Much of theÂ sukuma wikiÂ (kales) on sale in Nairobi is highly contaminated and poses a serious health risk to consumers.
Researchers from the University of Nairobi have sampledÂ sukuma wikiÂ grown in Athi River, Ngong and Wangige and that sold in Kawangware, Kangemi and Githurai markets and concluded it is toxic.
A team of nine scientists from the College of Agriculture and Veterinary Sciences in Nairobi say the case is also the same with the kales sold in supermarkets and high-end stores in the city.
The study, led by Carl Johan Lagerkvist of the Swedish University of Agricultural Sciences and published in the current issue of theÂ East African Medical Journal, blames poor cultivation and handling practices for the unhygienic state of the vegetables.
The researchers tested the kales for coliforms, a broad class of bacteria found in the environment including in human and animal waste.
Other organisms tested for wasÂ E.coliÂ a group of bacteria some which can cause diarrhoea, urinary or respiratory illness while the third candidate is salmonella bacterium which can cause serious food poisoning.
Sukuma wikiÂ from the open markets such as in Kangemi and Kawangware and those in supermarkets were found to have higher organisms associated with faecal matter than kales from farms.
These germs, mainly from water used on farms for irrigation and in the markets for washing the vegetables, was found to exceed levels recommended by the World Health Organisation.
High levels of contamination with salmonella were detected on samples collected from farms in Wangige and the open market in Kawangware.
An earlier study onÂ sukuma wikiÂ by the same group in Nairobi had indicated the presence of heavy metals, pesticide and fertiliser residue in the samples.
At the same time, say the researchers, to keep the kales fresh and appealing, most retailers sprinkle or moisten them with unclean and sometimes polluted water.
The study also documented possible contamination during transportation of the commodity.
Most traders in Githurai and Kangemi transported the vegetables using open trucks while in the former people carry them on their backs.