The contamination in the area is mostly coal tar, which contains polycyclic aromatic hydrocarbon. There are carcinogenic compounds in it, so it is a concern for aquatic life in the harbour. Yes, waves and shipping would disturb the sediment and move that around, dispersing the toxins.
After the cleanup of the tar ponds in Nova Scotia, which is in progress, this is the largest coal tar contaminated sediment site in Canada.