I can’t tell you the number of conversations I’ve had that go like this:
Me: Let’s go apple picking!
Mom-friend: Yes! Let’s find an organic or spray-free orchard, though.
Mom-friend: I want to avoid pesticides; I just don’t think the government does enough to guarantee our produce is safe.
Me: Really? Do you know what they do during that process?
Mom-friend: Um, no. Do you?
Me: Um, no. But I bet it’s a lot.
When I hear that line of argument against conventional produce (“I just don’t trust the EPA/USDA/FDA”) I want to drag that mom over to the computer and pull up the EPA’s website and walk her through some of the information they have on their website. But, believe me, it’s not very fun. I could write a whole post on why I think the EPA, USDA and FDA need serious help organizing and clarifying the information that’s on their websites. I’ve recently looked through a lot of it, for this and some future articles, and it’s almost as fun as trying to get your toddler to find the shoes they’ve hidden somewhere in your house when you’re late (never mind, you don’t need shoes, let’s go.) Perhaps this is why few consumers actually take the time to look into what the USDA and the EPA do. It’s tedious and science-y.
I thought it would be useful to actually investigate some of the things that I don’t think parents really think about when they toss aside the extensive work our regulatory bodies do to help reassure us that conventionally grown produce (those that are sprayed with synthetic pesticide) is safe. If you don’t read any further in this article (because I am going to talk about studies and use words like “tolerance level s” and “toxicology”) I will try to sum it up for you here: They do a lot. It’s extensive and exhaustive. At the end of the day, I feel very confident that they have looked at it from all angles and have put regulations in place that err on the side of caution to reassure us our produce is safe.
But don’t take my word for it. Let’s take a look at what happens when a company wants to start selling a pesticide. Those companies have to do both an environmental and human health assessment, but I’m going to focus here on the human health assessment. It’s a three pronged approach: toxicology studies, establishing a tolerance level and dietary risk assessment.
First, the company (who is really called the registrant) must do toxicology studies. The goal of these studies is to show what effect the pesticide could cause, and to establish a level at which there is no adverse effect in animal testing. The studies systematically expose different mammalian species (such as rats and mice) to the pesticide at varying amounts and measure the effect. The EPA outlines extensively how this must be done; it’s not left up to the registrant. They must measure toxicity arising from acute exposure, chronic exposure, and sub-chronic exposure. They measure inhalation toxicity, oral toxicity, dermal toxicity, carcinogenicity, reproductive toxicity, immunotoxicity, and neurotoxicity, just to name a few. Look here for the full testing requirements. The goal of these studies is to literally uncover the worst possible outcome from exposure to the pesticide. They take extensive tissue samples, analyze them all and determine the dose level at which there are no observed adverse effects, called the NOAEL. Then, because the studies aren’t actually done in humans, and because sensitivity can vary across individuals, a safety factor is applied to the animal NOAEL, which lowers the dose level anywhere from 100-1,000 fold less than the observed level. Using the NOAEL and the safety margin, the EPA establishes what is called a reference dose. A reference dose is an acceptable amount of exposure to a substance that has reasonable certainty it will cause no harm (also known as the safe exposure level).
The registrant also has to do field trials to establish a tolerance level. A tolerance means, assuming farmers use the pesticide according to the legal label (EPA-approved pesticide use instructions), we shouldn’t find produce with pesticide residue exceeding that amount. I don’t think the term “tolerance” is a great one, because I feel like it implies an impact to your health, like how much your body can tolerate. Tolerance is really talking about the maximum anticipated amount of residue on produce. Think of it like a speed limit, only one that you rarely even reach, and even if you go over by a teeny bit, it does not mean certain death. The EPA establishes that level by reviewing extensive registrant-conducted field trials in which the pesticide is sprayed at the maximum labeled rate and the produce is sampled at the shortest interval before harvest. For example, if pest control requires that the pesticide can be sprayed at a maximum of two pounds per acre and no later than seven days before harvest, the field trials will use those conditions. In practice, most farmers will likely not use the full two pounds (pesticides are expensive, they’ll use as little as possible to be effective). The scientists collect all the produce samples from the field trials (done over one or two seasons throughout the US growing region) and they establish a method to measure the pesticide residue (parent compound plus any metabolites that the pesticide may have been turned into as a result of its interaction with the soil and plant.) The samples are analyzed to determine the concentration of the pesticide residue in the samples collected from all the trials, which may range for example, up to four parts per million (ppm). Lots of factors affect the residue levels (rainfall, temperature, crop variety, etc.) and they often vary up to 10-fold across all the trials, due to these factors. The EPA then uses these results in a statistically-based calculation to establish a tolerance, such as five ppm in this example. The intent is to set a tolerance that is high enough so that it won’t be exceeded if the pesticide was used properly, but is still close to the maximum level measured in the trials.
So now we have the tolerance level (the pesticide shouldn’t occur in the produce above this amount) and the reference dose (people shouldn’t consume more than this in one day.) The only unknown is how much produce do people actually consume? How many apples, for example, do people eat on a daily basis? The EPA uses something called the Dietary Exposure Evaluation Model to figure that out. This database contains survey information for different age groups (infants, young children, teens, elderly, etc.) over different periods of time documenting how much of different foods they ate. The initial dietary risk assessment assumes that everyone is eating the produce for their whole lives that contain residues at the tolerance level. This means that they’re assuming every single acre of apples has been sprayed at the maximum rate and the shortest interval before harvest, and that there is no residue reduction from processing, washing, or cooking. They make the very conservative assumption that every apple you eat has the highest allowable pesticide residue on it, which the USDA knows from the Pesticide Data Program doesn’t happen (more on that in a future article on the Environmental Working Group’s Dirty Dozen List.) Assessments are made for both acute risk (a single day’s consumption) and chronic risk (a lifetime’s consumption). Acute risk assumes that you eat a very large (95th to 99.9th percentile of surveyed consumption) amount of apples in a single day. Chronic risk is based on average daily apple consumption over a lifetime. The amount of apples eaten under both scenarios is multiplied by the tolerance level to give the worst-case pesticide exposure, which is compared to the relevant reference dose (acute or chronic) to determine if the potential exposure is safe (below the reference dose; don’t forget that the reference dose incorporates a 100-1,000 fold safety margin). It’s especially important to note that these dietary risk assessments are not limited to exposure from a single food (e.g., apples) but are for aggregate summed exposure from all approved food uses of that pesticide, plus any potential exposure from drinking water. Total exposure must fall below the relevant reference dose (with its conservative safety margin) before a pesticide can be approved for use.
It’s also important to understand that the decisions of the EPA are legally binding. It is a federal crime to promote or use a pesticide in any manner that is not approved by the EPA and printed on the label. When a pesticide use is approved, the EPA reviews the exact text of the label that will be printed to describe its proper use, which cannot be changed without prior re-approval. States also have authority to review and approve pesticide labels. The residue tolerance levels are enacted by the EPA through rule making, and are printed in the Code of Federal Regulations; food containing residues in excess of the tolerance is adulterated and may not legally be sold or distributed. Only after both federal and state approvals of all these documents are complete is a pesticide “registered” for use.
Whew. See? Not as flippant as you might think. Not just one or two studies, not conspiracy theories about pesticide companies hiding data, not just someone from the EPA having dinner with someone from the chemical company and shaking hands about money-making over some scotch while they cackle ominously about the fate of our children’s health. I hope no one actually thinks that, but it would make a good caricature for the op-ed section, no? Real scientists doing real studies that actually try to guarantee safety. This is why I feel confident feeding my family conventional produce, and why I’m calling momsense on being afraid of conventional pesticides.
If you’re interested in the real data, and want to follow the registration of a pesticide from start to finish (ala “How a Bill Becomes A Law” only not animated, and not really fun to watch) follow the below progression. I’ve arbitrarily chosen the pesticide fluazinam, which is a broad spectrum contact fungicide often used on potatoes.
- Click here to view the CFR entry for fluazinam tolerances
- Open the PDF file at this link to see an example of an EPA dietary risk assessment for fluazinam
- Click here to see the Federal Register Rule arising from the fluazinam dietary risk assessment
- Click here to see the EPA approval of the fluazinam label based on the above decisions
- Click here to view the final printed label translating these regulatory actions into a real pesticide use label
* I have to give extensive credit to my dad for helping me with this article. He spent much of his career working on pesticide label registration and has expert experience navigating the regulatory websites and databases.