Points to Consider for the Use of Recycled Plastics
in Food Packaging:
Chemistry Considerations

This informal guidance was developed to assist manufacturers of food packaging in evaluating processes for producing packaging from post-consumer recycled plastic. The law, regulations and specific letters take precedence over these informal considerations. Comments on this document are encouraged.

This document supersedes the "Points to Consider" dated May, 1992. No substantive changes have been made.

The purpose of this document is to highlight the chemistry issues that manufacturers of recycled plastic should consider during the evaluation of a recycling process to produce material suitable for food-contact application. The possibility that chemical contaminants in plastic materials intended for recycling may remain in the recycled material and could migrate into the food it contacts is one of the major issues to be resolved before the safe use of recycled plastics for food contact can be assured. Other aspects of plastics recycling, such as microbial contamination and structural integrity, are also important, but will not be discussed in any detail in this document.

The suggestions expressed herein are expected to change as new knowledge is acquired and should not be regarded as fixed or all-inclusive. The general regulations under Part 177 of Title 21 of the Code of Federal Regulations (Indirect Food Additives: Polymers) and the requirements specified in 21 CFR 174.5 relating to good manufacturing practice serve as the framework for this document. In particular, 21 CFR 174.5(a)(2) states, "Any substance used as a component of articles that contact food shall be of a purity suitable for its intended use."

Historically, glass, steel, aluminum, and paper have been recycled for food-contact use. Post-consumer use contamination has not been a major concern with glass and metals. These materials are generally impervious to contaminants and are readily cleaned at the temperatures used in their recycling. In addition, pulp from reclaimed fiber in paper and paperboard may be used for food-contact articles provided it meets the criteria in 21 CFR 176.260.

Manufacturers of food-contact articles made from recycled plastic must assure that recycled material, like virgin material, is of suitable purity for food-contact use, and will meet all existing specifications for the virgin material. Several general methodologies exist by which plastic packaging can be recycled, and each introduces distinct concerns regarding the contaminant residues that may be present in post-consumer material. A preliminary discussion of the basic types of recycling is presented along with some specific concerns associated with each. Following this, an approach is described for estimating the maximum level of a chemical contaminant in the recycled material that would be acceptable and not compromise the public health. Finally, a protocol is suggested by which chemistry data can be developed that would be used to evaluate the adequacy of a recycling process to remove chemical contaminants.

Recycling Processes

There are three distinct approaches to the recycling of post-consumer plastic packaging materials. The packaging may (1) be reused directly, (2) undergo physical reprocessing (e.g., grinding and melting) and reformation, or (3) be subjected to chemical treatment whereby its components are isolated and reprocessed for use in manufacture. The Environmental Protection Agency (EPA) has adopted a now widespread nomenclature that refers to physical reprocessing as secondary recycling (2°), and chemical processing as tertiary recycling (3°). "Primary recycling" (1°) refers to use of pre-consumer industrial scrap and salvage to form new packaging, a common occurrence in industry.

EPA considers "recycling" to be the processing of waste to make new articles. Since bottles intended for reuse are not made to be discarded and become waste, reuse is not considered recycling by EPA. Rather, reuse is regarded simply as one form of source reduction, i.e., minimizing the amount of material entering the environment. Although EPA does not consider reuse to be a recycling process, using the 1°, 2°, and 3° conventions above, it could be considered "zeroth order" recycling. In simple rescue, the package remains intact and is reused in its original form. In secondary and tertiary recycling, the original package is destroyed and new packaging is formed from the remains.

Reuse

Glass bottles have a long history of being reused. Milk, bottled water, beer, and soft drinks can be purchased in bottles that are returned, washed, sterilized, and then refilled. Plastic bottles used in this manner must be cleansed by washing and sanitizing so that contaminant residue levels (including any food residue) are low enough so as to not adulterate the food.

The reuse of plastic bottles presents several special concerns. Plastic bottles are more likely than glass to absorb contaminants that could be released back into food when the bottle is refilled. Analytical protocols may need to be developed to demonstrate that, after cleaning, contaminant levels are sufficiently low so that the contents of the refilled bottle would not be adulterated. In addition, while washing and sanitizing or sterilizing the bottles must be shown to be effective for removing contaminants to an acceptable level, the cleansing operation should not have an adverse effect on the integrity of the bottles. Bottles must retain structural integrity and be functional after each cycle of washing and reuse. Plans for reuse of plastic bottles could include, for example, a limit on the number of use cycles a bottle will undergo, an expiration date for the use of such articles, a visual inspection system for gross contamination and damaged bottles, or some combination of these approaches. A limit on the number of use cycles could be difficult to implement, requiring a method for monitoring the number of times a bottle has been reused.

Safety concerns with plastic bottles intended for reuse can be minimized in a variety of ways. The most important may be educating the consumer to avoid storing household chemicals such as garden pesticides and automotive fluids in reusable containers. Labeling the bottles, for example "Food Use Only", is one part of the education process. Requiring a deposit on the bottles could be a useful strategy; the consumer would be less likely to contaminate a bottle that required an investment. Devices, such as hydrocarbon "sniffers" or color scanners, could be a part of the screening process for chemical contaminants. Reusable containers, unlike those intended for recycling, would be returned directly to the store by the consumer or collected at the home by the distributor, thereby adding a measure of control over the source.

Pre-consumer Scrap: Primary Recycling

Primary recycling of industrial scrap produced during the manufacture of food-contact articles is not expected to pose a hazard to the consumer. The recycling of this scrap ("home scrap" as defined by the EPA in 56 FR 49992) is acceptable, provided good manufacturing practices are followed. If the home scrap were collected from several different manufacturers, however, concern would arise that the level and type of adjuvants would not comply with existing regulations. Primary recycling will not be discussed further.

Physical Reprocessing: Secondary Recycling

Physical reprocessing involves grinding, melting, and reforming plastic packaging material. The basic polymer is not altered during the process. Prior to melting and reforming the polymer, the ground, flaked, or pelletized resin is washed to remove contaminants. The size of the resin flakes or pellets could influence the effectiveness of the washing. Smaller particles would provide a greater surface area for enhancing the effectiveness of the wash. Different resins may also undergo different reforming conditions, such as different processing temperatures, the use of vacuum stripping, or other procedures, that could influence contaminant levels. During the grinding or melting phases, the reprocessed material may be blended with virgin polymer.

Recyclers must be able to demonstrate that contaminant levels in reformed plastic have been reduced to sufficiently low levels to assure that the resulting packaging would not adulterate food. To produce a resin with the desired qualities, however, additional antioxidants, processing aids, or other adjuvants may need to be added to the recycled resin. The type and total amount of additives would have to be consistent with existing regulations. Any adjuvants already in the plastic should not react during the recycling process to form unregulated additives. Recycled resins that require new additive or amounts of additives in excess of what is currently regulated would require a food additive petition for food-contact use.

A secondary recycling process presents some unique problems that may cause it to be inappropriate for the production of food-contact articles, particularly if the recycler had little or no control over the waste stream entering the recycling facility. Where effective source control could be established, however, the problem of commingling post-consumer food-contact materials with other post-consumer plastics would be minimized or eliminated. Nevertheless, even if all the resin were from food-contact materials, limitations on food type or condition of use could be compromised. That is, an additive regulated for use with aqueous food or for refrigerated use, only, could be incorporated into packaging intended for high-temperature use with fatty foods. The result would be a food-contact article that does not comply with regulations. This concern may be mitigated by development of sorting procedures that result in reprocessing of only a single characteristic container, e.g., a polyethylene terephthalate ester (PETE) soda bottle.

Submissions to the Agency involving 2° recycling should address these concerns by incorporating appropriate information regarding controls on the source of the recycled resin, use limitations on the recycled packaging (such as use at room temperature or below), or food-type restrictions (such as dry or aqueous foods only).

Chemical Reprocessing: Tertiary Recycling

Chemical reprocessing may involve depolymerization of the used packaging material with subsequent regeneration and purification of resulting monomers (or oligomers). The monomers are then repolymerized and the regenerated or reconstituted polymer is formed into new packaging. Regenerated monomer, polymer, or both may be blended with virgin materials. The regeneration process may involve a variety of monomer/polymer purification steps in addition to washings, such as distillation, crystallization, and additional chemical reaction.

The primary goal in this type of recycling is the regeneration of purified starting materials. The use of additional adjuvants in tertiary recycling would have to comply with the regulations.

The Use of a Functional Barrier

The use of 2° or 3° recycled material as a non-food-contact layer of a multilayer food package is a potential application for recycled plastics. Such use would not present a concern about potential contaminant migration into food as long as the recycled resin was separated from the food by an effective barrier made from a regulated virgin resin or other appropriate material, e.g., an aluminum film.

To demonstrate that a regulated virgin resin functions as an effective barrier to migration of contaminants, the recycler should first subject intentionally contaminated resin (see below) to the recycling process. The recycled resin should then be incorporated into the finished article using virgin resin as the functional barrier, and extraction studies should be performed with food-simulating solvents to demonstrate the effectiveness of the virgin resin as a functional barrier. (See the Recommendations for Chemistry Data for Indirect Food Additive Petitions, June, 1995, from CRB {Recommendations}.) If other data are available that establish sufficient impermeability of a given thickness of a particular resin under anticipated time/temperature use conditions, those data could serve to replace extraction experiments.

Exposure to Contaminants

In the case of PETE, a density of 1.4 g/cm³ and an assumed container thickness of 20 mils gives a package with a mass-to-surface area ratio of 460 mg/in². Further assumptions include: 10 g of food contacts one square inch of container, a consumption factor (CF) of 0.05, and a food-type distribution factor (f_T) of 1.0 (the aqueous f_T for PETE is 0.97) reflecting the use of PETE almost exclusively in beverage bottles (see our "Recommendations"). The relationship between dietary concentration and the CF, f_T, and migration level from package to food is:

where M is the concentration of migrant into a food-simulating solvent, i, where i represents the four simulated food types: aqueous, acidic, alcoholic, and fatty foods. Using the parameters noted above leads to:

1 ppb in the diet = 0.05(M)(1.0)

and M = (1 x 10^-9g contaminant/g food) / (0.05)

= 2 x 10^-8g contaminant/g food.

Then, (460 x 10^-3g packaging/in²) / (10 g food/in²) = 0.046 g packaging/g food

4.3 x 10^-7 g contaminant/g packaging,

or 430 ppb of contaminant in the packaging material. In other words, if a contaminant were present at 430 ppb in the PETE container made from the recycled material and if 100% migration of the contaminant into food were assumed (a conservative assumption for room-temperature applications of a high barrier material like PETE), the concentration of the contaminant in the daily diet would be 1 ppb.

For polymers other than PETE, the amount of residual contaminant that would result in an exposure greater than the proposed upper limit would vary. Using the consumption factors for food packaged in various polymers from our "Recommendations" and conservatively assuming all food types are used with each polymer, the following table gives examples of the residue levels in several polymers that would give a dietary concentration of a contaminant below 1 ppb (assuming a 20 mil thick container):

Thus, to achieve dietary concentrations below 1 ppb, individual chemical contaminants should not be present at, for example, greater than 430 ppb in PETE or 96 ppb in polyolefin containers. The maximum acceptable contaminant levels calculated using the above assumptions are within the capabilities of modern analytical techniques. It must be emphasized that the calculated maximum acceptable contaminant levels depend on the thickness of the packaging as well as the intended use(s). The CF's given above assume that 100% of the food-contact applications will use recycled resin. If a specialized use for the recycled resin can be documented, a lower CF may be used to calculate a maximum acceptable contaminant level. The contaminant limits calculated above also assume 100% recycled resin content in the finished article. In many instances, recycled resin is expected to be blended with virgin resin; this will have the effect of lowering the exposure to the contaminant.

The preceding discussion results from using a worst-case assumption for articles entering the recycling stream. Currently, data that demonstrate or allow a prediction of the actual incidence of contamination of recycled articles are not available. When such data become available, that information can be factored into the exposure calculations and resulting contaminant levels.

Reuse of plastic bottles would not present the same concerns of chronic, low-level exposure to contaminants. Even if a contaminated bottle entered the food stream, it would affect only one or a few consumers at a time before being returned, washed, and refilled. It is unlikely that the same bottle would return to the same consumer. It is also unlikely that the same contaminant would be present in another bottle subsequently obtained by the same consumer. Because the bottles remain intact between uses, contaminants would not be dispersed into other bottles as during recycling processes. Therefore, for reuse of plastic beverage bottles, safety concerns would focus on acute exposure to toxic contaminants, not chronic exposure as for recycled materials.

Concerns regarding acute exposure to contaminants from reuse of plastic bottles are, in fact, currently addressed, with respect to milk containers, in the FDA publication Grade A Pasteurized Milk Ordinance--1989 Revision (Public Health Service/Food and Drug Administration, Publication No. 229, p. 73)⁽¹⁾. Three points are relevant to the current considerations. Part 7.d. states, "A device shall be installed in the filling line capable of detecting in each container before it is filled, volatile organic contaminants in amounts that are of public health significance...Any container detected by the device as being unsatisfactory must be automatically made unusable to prevent refilling." Part 7.g., "The container shall not impart into the product pesticide residual levels or other chemical contaminants in excess of those considered acceptable under the Federal Food, Drug and Cosmetic Act, as amended and regulations issued thereunder." Part 7.h. concludes, "The phrase 'Use only for food' shall appear on all containers." The ordinance also contains a list of cleaning and sanitizing criteria for multi-use plastic containers. These sanitation requirements for milk would be appropriate to reduce acute exposure to contaminants to levels low enough to protect the consumer for other applications where plastic containers may be reused.

Chemical Contaminants Analysis

The ability of 2° or 3° recycling to remove contaminants from plastic containers or packaging that has been subjected to consumer misuse or abuse, for example, through storage of pesticides or automotive chemicals, should be demonstrated. Consumer misuse can be simulated by exposing plastic packaging (either in container form or as flaked or ground resin) to selected surrogate contaminants. Following exposure of resin to the surrogate contaminants, the resin would be subjected to the recycling process. Subsequent analysis of the resin for those contaminants would demonstrate the efficacy of the recycling process.

The materials used for the simulation of consumer misuse should bracket a variety of chemical and physical properties. The model contaminants should be "common" materials accessible to the consumer and include a volatile nonpolar organic substance, a volatile polar organic substance, a nonvolatile nonpolar organic substance, and a nonvolatile polar organic substance. Examples of such materials would be toluene, chloroform, lindane, and diazinon, respectively. Toluene and chloroform may be components of cleaning solvents, while lindane and diazinon are common insecticides. A toxic salt, such as disodium monomethylarsonate (crabgrass killer), would complete the range of properties noted. The study should include a polymer-specific contaminant. For PETE, a solvent such as ortho-cresol, which is known to significantly swell the polymer, may be appropriate. For polystyrene, PVC, and polyolefins, a solvent such as acetone or trichloroethane may be appropriate.

If tests are to be performed in a commercial food-processing plant rather than in a laboratory separated from food processing or food packaging activities, the practicality of using toxic materials may be questioned. In such cases, the use of non-toxic model contaminants that have chemical and physical properties similar to the toxins suggested above may be used. Rather than lindane and diazinon, the use of vitamin A acetate as a nonpolar, nonvolatile model contaminant and benzophenone as a polar, nonvolatile contaminant would be acceptable. These are suggestions for the types of contaminants that should be investigated. The actual model contaminants used in any study should be discussed with the agency.

Plastic containers may be contaminated by filling with the model contaminants, either "neat" or in "at use" concentrations. An alternative that would reduce the amount of potentially hazardous wastes would be to soak several kilograms of flaked or ground plastic (the form actually used in the recycling process) in the selected contaminants, again either "neat " or with "at use" concentrations. A mixture, or "cocktail", of the contaminants often could be used. In this case, the components of the cocktail should not react with each other. Once the bottles are filled or after thoroughly mixing the contaminants with the flakes, the bottles or flakes should be stored sealed for two weeks at 40°C with periodic agitation. After draining the contaminants, the concentration of each should be determined. The contaminated resin should then be subjected to the proposed recycling process, and regenerated components or packaging material formed from the reprocessed polymer should be analyzed for residual contaminants. This approach represents a worst-case scenario, i.e., all material entering the recycling stream is assumed to be contaminated.

For 3° recycling only, the material to be depolymerized may be spiked with contaminant. A spiking level for each contaminant of 0.1% (1000 ppm) by weight of resin being subjected to depolymerization is suggested as a reasonable worst-case level. Because 3° recycling involves regeneration and purification of monomers (or oligomers) it is expected that the amount of residual contaminant in the regenerated polymer will be significantly less than 500 ppb (see "Exposure to Contaminants"). Thus, this spiking protocol may be a relatively straightforward means of simulating worst-case consumer abuse and be useful for demonstrating the ability of the 3° recycling process to remove contaminants.

Testing protocols should be submitted to FDA for comment before any contamination studies are done. All analyses should be validated as discussed in our Recommendations for Chemistry Data for Indirect Food Additive Petitions.

If a proposed recycling process cannot be shown to remove contaminants to an acceptable upper-limit of dietary exposure under the 100% consumer contamination scenario discussed above, then additional justifiable factors could still lead to a conclusion that the recycled package will not introduce contaminants into the diet at unacceptable levels. Additional factors relevant to the determination of the upper-limit of dietary exposure include the use of recycled/virgin blend, source controls, restricted uses, the fraction of contaminant that migrates into food or a food stimulant, or the use of a functional barrier. Consideration of each additional factor must be supported by adequate documentation (e.g., studies on a specific source control program, actual extent of contaminated material entering the recycling stream, and research to demonstrate that the recycled resin is separated from food contact by a functional barrier).

Conclusions

A general approach has been proposed for obtaining chemistry data that demonstrate the ability of a 2° or 3° recycling scheme to reduce chemical contaminants in recycled material to what may be considered acceptable levels. A recycling scheme reflecting GMP should produce a product that would result in a dietary exposure of the order of 1 ppb or less for any one chemical contaminant. Recycled material is expected to meet all specifications existing for the virgin material.

Contamination from consumer misuse is not the only consideration. The amounts and nature of any additives used in the recycling process must also be assessed by the recycler, and if the use of any additive is not consistent with current regulations, a food additive petition for its use in manufacturing a food-contact article is required.

For reuse of plastic bottles, the primary issues consist of adequate source controls, consumer education, package integrity over the lifetime of the container, and adequate cleaning and sanitation to eliminate chemical and microbial contaminants.

Footnote

Prepared by:
Chemistry Review Branch, Office of Premarket Approval, HFS-247, Center for Food Safety & Applied Nutrition, U S Food & Drug Administration, 200 C Street SW, Washington, D.C. 20204 (See updated contact information)

May 1992 (Version 1.1; December, 1992)

* Office of Premarket Approval, Center for Food Safety and Applied Nutrition (HFS-200), Food and Drug Administration, 200 C St., SW., Washington, DC 20204 (See updated contact information)