Shopping bags could be a threat to shoppers' health as they harbour deadly food poisoning micro-organisms, researchers have said.
Tests conducted on shopping bags of a total of 84 shoppers have revealed that almost half of them contained traces of E.coli, a lethal micro-organism that killed 26 people in Scotland in 1996 in one of the world's worst food poisoning outbreaks.
Scientists from the University of Arizona in the US also found many bags were contaminated with salmonella, The Telegraph reported.
Many of the shopping bags were made from jute or woven polypropylene. While they helped to reduce the amount of plastic used in carrier bags by 40 percent in just the last three years, the research says they could be harmful if not cleaned regularly.
The study revealed 97 percent of shoppers who used eco-friendly bags never washed or bleached them.
There are hundreds of people who use "permanent" shopping bags, and a vast majority do not wash their bags after each shopping trip, according to Wrap, the British government's anti-waste watchdog.
The researchers warned the levels of bacteria they found were high enough to cause a wide range of serious health problems and even death. Children may be in the greatest danger, they said.
"Our findings suggest a serious threat to public health, especially from bacteria such as E.coli, which were detected in half of the bags sampled. Consumers are alarmingly unaware of these risks and the need to sanitise their bags on a weekly basis," Charles Gerba, who led the study, said.
E. coli is a species of bacterium found in the intestines of animals and humans. It is passed on through faeces and can survive in the environment. It is usually transferred to humans by ingesting contaminated water, or contaminated food, such as meat, which has not been cooked properly.
A particular strain, known as E. coli 0157, can be lethal for children and older people.
E. coli cases in Britain are on the increase, the Health Protection Agency said, adding that there were 25,532 reported cases in 2009, a seven percent increase compared to 2008.