Tomatoes growing on the track at a railway station in Norfolk highlight the failure of train companies to fit waste tanks to on-board toilets, The National Union of Rail, Maritime and Transport Workers (RMT) has said.
Plants bearing fruit have been seen growing amid waste at Diss in Norfolk.
The RMT told BBC News that the Southend to London line had also become known for discharged human excrement, and for being a hazard for employees working on the track.
A spokesperson for train company Abellio Great Anglia, which operates the route, told BBC News some carriages would be upgraded with retention tanks next year.
Mick Cash, RMT general secretary, said: 'The tomatoes are an indication of just how bad the problem is, particularly on Greater Anglia.
'If it was bankers getting sprayed with excrement when they went to work, rather than track workers, this practice would end overnight.
'The profiteering train companies should fund the cost of fitting tanks to end this scandal, rather than offering up excuses and solutions that are decades away.'
Tomato plants at Diss station would be capable of germinating from tomato seeds found in human excrement.
An Abellio Greater Anglia spokeswoman said: 'A number of our trains already have retention tanks fitted.
'Our Mark III train carriages, which operate Intercity services between Norwich, Diss, Ipswich and London, are going to be upgraded with new toilets and retention tanks from next year as part of a major refurbishment programme, with the full programme completed by the end of our current short franchise in October 2016.'