I read an article about five years ago that backs up your statement.
A local public works sent a camera down their sewer pipes and found several pools of mercury in the pipes. The amount was "several pounds." No one knew how the mercury got there, but it was mentioned that it was not the dangerous kind, but was being removed via suction.
I played with mercury as a child, even swallowed some, probably a half ounce over the years.
Worked with it by the gallon as an adult in the mining- refining business.
Did get mercury vapor poisoning pretty bad once... Whole body hurt like hell for four days, but didn’t even lose a tooth.
Mercury only becomes a significant health hazard when you ingest mercury compounds, especially the ‘mercury salts’, or eat critters that have ingested them. Even then, it is over hyped you’d have to eat ‘mercurized tuna every day for months to have any significant effects.