[dainbramaged]

I would not consume shellfish pried off of pilings in South Puget Sound, where tidal action isn't that great and some contamination is possible. Hood Canal is another body of water that doesn't flush real well.
However, there are clam and mussel farms near the Straits of Juan de Fuca and the San Juan Islands up North that get lots of ocean water twice daily and produce a fine product.
I wouldn't harvest Dandelions for a salad at dog pee level, either. Cheers.

[PIF]

Shellfish on piling absorb the creosote they pilings are soaked in. HC flushes over a 7 year period.

Unless Victoria, BC has made a major investment in sewage treatment recently, they dump raw sewage directly into the Straits.