Methamidophos メタミドホス
Organophosphates: Block the action of the enzyme that stops nerve signals (acetylcholinesterase). Used for a long time.
In Japan
- Registration
- Not found in FAMIC's lists of registered or expired ingredients (never registered as a pesticide in Japan, or registered under another name).
- ADI (acceptable daily intake)
- 0.00056 mg per kg of body weight per day
- ARfD (acute reference dose)
- 0.003 mg per kg of body weight
- Evaluation
- Food Safety Commission of Japan, February 14, 2024
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 | 3 / 1,585 | 0.2% | 2 |
| Imported | 1 / 3,816 | 0.0% | 0 |
Found in domestic foods: turnip roots, carrot, tomato (max. 0.1 ppm)
Found in imported foods: corn (maize) (max. 0.2 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
- Ib (Highly hazardous), LD50 30 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: 0.001 mg/kg bw/day; ARfD: 0.003 mg/kg bw
- IARC (carcinogenicity)
- No matching entry in the IARC list (not evaluated or out of scope, including Group 3)
Good to know
- Not registered as a pesticide in Japan. It is also a substance formed when acephate breaks down, and maximum residue limits have been set for it. Methamidophos was what was detected in the 2008 poisoning incident involving Chinese frozen gyoza.
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 Methamidophos (February 14, 2024) (Japanese)
- MHLW, results of pesticide residue testing in foods, fiscal 2024 (Japanese)
- WHO Recommended Classification of Pesticides by Hazard 2019
- EU Pesticides Database (Methamidophos)
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.