Agroscope, Federal Food Safety and Veterinary Office (FSVO)

Co-formulants in Plant Protection Products and their Residues in Food

Plant protection products contain active substances and co-formulants. Agroscope studied the residues of co-formulants on treated plants for the first time, thereby furnishing the basis for assessing risks posed to consumers.

Even when applied according to the regulations, plant protection products (PPPs) can form residues in food products of plant origin. The residues of PPP active substances are regulated in food legislation. A permissible maximum residue level is stipulated for each combination of active substance and food item. The Cantons and federal government check whether this is complied with.

Need for research identified

In addition to one or more active substances, PPPs usually contain various co-formulants which provide them with the necessary properties for application.  Although co-formulants may account for a significant proportion of a PPP, scant attention has been paid to their residues to date. The National Action Plan for Risk Reduction and Sustainable Application of Plant Protection Products therefore stipulates the need to improve knowledge on possible risks posed by co-formulants to consumers.

Solvents and surfactants are common co-formulants in PPPs

On behalf of the Federal Food Safety and Veterinary Office (FSVO), Agroscope conducted several studies between 2017 and 2020 and provided first insights into co-formulant residues, investigating what PPP formulation types are most frequently sold in Switzerland and which co-formulants they contain. Solvents and surfactants were identified as the most important co-formulant categories in terms of quantity.

Solvents evaporate, surfactants are washed off

In field trials, Agroscope showed that residues of several milligrams per kilogram can occur under practical conditions for representatives of these two co-formulant categories. In general, these residues decreased rapidly. With surfactants the decrease was generally caused by rain or irrigation wash-off, whilst with solvents it was primarily evaporation that was responsible for the observed decline.

Methods for estimating co-formulant residues

Based on the field trials, Agroscope has suggested a simple method for estimating the amount of co-formulant residues in food of plant origin. The method is based on publicly available data on residue concentrations of active substances directly after PPP application and their decrease over time.


  • The PPPs sold in Switzerland consisted on average of around 50% active substance, 30% water and 20% co-formulants. The most important PPP co-formulant categories in terms of quantity were solvents and surfactants.
  • The field trials conducted at Agroscope show for the first time that, as expected, co-formulants can lead to residues in food of plant origin.
  • Since extensive measurement data on co-formulant residues in food will not be available for the foreseeable future, it is important that methods be available for estimating these residues.
  • Since the method presented here allows co-formulant residues to be estimated with sufficient precision, it can serve as a basis for assessing consumer exposure.
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