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We're constantly told to eat five portions of fruit and veg a day to stay healthy. But should these be washed first?
To wash or not to wash?
"Have you washed that?" The question that nearly always flies from your mother's mouth as you're about to bite into an apple or chomp on some grapes. It is usually followed by a trip to the kitchen sink.
Washing fruit is one of those habits that is drummed into children as soon as they are big enough to reach the fruit bowl. But is it really necessary?
The purpose of cleaning fruit and vegetables is to wash off any pesticide residues, from the chemical and biological substances used to kill or control pests that harm our food, health or environment.
The main use of pesticides is in agriculture to ensure that crops remain healthy, and wastage through disease and infestation is prevented. Government ministers must approve all pesticides before they can be marketed or used in the UK.
Small amounts of residue can remain behind in the crop after harvesting or storage and make their way into the food chain. According to the Pesticide Safety Directorate (PSD) a third of food contains pesticide residues.
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Fruit is also at risk of contamination from dust, dirt and bacteria as most of it has been stored in warehouses, travelled in containers and stored again in the premises of the retailers.
The role of the Food Standards Agency (FSA) is to protect consumers by ensuring that pesticide residues are as low as practically possible and within safe limits.
The FSA's Sam Montel, a nutrition expert and a registered public health nutritionist, says the risk from eating unwashed fruit is minimal but getting into the habit of washing and - where appropriate - peeling fruit and vegetables is simple good hygienic practice.
"It ensures that they are clean and that bacteria that might be on the outside are removed," she says. "If a vegetable or piece of fruit is especially dirty, washing might not be enough to get it clean, so then you could peel it."
When the FSA asked the independent Advisory Committee on Pesticides (ACP) to review its advice on washing fruit, the committee concluded that washing and peeling fruit and vegetables is a matter of individual choice - it is good hygiene but not required.
The FSA continues to advise people to wash or peel. Campaign groups say this is not good enough, as peeling and washing fruit may reduce residues but it will not eliminate them. And peeling removes fibre and important vitamins such as C.
Friends of the Earth says the best way to keep people safe is to not use chemical pesticides at all.
"The FSA's advice is ineffective - many residues survive peeling," says a spokeswoman. "We want effective action to ban the most dangerous pesticides, and to reduce to a minimum all use of pesticides in farming."