We asked Pierre Béland, a toxicologist who has studied the St. Lawrence for years at the St. Lawrence National Institute of Ecotoxicology for his insight.
"For one, it was a one-shot event that is now over.
However, it is well known that the Montreal wastewater treatment plant has for many years been, from time to time, diverting untreated water to the river — for reasons that are of a technical nature (malfunction, design, repairs, maintenance), or because it cannot cope with the high volume of water entering the plant at a given moment — storms in particular.
By the way, this is not unique to Montreal: All major cities have to deal with this kind of problem, especially as relates to stormwater discharge [note that stormwater, i.e. rain water flowing over hundreds of square kilometres of city streets, yards, dumps, etc., can be quite contaminated; for example, it has been shown that the influx of PCBs and other chemicals into Lake Michigan increases markedly following heavy rain events over Chicago.]
In other words, the recently well-publicized Montreal event did not really produce such an “unusual” inflow of tainted water into the St. Lawrence compared to the total of what has been dumped over the past several years.
Now, the other question: Does it affect belugas?
It is important here to remember that belugas live a few hundred kilometres dowmstream of Montreal. With regards to the recent dumping event, one must think in terms of, say, four very broad categories of items likely present in the discharge.
- Solids and particles: These usually settle down on the bottom near the discharge site or not too far down.
- Bacteria and other microorganisms such as coliforms: These are freshwater species that, if they make it that far, will not survive when they hit salt water where the belugas live.
- Hormones and pharmaceutical compounds: I am not too familiar with this group, but I surmise that they will have been ingested or transformed through the food chain and have exhibited any potential effect more locally than in the beluga range downstream.
Thus, the first three categories are much more of a threat locally and even as far down as Lake Saint Pierre, which is a sedimentation sink for the upper St. Lawrence.
This leaves category 4:
- Persistent industrial and agricultural organic and metallic compounds. These are the ones that our studies have shown to be prevalent in and detrimental to the belugas.
Of course, for this, Montreal has for many decades (almost a century now) been one of the sources, as well as the upper St. Lawrence (New York State, Ontario), the Great Lakes, and atmospheric transport.
Nevertheless, I doubt very much that one could pinpoint to any specific effect that could be traced back to the much-publicized recent dumping, especially since there is such a time-lag (5, 10 years or more?) between the moment a given molecule is discharged near Montreal and the time it ends up in the mouth a beluga.
That is not to mean that I condone such dumping, on the contrary."