If you were to ask a group of medical professionals to name the most significant public health achievements of the past century, antibiotics and widespread vaccination against infectious diseases would almost certainly top the list. The US Centers for Disease Control and Prevention2 (CDC) would add motor vehicle safety, fluoridated water, workplace safety, and a decrease in cigarette smoking.
If you were to say pesticides not only belonged on the list, but well toward the top of it, you would likely be greeted with skepticism, if not incredulity. On this topic, highly educated professionals are little different from general consumers, who get most of their information from media stories that overwhelmingly portray pesticides as a health threat or even a menace. At best, some open-minded interlocutors might concede that pesticides are a necessary evil that regulators should seek to limit and wherever possible, eliminate from our environment.
Yet by any of the standard measures of public health – reductions in mortality, impairment, and infectious diseases, as well as improved quality of life – the contribution of modern pesticides has been profound. An adequate supply of food is absolutely foundational to human health. Denied sufficient calories, vitamins, and other micronutrients, the body's systems break down. Fat stores are depleted and the body begins to metabolize muscles and other organs to maintain the energy necessary for life. Cardiorespiratory and gastrointestinal functions falter and the immune system is seriously compromised.
A 2019 report3 from the United Nations Children's Fund (UNICEF) found that "one-third of children under age five are malnourished – stunted, wasted or overweight – while two-thirds are at risk of malnutrition and hidden hunger because of the poor quality of their diets." And according to the World Health Organization1, undernutrition is currently an underlying cause in nearly half of deaths in children under five years of age. Inadequately nourished newborns who survive early childhood can suffer permanently stunted growth and lifelong cognitive impairment. Death results more often from undernutrition than insect-borne killers like malaria, Lyme disease, Zika virus, dengue and yellow fever combined. In addition, it makes people more susceptible to such infectious diseases. Pesticides help to address all of these problems by increasing the food supply, controlling the growth of harmful mycotoxins, and preventing bites from mosquitoes, ticks, other disease-transferring insects, and rodents.
Food Security is a Recent Phenomenon
The medical community knows all of the broad strokes above, at least in the abstract. But living in a time of unprecedented agricultural abundance, we often take for granted the provision of adequate diets. We shouldn't.
As the economist Robert Fogel noted in a 2004 book,4 even in advanced, industrialized nations, widespread food security is a relatively recent phenomenon. According to Professor Fogel, per capita calorie consumption in mid-nineteenth century Britain barely equaled what the World Bank would designate today as that in "low income" nations. The availability of calories in early nineteenth century France would place it today among the world's most food insecure. It wasn't until well into the twentieth century that even the wealthiest nations reached the level of per capita calorie consumption necessary to escape chronic undernutrition.
What made that possible was a rapid increase in farm productivity following World War II. Crop yields had been improving during the previous two centuries, to be sure, but as can be seen in charts of historical yield trends,5 progress was slow and uneven. That changed dramatically in the mid-1940s, when the gradually ascending yield curves suddenly turned sharply upward, climbing almost vertically to where they stand today.
Average wheat yields in Great Britain in 1942, which stood a mere thirty percent above their level a century earlier, doubled by 1974. By the late 1990s, they had tripled compared to 1942. Crops throughout Western Europe and the United States followed a similar trajectory: slow growth or stagnation in the pre-WWII era, followed by rapid acceleration starting in the late 1940s. US corn yields per acre, which had increased only eighteen percent between 1900 and 1945, tripled in the next forty-five years, and by 2014, had increased more than 460 percent.5
The Essential Role of Pesticides
So, what changed to produce such dramatic improvements? The two factors most often cited are cheaper nitrogen fertilizers produced by the Haber-Bosch method of fixing nitrogen6 directly from the air, which came on line after 1910, and new hybrid crops created by Henry Wallace, which were first marketed in 1926 by his seed company, Pioneer Hi-Bred Corn Company (later Dupont Pioneer and now Corteva Agriscience). Both innovations were rapidly adopted by farmers in the first half of the nineteenth century – the use of artificial nitrogen fertilizer by US farmers increased ten-fold7 between 1900 and 1944, and sixty-five percent8 were planting hybrid crops by 1945 – but their use and development increased enormously in the post-war years.
Often ignored, however, was the post-WWII introduction of new, synthetic chemical pesticides that dramatically reduced crop losses and made possible much of the yield growth stimulated by new fertilizers and seeds. Farmers had been using chemical pesticides since the earliest days of agriculture, but up until the mid-1940s, these were largely simple chemical compounds containing sulfur and heavy metals. An example was copper sulfate, which organic farmers still rely on today due, ironically, to its high toxicity, indiscriminate pesticidal activity, and long-lasting effects (i.e., persistence in the environment). Advances9 in organic (i.e., carbon-based) chemistry, however, provided farmers in the post-WWII era with a broad array of highly effective and increasingly targeted pesticides that have revolutionized agriculture.
According to one of the world's leading experts in plant diseases, E.-C. Oerke of the University of Bonn, these pesticides were responsible10 for nearly doubling crop harvests, from forty-two percent of the theoretical worldwide yield in 1965 to seventy percent by 1990. It has been estimated11 by others that herbicides (which are a subset of pesticides) alone boosted rice production in the United States by 160 percent and are responsible for a full sixty-two percent of the increase in US soybean yield. Modern fungicides contributed11 somewhere between fifty and one hundred percent of the yield increases in most fruits and vegetables.
Yet even these numbers vastly understate the contribution of modern pesticides. As Professor Oerke and others8 have pointed out, many of the critical attributes of modern crop varieties that enable higher yields make modern crops more attractive to pests; these include shorter stalks (which prevent damage from the elements but increase competition from weeds), increased resistance to cold (which enables earlier spring planting and double-cropping), higher crop density and increased production of nutrients stimulated by synthetic fertilizers. Without the innovation of new pesticides, much of the benefit of enhanced fertilizer use and even the survivability of new plant varieties that define agriculture today would be severely curtailed or even blocked.
The 'Green Revolution'
In the 1960s, rapid population growth worldwide raised alarms of mass starvation. Many of the fears were exaggerated, but the urgency was real. Over the next half century, world population doubled, with much of the increase taking place in poor nations already chronically unable to feed their populations. That the world averted widespread famine is largely credited to one man: Norman Borlaug. Known as the "Father of the Green Revolution" and "the man who saved a billion lives," he received the Nobel Peace Prize in 1970 for his tireless efforts to export the benefits of agricultural technology to struggling farmers around the world. The effects were dramatic: New high-yielding, disease-resistant wheat hybrids Borlaug introduced in Mexico, Pakistan and India doubled yields within a matter of years and helped turn those nations into net exporters.
Borlaug was adamant12 throughout his life that the success of the Green Revolution was only possible because of modern pesticides. In a speech he delivered a year after receiving the Nobel Prize, he forcefully condemned12 the environmental movement's "vicious, hysterical propaganda campaign" against agricultural chemicals.4 Insisting that chemical inputs were "absolutely necessary to cope with,12" he expressed alarm that legislation then being pushed in the US Congress to ban pesticides would doom the world to starvation.
Starting in the 1960s, led by dramatic gains in developing nations, global crop production began an impressive13 ascent. Tufts University Professor Patrick Webb13 has calculated, "In developing countries from 1965 to 1990, there was a 106 percent rise in grain output, which represented an increase from roughly 560 kilograms per capita to over 660 kilograms per capita." And according to the United Nations' Food and Agriculture Organization, the rapid rise in food production caused a reduction in world hunger – which is defined as not having adequate caloric intake to meet minimum energy requirements – by more than half14 between 1970 and 2014. Behind that single statistic are billions of premature deaths averted, billions of lives rescued from chronic disease and suffering, and whole communities and even nations saved from an endless cycle of underdevelopment and grinding poverty.
From a public health perspective, those achievements can hardly be overstated. Unfortunately, they are rarely stated at all these days.
Fear, Not Facts, Prevail
The discussion of pesticides today largely ignores the challenges inherent in producing food at the necessary scale and focuses instead on inflated fears surrounding them, although they are among the most rigorously tested and tightly regulated of any class of products. The result is a growing political and public backlash that retards the innovation of new products, restricts, and even bans from the market perfectly safe, effective, and established products.
The increasing momentum toward expanding bans on pesticides in Europe has called into question the very viability of agriculture15 on that continent. An avalanche of lawsuits16 in the United States against pesticides (such as the herbicide glyphosate17) universally deemed safe by regulators could put our country on a similar path. Meanwhile, international development agencies such as the UN's Food and Agriculture Organization – which once championed the Green Revolution – are pushing the world's poorest farmers to adopt "agroecological" approaches that prohibit modern pesticides (and other technologies and products) and are as much as fifty percent less productive.18 That is a prescription for potentially deadly challenges to food security.
It would be one thing if this broad-based attack on modern pesticides approved by regulators had scientific merit, but the obsessive focus by politicians, activists, and media on the perceived risks to consumers collapses under scientific scrutiny. In this, it closely parallels the public health challenge presented by the anti-vaccination movement, which is led by many of the same environmental groups. A critical difference is that the anti-pesticide movement is supported by billions of dollars of annual funding from wealthy non-profits, governments (largely in the EU), and a burgeoning organic agriculture/food industry that seeks to increase its market share19 by spreading false and misleading claims20 about conventional farming.
And unlike anti-vaccination propaganda, the media reflexively repeats and amplifies the anti-pesticide message with little qualification. ("If it bleeds, it leads.") Even seemingly authoritative voices in the health community, such as the American Pediatrics Association,21 advise the public to eat organic food, mistakenly assuming that organic farmers don't use pesticides (they do,22 lots of them23) or perhaps believing that "natural pesticides" made with heavy metals are somehow less toxic than synthetic ones. (The EU has considered banning copper sulfate24 due to its human and environmental risks, but has continued to reauthorize it because organic farmers have no viable alternatives.) Ironically, many organic pesticides are considerably more damaging to the environment.25
One of the most successful examples of anti-pesticide propaganda is the annual "Dirty Dozen" list26 produced by the US activist Environmental Working Group (which also spreads vaccine fears),27 highlighting fruits and vegetables that have the highest detectable pesticide residues. The ability of modern technology to detect substances measured in parts per billion or even per trillion is extraordinary, but the infinitesimal residues found on food are almost certainly too small to have any physiological effect and by any reasonable measure, represent a negligible risk to consumers.
Pesticide regulatory "tolerances" (safety levels) are calculated28 by dividing the highest dose of a pesticide found to have no detectable effect in laboratory animals by a "safety margin" of one hundred to one thousand,28 which sets a maximum exposure limit on the cumulative amount of residue from all approved products – meaning regulators consider the sum of current tolerances while determining the tolerance level for a new product. For trading purposes, maximum residue limits (MRLs) are set based on safety levels multiplied by an additional safety margin. So even if MRLs are exceeded, there is very low risk of any health effect.
For example, the European Food Safety Authority29 noted in its most recent annual monitoring report on pesticide residues (2017), that more than half (fifty-four percent) of 88,000 samples in the European Union were free of detectable residues. In another forty-two percent, residues found were within the legal limits (MRLs). Only about four percent exceeded these limits, which still were unlikely to pose a safety issue due to their trace amounts and built-in safety margins.
Paradoxically, regulators don't apply such large, conservative safety factors to other, more toxic substances we consume safely in much larger quantities every day. Consider, for example, the difference between drinking one or two cups of coffee and drinking one hundred to one thousand cups all at once. Given that a lethal dose of caffeine is about ten grams30 and a cup can easily contain 150 milligrams, sixty-six cups might well be fatal. Similarly, the absurdist nature of the Environmental Working Group's claims is seen in the calculations31 of the impossible quantities one would have to consume in a single day – e.g., 1,190 servings of apples, 18,519 servings of blueberries, 25,339 servings of carrots per the Alliance for Food and Farming – just to reach the no effect level.
Similarly, discussions of cancer risks commonly fail to acknowledge that most of the fruits and vegetables that are part of a healthy diet naturally contain32 chemicals that are potential carcinogens at high enough doses. Many, such as caffeine and the alkaloids in tomatoes and potatoes, are natural pesticides produced by the plants themselves for protection against predators. Dr. Bruce Ames, who invented the test still used today to identify potential carcinogens, and his colleagues estimate33 that 99.99 percent of the pesticidal substances we consume are such natural pesticides – which, of course, we consume routinely and safely.
The role of pesticides in protecting public health is broad, varied, and sometimes unobvious. For example, the addition of the pesticide chlorine to public drinking water kills harmful bacteria. Hospitals rely on pesticides called disinfectants to prevent the spread of bacteria and viruses, and fungicides in paints and caulks prevent harmful molds, while herbicides control allergen-producing weeds such as ragweed and poison ivy. Rodenticides are used to control rodents that spread diseases such as bubonic plague and hantavirus, and there are over 100,00034 known diseases spread by mosquitoes, ticks and fleas, which infect more than a billion people35 and kill more than a million of them every year; those diseases include malaria, Lyme disease, dengue fever, West Nile Virus, and Zika.
Even as the numbers of tick- and mosquito-borne infections in the United States have surged,34 the CDC warns34 that we are dangerously unprepared – in large part because of opposition36 to state-of-the-art pesticides by well-funded environmental organizations and the organic food and natural products industries, and the public fears37 they arouse.
Finally, naturally occurring toxins called mycotoxins,38 produced by certain molds (fungi), can grow on a variety of different food crops, including cereals, nuts, spices, dried fruits, apples and coffee beans. The most concerning of them are genotoxic aflatoxins, which can cause acute poisoning in large doses. Crops frequently affected by aflatoxins38 include cereals (corn, sorghum, wheat and rice), oilseeds (soybean, peanut, sunflower and cottonseed), spices (chili peppers, black pepper, coriander, turmeric and ginger) and tree nuts (pistachio, almond, walnut, coconut and Brazil nut). Pesticides are effective in controlling the growth of these and other mycotoxins.
Certainly, just as with pharmaceuticals and medical devices, pesticides need to be well-regulated and monitored, especially for potential effects on certain segments of the population, such as farmers, who have the most direct contact (but have lower rates of cancer than the general population). (See here,39 here,40 here,41 and here.42)
The control of pests has come a long way. The toxicity1 of modern pesticides has already dropped ninety-eight percent and the application rate1 is down ninety-five percent since the 1960s. I grew up in the era of "Better Things for Better Living ... Through Chemistry" (DuPont's advertising slogan from 1935 to 1982) and lived through the worst of the backlash toward chemicals spawned in large part by the publication of Rachel Carson's compelling but often dishonest book Silent Spring. Now, chemicals are being complemented, and sometimes supplanted, by biotechnology, but that's beside the point; the net benefit of pesticides, whether chemical or biological, is irrefutable.
Our greatest public health challenge today isn't chemicals; rather, it is the institutionalized ignorance and fear-mongering that threatens to undo some of the twentieth century's greatest technological and humanitarian uses of them.
Henry I. Miller, M.S., M.D., a physician and molecular biologist, is a senior fellow in healthcare at the Pacific Research Institute. He was formerly a research associate at the National Institutes of Health and the founding director of the US Food and Drug Administration's Office of Biotechnology. Please follow him on Twitter at @henryimiller.
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