What is zearalenone (ZEN)?
Zearalenone is unusual among mycotoxins: its principal effect is hormonal. It is a non-steroidal compound that binds oestrogen receptors, which makes it a reproductive problem in livestock long before it is a toxicological one.
Last reviewed 2026-11-11 · compiled by TripleBond Scientific Inc., Guelph, Ontario
Where it comes from
Zearalenone (ZEN, sometimes ZEA, CAS 17924-92-4) is a resorcylic acid lactone produced by Fusarium graminearum and Fusarium culmorum — the same field fungi that produce deoxynivalenol, which is why the two very often appear together in the same sample. Cool, wet conditions after flowering favour its formation, and it can continue to be produced in grain stored at high moisture.
It is metabolised to α- and β-zearalenol, of which α-zearalenol is substantially more oestrogenic than the parent compound, and it forms plant conjugates such as zearalenone-14-glucoside. As with DON, these modified forms can escape methods that target only the parent.
Commodities most affected
Maize above all, then wheat, barley, oats and sorghum, and the derived flours, feeds and silages.
What it does
Zearalenone and its metabolites bind to oestrogen receptors and produce effects that look like oestrogen excess. In pigs, which are the most sensitive farm species, this means vulval swelling and reddening, swollen mammary glands, infertility, reduced litter size and, in young animals, precocious development. Commercially the damage is reproductive performance, not mortality.
IARC classifies zearalenone in Group 3, not classifiable as to its carcinogenicity to humans.
The EFSA CONTAM Panel set a tolerable daily intake of 0.25 µg/kg body weight per day in 2016. JECFA had earlier set a provisional maximum tolerable daily intake of 0.5 µg/kg body weight per day. Exposure assessments in several European populations put intake close to the EFSA value for some consumer groups, which is part of why it stays on the regulatory agenda.
Regulatory limits in brief
In the EU, maximum levels are set under Regulation (EU) 2023/915, with particularly low levels for processed cereal-based foods for infants and young children. In Canada, the CFIA's RG-8 values for zearalenone in feed are regulatory guidelines. The full tables are on our mycotoxin limits page.
How laboratories measure it
Zearalenone fluoresces natively, so HPLC with fluorescence detection after immunoaffinity clean-up is a well-established route and remains common in dedicated ZEN methods. LC-MS/MS is the standard choice for multi-toxin panels and is necessary when α- and β-zearalenol or the glucoside conjugates have to be reported separately. ELISA is used for screening, with the caveat that antibody cross-reactivity with the zearalenols varies between kits and has to be understood before results are compared.
Because ZEN co-occurs with DON so reliably, many laboratories calibrate both in the same run, and a consistent supply of both standards from the same source simplifies method maintenance.
Zearalenone (ZEN) reference standard
Produced in our own Canadian laboratory, from analytical quantities through to gram and kilogram scale. Catalogue pricing is published for analytical sizes.
See the standard →Common questions
Is zearalenone an oestrogen?
It is not a steroid, but it binds oestrogen receptors and produces oestrogen-like effects. Its metabolite alpha-zearalenol is considerably more oestrogenic than zearalenone itself.
Which animals are most sensitive to zearalenone?
Pigs. The typical signs are vulval swelling and reddening, swollen mammary glands, infertility and reduced litter size, and precocious development in young animals.
What is the tolerable daily intake for zearalenone?
The EFSA CONTAM Panel set a tolerable daily intake of 0.25 micrograms per kilogram of body weight per day in 2016. JECFA had earlier set a provisional maximum tolerable daily intake of 0.5 micrograms per kilogram of body weight per day.
Does zearalenone occur together with deoxynivalenol?
Very often. Both are produced by Fusarium graminearum and Fusarium culmorum, so the two are commonly found in the same sample and are usually screened together.
Is zearalenone carcinogenic?
IARC classifies it in Group 3, not classifiable as to its carcinogenicity to humans. The established concern is its oestrogenic activity.
Sources
- IARC Monographs, Agents Classified by the IARC Monographs
- Commission Regulation (EU) 2023/915 on maximum levels for certain contaminants in food
- Canadian Food Inspection Agency, RG-8 Regulatory Guidance: Contaminants in Feed