New Chlorpyrifos Heart Study: What It Says, and the One Place the Pesticide Is Still Legal Indoors
A study published on 23 August in the Journal of Applied Toxicology reports that chlorpyrifos and dimethoate — two organophosphate insecticides — caused heart and blood-vessel injury in rats, and that chlorpyrifos alone damaged cultured human endothelial cells. It is not a study of people, and it does not describe anything that happened in anybody's house. It is still worth ten seconds of your attention, because there is exactly one place chlorpyrifos can legally be inside a US home, and it is a box you may already own.
What the study found
A team led by Jasmeena Jan exposed female Wistar rats by mouth to chlorpyrifos, to dimethoate, and to the two combined, for 30 days, and compared them with unexposed controls.
According to the published abstract, tissue analysis showed myocardial disarray, interstitial oedema, inflammatory infiltration and disruption of the aortic lining, with the combination group showing the most severe injury. Blood counts shifted — red cells and haemoglobin down, white cells and platelets up — and hydroxyproline rose in both heart and aorta, which the authors read as early fibrotic remodelling. At the molecular level they found "marked upregulation of NF-κB, NLRP3, IL-1β, IL-18 and TNF-α, along with suppression of eNOS."
In the cell-culture half of the work, chlorpyrifos — but not dimethoate — reduced the viability of human umbilical vein endothelial cells and drove oxidative stress. Blocking the NLRP3 inflammasome with the compound MCC950 "mitigated CPF-induced inflammatory signaling and restored endothelial function." That is the finding the authors are most interested in: it points at a mechanism, and therefore at what they call "a potential therapeutic target."
Their conclusion, in their words: exposure "induces cardiovascular injury mediated through oxidative stress, inflammasome activation and nitric oxide dysregulation."
What it does not say
No people were studied. This is animal and cell work, and it measures tissue damage and signalling molecules, not heart attacks or heart failure in exposed humans. It does not establish that any product sold in the US harms anyone at label rates, and the authors do not claim it does. Read it as mechanism, not as a body count.
Where chlorpyrifos actually is right now
The regulatory picture is genuinely confusing, so here it is in order. EPA revoked all chlorpyrifos food tolerances in August 2021. The Eighth Circuit vacated that order, and its mandate on 28 December 2023 reinstated every tolerance. EPA then proposed, in December 2024, to revoke all of them except those covering 11 crops; the comment period reopened on 20 February 2025 and closed on 24 March 2025. No final rule has published since, and EPA's own status page says the reinstated tolerances stand until one does.
That is all about food. The non-food registrations are a longer list than people assume — EPA's status page runs to more than a dozen categories, including commercial ornamental production, forest trees, tobacco, cattle ear tags, golf-course turf, warehouses and ship holds, and utility poles and railroad ties. Almost all of it is commercial or agricultural. Only two of EPA's entries are residential at all: "Outdoor residential public health uses: fire ant mound (individual), mosquito control," and "Indoor residential: Ant and roach bait (containerized)."
The National Pesticide Information Center at Oregon State puts the indoor half in one sentence: "The only legal indoor use for chlorpyrifos is in containers with treated baits."
So there is no legal chlorpyrifos home spray and no fogger, and nothing you can broadcast around the inside of a house. Indoors, the only way it comes through your door is sealed inside a bait station. Outdoors, one residential use does survive — treating an individual fire ant mound — which is worth knowing if you treat mounds yourself.
What to do about it
Turn the box over and read the active-ingredient line. That is the whole action.
Our ant guide names borax, thiamethoxam and fipronil; our roach gel bait protocol names fipronil and indoxacarb. None of those is chlorpyrifos or any other organophosphate. If a station in your cupboard does name chlorpyrifos, swapping it for one of the baits those guides describe is the whole fix.
If a company treats your home rather than you doing it yourself, ask which product was applied and ask to see the label. A technician who will not tell you is telling you something. Our DIY versus professional guide covers what to look for.
What this changes on our pages
Nothing, and we would rather say so than manufacture urgency. None of the five brands in our comparison table is named in this research, and none of the products our guides point you at is an organophosphate. There is no purchase to make here and no commission in it for us. The useful move is reading a label you already own.