Fenitrothion フェニトロチオン（MEP）
Also known in Japanese as MEP・スミチオン
Organophosphates: Block the action of the enzyme that stops nerve signals (acetylcholinesterase). Used for a long time.
In Japan
- Registration
- Registered as a pesticide (first registered December 26, 1961). 50 formulated products contain it.
- Main registered crops
- rice (paddy), Japanese pear, legumes, trees, peach, soybean and others (110 crop names in the registered uses)
- Toxicity class
- Active ingredient: Ordinary substanceClasses of the 50 formulated products (diluted products sold): ordinary substance 45, deleterious substance 5Classes under Japan's Poisonous and Deleterious Substances Control Act.
- ADI (acceptable daily intake)
- 0.0049 mg per kg of body weight per day
- ARfD (acute reference dose)
- 0.036 mg per kg of body weight
- Evaluation
- Food Safety Commission of Japan, November 16, 2023
ADI: the amount considered to have no effect on health even if eaten every day for a lifetime. ARfD: the amount considered to have no effect on health when eaten at one time (within 24 hours). Both are set by the Food Safety Commission of Japan, mainly from animal studies.
In Japan's national residue testing (fiscal 2024)
| Produce | Detected / tested | Detection rate | Over the limit |
|---|---|---|---|
| Domestic | 10 / 4,787 | 0.2% | 1 |
| Imported | 0 / 3,503 | 0.0% | 0 |
Found in domestic foods: edamame, turnip roots, shungiku (garland chrysanthemum), other citrus fruits, Welsh onion (including leek), apple, lemon, Japanese pear (max. 0.5 ppm)
Tests are counted as pesticide × sample. Any detection counts as “detected” — it does not mean the limit was exceeded. For pesticides outside the top 20, figures are summed from the food-by-food tables of the full report.
Evaluations abroad
- WHO acute toxicity class
- II (Moderately hazardous), LD50 503 mg/kgBased on the toxicity of the undiluted active ingredient given once, mainly to rats by mouth (LD50 = the dose that kills half; the smaller, the stronger the acute toxicity). It is not an assessment of the safety of residues in food.
- EU
- Not approved in the EUEU ADI: 0.005 mg/kg bw/day; ARfD: 0.013 mg/kg bw
- IARC (carcinogenicity)
- No matching entry in the IARC list (not evaluated or out of scope, including Group 3)
Good to know
- An organophosphate insecticide used in Japan for a long time (brand names such as “Sumithion”).
- In the MAFF survey of honeybee poisoning incidents (fiscal 2013–2015), among the insecticides found in honeybees that died during the rice stink bug control season, this active ingredient accounted for 1 (38 in total, with overlaps).
Related explainers
Sources
- FAMIC (Food and Agricultural Materials Inspection Center), pesticide registration information (as of Sept. 30, 2026) (Japanese)
- Food Safety Commission of Japan, risk assessment report on Fenitrothion (November 16, 2023) (Japanese)
- MHLW, results of pesticide residue testing in foods, fiscal 2024 (Japanese)
- WHO Recommended Classification of Pesticides by Hazard 2019
- EU Pesticides Database (Fenitrothion)
Last checked 2026-10-01. Registrations and evaluations change over time. This page is a translation of our Japanese page; if they differ, the Japanese page is the reference.