Dirty Dozen: Organic Strawberries vs. Conventional Strawberries.

Dirty Dozen: Organic Strawberries vs. Conventional Strawberries.

[Organic Strawberries vs. Conventional Strawberries – wondering what the answer is? I’ll give it to you: conventional. Now if you want to know why then please read below.]

A few months ago my husband and I were having brunch with another couple and their three-year-old son. We started talking about organic and non-organic food. I told them that studies say organic food does not have any significant nutritional benefits and it’s just as good as conventional – only cheaper.

This was hard for my parent friends to get a grasp on. “But what about strawberries?” my friend asked. She said that because of the fuzzy strawberry skin she prefers to buy organic just in case. She also mentioned the Environmental Working Group and their “Dirty Dozen” list. Conversation closed, she was not interested in discussing that subject further. When just in case gets in the way, then fear is around, which means it’s really, really hard to fight with facts.

A month or two later, the Environmental Working Group released the newer Dirty Dozen list. Guess what? Strawberries “topped” the list as the “dirtiest” produce. But the EWG is unfair in their assessment. Let’s see why.

Organic Strawberries vs. Conventional Strawberries: Why the “Dirty Dozen” list is unfair.

The Environmental Working Group (EWG) is a non-profit organization known for their annual “Dirty Dozen” list. In this list they declare the produce that’s most contaminated with pesticides. In this year’s list the “winner” was strawberries. The EWG’s recommendation? That “you always buy organically grown berries.”

The EWG bases their research on work done by the government. In particular, the United States Department of Agriculture (USDA) conducts annual sampling of different fruits and vegetables and then tests them for pesticide residues. They then release their data in public at the Pesticide Data Program page.

The EWG took the government’s data and ran further statistical analysis. That’s how their “Dirty Dozen” was born.

Part of the reason that strawberries topped this year’s Dirty Dozen is that almost all 176 samples of strawberries that were measured had detectable pesticide levels and about 40% of them had residues of 10 or more pesticides. There was even a strawberry sample with 17 different pesticide residues!

Now the recommendation to go organic sounds like it’s fair, right?

Before you jump to this conclusion, let’s see what the Environmental Protection Agency says:

Overall pesticide chemical residues found on the foods tested are at levels below the tolerances established by the Environmental Protection Agency (EPA) and do not pose a safety concern.

The EPA did not single out strawberries as “bad.” Instead, the EPA is happy with the results. Why? Because those pesticide residues are in the “safe zone.” Actually, more than 99% of all produce tested was found with pesticide residues below the EPA tolerance level.

This refers to the common saying “the dose makes the poison.” Take one aspirin and you’re good. You no longer feel your headache too! Take a packet of aspirins and things might not look that good for you.

Or eat a pear and you’re good, despite the fact that pears naturally contain formaldehyde, a highly toxic compound that can even cause death. Pears just don’t have enough formaldehyde to affect your health.

This is what is happening with those pesticide residues too. Because they are in the safe zone, the fact that strawberries contain many different pesticide residues is not particularly meaningful.

This is part of the reason why the EWG’s Dirty Dozen method has been criticized over and over. They focus on counting the number of pesticide residues but they don’t take into account whether that has any effect on our health. They don’t take into consideration that some pesticides are more or less toxic than others. They just lump everything together as if they’re equal and discard tolerance levels. Oh-oh.

In fact, in 2011 Winter and Katz published in the Journal of Toxicology a scientific paper criticizing the EWG’s methods:

It is concluded that (1) exposures to the most commonly detected pesticides on the twelve commodities pose negligible risks to consumers, (2) substitution of organic forms of the twelve commodities for conventional forms does not result in any appreciable reduction of consumer risks, and (3) the methodology used by the environmental advocacy group to rank commodities with respect to pesticide risks lacks scientific credibility.

In fact, they found that “all pesticide exposure estimates were well below established chronic reference doses (RfDs). Only one of the 120 exposure estimates exceeded 1% of the RfD (methamidophos on bell peppers at 2% of the RfD), and only seven exposure estimates (5.8 percent) exceeded 0.1% of the RfD.”

Ok let me explain what a reference dose means (Wikipedia).

A reference dose is the United States Environmental Protection Agency’s maximum acceptable oral dose of a toxic substance. An oral reference dose (abbreviated RfD) is:

An estimate, with uncertainty spanning perhaps an order of magnitude, of a daily oral exposure to the human population (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a lifetime.

In other words, consume a toxic substance at the reference dose every day for the rest of your life and you’ll be fine.

So when Winter and Katz say that only one of the 120 exposure estimates exceeded 1% of the RfD – this means that the exposure level was 100 times lower than the reference dose.

Yup, we’re talking about THAT level of magnitude.

Organic Strawberries vs. Conventional Strawberries: No good reason to invest double for organic.

So if pesticide residues are not really a cause for concern for strawberries, then why does the EWG recommend to buy organic?

From the EWG website:

“It is startling to see how heavily strawberries are contaminated with residues of hazardous pesticides, but even more shocking is that these residues don’t violate the weak U.S. laws and regulations on pesticides in food,” said Sonya Lunder, EWG Senior Analyst.

In other words – the pesticide residues are in the safe zone. So they blame the government tolerance levels as “weak” to support their claim to go organic.

A few thoughts about this.

  • First, they don’t specifically say what tolerance levels are weak and for which substances. They just make a generic claim.
  • Another thought – they trust the government to collect the produce samples and do the analysis for them, but they don’t trust them when it comes to tolerance levels.
  • Final thought – making a “trust” claim invokes fear. If you can’t trust the tolerance levels, then of course you’ll buy organic – just in case.

So let’s address this generic, non-specific claim with a brief overview about how scientists establish reference doses.

We talked about the reference dose earlier, or the amount you can consume daily for years and be fine. How is this really calculated?

Scientists review studies examining the health effect of a substance. They find the upper level of a substance that gives no “statistically or biologically significant indication of the toxic effect of concern.”

So consuming this substance at this level daily gives no effects whatsoever.

Then, they divide this level by 10 if the studies are on humans, or 100 if the studies are done on animals. This is called the uncertainty factor.

So just in case, the government takes the safe level and decreases it by a magnitude of 10 or 100 depending on where the studies are coming from.

You see, the “just in case” thinking is already embedded in the regulations to keep us safe.

Food and agriculture speaker Dr. Steve Savage helped me see this from another perspective as well. Remember that more than 99% of samples were below tolerance levels? Let’s check this out about the samples that exceeded tolerance levels:

If you just look at the rare cases where detections were over the tolerance it is usually by a small factor. The tolerances typically have a 100x safety factor. Green beans had the biggest issue with being over tolerance but they come out as #20 for EWG.

So maybe it’s green beans that should have been ranked by the EWG, but no, they weren’t.

Organic Strawberries vs. Conventional Strawberries: But what about fumigants?

organic strawberries vs conventional strawberries
Fumigants are substances that control soil-borne fungal diseases and weeds. The EWG goes at length about them on their strawberry page

Right at the beginning of their write-up the EWG warns: “What’s worse, strawberry growers use jaw-dropping volumes of poisonous gases – some developed for chemical warfare but now banned by the Geneva Conventions – to sterilize their fields before planting, killing every pest, weed and other living thing in the soil.”

I don’t even know where to start with this. Jaw-dropping volumes? So they suggest farmers don’t follow labels and just do whatever – even though they later suggest that it’s the farmworkers’ health that’s most at stake here? Also, note the (scary) associations they want you to make by talking about “chemical warfare” and “killing every pest, weed and other living thing in the soil.”

There are two interesting facts about their recommendation to go organic based on the fact that organic growers don’t indeed use fumigants.

First, you the consumer cannot ingest fumigants. The soil is treated with them, not the plants themselves. You won’t find leftover fumigants on your strawberries. So whether you go organic or conventional makes no difference to you personally.

The EWG recommends fumigants so that you support the organic industry because fumigants may be bad for farmworkers’ health and for the people who live near strawberry farms.

Second, strawberry nurseries do use fumigants. And organic farms buy plants that have been born on fumigated soil.

What are strawberry nurseries? They are facilities that grow baby strawberries. Farmers buy strawberries from them to plant on their fields. Both organic and conventional farmers buy from the same nurseries.

If the strawberries are matured in an organic farm, then they’ll gain the certified organic label.

However those strawberries as babies were living in fumigated soil. The federal code allows organic farmers to use strawberry starts grown in fumigated soil if there are no organic starts “commercially available.”

So even organic strawberries are not really organic.

EWG also mentions methyl bromide, a fumigant that was found to be dangerous for the Ozon layer and is now being phased out.

I asked strawberry expert Prof. Kevin Folta from the Horticultural Sciences Department at the University of Florida, Gainesville, to explain the controversy:

Methyl bromide has been banned by the Montreal Protocols since 2003. It has been used in CA under what’s called a “Critical Use Exemption” which means that growers can use it, if they can find it and pay for it. It is not being produced for agriculture and we have not had it available in FL for some time.

Growers scale back, using small amounts in conjunction with other fumigants. Fumigants control fungus, nematodes and weeds. It is applied under the plastic where the plants are grown rather than sprayed above. They worked great. Methyl bromide was very effective but had environmental concerns, so it was appropriately banned. Now we see new weeds, new diseases, and unprecedented nematode pressure. It is amazing what Methyl bromide was able to suppress! But farmers continue on.

Methyl bromide is set to be completely phased out by 2017, so this is not going to be an issue in the near future anyway. Scientists are now researching new strawberry varieties that are less susceptible to soil-borne illnesses. However, this process will take years. In the meantime, farmers need to make due with less effective ways to control soil diseases and somehow manage to keep strawberry production up.

Organic Strawberries vs. Conventional Strawberries: The verdict.

  • Do organic strawberries contain fewer pesticide residues? Yes, that’s usually the case with organic produce.
  • Are organic strawberries pesticide-free? No, they are not. Organic uses pesticides too, and the substances that they use can be more toxic than the ones used on conventional farms.
  • Do pesticide residues really matter? No, they are in the safety zone (and remember that “just in case” mentality is already embedded in how those government limits are set.)
  • Do fumigants make a difference? No, you cannot find them on your berries, plus organic strawberries are grown in fumigated soil making them not really organic.
  • Are organic strawberries more expensive than conventional? Absolutely. They often cost 50% or even 100% more.

So what’s the verdict here?

In my opinion, if you have the choice between those two, and if you have the money too, then choose based on how fresh or ripe they seem when you are at store.

Now if price is an issue, I’d say go conventional. I know some people just buy fewer strawberries so they can buy organic within their budget, but the result is they don’t really gain any benefits from that choice while they miss out on the health benefits of strawberries.

When I asked Nutrition Prof. Tim Crowe from the School of Exercise and Nutrition Sciences at Deakin University in Melbourne, Australia about why we should eat strawberries anyway, he directed me to this 2007 study:

While blueberries get lots of attention for their health benefits, all berries which include strawberries have plenty of health positives. While strawberries a good source of fibre, vitamin C and antioxidants, they’re also high in the plant pigment anthocyanin. Anthocyanin gives strawberries their red colour and for us, it has anti-inflammatory, antimicrobial and anti-carcinogenic activities and is also linked to improved heart health.

Do you really want to eat less fruit, just in case, esp. when the government has already taken the “just in case” factor into consideration before you?

As for the “Dirty Dozen” Prof. Folta was blunt: “The Dirty Dozen is another pack of lies that are being used to trash conventional growers.”

What strawberries are you buying at the store? What helps you make that choice? Post your answer in the comments below.



The Pesticide Data Program of the USDA

United States Department of Agriculture, Pesticide Data Program, Annual Summary, 2014

United States Department of Agriculture, 2010 – 2011 Pilot Study Pesticide Residue Testing of Organic Produce, November 2012

Not easy for strawberry growers to avoid methyl bromide, Visalia Times-Delta, 2015

Melody M. Bomgardner, Strawberries In Peril Because Of Fumigant Phaseout, Chemical & Engineering News, Volume 93 Issue 23 | pp. 18-19

Carl K. Winter and Josh M. Katz, Dietary Exposure to Pesticide Residues from Commodities Alleged to Contain the Highest Contamination Levels, J Toxicol. 2011; 2011: 589674.

Mazza GJ, Anthocyanins and heart health. Ann Ist Super Sanita. 2007;43(4):369-74.