Two Radically Different Views of Celery

  • Published on May 12th, 2010


The Environmental Working Group (EWG, an activist organization) and the California Department of Pesticide Regulation (a state agency) each have radically different views of the safety of eating celery.  EWG recently put celery on the top of their annual “dirty dozen” list – a ranking of fruits and vegetables by the “number” of pesticides that are used by the farmers that grow them.  They claim that celery is sprayed with the most pesticides and that they are “difficult to wash off.”  Is that sort of analysis meaningful?

An Analogy

The EWG’s list is the equivalent of ranking countries for risk by the number of spider or snake species which live there without saying anything about how many are poisonous or how common they are.  Advice like this is unhelpful at best and actually irresponsible.  

Celery, like most fruits and vegetables, is a good thing to include in a healthy, diverse diet.  So is there really some unacceptable risk associated with the pesticides used to grow a healthy celery crop?

The People Who Actually Do The “Work” To Answer This Question

EWG counts pesticides.  The California Department of Pesticide Regulation works much harder.  They collect and store all the pesticide use data from farmers in California, and maintain an excellent and user-friendly site where this data can be accessed (which I did for four major celery growing counties).  They also conduct annual pesticide residue surveys on the fruits and vegetables that are actually in the market.  In 2008 that included 3,483 samples.  They looked for residues of 200 different pesticides or breakdown products.  70% of the samples had no detectable residue at all. 29% of samples had residues that were lower than the cautious limits that have been set for each material.  1% (39) of the samples had residues that were from chemicals not registered for the crop, and these were almost all on imports (Mexico, Guatemala, China). 1 sample (0.03%) had a higher than tolerance residue.  So, the contamination that EWG is implying does not seem to happen.

Doing The Math

I did a little more of the work that this “working group” failed to do.  The California data says that on average, 10.8 pounds of pesticide active ingredients were applied to each acre of celery throughout a growing season (California accounts for 75% of US celery production).  Since typical celery yields are 33 tons/acre, that means that there would be 0.07 grams of pesticide on each pound of celery if 100% of it stayed on the celery after application.  In fact, pesticides break down in sunlight or by microbial digestion so any residue would be far smaller than that, and the residue of any single chemical only a fraction of that.

All Pesticides are not Created Equal

A little more “work” would have allowed the EWG to show that most of the pesticides used on Celery are far from scary.  Only one is listed on the Prop 65 list of potential carcinogens. It represents only 1% of the total use and at low to non-existent residue it represents no real risk.  With a little Google searching one can also find out how acutely toxic each of the chemicals is to mammals by looking at the “MSDS” sheets for each chemical.  It lists the “Oral ALD50 Rat” – the larger the number the less hazardous it is, the lower the more hazardous.  I went ahead and classified all the chemicals in the use data and made graphs showing how much of the chemical use fell into different ranges of toxicity divided using familiar references for relative hazard.

Depending on the county, 26-67% of the pesticide used was less toxic than table salt (ALD >3000 mg/kg).  When you add the pesticides that are less toxic than the natural food flavoring, vanillin (1680 mg/kg) you get to around 3/4 of all the use.  These are all very low toxicity materials.

EWG’s advice was to buy organic celery.  EWG should know (but fails to mention) that there are pesticides that are used on Organic crops as well.  One typical example, Copper Sulfate, has an oral ALD50 of 300 mg/kg.  Thus an average of 94% of the pesticides used on conventional celery are safer than common pesticides used on Organic.

There are a few more of the pesticides that are still less toxic than the caffeine that so many of us intentionally ingest each day (192 mg/kg).  Finally, there are just three pesticides used on celery that are more toxic than caffeine averaging 5% of total use.  These are oxamyl, methomyl and rotenone (a rarely used natural product that used to be allowed on Organic by the way).  The most toxic of these, oxamyl (9-10 mg/kg), is restricted such that it can’t be used within 28 days of harvest.  Any residue left after that time would be insignificant and still spread over the 33 tons of celery.

So, it seems that Celery is just fine and the US EPA and California EPA are doing their work.  If the Environmental Working Group wants to be credible, it needs to do a lot more work than counting pesticides.  They are promoting Organic, but they do that industry a disservice by unfairly attacking growers who don’t deserve this sort of smear campaign. A lot of organizations, bloggers and journalists that uncritically passed along the “dirty dozen” list could also stand to do a little work of their own.

Celery image from  Fir0002,

Graph by me based on CALPIP and MSDS data

You are invited to comment on this site and/or to write me at

About the Author

Born in Denver, now living near San Diego. Agricultural scientist for 30+ years with a Ph.D. in Plant Pathology. Have worked for Colorado State University, DuPont and Mycogen and for the last 13 years consulting for all sorts or companies, universities and grower groups. Experience in biological control, natural products, synthetic chemicals, genetics, GMOs and agronomic practices. Have given multiple invited talks on the interaction between agriculture and climate change (both ways)


  • EWG has a phone ap or you carry a list with you of the no no’s. Thinking one more time about the high price of organic celery I stumbled across your article and want to thank you for it.

  • Excellent post as always Steve – thanks!

    I have a way of handling the EWG warnings – I just use them to remind me of what is good and buy some of the ‘dirty dozen’ each time I go to the market – celery, peaches, plums, strawberries, grapes are always on my list when in season.

    I read about another group that rated cruise lines by looking at their web sites for green statements. No contact, no in depth review and the kids were so happy about their work. In reality their analysis was meaningless.

    A bad side of the net today is that EWG and similar groups can publish their ‘stuff’ and get it out to a large uninformed audience who have no idea what they are talking about and are easily scared.

    They suffer zero consequences for publishing intentionally misleading or incorrect work. EWG and their type don’t care about publishing complete lies as they think they are at war.

  • Wow. I love celery. I mean I could eat a bunch a day. I love it’s crispy juicy-ness. I eat it all the time and am the pinnacle of heath after having 5 kids, and being 43 years old. I have NO health problems. I was devastated when I heard about the dirty dozen on the news..I live near the north pole in Calgary Alberta, and if I had to eat local….boo hoo no more celery. I’m so happy to find this article, because I can go back to my celery habit…it all it’s crunchy tasty glory..thank you growers for growing such a beautiful vegetable. I have bought organic on occaison when I see it on sale (otherwise can’t afford it) but it’s dark green and tough. I love my regular grocery celery, most surely grown in California. Strawberries scare me with their pesticide residues, but I’m going to keep eating my celery. Thanks for the informative post. -Celery girl in Alberta

  • As usual you provided an excellent article Steve.

    The EWG doe the best that can be expected from a group with an agenda and zero (or near zero) expertise.

    That means they are worse than useless as they provide knowingly false information to the public while telling everyone how wonderful they are.

  • Congratulations Steve.
    At last you are one to have put the subject in perspective.
    From a different part of the world, as a farmer, I have specialized in celery production exclusively, for nearly 50 years.
    During that time, all of the crop spraying has been done by me.
    As far as I know, I do not have any health issues from that activity or consumption of the celery.

  • Steve,

    The Methodology pages from EWG says this at the end:

    "The EWG’s Shopper’s Guide is not built on a complex assessment of pesticide risks but instead reflects the overall pesticide loads of common fruits and vegetables. This approach best captures the uncertainties of the risks of pesticide exposure and gives shoppers confidence that when they follow the guide they are buying foods with consistently lower overall levels of pesticide contamination."

    I think they are pretty clear on how they conducted their analysis. You have a somewhat valid point on the relative effects of different pesticides, but this in itself does not negate the rest of the data. Sure, it would be great if someone provided that analysis as well, but I'm glad to have the analysis that they have conducted in helping me make my choices.

  • I heard one anecdotal story that an organic farmer had sprayed down some diesel fuel between rows to keep the weeds down – and it was allowed by whatever organic lobby he had bought into. These are the same ideas borne out of necessity/desperation when farmers can get more money for the coined niche called “organic”. It’s how pesticides got started but are now regulated. I’m not into big government but the pesticide systems we live with in North America are really not bad-for being government regulated. I am a farmer, licensed to apply heavily regulated pesticides. As a farmer I want quality, control and consistency. As a farmer, I want to apply as little as possible because its dumb expensive. When I experience the regulations and hear that others are being paid more for crops that have virtually unregulated pesticides applied at unregulated rates AND have poorer quality, I am fascinated. Fascinated by the organic lobby/fad. As a consumer, you want accountability? Know your grower. Ask them what’s on it. This will mean local – this means a demand for smaller, more diverse farms. When you can’t get local for the season, then either can your own food for the winter or depend on the system that “we, the people” are regulating. Organic is old school. Just how old school do we want to be?

    • Know your grower. Ask them what’s on it. This will mean local – this means a demand for smaller, more diverse farms

      Channing – couldn't agree more. Going local is the best thing we can do on SO many levels….

      – Jeremy


  • I like your mindset and agree with your analysis but I still feel uninformed. Maybe EWG doesn't go into enough detail or perform/analyze in a way that may be more appropriate and fair but where is the "fair" analysis? I don't see any other groups performing an analysis that you might agree with so, unless i can find another person or agency willing to put in the work, I will have to stick with the dirty dozen to make my decisions. Any suggestions for a better list?

    • RE: Garret’s query “I don’t see any other groups performing an analysis that you might agree with so, unless i can find another person or agency willing to put in the work, I will have to stick with the dirty dozen to make my decisions. Any suggestions for a better list?”

      Yes there is another group doing an analsys. The EWG doesn’t generate any data themselves, they just put their own spin on data from the USDA Pesticide Data Program. Their summary report (and the raw data if you to see it) are online at
      What you will see there is a rigorous testing program that will make you feel good about the rigor with which your government is keeping an eye on things in this regard. And as USDA says it “This report shows that overall pesticide residues found on foods tested are at levels below the tolerances set by the U.S. Environmental Protection Agency (EPA).”
      And as alluded to this blog, those EPA thresholds are set at no more than 0.1 to 1% of the level at which No Observable Adverse Affect was seen in laboratory testing. They feed rates at different dosages, find the level vbelow the lowest level that showed any negative effect, then divide that by a MINIMUM of 100, sometimes by 1000, sometimes more and that is the threshold. Then USDA tests food and finds levels that generally speaking not present with tests sensitive enough to find molecules at levels only a small percent of the threshold and in most cases find nothing, or where there are postive detections at levels only a few percent of the threshold (which already has large margin of safety built). EWG doesn’t use any standard toxicologial methodology, their Dirty Dozen has been critiqued by respected toxicologists as non scientific mumbo jumbo.

  • Lisa,

    That link is interesting. It says that all pesticides are treated the same in the counts which is exactly the problem I described in my post. The excuse is that this is because of unknowns. Millions of dollars are spent on toxicology before and after any pesticide is registered by the EPA. We know a tremendous amount about these molecules – far more than we know about the various, sometimes toxic chemicals if the food itself (made by the plant or sometimes by fungi that infect the plant). Dose also matters a great deal but that is largely ignored in

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