By now you may have seen the Environmental Working Group’s (EWG) Dirty Dozen and Clean 15 list. The two lists can be found as part of the EWG’s annual Shopper’s Guide To Pesticides in Produce and is meant to inform the public about which produce contains the most and least pesticide residue. However, there are some that feel the EWG’s list is a bit sensationalist and unreliable. So, what are the facts? Are the foods listed on the EWG’s Dirty Dozen list as contaminated as they say? Are we actually at risk if we eat conventionally produced, rather than organic, produce?
Let’s start with the EWG. Who are they and how did they come up with the Dirty Dozen list?
Founded in 1993, the EWG is a non-profit organization that advocates for public awareness regarding the use of chemicals in cosmetics, agriculture and the environment. Their aim is to decrease chemical exposure to both people and the environment and to encourage the public to make informed decisions about their consumer habits.
In terms of their work with agricultural pesticides, the group is credited with helping implement the Food Quality Protection Act (1996) which requires the Environmental Protection Agency (EPA) to assess pesticides used in food production and to ensure they provide a “reasonable certainty of no harm” (1). The Act also ensures that all pesticides are assessed under a single set of health-based criteria, that approval of safer pesticides are prioritized and that safety of pesticides are reevaluated on regular intervals (2). Since the onset this Act, pesticide residues have decreased and some of the more dangerous agricultural chemicals have been banned for use in the United States (3).
The EWG claims that the implementation of the Food Quality Protection Act is only a partial success. Although there are now better standards and assessment practices for pesticide use in the United States, the EPA has failed to fully implement all terms of the Act. The “Consumer Right to Know” section of the Act was intended to inform the public about current pesticides in use and the risks these chemicals pose to human health. The EWG alleges that the EPA has not been following through with keeping the public properly informed and for this reason the EWG implemented the Shoppers Guide to Pesticides in Produce (1).
What do critics of the EWG’s Dirty Dozen say?
Critics of the EWG’s Shopper’s Guide feel the information being disseminated is deceptive and ‘bad science’ (5, 6). One criticism of the Dirty Dozen list is that the EWG does not reference the type or amount of pesticides present nor do they relate their findings to the pre-established safety limits. The EPA has a set of science-based guidelines for pesticide use in agriculture and for acceptable amounts of pesticide residue found on fruits and vegetables. The chronic reference dose (RfD) is an “estimate of daily oral exposure to the human population that is likely to be without appreciable risk of deleterious effects during a lifetime” (7-10). In other words, the RfD is set at a level that, if consumed every day for a lifetime, will not cause any harm. The determination of this limit is based on animal models and is set 1000 times lower than will cause harmful effects on animals. The toxicologists determining these values base their recommendations on estimated duration of exposure, consumption patterns of fruits and vegetables, susceptibility of vulnerable peoples (i.e. infants, children, pregnant women and the elderly) and any unique characteristics of the pesticide itself (9). A pesticide residue calculator was designed to put the RfD into perspective, for example an adult women would have to consume 2042 servings of strawberries, 99 681 servings of carrots, 2332 servings of kale and 529 servings of apples each day without any estimated negative effects from pesticide residues (11).
If the EWG were to publish its Dirty Dozen list and compare it to these established guidelines, the public would see that all, yes ALL, of the items on the Dirty Dozen list are well below the RfD (5, 6, 12). In a study analyzing the 2010 Shoppers Guide to Pesticides in Produce, it was found that in 90% of the examples, the pesticide residue present was more than 1000 times lower than the RfD. Pesticide residues present on blueberries, kale and cherries which ranked 5th, 9th and 10th, respectively, were all more than 30,000 times lower than their RfDs (5). Forty percent of the items on the 2010 Dirty Dozen list registered at only 0.001% of their RfDs which is 1 million times lower than the dose in which adverse effects are seen in animal studies (5). In an analysis comparing the USDA's 2011 Pesticide Data Program results and the corresponding Dirty Dozen list, no correlation was found between the Dirty Dozen rankings and the pesticide amounts detected. Interestingly, some fruits and vegetables that were ‘dirty’, as per the EWG, had more samples with less pesticide residues than some of the ‘clean’ produce (6).
The EWG’s methodology for determining their rankings has also been scrutinized. Information from the Pesticide Data Program is used to make the Dirty Dozen list but instead of reporting which fruits and vegetable have the most pesticides the EWG has developed its own ranking system by creating six categories by which it evaluates the produce (4):
- Percent of samples tested with detectable pesticides
- Percent of samples with 2 or more detectable pesticides
- Average number of pesticides found on a single sample
- Average number of pesticides found (in parts per million)
- Maximum amount of pesticides found on a single sample
- Total number of pesticides found on the commodity
The EWG itself admits that its ranking is “not built on a complex assessment of pesticide risks but instead reflects overall pesticide load” (4). And “load” in this context is heavily weighted towards the number of different pesticides found on the samples and not toward the total amount. This is one of the very reasons some feel that the EWG’s rankings are not a reliable depiction of the risks associated with eating non-organic produce. However, there have been studies that do show that when pesticides are mixed together in the lab setting that their side effects are amplified indicating that we probably should take into consideration the presence of multiple pesticide residues (13, 13b). Whether or not the presence of multiple pesticide residues should be weighted as heavily as it is in the EWG's analysis is uncertain. Some critics feel that the EWG should balance their evaluation criteria more fairly in order to give the public a clearer picture of the risks associated with pesticide residues (5, 6). Acceptance of their findings also could be improved if they subjected their methodology to the peer review process, like is done with other scientific work (14, 15).
Another interesting question to ask the EWG is whether or not any of the pesticides residues reported on are also approved for organic farming. In 2009, in California the number one and number three most used pesticides (accounting for about 30% of the pesticides used) were also approved for organic farming (16). It should be noted that just because a pesticide is approved for organic use does not guarantee its safety. It does, however, bring home the point that this is a complicated subject matter and there are many factors that need to be considered when making recommendations to the public (12, 17-19).
What are the risks of pesticide exposure?
Are there risks to pesticides exposure? Yes. The fact is that pesticides are toxic chemicals used to kill insects, fungi, molds, weeds and rodents. There is an adage among toxicologists that says ‘the dose makes the poison’ which begs the question, are the doses in which humans are exposed to from pesticide residues on fruits and vegetables enough to cause damage?
First let’s take a look at what we do know about the effects of pesticides on human health. There have been a number of studies linking pesticide exposure to ill health effects in children, particularly when the timing of pesticide exposure is during pregnancy (20-26). Epidemiological research has found associations between prenatal pesticide exposure to decreased IQ scores, poor cognitive development, memory issues, attention deficit hyperactivity disorder and autism (20-26). Other studies have linked prenatal and early life exposure to onset of childhood cancers including acute lymphocytic leukemia, brain cancer, non-hodgkin’s lymphoma and neuroblastomas (23). In the adult population, a 2012 literature review found an association between long-term pesticide exposure and neurological deficits while another investigation found that exposure to the organic pesticide, rotenone, was associated with onset of Parkinson’s Disease (19, 27). What is important to note is that NONE of the these studies were looking at dietary exposure of pesticides, rather they were focusing on pesticide exposure of agricultural workers, those living in farming communities, urban fumigations (i.e. spraying for mosquitos) and from household use of insecticides, herbicides and fungicides (20-26). Pesticide exposure levels from these routes are much higher than one would be exposed to via eating conventional fruits and vegetables. Some estimate that personal pesticide use may often be at a greater concentration than in agricultural settings since there are no regulations for pesticide application in the home (28).
Can we draw conclusions that pesticides are bad at high exposure levels? Certainly, we can. Although it is important to note that not all studies examining agricultural pesticide exposure found associated health effects (23).
Are these studies evidence that consuming the amount of pesticide residue found on fruits and vegetables leads to health problems in humans? Not really. Surprisingly, there are not many studies comparing the outcome of consuming an organic to a conventional diet. In a 2012 literature review, only 3 studies were found that compared organic to conventional diets but they were small, short-term studies that found no significant health benefits between the diets (29). More recent research concluded that there was not sufficient evidence of an organic diet decreasing overall cancer risk in middle aged women. It did, however, find a slight increased in non-hodgkin’s lymphoma in women eating non-organically and, conversely, an increase in breast cancer in those eating organic diets. A shortfall of this study is that it did not monitor activity level or weight of the participants and both of these factors are known to alter cancer risk (30).
There are several studies that do show that switching from a conventional to an organic diet will substantially decrease the amount of pesticide metabolites in urine, unfortunately, no one has linked traces of pesticides in urine at the levels measured in these studies to onset of disease (30, 31). With the organic food industry earning $35 billion in the 2013 in the United States alone, it’s perplexing why there are not more well designed studies comparing organic to conventional diets (32).
What does this all mean?
Let’s recap the details. The EWG publishes an annual list of the most pesticide contaminated fruits and vegetables. Although their motives may be well meaning, they fail to mention that all the fruits and vegetables on their list register below the EPA’s limit for allowable pesticide residues. The EPA sets this limit at a level that should be safe to consume everyday, for a lifetime. What we do know is that pesticides at high exposure levels have been linked to health effects in both children and adults but we don’t know if the small amount of residues in our food supply cause long-term damage. At this time, there unfortunately isn't enough evidence to recommend that everyone choose organic fruits and veggies, over conventional ones.
Of course there are other reasons to choose organically grown produce including the environment and the for well being of farm workers but on the basis of health risks, to the general population, the information is not clear. Hopefully, in time there will be more evidence available so concrete recommendations can be made one way or the other.
What we do know is that consumption of fruits and vegetables, whether organically or conventionally grown, provide disease fighting nutrients that decrease risk of chronic diseases like cardiovascular disease, cancer and diabetes (33-36). Inaccessibility of organic produce, whether because of cost or availability, should not discourage fruit and vegetable consumption. It is far better to be consuming the 7-10 servings of fruits and vegetables each day, even if conventionally grown, than to not consume them at all. This is something that even the EWG agrees with (3).