Dimethylthiophosphate (DMTP)

If you eat a lot of fresh produce, live near farmland, or use pesticides at home, your body is almost certainly absorbing small amounts of insecticide. This urine test is one of the few ways to see that exposure directly, rather than guessing.

It captures a short window, roughly the past day or two, so it works best as a snapshot of recent contact with a common family of bug-killing chemicals. It is a research and monitoring tool, not a diagnosis, and a single reading tells you less than a pattern over time.

What This Marker Actually Reflects

DMTP (dimethylthiophosphate) is a leftover fragment your body creates when it processes organophosphate insecticides, a widely used class of bug-killing chemicals. It belongs to a group of six urine markers scientists call dialkylphosphates, which together are the standard way to check for recent organophosphate exposure.

The one thing to understand up front is that this marker is not specific to any single pesticide. It can come from the breakdown of more than a dozen different organophosphate insecticides, and it can even show up from pre-formed residues already sitting in food and the environment. So a high number tells you that dimethyl-type organophosphates got into your body recently, but not exactly which product or where.

It is also fast-clearing. Studies of these urine markers report elimination over roughly 6 to 24 hours, with most of an absorbed dose gone within one to three days. A spot urine sample therefore mostly reflects the previous 24 to 48 hours, not a long-term buildup stored in your body.

Where the Exposure Comes From

For most people who do not work with pesticides, food is the main route. In large population studies, this marker was one of the most commonly detected of the six urine markers, found above the detection limit in about 80.3% of U.S. samples between 2003 and 2012, and detectable in nearly every sample in some urban cohorts.

Diet repeatedly stands out as a driver. Higher fruit intake, fresh apples in particular, was linked to higher dimethyl-type marker levels in several groups, and in one urban Chinese study pork and poultry together explained over a third of the variation in organophosphate markers. Living in an agricultural area, having a garden or yard treated with pesticides, and applying pesticides at home also predicted higher exposure.

Occupational and take-home exposure produces the highest numbers. Children of pesticide applicators had a median around 25 micrograms per liter versus roughly 6 micrograms per liter in comparison children, children in agricultural communities ran medians of 17.5 to 41.0 micrograms per liter versus 6.5 micrograms per liter in an urban reference group, and workers actively thinning apples had levels about 50 times higher than farmworkers sampled outside peak spraying. (One microgram per liter is the same amount as one nanogram per milliliter, so these figures are directly comparable.)

Liver Function Signals

In large U.S. survey analyses, people with higher levels of this marker tended to have a higher AST/ALT ratio and a higher FIB-4 score, two combinations of blood tests used to flag possible liver strain or scarring, along with lower blood albumin and total protein. Albumin and total protein are proteins the liver makes, so lower values can hint at reduced liver output.

These are associations from snapshots of the population, not proof that the marker causes liver damage. Still, if your result is high, it is reasonable to look at your standard liver blood tests alongside it rather than treating either in isolation.

Heart Disease and Cancer Associations

One analysis of older U.S. women found that non-smokers aged 60 to 85 in the highest quarter of this marker were about 3 times as likely to have cardiovascular disease as those in the lowest quarter (odds ratio 3.0, 95% CI 1.4 to 6.4), and about 2.7 times as likely to have had cancer (odds ratio 2.7, 95% CI 1.3 to 5.9).

This is a cross-sectional comparison, meaning exposure and disease were measured at the same time, so it cannot establish cause and effect. It is a reason to pay attention and reduce avoidable exposure, not evidence that the marker predicts your personal odds of these diseases.

Reproductive and Developmental Findings

Reproductive findings are mixed. In men attending an infertility clinic, higher levels of this marker were linked to lower sperm motility, and in Mexican agricultural workers it was tied to lower FSH and LH, two hormones that regulate fertility. In healthy male sperm donors, this marker again stood out as the main contributor to reduced sperm movement.

Pregnancy and child studies do not point in one direction. One high-risk cohort found no overall link to autism, though girls showed a possible trend, with about 1.64 times the odds per doubling of the pregnancy level (95% CI 0.95 to 2.82, a range that includes no effect). Separate research on the broader summed dimethyl marker group, not this marker alone, linked the highest prenatal exposure to about 7 fewer IQ points at age 7 compared with the lowest. Whether that finding applies specifically to this single marker has not been shown.

Why One Reading Is Not Enough

Because this marker clears within a day or two, a single test is a mood ring, not a portrait. Repeated-measures studies make this concrete: in children, day-to-day variation within the same child was 3 to 7 times larger than the differences between children, and during pregnancy the marker had poor reproducibility across visits, with reliability scores between 0.19 and 0.28 (where 1.0 would mean perfectly stable readings).

The practical takeaway is that trends beat single numbers here. A baseline, a repeat after you change your diet or home pesticide habits, and periodic checks tell you far more than one value. If you want to know whether cutting back on a suspected source actually reduced your exposure, retesting a few times is the only way to see it, since the number responds quickly to recent intake.

When Results Can Be Misleading

The biggest source of confusion is timing and diet. A meal of conventionally grown produce in the day before your test can lift the number even in someone with low overall exposure, and a quiet couple of days can make a habitually higher-exposed person look clear.

• Recent food: fruits and vegetables shortly before testing can raise the reading without reflecting your typical exposure.
• Urine dilution: how concentrated your urine is affects the raw number, which is why labs adjust for creatinine or specific gravity.
• Short clearance window: the marker mostly reflects the past 24 to 48 hours, so one sample can miss or exaggerate your usual level.
• Non-specific source: it cannot tell you which pesticide you encountered, or whether it came from an intact product or a pre-formed residue in food.

What to Do With an Unexpected Result

If your level is high, the first move is not treatment, it is a source hunt. Review recent diet, home and garden pesticide use, and any occupational or take-home contact, then retest after adjusting the most likely source. A high value that drops after you switch to more organic produce or stop a home spray tells you the source was real and controllable.

For interpretation in context, this marker is usually read alongside the other five dialkylphosphate urine markers to gauge total exposure, and sometimes with pesticide-specific markers that can point toward a likely parent chemical. In suspected poisoning or heavy occupational exposure, blood cholinesterase tests measure whether the chemical is actually affecting nerve enzymes, which this exposure marker does not. If you are pregnant, exposed at work, or have a persistently high result, an occupational or environmental health clinician is the right person to help you build a workup rather than acting on one number alone.