The average business email user is responsible for 131kg of CO2 per year in email-related emissions, with 22 per cent spam related, according to a new report.
McAfee's Carbon Footprint of Spam' equated the energy used by spammers to the emissions that resulted if every user burned an extra 3.3 gallons of gasoline each year.
It also said that the total energy used by spammers totalled 33 billion kilowatt-hours (KWh), which could power 2.4 million homes for a year.
The report, conducted by climate-change consultant ICF, looked at the global energy expended to create, store, view and filter spam across 11 countries including the UK and US.
Dave Marcus, director of security research and communications at McAfee Avert Labs, said in a statement that spam was tied to the environment as well as identity theft and malware.
He said: "This is a global problem, with the UK being the fourth biggest emitter of carbon dioxide from spam."
Last November, when massive spam contributor McColo went down, the temporary drop in total spam traffic was equated to taking 2.2 million passenger vehicles off the road.
