According to this 1849 illustrated poem, what was one reason london’s drinking water was polluted?

By looking at the 1849 poem, one reason that London's drinking water was polluted was because the Thames River was polluted. The river was polluted because it was filled with sewer, factory waste, and sink waste. Officials were paid off to ignore all of the pollution being dumped into the Thames River. 

Not sure this is a hard one huh