Toxic Metals in Wheat: Fertilizer Link Revealed

The invisible dilemma in the wheat grain: Where do the toxic metals come from?

Plants are the basis of our diet, but they sometimes pose invisible risks. They not only absorb vital nutrients through their roots, but also potentially toxic metals such as cadmium. For a long time it was unclear whether these undesirable substances mainly come from the soil or rather from the fertilizers used in agriculture.

A German-American research team led by the Helmholtz Center for Environmental Research (UFZ) and Duke University in the USA has now shed light on this mystery. The results of their study, published on November 27, 2025, show something astonishing: The majority of the toxic metals in wheat grains do not come primarily from the soil, but from mineral fertilizers.

• To determine the origin of the metals, the researchers used a special strontium isotope signature method. The chemical element strontium (Sr) exists in two isotopic forms, ⁸⁷Sr and ⁸⁶Sr, the ratio of which serves as a unique “fingerprint” for soils and fertilizers.
• By comparing the isotope ratio in wheat grains with that of the soil and fertilizer, they were able to prove where the strontium came from. Since strontium and cadmium are absorbed by plants via similar pathways, conclusions can also be drawn about cadmium.
• The studies, for which samples from 20 years were archived, showed that the toxic metals in the analyzed wheat grains mainly come from the fertilizer applied.
• Particularly high metal contents were found with exclusively mineral fertilization compared to organic fertilization. The studies were carried out in a region with very fertile black earth soils.
• Robert Hill, a doctoral student at Duke University and co-first author of the study, explained the method of “fingerprinting” the isotopes.

This groundbreaking finding has far-reaching implications for agriculture and food safety. The researchers conclude that a combination of mineral and organic fertilization could not only help reduce the content of toxic metals in grain, but also simultaneously increase the proportion of metals important for human nutrition. This opens up new avenues for more sustainable and healthier food production and shows once again how complex and yet decipherable the interactions between plants, soil and our ecosystem are.

Image: AI generated (Gemini)

Report (November 28, 2025) – Scientist