Residues of quaternary ammonium compounds in food

Quaternary ammonium compounds (QAC) are active biocide substances widely used in disinfectants utilised in the food industry to sanitise surfaces and facilities. Its main use derives from its properties:

• They have a broad biocide spectrum, being effective against the most common pathogens in the food industry
• They are safe when properly handled by operators
• They do not cause corrosion or staining of most materials used in the food industry
• They have certain detergent properties
• Their cost is moderate

The QACs mainly used in biocides for food industries are didecyldimethiamonium chloride (DDAC) and benzalkonium chloride (BAC), whose structure is shown in Figure 1.

Figure 1. Molecular structure of didecyldimethylammonium chloride (DDAC) and benzalkonium chloride (BAC)

Coincidentally, QACs are used as pesticides as well as biocides in Europe. This fact, together with bad practices detected in the use of QACs as pesticides and biocides, has caused some confusion in the food sector in the last 3 years about the use of biocides on surfaces in contact with food and the potential contamination of food for this reason.

Specifically, the following bad practices  have been detected as a potential source of food contamination by QACs:

• Improper use as a phytosanitary product.
• Presence as preservative in phytosanitary products, fertilisers and other plant defence means.
• Contamination during cultivation through treated irrigation water, soil or harvesting crates.
• Cross contamination due to the disinfection of the washing water.
• Cross contamination from equipment, surfaces and even hands of employees disinfected with this type of chemicals.

With regard to residues in food, all pesticides have maximum residue levels (MRLs) assigned for the foods mentioned in Annex I of Regulation (EC) 396/2005  (infant and baby foods are excluded). This regulation by default sets forth an MRL of 0.01 mg/kg for most pesticides in food and feed. As of 2012, the LMR value for DDAC and BAC has undergone several modifications due to the detection of residues of these compounds at levels higher than those allowed in different foods and, consequently, as a result of the study of QACs residue presence in different foods and the assessment of the potential danger to consumers from exposure to these levels. Thus, a temporary MRL of 0.5 mg/kg was established in July 2012 for DDAC, which was later reduced to 0.1 mg/kg in October 2014 (Regulation (EU) 1119/2014). Additionally, a transitory period was established to enable the adaptation of the Member States, Authorities and operators of the food industry to this 0.1 mg/kg value. This transitional period ended on 11^th August 2015 and after that, foods with residual QAC levels above 0.1 mg/kg were not be allowed on the market.

On the other hand, QACs, as biocidal active substances, are regulated by Regulation (EU) no. 528/2012, on the marketing and use of biocidal products, known as the BPR Regulation. Very briefly, this Regulation sets forth a procedure to evaluate active biocide substances according to their biocidal, toxicological and harmful properties, among others. Once an active biocide substance has been approved, biocidal products containing such active substance must undergo a similar evaluation and authorisation procedure to reach the market. Article 19(1)(e) of the BPR Regulation requires establishing MRL values for active substances under evaluation, which will be applicable once the biocidal products formulated with these active substances are approved under this Regulation. Both DDAC and BAC are in their evaluation period under the BPR Regulation, and their approval to be used in the food industry is expected to occur during 2016. At this time, the MRL values established for these compounds will be known according to the BPR Regulation, which may coincide or not with those established by Regulation (EU) 1119/2014.

While this approval takes place, biocides used in the food industry are regulated by the respective national regulations. In Spain, the current regulations are Royal Decree 3349/83. This regulation establishes, for all biocides used in the food industry, the obligation to rinse the surfaces in contact with food with drinking water after applying the disinfectant, in order to eliminate the biocide residues and prevent their transfer to the foods. Therefore, the application of biocides in the food industry in compliance with the current regulations should not lead to food contamination by biocides residues.

Therefore, the regulatory framework in force regarding the presence of biocide residues in food, more specifically those based on DDAC or BAC, establishes that:

1. The use of biocides based on DDAC or BAC in the food industry meets all legal requirements and there are no restrictions for their use in this regard.
2. Foods on the market cannot contain DDAC or BAC levels higher than 0.1 mg/kg (0.5 mg/kg temporarily until 11^th August 2015), according to Regulation (EU) 1119/2014, on pesticide residues in food.
3. The surfaces in contact with food must be rinsed with drinking water after applying biocides to eliminate the residues.
4. The approval of biocidal active substances according to the BPR Regulation will set MRL values for these active substances that may or may not match those previously established.

Therefore, the presence of DDAC and BAC residues below the MRL values established for foods in the market is currently allowed. However, according to the current regulation, these potential residues should not originate from the use of biocides in disinfection tasks in the food industry, since the current regulation establishes the obligation to rinse surfaces in contact with food.

On the other hand, the industry involved in the manufacture and marketing of QACs has strongly opposed the MRL values established in Regulation (EU) 1119/2014. This opposition is based on the fact that QACs are predominantly used as biocides and not as pesticides. Therefore, the current MRL values, applied on the basis of their use as a pesticide, do not adequately reflect the conditions and safety of their use in the food industry. As a reference, in the United States the use of biocide solutions containing QACs in a range between 200 and 400 ppm without the need to rinse the surfaces is allowed. In this case, the Environmental Protection Agency (EPA) considers that the consumption of food in contact with these unrinsed surfaces does not represent a health risk.

This situation can potentially change within a few months or years due to the fact that different MRL values or usage indications are established for DDAC and BAC as a result of their approval according to the BPR Regulation or to the modification of MRL values based on the allegations made by the industry or as a result of the evaluation of new data in the coming years. In any case, biocides based on quaternary ammonium compounds continue to be the preferred choice in the food industry, due to their excellent properties and relative safe application. These biocides are an effective tool to ensure the safety of food and its correct use for disinfecting surfaces in the food industry should not cause problems from the food residues point of view.