Adhesives: The glue that binds us together, or just a sticky situation?
If you find yourself stuck when it comes to the US Food and Drug Administration's (FDA) regulation of adhesives in food packaging, fear not – we've got plenty of puns ready to go. Stay glued to your screens to learn more...
Adhesives are an important and often necessary part of food packaging materials and articles across a variety of applications. From labels and tapes to multi-laminate, multi-layer constructions, adhesives are used to hold together the packaging that, in turn, holds many different types of food, under all foreseeable temperature conditions. Despite the ubiquity of adhesives in food packaging, the history of the regulation of such materials is surprisingly opaque, due in large part to how substances used as components of adhesives were historically addressed by the Agency in the past, and how they are assessed today...
21 C.F.R. Section 175.105
FDA's food additive regulation for adhesives appears in 21 C.F.R. Section 175.105 (Adhesives), and contains a list of substances that may be used in adhesive formulations. Unlike most other food additive regulations, however, this list is not exclusive. Indeed, many of the substances listed in Section 175.105 were never actually evaluated for use in food-contact applications when the food additive regulations were first promulgated, because it was largely assumed that adhesives would not contact food in significant quantities; instead, the adhesives regulation was promulgated as a matter of administrative convenience in response to a request from adhesive manufacturers that a regulation appear in the C.F.R. to identify those substances that were commonly in use at the time. Because of the unique nature of how adhesives are regulated, companies may potentially use substances that do not appear in Section 175.105 when evaluated in accordance with the discussion that follows below.
Stuck on the Adhesives Regulation
Section 175.105 describes a number of principles when contemplating the 'authorization' of the use of substances in adhesive formulations:
(1) The adhesive is either separated from the food by a functional barrier.
(2) It is used subject to the following additional limitations.
(i) When used in contact with dry foods, the quantity of adhesive that contacts packaged dry food shall not exceed the limits of good manufacturing practice.
(ii) In fatty and aqueous foods, the quantity of adhesive that contacts packaged fatty and aqueous foods shall not exceed the trace amount at seams and at the edge exposure between packaging laminates that may occur within the limits of good manufacturing practice.
We briefly discuss both situations below.
Functional Barriers
To understand the first possibility contemplated in Section 175.105, one first needs to appreciate the importance of the food additive definition and the Functional Barrier principle. As we discuss in part three of our StepLadder Series on Functional Barriers, a food additive is defined in the Federal Food, Drug, and Cosmetic Act as:
Any substance the intended use of which results or may reasonably be expected to result — directly or indirectly — in its becoming a component [of] or otherwise affecting the characteristic of any food.1
The term "functional barrier" is a legal term of art by which a component of packaging completely prevents migration of a packaging material to food, such that the component of food packaging necessarily cannot – by definition – be a food additive. Arguably, therefore, components of adhesives (including both substances listed in Section 175.105 and substances that do not appear in the food additive regulation), do not require a food additive regulation at all, because they are fully separated from food by a functional barrier and, by definition, are not "food additives" as that term is defined by the Federal Food, Drug, and Cosmetic Act. Indeed, one could argue that a listing in the adhesives regulation (or a lack thereof) when used in combination with a functional barrier is not legally... binding.
Adhesives in Contact with Dry Foods and Other Food Types
The other portion of Section 175.105 contemplates situations where a functional barrier may or may not be present – but where exposure to individual components of the adhesive will be de minimis because of how the adhesive is used in the construction of the food packaging material. Two common situations contemplated by the regulation are: (1) adhesives used in contact with dry foods; and (2) adhesives used in contact with aqueous and fatty foods where exposure occurs only in trace amounts at the seams and edges of the bound material(s).
Adhesives in Contact with Dry Foods
Historically, FDA assumed that adhesives that were used in contact with dry foods would not migrate in significant quantities to the dry food, based on a combination of the characteristics of the food, and the general absence of a suitable medium (i.e., aqueous or fatty food) for the adhesive to transfer. One common example of adhesives used contact with dry foods includes adhesives used to hold together paper and paperboard containers or plastic packaging that hold cereals and pasta. When used as intended, FDA largely expected that only a small fraction of the food would actually come into contact with the adhesive. For many years, FDA further accepted a default assumption that no more than 50 parts per billion (ppb) of the finished adhesive would contact dry food; therefore, individual components of the adhesive would contact food at proportionally lower quantities, and the further application of the Consumption Factor for adhesives would result in an upper-bound (100%) dietary concentration value significantly smaller than this amount. All of which is to say that, FDA assumed that the amount of adhesive that could be present in the diet resulting from its use in dry food applications, if any, would be very small.
Advances in analytical techniques and experience with adhesives in dry food applications has demonstrated that this assumption is quite accurate in certain instances – and perhaps less so in others. Where a functional barrier is not present, an adhesive or its constituent components could otherwise potentially migrate to food, and must be evaluated as a potential "food additive." Components of the adhesive used in this fashion, therefore, should be evaluated in a similar manner to other food-contact materials and articles. Further, companies are obligated to ensure that their food-contact materials and articles are safe for the intended use in accordance with FDA's suitable purity and Good Manufacturing Practice (GMP) requirements; therefore, the potential presence of impurities and byproducts of used adhesives in contact with dry foods is evaluated on a case-by-case basis, taking into consideration the actual intended use conditions and any available supporting information and data.
Adhesives in Contact with Aqueous and Fatty Foods
In contrast with the dry food assumptions set forth above, FDA assumes that adhesives used in food packaging materials placed in contact with aqueous and fatty foods may transfer constituents of the adhesive to food, when the food contacts the adhesive in trace amounts at the seams and edges of the food packaging. Implicit in both the food additive regulation and FDA's GMP requirements is that companies that use adhesives in food packaging should take reasonable steps to minimize contact between the adhesive and the food. This is achieved by, for example: (1) using only the amount of adhesive necessary to achieve the binding effect; (2) designing packaging such that the adhesive is applied in such a fashion that it should not remain exposed to contact food; and (3) taking appropriate measures to cure and cross-link the finished adhesive formulations such that any incidental contact that may occur will be minimized by proper manufacturing and drying.
Nevertheless, despite best efforts to minimize adhesive transfer between packaging and food, FDA recognizes that transfer can and does occur, and the potential exposure to components of the adhesive is often greater when placed in contact with aqueous and fatty foods than when placed in contact with dry food. Therefore, a company again has a responsibility to evaluate the suitable FDA status of the components of the adhesive itself, and the suitable purity of any potential impurities or byproducts in due course.
Practical Tips on the Evaluation of Adhesives Today
Due in no small part to the unique nature of how adhesives first appeared in FDA's food additive regulations, the default assumptions that were historically used, and how the state of the science has advanced in the years since, an evaluation and determination regarding the suitable FDA status of an adhesive used in food packaging applications today is often more sophisticated. One should consider, at a minimum:
- Whether a functional barrier (a legal term of art) is present or absent.
- In the presence of a barrier when the adhesive is used in contact with aqueous or fatty foods, the potential exposure resulting from contact that could occur at trace seams and edges.
- In the presence or absence of a functional barrier when the adhesive is used in contact with dry foods, an analysis as to whether the 50 ppb default assumption is reasonable, or if migration is known or expected to be higher.
- For steps 2 and 3, an evaluation of the upper-bound potential migration of, and dietary exposure to, the adhesive and its constituents, as well as a suitable purity assessment regarding the presence of potential impurities and byproducts that also could migrate from packaging to food.
Stick Around for More... FDA Regulation of Specialized Applications for Adhesives
Finally, note that adhesive substances used in specialized applications (e.g., pressure-sensitive adhesives used in the absence of a barrier for placement in direct contact with food, as in the case of produce labels; or multi-laminate adhesives used high-temperature applications, as in the case of retort pouches), are evaluated elsewhere in the food additive regulations, including Sections 175.125 ("Pressure-Sensitive Adhesives"), 177.1390 ("Laminate structures for use at temperatures of 250°F and above.") and 177.1395 ("Laminate structures for use at temperatures between 120°F and 250°F"), and will be the subject of future StepLadder discussions.
All of which is to say that adhesives are uniquely regulated, and should always be carefully evaluated for the intended use in food-contact applications (or... perhaps in not-food-contact applications!) on a case-by-case basis.
The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.