a foul-smelling outflow or vapor (especially a gaseous waste)
With that, Jessica’s small, desperate hope— that her inner disturbances had been a feverish reaction to the effluvium emanating from the open gutter in front of Champtois’ shop— died a quick, brutal death.
Chase, Loretta (2009-10-13). Lord of Scoundrels (p. 43). Harper Collins, Inc.. Kindle Edition.
Definition from http://www.onelook.com/?w=effluvium&ls=a