Food & Drink / Compounds / Maleic hydrazide

Maleic hydrazide in food: ingestion safety

Low risk

(People-specific data is limited; this page draws from human adult context.) Low acute oral toxicity (LD50 >5000 mg/kg in rats). Not irritating to skin. Dietary exposure from potato/onion residues well within safety margins. Historical mutagenicity concern (positive Ames test in some systems) largely attributed to contaminant hydrazine in early formulations; purified MH is negative in most modern genotoxicity assays. EPA: not likely carcinogenic.

What is maleic hydrazide?

The IUPAC name is 1,2-dihydropyridazine-3,6-dione.

Also known as: 1,2-Dihydro-3,6-pyridazinedione, MH, Royal MH-30, Slo-Gro.

IUPAC name
1,2-dihydropyridazine-3,6-dione
CAS number
123-33-1
Molecular formula
C4H4N2O2
Molecular weight
112.09 g/mol
SMILES
O=C1C=CC(=O)NN1
PubChem CID
5367

Risk for people

Low risk

Low acute oral toxicity (LD50 >5000 mg/kg in rats). Not irritating to skin. Dietary exposure from potato/onion residues well within safety margins. Historical mutagenicity concern (positive Ames test in some systems) largely attributed to contaminant hydrazine in early formulations; purified MH is negative in most modern genotoxicity assays. EPA: not likely carcinogenic.

Regulatory consensus

3 regulatory and scientific bodies have classified Maleic hydrazide. The classifications differ — that's the data.

AgencyYearClassificationNotes
EPA—Registered pesticide (plant growth regulator). Tolerances for potatoes, onions, tobacco, and other crops (40 CFR 180.175).
EU—Approved active substance. MRL 60 mg/kg for potatoes; 15 mg/kg for onions.
IARC—Group 3 — not classifiable as to carcinogenicity

Regulators apply different standards of evidence — animal-data weighting, exposure-pattern assumptions, epidemiological power thresholds — which is why two scientific bodies can review the same data and reach different conclusions. The disagreement is the data.

Where you encounter maleic hydrazide

  • Agriculture Post Harvest — potatoes (sprout suppressant), onions (sprout suppressant), garlic
  • Agriculture Field — tobacco (sucker control), turf/grass (growth retardant to reduce mowing)
  • Food Residues — stored potatoes, onions, tobacco products

Safer alternatives

Lower-risk approaches that achieve a similar outcome to Maleic hydrazide:

  • Chlorpropham (CIPC)
    Trade-offs: Withdrawn from EU market (2020) due to residue concerns. Still used in some countries. More effective at low temperatures.
  • 1,4-Dimethylnaphthalene (1,4-DMN)
    Trade-offs: Natural potato volatile. Low mammalian toxicity. US EPA registered. More expensive than MH.

Frequently asked questions

What products contain maleic hydrazide?

Maleic hydrazide appears in: potatoes (sprout suppressant) (agriculture post harvest); onions (sprout suppressant) (agriculture post harvest); tobacco (sucker control) (agriculture field); turf/grass (growth retardant to reduce mowing) (agriculture field); stored potatoes (food residues).

Why do regulators disagree about maleic hydrazide?

Maleic hydrazide has been classified by 3 agencies including EPA, EU, IARC, with differing conclusions. Regulators apply different standards of evidence (animal data weighting, exposure-pattern assumptions, epidemiological power thresholds), which is why two scientific bodies can review the same data and reach different conclusions. See the regulatory consensus table on this page for the full picture.

See Maleic hydrazide in the food app

Look up products containing maleic hydrazide, compare to alternatives, and explore the full data record.

Open in food View raw API data

Sources (1)
  1. — expert_curation

Reference data, not professional advice. Aggregates publicly available regulatory and scientific data; not a substitute for veterinary, medical, legal, or regulatory advice. Why we built ALETHEIA →