1970s.
It all really started on Scotch Bonnet Island on Lake Ontario. That is where we really started to see the effects of environmental pollutants in the Great Lakes. This was work done by Environment Canada scientists back in the 1970s, first when they discovered 100 nests, but only 10 young. This was the first sign of the kinds of serious problems that began to emerge in the 1970s and that really began to be noticed in the 1970s.
We have since seen the effects of DDT and the impacts on eggshell thinning and the deformities and birth defects in birds that became prevalent and well known in that part of the world, along with some even more pronounced effects, like crossed bills in cormorants. That was not a rare occurrence back in the 1970s. These were the sorts of things we were facing back in those days.
When we looked at some of the sites that tended to have more of these contaminated effects versus ones that had less contaminated effects, we saw that places like the Detroit River and western Lake Erie were some of the more contaminated areas, places like the Hamilton harbour, whereas in the northern lakes we were seeing sites that were much less contaminated.
On this slide, you can see that some of the most contaminated sites were in places around Lake Erie, the Detroit River, and Lake Michigan, whereas some of the less contaminated sites were focused around places like Lake Huron and Lake Superior.
When we look at some of the kinds of things that we see in places that are more contaminated, we have one example here from the St. Clair River that shows specific effects that are quite clearly from contamination, right downstream from Sarnia and some waste water treatment plants around Stag Island. We can compare that with places like Port Lambton, which is a reference site.
One of the factors we see in some of these contaminated sites includes effects like—I'm a scientist, so of course I'm going to focus on the science side of things—the feminization of fish, which is most pronounced in the most contaminated sites, such as the St. Clair River. One of the things that is apparent is the fact that we see this biomarker called vitellogenin. It's essentially an egg yolk protein that we typically see in females but we don't ever see in males unless they are exposed to environmental estrogens.
As you can see in this slide, males are showing measurable levels of this vitellogenin, an egg yolk protein, in their blood. This is a very clear indication of the feminization that takes place in some of these contaminated sites. It's a product of environmental estrogen exposure. These are chemicals that are coming from industrial sites and from residential waste water treatment plants.
Another expression of this feminization is seen in what we call intersex, which is the presence of female cells in male testes. Shown in this slide is an oocyte, which is an egg cell that is found in males' testes and is another very clear indication of feminization.
Those are some of the manifestations of environmental estrogens that we see in some of these contaminated sites.
Another factor we've been focusing on is what we call biotransport. Historically, contaminants were released into the lakes. Since the 1970s, some of those contaminant levels have come down, but what we find now when we look at the distribution of these contaminants is that they're not so much distributed near where we find industrial sites, but are more closely linked to the life cycles of some of these animals.
One of the examples I have here is of migratory salmon, which spend most of their life and acquire most of their body mass in the lakes, but then they swim upstream to spawn and they transfer many of those contaminants to those resident fish in their spawning lakes.
An interesting thing that we now see in the Great Lakes is migratory animals like salmon that swim upstream to spawn. They contaminate because they accumulate contaminants from the lakes. They transfer these contaminants such that the resident fish in some of their spawning lakes are now in some of the most contaminated places that we see. We call this a biotransport.
I have an example here showing the PCB concentrations in stream resident fish from reaches with and without salmon spawners. This is a study from the United States. You can see in reaches of the river where there are no salmon spawners, the resident fish have much lower contamination levels, but they have 20 to 50 times higher contamination in the reaches of the streams where salmon are spawning. We call this biotransport a biovector transport of pollutants, and we see this in the Great Lakes.
PCBs have come down to maybe 5% of what they were back in the 1970s, but we can't make that generalization across the board because there are locations—whenever we make a generalization, we have to list a number of caveats because generalizations tend to be wrong. One of the things we see here when we look at the distribution of these contaminants today is that they aren't widely distributed across these lakes, but we do see hot spots of contamination, not near industrial sites but near sites where salmon are spawning. This goes to show that when we release chemicals into the environment, ultimately they become part of that natural world and they take on a life of their own.
To summarize some of the important things that have been collected over this time period and some of the important sources of information that we have, a survey has been done of herring gulls since the early 1970s, and this provides us with a history of contamination spanning different areas of the Great Lakes. Our best indication of the history of contamination is provided by this tissue archive, which is stored at the National Wildlife Research Centre here in Ottawa. There are tissue archives that allow us to reconstruct a history of contamination over time.
If we want to see the history of contamination, we have that tissue archive available to us so we can track the movement of contaminants that we haven't even discovered yet.
Some of the oldest annual wildlife contaminant monitoring programs in the world are found in the Great Lakes. Environment Canada is credited with having the foresight to provide us with these tissue archives.
Some of the spatial analysis shows that the cleanest eggs and the cleanest tissues we tend to find are in places like eastern Lake Superior, eastern and northern Lake Huron, whereas the dirtiest sites are in places like the Detroit River and western Lake Erie.
Our temporal analysis, our historical analysis, is showing that many of the legacy contaminants that produced some of the disfiguring effects that I showed early on have declined. Chlorinated chemicals have declined by over 90% since 1974, but we add the caveat that some places are still showing high contamination because of migratory species that can funnel contaminants and maintain them at high levels. Mercury has declined, but only slightly, and there are emerging chemicals, like the brominated flame retardants and perfluorinated acids, and the personal care products and pharmaceuticals that we are starting to learn more about.
We do see health effects to this day in the more contaminated parts of these lakes, relating to things like immune response, sex ratios, and feminization as shown by things like vitellogenin and embryonic viability, which show association with more contaminated sites.