Many non-Japanese think that sushi is very luxurious dish in Japan but it used to be a fast food during Edo era, when Tokugawa shogunate ruled Japan till mid 19th century.
Sushi stands were on the streets of Edo(former name of Tokyo. The first city to surpass one million inhabitants in the world!
) and people enjoyed the fresh fish from the Bay of Tokyo.
Therefore one of the sushi types are still called EDOMAE sushi. Edomae means in front of Edo.
The water quality of Bay of Tokyo was damaged during the economical boom in 60s/70s, when Japanese did not think about the environment so much. Of course, the quality is much better now.