Bad smell halves unflushables in Genoan households and businesses study shows

Researchers in Genoa, Italy have reported a near halving of incidences of disposal of fat and unflushable items into the medieval city’s sewer system by tapping into the powerful psychological influence of smell.

By infusing the subliminal smell of raw sewage into a public advice note on the hazards of throwing non-flushable items into the drains, the researchers have claimed to have reduced the volume of drain-blocking material in the sewers by 47% over a six-month period.

Leader of the study, Professor Nadia Gnecco, from the Liguria Institute of Applied Psychology said the advice message – issued by the Genoa municipality – included a warning of the risk of sewer flooding which Gnecco said was reinforced by the subliminal odour. The pilot study was carried out with householders and businesses in the centre and ancient port region of the city which has a population of some 25,000 people.

She said the impact of the message was exceptional compared to the use of similar, less offensive, odours used in similar experiments where written information was reinforced by subliminal smells.