Is there any way to tell if lemons contain a residue of something that is harmful to humans?

The last two winters we have been buying oranges in bulk through a website, directly from the farm and i really like it. I would like to buy lemons in bulk too. They say their lemons are not treated with anything but I would like to have a little more reassurance. The fruit is not certified organic.

When buying in a store I assume the person buying the fruit for the store tests occasionally and consumer organizations and governmental organizations also sometimes test. But now I will be buying directly from the farm, without the middleman so to speak.

Related: Lemons and oranges coated with imazalil

EDIT: The type of answer I am looking for is how can I test, at home, in the kitchen if the fruit is covered with something like fungicides. I know citrus is often waxed, but that can be washed off, and I will wash the fruit anyway before eating.

Alternatively, maybe pesticides and fungicides are so expensive that farmers are likely to avoid it if they can. Remember, these fruits are shipped straight from the farm, only fruit that is in season is sold, so there is no reason to keep them long.

  • 1
    Hi, this is a legal question. You would have to provide a jurisdiction before someone can look up and tell you which treatments are legal and which of the legal ones have to be disclosed.
    – rumtscho
    Commented Jun 20, 2020 at 13:51
  • 6
    If you are buying from the same farm, it is very very likely that the lemons and oranges are treated exactly the same. Organic also doesn't mean no pesticides, it just limits the types that can be applied -often more pesticides are used in organic farming than non-organic because the organic ones are less effective.
    – bob1
    Commented Jun 20, 2020 at 22:01
  • @rumtscho, this is not a legal question at all. My question is: i want to eat a whole lemon, can i know if it has been treated with something that will cause me harm?
    – Ivana
    Commented Jun 21, 2020 at 10:40
  • After rethinking it, I realized that if it was not clear to you that you have to use legal information, then the explanation how you can use it is already an answer. So I reopened and wrote it up.
    – rumtscho
    Commented Jun 21, 2020 at 11:45
  • 1
    Also, "safe to eat" is always a legal question - of course people's emotional feeling of "being safe" (or disgust, or whatever else is involved) is frequently not overlapping with the legal definition of "safe", but we cannot help with this kind of subjective conclusions.
    – rumtscho
    Commented Jun 21, 2020 at 11:48

4 Answers 4


this may be too simple. But I would think you could ask the owner of the website what chemicals the farmers use. Especially if you are concerned about particular ones. I haven't seen a web store without a "Contact us:" link

I guess the owners could lie to you, but without knowing a lot about chemical tests, that's the best I've got.


I am adding another answer to respond to the edit.

There is no way that you can, personally, in your kitchen, test for specific chemical substances. Unless you are a trained chemist and own a chromatograph - in which case you wouldn't be asking this - you can forget going into that direction.

Alternatively, maybe pesticides and fungicides are so expensive that farmers are likely to avoid it if they can.

No, the opposite is actually true. The reason why pesticides and fungicides are used to a much larger extent than the public wants is that this practice leads to highest profits. Insects, viruses, fungi and bacteria tend to kill plants and/or spoil fruit long before it can be picked and sold. If no poison is used against them, part of the produce (or in some years, all of it) becomes unusable after the farmer having invested many workhours and maybe having gone into a debt they intend to pay after selling it. The price of the chemicals is negligible in comparison. So farmers always have an incentive to use more and more incecticides, herbicides etc. than is technically needed, as a kind of "insurance".

Again, the conclusion is - if you can't trust someone who should know (either the farmer themselves, or a government agency which takes random samples of fruit available on the public market to ensure its regulations are followed) you have no way to know.

(By the way, this "you cannot test it yourself" part is a basic statement about food safety, it applies to pretty much anything you eat, not just pesticides on lemons).


No. There are so many products used in so many different ways in crop protection and as preservatives for harvested fruit, that it is impossible to say beforehand what the most likely contaminants are and how to test for them. I was hoping only waxed fruit is treated with preservatives, and that i could test for wax easily, but it is impossible to say if a lemon was waxed, and unwaxed lemons may be contaminated also.

I have not even been able to find a top 10 list of most-often found pesticides and preservatives on/in lemons. The name that does come up very often as a preservative applied after the harvest is Imazalil. The up-side is, it can be washed off to some extent.

But this only focuses on the zest, and unfortunately 1/5 of Spanish lemons (and 1/2 of the Turkish) contain chlorpyrifos, which is neurtoxic pesticide that will be banned at the end of this year (2020). It is added to the ground so it is in the fruit, not just on it.

In general however most of the preservatives and pesticides stay within safe margins (Dutch link). If the farm also sells to supermarkets and such the product will have to be clean enough to pass tests, which most fruit does.

I have found little info about what organic farmers use to protect their crops, what i found seems pretty ok (Dutch link). Also the lemons are in season currently so they are anyway less likely to be treated after harvest.

The best options are to contact the farm and decide how much to trust them or to rely on store-bought food that has some labelling and certification.


As always in life, you can never prove a negative. Your goal becomes even more utopic when you state it as "something that will cause me harm" - it's not always clear what will cause you harm. But you might be able to use labeling to sift out the most egregious cases.

Governments help you protect yourself from harmful pesticides in two ways: First, they forbid use of the worst offenders. Second, for some of the allowed pesticides, they require that they are listed on a label. Then there are also certification organizations which have a similar role: they set up more stringent criteria for use and labeling, and only allow their certificate on foods that meet the criteria.

So, there is a possibility you can know it (barring fraud) for some substances in some jurisdictions. The way to go about it would be:

  1. Check if substance X is listed on the label. If it is, you know for certain it is there. If it isn't, go to the next step.
  2. Check if substance X is legal in your jurisdiction. If not, you can stop worrying about it. If yes, go to the next step.
  3. Check if substance X is required to be listed on the label. If there is such a requirement, then you know for sure it has not been used. If there is no such requirement, there is no reasonable way to know it.
  4. Repeat with the next substance you care about.

If you are buying fruit with a certification, you have to compare both the government's list and the certification organization's list. Also, sometimes there are government-restricted certifications like "Bio" in Germany (note that comparable words may have no legal meaning in other places, e.g. "organic" is AFAIK not regulated in the USA).

So generally, if you want to get more knowledge on the subject, you have to study local regulations.

  • I am not buying from a store, so there is no labelling. Also i have no way of knowing if any regulations are followed.
    – Ivana
    Commented Jun 22, 2020 at 7:31
  • 1
    Then I'm afraid the question is moot - there is no reasonable way of knowing it. Theoretically, if you are always buying from the same farm, you could try finding a lab which can test a batch for you once, but 1) the labs who specialize in this kind of test usually don't do work-for-pay for individuals, they do random sampling for the government to detect whether regulations are being broken, 2) from a single batch, you can't conclude much about other batches, and 3) if you find it as a service, it will be prohibitively expensive.
    – rumtscho
    Commented Jun 22, 2020 at 7:51
  • 2
    @Ivana Could you just ask the farm?
    – LSchoon
    Commented Jun 22, 2020 at 7:54

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