Researchers find rubber-related chemicals in Swiss milk

The researchers say one possible source of contamination could be cow milking systems. Keystone-SDA

Swiss scientists have detected several rubber-related chemicals in Swiss raw milk. Their study suggests that dairy equipment may be an overlooked source of contamination.

For the study, a research team analysed milk samples from 17 Swiss farms, the Swiss Federal Institute of Technology Lausanne (EPFL) said on Monday. At least one of the four rubber chemicals being tested for was detected in seven of the 17 samples. In three samples from Alpine farms located far away from busy roads, the researchers found none of the substances.

The effects of the substances found on human health are as yet unknown. Follow-up studies are planned. However, the concentrations measured in the raw milk were generally low. The results of the study were published in the journal Food Chemistry X.

Milking systems or tyres

The researchers considered one possible source of contamination to be particularly surprising: the milking systems themselves.

While examining hoses, seals and other rubber components used in milk production, they identified 14 different chemicals. According to study leader Florian Breider, it is astonishing that these compounds originated from materials that are legally approved for contact with food.

Among the materials from the milking systems examined, the researchers found, among other things, the compound 6PPD-quinone, which is known to be harmful to certain fish species. This substance is not intentionally added to rubber but is produced by oxidation as the material ages.

Another possible source of the contaminants is the abrasion of tyres and road surfaces. Worldwide, an estimated six million tonnes of rubber particles are released into the environment every year as a result. These particles can reach agricultural land and enter the food chain via the air, runoff water or fertilisers.

Further studies are now set to investigate how concentrations fluctuate across the seasons. In addition, the exact pathways by which the chemicals enter milk are to be investigated, in order to support the development of safer materials for contact with food.

The Federal Office for Food Safety and Veterinary Affairs and the Agroscope research institute also collaborated on the study.

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Translated from German, reviewed by an English Department journalist.