> ## Content Index > Fetch the complete content index at: https://www.organicfoodtogether.nz/llms.txt > Use this file to discover other available public pages before exploring further. # Change the Food and the Pesticides in Your Urine Change Too - URL: https://www.organicfoodtogether.nz/change-the-food-and-the-pesticides-in-your-urine-change-too/ - Published: 2026-10-01T17:31:07.000Z - Updated: 2026-10-01T19:23:01.000Z - Description: A Massey study found NZ children carried more of one pesticide marker than American kids, mostly from food. Studies that switched people to organic saw urine levels fall within days. What that does and doesn't prove, including the finding an organic site might skip. - Author: Luke Nicholas - Tags: Health, pesticides, organic, Food Research, science Between 2015 and 2017, 501 New Zealand children handed over a cup of morning wee for science. Most of them did it twice, once in summer and once in winter. A Massey University team sent the samples to Queensland and tested them for 20 pesticide markers. The paper says it was the [first large survey of pesticide exposure ever done in New Zealand](https://www.fs.usda.gov/pnw/pubs/journals/pnw%5F2022%5Fli001.pdf?ref=organicfoodtogether.nz). Nine of those markers turned up in more than 80% of samples. One stood out. It's called TCPy, and it's what your body makes from chlorpyrifos, an insecticide, and triclopyr, a weed killer. New Zealand children had 2.2 to 7.3 times more of it than children in countries such as the US, Spain and Thailand. Of the countries compared, only Australian kids were higher. That's worth sitting with for a second. American food has a reputation. Ours has a brochure. ## Where it was coming from The obvious suspect is spray drift. Farm kids near orchards, that sort of thing. That isn't what the numbers said. Several markers, TCPy included, were *higher* in the low-spray months, April to October. Farm children only came out ahead on TCPy in the high-spray season, by about 40%. The researchers' best guess for the winter rise is food. More fruit and vegetables are imported in the colder months, and post-harvest treatments may play a part. They're careful to say they can't pin it down, because New Zealand publishes very little data on what pesticides are used where. Their conclusion is blunt for a scientific paper. The biggest gains in cutting children's exposure, they write, would likely come from reducing pesticide residues in food, both locally grown and imported. Two things need saying straight away. First, every level they could compare against a health guidance value came in below it. For TCPy, the children's median sat about a hundred times under the adult guidance value. The authors also note studies suggesting chlorpyrifos can affect brain development below the threshold those values are built on. Both of those are true at once. Second, TCPy can't tell you whether it came from the insecticide or the weed killer. So "New Zealand kids full of chlorpyrifos" is not a sentence this study supports. "New Zealand kids carried more of a marker for chlorpyrifos *or* triclopyr" is. For what it's worth, chlorpyrifos is on its way out here. The EPA has [revoked approvals in stages](https://gazette.govt.nz/notice/id/2025-au4759?ref=organicfoodtogether.nz), and most products have been banned from use since January 2026\. The last two stay lawful until July 2027. ## The awkward finding Here's the part an organic publication would be tempted to leave out. The same study asked parents how often their kids ate organic fruit. Eating organic fruit made no measurable difference to the children's levels. Eating other organic food was linked to lower TCPy, but only in summer. That needs context, not burial. One urine sample, set against a parent's best memory of a typical week, is a blunt tool. And more than 60% of these children rarely or never ate organic produce, so there weren't many organic eaters to compare. Still, it's in the paper, so it's in this post. To actually answer the question, you need a different kind of study. Change what someone eats, and measure what happens. ## When researchers changed the food The cleanest version of that experiment is more than twenty years old. In summer 2003, researchers in Seattle [tracked 23 children aged 3 to 11](https://pmc.ncbi.nlm.nih.gov/articles/PMC1367841?ref=organicfoodtogether.nz) for 15 days straight, collecting urine morning and night. For three days the kids ate their normal food. For the next five, their fruit, vegetables, juice and wheat- or corn-based foods were swapped for organic versions. Then they went back to normal for a week. The researchers had the organic food tested in a lab first. No pesticides were detected in it. The result looks like a light switch. Markers for two insecticides, malathion and chlorpyrifos, were in every child's urine at the start. The median levels dropped to undetectable as soon as the organic food arrived. They stayed there for five days, then came back when the normal food did. The study was funded by the US Environmental Protection Agency, and the authors declared no competing interests. Meat and dairy weren't swapped at all, because those organophosphate insecticides rarely show up in them. Other teams have found the same direction, though not always the same size. - **Melbourne:** a [2014 crossover trial in 13 adults](https://www.sciencedirect.com/science/article/abs/pii/S001393511400067X?ref=organicfoodtogether.nz) found total organophosphate markers 89% lower after a week of eating at least 80% organic. The urine was measured by AsureQuality in New Zealand, so the capacity to do this has existed here. - **California:** a [2015 study of 40 children](https://drum.lib.umd.edu/bitstreams/6625a67a-339a-46c6-bd85-126e08e99d17/download?ref=organicfoodtogether.nz) from low-income city and farming communities found a smaller drop, around 40%. Several individual markers didn't move significantly. Children in the farming community had generally higher levels whatever they ate, which the authors say points to other sources of exposure. - **Four US families:** the most-quoted results come from [16 people in 2017](https://www.sciencedirect.com/science/article/pii/S0013935119300246?ref=organicfoodtogether.nz), with a malathion marker down 95% and a neonicotinoid insecticide down 83%. A [follow-up paper on the same urine](https://www.sciencedirect.com/science/article/pii/S0013935120307933?via%3Dihub&ref=organicfoodtogether.nz) found glyphosate down about 71%. You should know who paid for it. The first paper states it was funded by Friends of the Earth, an advocacy group. A Friends of the Earth scientist co-authored both papers. Then there's the [randomised trial I covered in September](https://www.organicfoodtogether.nz/i-went-looking-for-proof-organic-food-is-better-for-you-heres-what-a-proper-search-turned-up/), where the organic group excreted 91% less pesticide residue than the conventional group. None of these studies is perfect on its own. Every one of them points the same way. ## What a sceptic would say The best objection was written in 2006, in a letter to the journal that published the Seattle study. [Robert Krieger and colleagues](https://pmc.ncbi.nlm.nih.gov/articles/pmid/17035114?ref=organicfoodtogether.nz) argued the result was obvious. Of course levels drop when you stop eating the source. If they didn't, "one might expect parked cars to get speeding tickets." Their real point was that these exposures were already far below levels where anyone has seen harm, so calling organic food "protective" was misleading. That's a fair hit. A drop in a urine marker is a change in exposure. It isn't evidence that the previous level was hurting anyone. There's a technical catch too. Some urine markers, the broad organophosphate ones especially, can come partly from breakdown products already sitting on food, which may be less toxic than the pesticide itself. The researchers say so in their own papers. The largest drops, though, were in markers tied to one specific chemical, and in Seattle the organic food was tested clean. ## So what are they doing in there? If something leaves your body within a day or two, does it matter? That breaks into a few separate questions, and they have different answers. **Do they build up?** The older ones did. DDT is the textbook case. The US health agency ATSDR says DDT and its breakdown products [collect in body fat and breast milk](https://www.atsdr.cdc.gov/ToxProfiles/tp35-c1.pdf?ref=organicfoodtogether.nz) and leave the body slowly. What a person carries reflects exposure from years ago as well as now. New Zealand banned DDT in 1989, and the 2009 Total Diet Study [was still finding it in our food](https://sciencemediacentre.co.nz/?p=13929&ref=organicfoodtogether.nz). Most pesticides in use today are different. The [Massey paper](https://www.fs.usda.gov/pnw/pubs/journals/pnw%5F2022%5Fli001.pdf?ref=organicfoodtogether.nz) notes they generally have half-lives of under a day in the body, which is why they're measured in urine rather than blood. For chlorpyrifos, it puts the figure at about 24 hours. The Cyprus researchers put pyrethroids at roughly 6 to 17 hours. In the US families, [glyphosate was back to baseline within three days](https://www.sciencedirect.com/science/article/pii/S0013935120307933?via%3Dihub&ref=organicfoodtogether.nz) of switching to organic. But clearing quickly isn't the same as not being there. If it's in your food most days, it's in you most days. The Seattle children's levels only dropped to undetectable when their food changed, and went straight back up when it changed back. It's a bath with the plug out and the tap still running. **What do they do while they're in there?** At high doses, some of this is well understood. Organophosphate insecticides, the family chlorpyrifos and malathion belong to, [block an enzyme that stops nerve cells firing non-stop](https://npic.orst.edu/ingred/chlorpyrifos.html?ref=organicfoodtogether.nz). With that enzyme blocked, nerves can't send normal signals. That's how they kill insects. At high enough doses, it's how they poison people. How well you deal with them varies. Most are broken down in the liver, and the enzymes doing that work differ from person to person. The Melbourne researchers note young children have lower activity of some of those enzymes. At the levels found in food, it gets much less certain. A [2023 systematic review](https://ehjournal.biomedcentral.com/articles/10.1186/s12940-023-01020-8?ref=organicfoodtogether.nz) summarises the pathways lab experiments have found for various pesticides. They include oxidative stress, interference with hormones, damage to DNA and changes to gut bacteria. Those are mechanisms seen in experiments, often at higher doses. They aren't effects anyone has measured in people eating ordinary food. **Do they interact with each other?** Nobody eats one pesticide. The four US families had 14 different pesticide markers in their urine, pointing to more than 40 possible pesticides between them. Residue limits are set one chemical, in one food, at a time. Some regulators do look at combinations. The UK runs a [combined risk assessment](https://gov.uk/government/publications/pesticide-residues-in-food-quarterly-monitoring-results-for-2024/quarter-2-2024-report-on-the-pesticide-residues-monitoring-programme?ref=organicfoodtogether.nz) when a sample holds pesticides from groups with similar toxic effects. The 2023 review argues research should study mixtures rather than single chemicals, because effects could add up or amplify each other. How much that happens at food levels is mostly unmeasured. **Has anyone actually found harm from food-level exposure?** The 2023 review went looking for long-term studies linking dietary pesticide exposure to disease in ordinary adults. Out of 52 candidates, six met its criteria, all from France or the US. Three looked at cancer, and the reviewers rated that evidence low. The other diseases had one study each, too few to grade. Where the studies found anything, it pointed towards harm, but the reviewers went no further than "a possible role." Worth knowing: the review comes from the same French research group behind several of the organic studies in my September post. The only trial I found that looked for a change in the body itself [ran for 40 days in Cyprus](https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0219420&ref=organicfoodtogether.nz). The 149 schoolchildren on organic meals had lower pesticide markers, and less of one marker of oxidative damage. They were also eating fewer calories, so the authors couldn't say the food caused it. ## Where that leaves it Change what you eat and the pesticides in your body change with it, within days. That part is solid. Most of today's pesticides don't build up the way DDT did. They pass through. But if they're in your food every day, they're in you every day. What they do on the way through, at the levels found in food, nobody has pinned down. There aren't enough of the right studies to call them harmful, or to call them harmless. For New Zealand kids, the one big study says food is the main way in. Which makes it the part you get to choose. ## Before you go If this was useful, you can [sign up free](https://www.organicfoodtogether.nz/#/portal/signup) to get new posts by email, or [leave a one-off tip](https://www.organicfoodtogether.nz/#/portal/support) to help keep the research going.