One analytical challenge has remained a primary focus of Dr. Charles Benbrook over his 50-year  career — quantifying the risks of pesticide residues in our diet. His painstaking, undervalued work has created the Dietary Risk Index (DRI). The system’s roots and evolution are described on the Heartland Health Research Alliance (HHRA) website. The DRI significantly advances how we can quantify and better comprehend the human-health implications of pesticide use — “like going from a rotary phone to an iPhone 15 in one step,” he says.

This powerful tool, and its underlying residue datasets, allows quick, easy on-line access to tens of thousands of detailed annual tables spanning the early 1990s to the most recent data available from the USDA’s Pesticide Data Program and the UK Food Standards Agency (UK-FSA). The DRI provides users the opportunity to slice and dice pesticide dietary risk metrics in dozens of ways: by food, by pesticide, imports versus domestically grown food, organic versus conventional production systems, at varying levels of aggregation ranging from individual samples up to across the whole food supply, and most combinations of the above parameters. The following is our interview with Benbrook.

What drives the DRI and how does the DRI compare to other systems used to assess pesticide dietary risk?

There is no other system that does what the DRI does. The core metric in the DRI is the ratio of pesticide exposure in one serving of food relative to the maximum amount of the pesticide that can be ingested daily in the food without exceeding the “level of concern” determined by the EPA. DRI risk metrics are driven by EPA-set chronic Reference Doses taking into account all the residues found in a sample of food. The DRI also aggregates risk levels of multiple residues in an individual sample, or in a given food, based on the assumption that risk levels from each individual residue are additive.

Please briefly define “chronic toxicity” and point readers to where they can learn more about the technical details and methods embedded in the DRI.

Important question. DRI risk metrics are driven by two things – the level of a pesticide detected in a given sample of food, and second, the chronic toxicity of the pesticide as set by the EPA. All DRI metrics reflect risk levels for four-year old children weighing about 16 kilograms. Food serving sizes are set at two-thirds of adult serving sizes as published by USDA. With these variables – food serving size, weight of a child, the residue level in a sample/serving of food, and the pesticide’s chronic Reference Dose – the core DRI risk metric is simple math. DRI data sources and methodologies were published in Environmental Health in 2020, and the novel methods we use to calculate and analyze individual-sample risks are explained in an Environmental Sciences Europe paper published in 2022.

One point warrants emphasis. DRI risk metrics are accurate to the degree that current, EPA-set chronic Reference Doses (cRfD), or Population Adjusted Doses, are accurate proxies of a pesticide active ingredient’s chronic dietary toxicity. Some cRfDs are likely protective of health for most Americans, but others clearly are not.

So isn’t the EPA already tracking pesticide dietary risks in the same ways the DRI does?

No, it is not. The EPA, and indeed regulators worldwide, lack a system like the DRI that allows a comprehensive appraisal of dietary risk levels and trends across foods, pesticides, production systems, and countries of origin. The EPA’s job under FIFRA (the federal law governing pesticide regulation) is to set hopefully “safe” tolerance levels covering residues of a single pesticide in all the foods on which a pesticide is applied. The EPA has sophisticated, data-rich methods to do so, but it has no capacity, nor a mandate to quantify and track overall pesticide dietary risk levels and trends.

Might the EPA someday use the DRI?

It already has. The EPA’s Office of Inspector General was called upon in the mid-2000s to assess whether the 1996 Food Quality Protection Act (FQPA) was achieving the goals set out by Congress. They hired Benbrook Consulting Services to quantify the impact of the FQPA about a decade after passage. We did so using the DRI. Updating that analysis of the impact of the FQPA is high on my personal bucket list of things to get done before hanging up my spurs. But back to your question, the EPA needs a system that does what the DRI does. They can start by using the DRI, but really should create a more sophisticated gen-two DRI drawing on the wealth of data and analytical tools and talent they have access to.

You’ve worked on the Hill and for the National Academy of Sciences (NAS). How did your career keep bringing you back to the need for a system the DRI?

In the mid-1980s, I helped start and manage a NAS project focused on the Delaney Clause. The Delaney Clause requires that the Food and Drug Administration (FDA) ban or not approve food additives which are found to cause or induce cancer in humans or animals. To support the NAS Committee’s work, we created the first-ever cumulative oncogenicity risk assessment of pesticides in food. Later in the 1980s, we started another EPA-funded NAS project assessing the health impacts of pesticides on pregnant women and children. The 1993 NAS report entitled Pesticides in the Diets of Infants and Children set the analytical and political stage for passage of the FQPA in 1996. It contained the results of the first-ever cumulative risk assessment of a major class of pesticides, the organophosphate (OP) insecticides. The system we used to conduct that OP risk assessment in the early 1990s evolved over the next 20 years into today’s DRI.

After the NAS years, who supported the analytical work required to enhance the DRI’s analytical capabilities?

A long list of foundations, NGOs, and companies supported the work required to incrementally build DRI capabilities. By far the most important and long-term supporter has been Consumers Union and Consumer Reports magazine. Others included the Gerber Products Company, World Wildlife Fund, Union of Concerned Scientists, NRDC, EWG, and many others. The Sheepdrove Trust in the UK financed the complicated process required to incorporate the UK-FSA’s residue data in the DRI. HHRA and its funders have supported the major DRI-system upgrade we have just finished, as well as the transfer of the system onto the HHRA website. These tasks took three years and cost far more than I had initially projected.

What is your plea to policymakers for acting on this information?

There’s an important window of opportunity in the current Farm Bill. I hope Congress will give the National Organic Program (NOP) a nudge sufficient to get the NOP behind what we call OrgTracker. HHRA policy consultant Mark Lipson and I are encouraged by the interest in OrgTracker among certifiers. OrgTracker would upload the pesticide residue data that the NOP requires certifiers to collect, and will run the residue data through a customized, new module of the DRI (OrgTracker). Result tables will make it easy for certifiers and the NOP to identify food samples with possibly worrisome residues. Certifiers and the NOP could then focus like a laser on the rare samples of organic food containing residues of concern. If the NOP developed new, rapid-response enforcement capabilities and used OrgTracker to target growers shipping organic food with questionable and/or illegal residues, the NOP and organic community could quickly eliminate ~90% of the already very low pesticide dietary risk from certified organic food chains. And to me, that is how the NOP and organic community can retain consumer confidence in the integrity of the USDA organic seal and deliver on the promise embedded in each serving of organic food a family chooses to place on its table.

If the NOP is serious about making incremental progress in reducing pesticide dietary risk, we know how to do it via OrgTracker, and the community’s overall efforts will become increasingly cost-effective and irrefutably positive.

Which groups are the most vulnerable to pesticide risks in our food supply?

The most serious risks come during the two bookends of life: infancy and childhood and older adulthood. The science pointing to pesticide-exposure impacts on children’s neurodevelopment is regrettably solid now and new, CHAMACOS project evidence of adverse impacts on metabolic health among children is deeply worrisome.

There are many reasons why organic food enhances the health of aging Americans. Our bodies’ ability to produce indigenous antioxidants weakens as we age and as our immune systems get rusty. Both of these unavoidable consequences of aging enhance the importance of food safety and nutrient-dense food. A lot of food isn’t palatable to older people, and they struggle to get enough nutrients from the few foods they consume regularly. But you can make a healthy and delicious diet out of fresh organic berries, broccoli, beans, and spinach, cheese and dairy products, and many other foods. Antioxidants delivered through organic food fight inflammation, which is linked to most of the mental diseases of aging. And to anyone combating cancer, organic foods can help eliminate exposures to chemicals that can trigger or promote tumor growth.

What does the DRI data say about how conventional and organic produce differ in potential chemical exposure?

A lot and almost all the data are positive. There are a few hot spots of pesticide risk in imported organic – e.g., frozen cherries from Turkey and some of the spices and food ingredients coming from Southeast Asia. But it’s safe to say that overall, both domestically grown and imported organic food eliminates 90%-plus of the pesticide risk routinely in conventional foods, and especially in fresh fruits and vegetables.

I feel that, from a scientific perspective, the most significant and proven benefits of organic food and farming arises from the reduction in exposure to toxic pesticides.

The science is clear. So why isn’t this widely accepted by the general public?

Unlike many European consumers, the American public does not understand nor appreciate the enormous human health and environmental benefits stemming from organic food and farming. Why? Because USDA policy still asserts that organic food is neither safer nor more nutritious, despite the fact that hundreds of USDA-funded research projects confirm that organic food is both safer and more nutrient dense. The Congress needs to drag the USDA into the current century and deep-six that policy statement. Science supports the idea that organic food has both environmental and human health benefits.

The other enormous institutional constraint arises from the fact that researchers can’t get public funding nor publish findings about the human health benefits of organic food without triggering the immune system of what I call “US Ag Inc.” I’ve seen it happen many times. The agribusiness and food companies that are profiting from our current high-volume, low-quality  industrial food system have captured the keys to the city, and they’re not going to hand them over without a fight. There is almost no space nor tolerance for “sound” science as the battle rages on.

How could we make food safer?

Government agencies and commodity groups and the food industry spend a lot of time and effort and money in PR efforts promoting the safety of the food supply. If instead they just used the [DRI] and went after the relatively few risk-driver pesticide-food combinations and banned them, it would immediately improve food safety. Just reduce or revoke the tolerance levels! It’s not a complicated thing for the EPA to reduce or revoke a tolerance.

Between 2000 to the 2004 period the EPA didn’t do a lot of revoking of tolerances; instead they nudged companies toward seeking voluntary revocations of tolerances by imposing requirements to generate and submit to the EPA substantial new data. In some cases, registrants were reasonably sure that the new studies would raise EPA’s level of concern. This could, in turn, lead to stricter regulation and negative consequences in markets around the world. Instead of pursuing that course of action, most registrants agree to a phase out of current labels and tolerances. Unfortunately, some of the high-risk OPs abandoned by major companies have been picked up by “Bottom-Feeder Companies” that try to keep high-risk chemicals on the market for a couple of years because it costs them almost nothing to do so and they can generate some sales and profit in the interim. Contemporary examples include the ongoing efforts to restore a limited number of food uses of chlorpyrifos and aldicarb, two of the most toxic insecticides ever brought to market.

Other than the dangers of pesticide residues, what are other negatives of conventional food production?

More nutritious, safer food is going to cost more than nutrient-diluted, unsafe food. That’s a given. The conventional food system externalizes to the public and society at large the sizable costs stemming from unsafe and nutrient-devoid food. And because the USDA is running cover for the problems in conventional agriculture, the general public doesn’t understand how bad many conventional ag systems are for soil health and water quality, farm animals, and people.

Much of the US food and fiber system has sacrificed resilience for simplicity and high yields of poorer quality food. Let’s admit it: It is remarkable how much food three people on a 2,000-acre Midwestern corn-soybean farm can produce, but they can only produce it with heavy reliance on pesticides and synthetic fertilizers. These systems degrade and otherwise damage the natural resource base, rural communities, and the environment and biodiversity. It’s a costly way to grow food, both for farmers and society. These systems are also vulnerable to huge losses of yield and productivity, and death of animals, all of which raises the cost of food and requires the government to spend more money on disaster payments and crop insurance subsidies.

How can messaging for organic food and farming improve?

I feel that the organic community, the public health community, and the government have to do a better and clearer job in educating the public about the easily attainable benefits of switching to organic systems. And given the many interests working to actively undercut this message, respected government agencies and scientists need to become more forceful in explaining what science now has proven.

The public needs to understand that the safer and more nutritious organic food produced on organic farms also delivers all kinds of societal benefits: cleaner water, more pollinators, fewer farmworker poisoning episodes, a more diverse agriculture land base, fewer reproductive problems and healthier children, more wildlife, more birds, fish… among other secondary benefits. Public demand for public institutions and private businesses to help capture these benefits is why Europeans have invested so much more in support of organic farming systems, infrastructure, and marketing.

Why hasn’t there been a shift toward organic food already?

It’s simply a question of investment in infrastructure and giving consumers honest, accurate information about the benefits to them and their families if they buy organic food whenever they can.

In my opinion, the US department of agriculture has consciously and effectively depressed the demand for organic food over the last 20 years because of political intervention from the conventional food and agribusiness industry that regards organic food and farming as an existential threat to their business model and to their income. If you’re making most of your income selling toxic pesticides in Washington State, for example, the organic sector is definitely already an existential threat to your livelihood.

What keeps you awake at night?

The people and organizations in control of federal policies, payments to farmers and ranchers, and investments in R+D and infrastructure are reluctant to acknowledge that false promises and bad bets on certain technology has eroded the productively and resiliency of too many farming systems.

To get carbon back in soil, to deal with climate change, to sever the impact of resistant weeds and insects on pesticide dependence, to improve water quality, to improve the nutritional quality of food coming out of the Midwest, organic farming and organic systems are exactly what the doctor ordered. I could imagine in 20 years, 80 percent of fruit and vegetable production in the west coast being organic. I think it’s going to eventually happen because it’s going to make farmers more money. The longer good farmers follow organic practices, the more resilient their systems become. If smart investments are made in the infrastructure needed to support organic farming and food chains, costs will come down over time and food quality and safety will incrementally improve. The missing link, or spark, is consumer demand sufficient to overcome reticence among those content with the status quo.

I feel that the organic community has got to tackle the systematic, anti-organic bias in the USDA that is muddling the message to the American consumer about the benefits of organic food and farming for our health, the environment, and the people and animals we depend on to put food on the table.