Today I got an email from a Canadian farmer that attended a talk I gave last February at a grower meeting in Ontario. He was reminding me to send him some of the charts I had used in a presentation titled “Talking to a Skeptical Society About Pesticide Safety.” His family has a farm that does a great deal of “direct marketing” to consumers who come to the farm to buy fruits and vegetables. He is often asked the question, “Why are you not Organic?” or “Do you use sprays?” He explains that he only sprays when it is absolutely necessary, that he follows all of Health Canada’s guidelines, and that he takes regular spray safety classes through Ontario Ministry of Agriculture Food and Rural Affairs (OMAFRA). His farm uses manual pest control where possible and employs IPM (Integrated Pest Management).
His story is quite compelling, but he was interested in the data to show that most pesticides are a lot less scary than most people think and that there are some pretty toxic natural things that most of us happily include in our diet. I sent him the slides and then decided that I would like to share them with the readers of Sustainablog. There is nothing “sustainable” about squandering the land/energy/fertilizer/water/labor/fuel inputs to a crop by letting it be diminished by pest damage. This farmer knows that, but it isn’t that easy to communicate that story to urban/suburban customers. These customers don’t have much context for their concept of “toxicity.”
How Toxic is Toxic?
The US EPA classifies the acute toxicity of chemicals in four categories (I, II, III and IV). This is the kind of toxicity we all know as how poisonous things are – could they kill you and at what dose? It is only one of many “dimensions” of human and environmental toxicity, but it is a good starting point to see that “toxins” are certainly not “created equal.” This is one of those annoying scales where a bigger number is better – the amount of the chemical it takes to kill half of the test rats ranges from >5000 mg/kg for Class IV to <50 mg/kg for Class I. The chart below shows that there are familiar “natural products” that fall into all four EPA categories of toxins and that things we think of as good (e.g. vitamins, pharmaceuticals…) or desirable (caffeine, capsaicin…) fall into the more toxic ranges.
Many of the most widely used “pesticides” in agriculture in Canada and elsewhere fall into category IV, “Relatively Non-toxic.” They are probably even safer than their official toxicity rating because it is hard to even feed the poor rats more than 5000 mg/kg so that is usually the maximum rate that is tested.
Many natural products and drugs that we all consume fall into EPA Class III. So do some very important pesticides. In the case of the pesticides, they have had ample opportunity to degrade to non-toxic metabolites before the crops are harvested while the natural products are present at significant levels in foods and the chemicals in pharmaceuticals. Most people think that Organic means no pesticides while in fact it often means the substantial use of Class III toxins.
Class II, “Moderately toxic” chemicals include some important pesticides but also common Organic pesticides, drugs, and my favorite food-based toxins. There are certainly Class I pesticides that actually fit the image of what most people imagine when they hear the word “pesticide.” The second graph below shows that this kind of pesticide is a small part of the story in agriculture and getting smaller (the trend would be similar for most crops and geographies. I suspect that the trend is even more dramatic in Ontario). Nature has even more toxic offerings, but our food system is quite good at protecting us from these threats.
Will Data Like This Help This Ontario Farmer?
I don’t know. I hope he will let me know how it goes with his customer interactions during the 2011 growing season.
Ontario farm stand image from Andrea_44
Please comment here or email me at [email protected] Also email me if you would like higher quality versions of these charts. My website is Applied Mythology.
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“There is nothing “sustainable” about squandering the land/energy/fertilizer/water/labor/fuel inputs to a crop by letting it be diminished by pest damage.”
Highly questionnable. If sustainable means that it can be reproduced over time without requiring non-renewable resources, it is more sustainable to grow corn the way american-indians did 600 years ago than the way modern american farmers do. I have the strong impression that you mix sustainable and economical.
Your post only takes acute toxicity into account. From a sustainability point-of-view, chronic toxicity seems to me even more important.
“In the case of the pesticides, they have had ample opportunity to degrade to non-toxic metabolites before the crops are harvested while the natural products are present at significant levels in foods and the chemicals in pharmaceuticals.”
Not all sources share your optimism about the non-toxicity of metabolites. With hundreds of molecules registered and many more formulations, it is difficult to be assertive ?
The half-life of chlorpyrifos in soil, or the time that it takes for half of the insecticide to be broken down, is usually between 60 and 120 days, but can range from 2 weeks to over 1 year, depending on the soil type, climate and other conditions.
Malathion breaks down into Malaoxon. In studies of the effects of long-term exposure to oral ingestion of malaoxon in rats, malaoxon has been shown to be 61 times more toxic than malathion.[
It was found that a combination of five widely used insecticides (carbaryl, chlorpyrifos, diazinon, endosulfan, and malathion) in concentrations far below the limits set by the EPA killed 99% of leopard frog tadpoles.
A May 2010 study found that children with higher levels of malathion metabolites in their urine seem to be at an increased risk of ADHD. Each 10-fold increase in urinary concentration of organophosphate metabolites was associated with a 55% to 72% increase in the odds of ADHD.
Residential uses of diazinon were outlawed in the U.S. in 2004 but it is still approved for agricultural uses. The California Department for Pesticide Regulation reports that the use of diazinon dropped from 450,000 lbs in 2003 to 350,000 lbs in 2007. A 25% decrease but still a significant figure for a product whose usage on golf courses was banned after it was noticed that it killed bird flocks that congregated there.
“Most people think that Organic means no pesticides while in fact it often means the substantial use of Class III toxins.”
A few comments.
1. You either deem legitimate and sustainable to protect crops or not but it is not fair to consider it legitimate for conventional agriculture and hazardous for organic farming (“He explains that he only sprays when it is absolutely necessary” and ” Most people think that Organic means no pesticides while in fact it often means the substantial use of Class III toxins.”) This shows almost undisputably a strong bias. Do you seriously think that I enjoy handling sulfur and spending several hours in a noisy tractor, being shaken while spraying my orchard to protect it against scab ? Do I wake up singing at 4 am to go and spray sugar against coddling moth ? Of course not : I try to spray as little as possible because I have better to do with my time and money.
2. To my understanding, copper compounds are by no mean natural. Even though copper is used by plants, spraying more copper than what is used by plants can harm soils over time. As an organic fruit farmer, I try to use as few copper as possible. This is also the trend that my advisor tries to follow and make his other customers follow. Bicarbonate potassium appears in the same class while they are completely different in terms of persistence and decomposition.
3. While some of my colleagues achieve zero-spray organic farming, it is in the field of vegetables that are rotated every year. Perennial plants (apples and pears in my case) suffer from insects and fungus that thrive over the years as their host remains in place. During the 2nd half of the 20th century, trying to achieve higher yields by selecting productive varieties without any concern for resistance and increasing the density of trees have probably made the situation worse. It may be time to realise that yields is not the only aspect to take into account in agriculture. It is a mistake for organic farmers and for the promoters of organic farming to claim that they do not need pesticides. They should instead insist on their will to reduce the need for pesticides or to use pesticides with a limited effect on the environment.
Thanks for your thoughtful comment and I always appreciate something coming from someone that actually is farming.
The way the American indians farmed 600 years ago wasn’t all that sustainable if you look at what happened to the Anisasi. They depleted their soils of nutrients and abandoned their cave dwellings. If we grew corn at the yields they achieved it would take >20x as much land.
I agree that chronic toxicity is also important, but the EPA scrutinizes that as well and when you look at residues on food things have only been improving with regard to that and a dozen other dimensions of toxicity.
I’m fully aware of the issues surrounding OPs and carbamates and very happy that their use continues to decline because of the introduction of safer alternatives. If you would like to see that happen sooner, then focus on the generic companies that still sell most of these things, but also ask growers whether they are using them because that is what is cheap or because that is still the best option for pest control. By the way, the ADHD linkage is far from proven as causal and my personal theory about why kids are still being exposed to OPs is that they eat food sweetened with apple and other fruit sweeteners that come from China where there isn’t really meaningful pesticide use regulation.
There is no doubt that diazinon is toxic to birds. It’s use patterns need to be replaced with safer alternatives.
You are right that neither Organic or Conventional farmers spray “for fun” because it is expensive and labor intensive. As to whether copper compounds are natural, they have been deemed so by OMRI and the USDA. Bicarbonate is ok, but there are some really safe synthetic options that also work a heck of a lot better. My old friend in Davis CA that grows Organic apples gets wiped out many years by scab because he does not have effective fungicide options. That is just dumb.
I would totally dispute the idea that plant breeders have stopped working on resistance to diseases and other pests. With perennial plants it is very difficult and long-term, but it certainly happens. “Heirloom” varieties of vegetables are notorious for their pest susceptibility. Pest resistance is a constant challenge for all growers.
Responsible growers of all type use IPM methods to reduce the need for pesticides of any type – this makes economic sense.