Is tap water enough to wash away pesticides?

When it comes to washing fruit and vegetables before eating or cooking in my experience the majority of people fall into one of three categories. You should be aware that a recent study conducted by Dr Lili He, a food scientist at the University of Massachussets, in the USA, proved that none of the above methods is effective in removing pesticides.

When it comes to washing fruit and vegetables before eating or cooking in my experience the majority of people fall into one of three categories:

1. Those who’ll take an apple (or other fruit) and rub it against their sleeve and then eat it;

2. Those who consume fruit and vegetables as they are, trusting that the seller/farmer has already washed the produce so they don’t need to bother;

3. Those who will quickly run the fruit or veg under the cold water tap for a few seconds, dry and/or remove the peel, and then eat/cook them.

Whichever of the above groups you fall into, you should be aware that a recent study conducted by Dr Lili He, a food scientist at the University of Massachussets, in the USA, proved that none of the above methods is effective in removing pesticides.

But why should you (re)wash your food at all?

Asides from the fact that your fruit and vegetables have been in contact with a number of other surfaces from the moment they were picked, to the moment they land on your plate or chopping board (just think what your sleeves have touched and what could be on your sleeves! Ugh!), and that most of these surfaces will be less than sterile, pesticides have been linked to a number of health issues. Even chronic, low-level pesticide exposure has been linked to hyperactivity in children, diabetes and a host of hormonal problems including low sperm count and infertility in both sexes, to name but a few.

What if we are buying organic?

The myth is that organic foods are pesticide free. Unfortunately, that is simply not the case.  Consider that not all countries have the same standards when it comes to what is considered organic farming, plus the fact that years of pesticide and other chemical use will have left some residue in the same lands which recently converted to organic farming, or that the non-organic farm next door could be leaking unwanted chemicals across the hedge into the organic plots. In some countries pesticides are sprayed from aeroplanes. How can you possibly control exactly where the wind will take these?

If that wasn’t enough, organic practices also use a minimum amount of pesticides. So washing organic produce is still something you should be doing. I would hasten to add you should also be re-washing your pre-washed produce, including lettuce. But how?

The results of the study

The results of study carried out at the University of Massachussets and published in the Journal of Agricultural Food Chemistry, in October 2017 are that washing the fruit and vegetables with cold water under the tap does little to remove pesticides.

The researchers took organic apples and sprayed them with two of the most common pesticides: Phosmet (an insecticide) and Thiabendazole (an antifungal used to prevent mould and rot). They then waited for 24 hours before trying three different methods to wash them:

a.      a Clorox bleach solution like the one used by commercial fruit producers;

b.      plain tap water ;

c.      a solution of baking soda (sodium bicarbonate) and water.

They found that leaving the apples to soak in the baking soda solution (approximately 1 teaspoon of baking soda to 2 cups of water) for 15 to 20 minutes, then rinsing them with (filtered) water, removed 80% of the thiabendazole and 95% pf the phosmet. 

In comparison, the tap water did little or nothing, and the bleach solution only removed a minimal quantity of pesticides.  This is because the alkaline pH of the baking soda solution breaks down the compounds and helps to wash them away.

This is good news for us at home, since, not only is bicarbonate readily available (it is the same one used in baking), it is also cheap. I am also a great believer in ‘I wouldn’t put anything on my food, that I cannot put into my body’, I mean, would you drink Clorox?.  Bicarbonate, unlike bleach or other chemical substances, is natural. It can be safely ingested, indeed a spoonful in a glass of water can help indigestion and to fight acid reflux.  It is also better than using commercially produced soaks to wash vegetables and fruit at home. At least you can be sure what’s in your soaking solution!

It is worth noting that the thiabendazole was also partially absorbed through the apple skin. The suggestion to peel the skin before eating only partially solves the problem of removing pesticides. Not only does peeling fruits and vegetables reduce their nutritional value (most fruits and vegetables have a higher concentration of nutrients just under the skin), it will obviously not always remove all the pesticides absorbed into the fleshy part.  However, the good news, as Dr He points out, is that the amounts of pesticides used in the studies are probably much higher than those found on normal produce. Or so we hope!

Another point to consider is that this tested only two of the approximately 50 different pesticides which might be used. Clearly more research needs to be done in this field. In the meantime, ponder this when you decide on whether or not it is worth buying organic, especially if you are planning on eating the peels. If nothing else, you should be getting fewer pesticides, if not less harmful ones.

How can you wash fruit and vegetables at home?

Long before the scientific study to prove the best way to remove pesticides, healthy conscious cooks like myself had been washing fruit and vegetables using one of these ways:

1. By soaking them for at least 10 minutes in a bicarbonate and water soak (2 tsp bicarbonate in a small bowl of filtered tap water)- this is a gentle solution and works well with everything.

2. In a white vinegar or apple cider vinegar and water soak (about 1 tbsp vinegar to a small bowl of filtered tap water) - which I would not recommend for berries as they will keep some of the vinegar taste, but is excellent for salad. Vinegar is the natural alternative to bleach, and is a natural disinfectant.

3. The natural version of the bleach solution: a mix of bicarbonate, vinegar and water (1 tsp bicarbonate, 1 tbsp vinegar and a small bowl of filtered water)- which I use when I am looking for a more powerful combination. Still edible, and more natural (and safe) than any Clorox or commercial solution.

I will also soak fruits that I would normally peel before eating (such as oranges), in particular the non-organic variety, as a way to avoid infecting the flesh with the pesticides on the surface as the knife cuts through.

Since time is not always on my side, I might soak fruit and vegetables overnight (except for berries), or leave them in the soak from breakfast to lunch, or from lunch to dinner.  Kale, especially, is revived in the soaking, so it is well worth doing.

Now that you know the best way to wash fruits and vegetables to remove pesticide residues, If you are soaking apples and other fruit, don’t forget to remove the stickers first!



-  ‘Pesticides: How about washing them apples?' By Michael Nedelman, CNN Health, October 25, 2017

-  Chemical and Engineering News website (, 3 November 2017

- Healing with Whole Foods by Paul Pitchford, 3rd edition, published by North Atlantic Books, 2002.


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