Yeah, waterways are viewed as toilets and dumps to humans. It is disgraceful.

I don't believe I will ever eat another oyster.

Filter feeders pretty much get exposed to everything in the water. I will eat raw fish or cephalopods but I will not eat raw filter feeders for that reason. They also concentrate heavy metals but usually the beds are tested for those and closed if they are in areas where heavy metal toxicity could be a problem.

Not unsurprising. Shellfish are renowned for thriving around sewage outlets. What we flush away is their all you can eat buffet. It's part of the natural cycle of life, but unfortunately it provides a vector for human pathogens to reinfect.

Tenuously on topic: this is probably why the Bible prohibits the consumption of shellfish: eating it (not suitably cooked) made people ill (or even dead.) In a culture that doesn't understand the concepts of bacteria and viruses, clearly this means you've done something to massively offend the bloke with the halo.

I'm safe, I can't even stand to look at them shelled or shucked let alone eat them.