Lake Washington: still toxic after all these years?

Late this summer, the State Department of Health (DOH) posted a “Lake Washington Advisory” sign at the E. Madison Street road end that I, for one, found a bit shocking. The advisory warns that eating certain fish from the Lake could be harmful due to “chemical pollution.” In fact, two fish (the carp and the northern pikeminnow) are singled out—in no fewer than seven languages—as too dangerous to be eaten at all; and another fish, the cutthroat trout, is listed as being worthy of only one serving per month.

Sounds bad, but what’s going on here? I thought that Lake Washington had been cleaned up long ago. Is the Lake getting cleaner, as I had previously supposed, or is the water quality here actually deteriorating?

I decided to find out, so I called the number helpfully listed at the bottom of the advisory. I was connected with Dave McBride, Lead Toxicologist with the DOH’s fish program, who assured me that things are not as bad as they may seem from a cursory review of the new advisory. First of all, he said, this is not really new information, even though there had previously been no posting on the subject. What happened, he said, is that the department recently received funding for some new signs. In fact, he said, there already had been an interim advisory concerning Lake Washington fish. The new signs coincide with the decision to make the advisory a permanent one.

So why are these fish so bad for our health? PCBs and mercury are the primary contaminants, according to McBride. PCBs have been banned for 30 years or so, but they still exist in plentiful supply in the environment, he told me. “There’s not really any new input (of PCBs),” he noted, “so much as there’s a recycling of existing PCBs within the system.” What this means for big, fatty, long-lived bottom fish such as carp, he said, is that they have time to build up an unhealthful supply of these chemicals and mercury, which occurs both naturally in the environment and as a result of human intervention. Chemicals continue to be introduced into Lake Washington through such means as the leaching of landfills and the draining of old transformers into the Lake, McBride told me. Fossil fuels also cause pollution, he noted; and any lake located in an urban environment, such as ours, will never be pristine.

The good news is that the trend is in the right direction. “The Lake is definitely cleaner than it was twenty or thirty years ago,” he said, “but it’s still not perfect.” Lake Washington is not worse than most other lakes in the state, McBride said, and it probably could be rated a ‘moderate’ lake in terms of fish contamination.

There really aren’t all that many carp in Lake Washington in the first place (and perhaps no northern pikeminnow), according to McBride. There are cutthroat trout in the Lake, but the “Good to Eat” lake fish are much more plentiful, fortunately. The yellow perch is good for a meal a week, but the sockeye, rainbow trout (shown above), and pumpkin seed are all good for two to three meals a week. So go ahead, knock yourself out--assuming you can catch any of them!