Recycled Plastics for Food-Contact Applications - ACS Symposium

Chapter 32

Recycled Plastics for Food-Contact Applications Downloaded by UNIV OF CALIFORNIA SAN DIEGO on September 14, 2016 | http://pubs.acs.org Publication Date: May 5, 1995 | doi: 10.1021/bk-1995-0609.ch032

Science, Policy, and Regulation P. M . Kuznesof and M . C. VanDerveer Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, Washington, DC 20204

The use of recycled plastics for food packaging raises concerns about unregulated substances that may migrate into food and the possible adulteration of the food. In May, 1992, the Center for Food Safety and Applied Nutrition made available a document entitled "Points to Consider for the Use of Recycled Plastics in Food Packaging: Chemistry Considerations." The document highlighted those issues that manufacturers of recycled plastic should consider during the evaluation of a recycling process to produce material suitable for food-contact applications. This paper briefly reviews the highlights of the "Points," discusses the basis for some recent opinions that the Center has given for specific recycling applications, and comments on the agency's developing regulatory policy on the use of recycled plastic for construction of food-contact articles.

"A Guilt-free Guide to Garbage" was the headline for an article in the February, 1994, issue of Consumer Reports magazine (i), and the August, 1993, issue of ASTM Standardization News featured an article entitled "From the Garbage Heap to Your Home" (2). The interest in recycling municipal solid waste (MSW) has taken a firm hold in the public's mind because recycling is viewed as a "green" technology. Over the last several years, local, state, and federal government activity aimed at developing legislation mandating recycling of various components of MSW has provided a strong incentive for many industry groups to enter the recycling business. Among the industries, the food and foodpackaging sectors have also recognized that use of recycled packaging may be a valuable adjunct to their marketing and public relations strategies. Glass, paper, aluminum, and ferrous metals have been recycled at relatively high efficiencies for some years. Only recently has plastic, principally plastic This chapter not subject to U.S. copyright Published 1995 American Chemical Society Rader et al.; Plastics, Rubber, and Paper Recycling ACS Symposium Series; American Chemical Society: Washington, DC, 1995.

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390

PLASTICS, RUBBER, AND PAPER RECYCLING

packaging, begun to be recycled to any significant degree. The composition of MSW based on 1992 information is illustrated in Figure 1, which is based (7) on Franklin Associates' report prepared for the US Environmental Protection agency. According to Franklin Associates (7), the recycling rate for 1992 was highest for aluminum cans/foil - 68%. Paper, container glass, and steel cans were also being recycled at reasonably high rates: 38%, 33%, and 41%, respectively. However, only 6.5% of plastic packaging was recycled in 1992. The major plastics currently recycled are polyethylene terephthalate (PETE) - 450 million pounds recycled, high-density polyethylene (HDPE) - 450 million pounds, and lowdensity polyethylene (LDPE) - 110 million pounds (5) (figures are for 1993), all of which are extremely important to the food-packaging industry. Recycle feedstock from food-packaging material included approximately 360 million pounds of PETE soda botdes, 30 million pounds of PETE "custom" containers, i.e., for liquor and other foods, cosmetics, toiletries, and pharmaceuticals and 285 million pounds of HDPE milk and water jugs (5). Recyclate used to manufacture food-contact articles was limited essentially to PETE soda bottles in 1993. Only 25 million pounds was produced from postconsumer recycled bottles. This represents 2.5% of PETE soda bottle poundage for 1993. These figures suggest that plastic material fabricated for food-contact use and recycled for additional food-contact purposes is currently having little effect on mitigating the MSW crisis. However, this effect is not insignificant with respect to issues that relate to the safety of the US food supply. The purpose of this paper is to highlight these issues and to describe the efforts of the US Food and Drug Administration (FDA) to ensure the safe use of post-consumer recycled plastics for food-contact applications. The desire to use post-consumer recycled plastics to manufacture food-contact articles raises concerns about adulteration of the food by contaminants and unregulated substances that may migrate into the food from the articles. For example, how does one address the potential for consumer misuse or abuse of plastic containers or packaging through storage of household, garden, or automotive chemicals, and how can the potential risk to the public health from exposures to these toxic substances be assessed if post-consumer recycled plastics are to be used in food-contact applications? In May, 1992, FDA's Center for Food Safety and Applied Nutrition (CFSAN) made available an informal document entitled "Points to Consider for the Use of Recycled Plastics in Food Packaging: Chemistry Considerations." (Copies are available from the Office of Premarket Approval, HFS-220, Center for Food Safety and Applied Nutrition, US Food and Drug Administration, 200 C Street, SW, Washington, DC 20204.) This document (the "Points") was intended to provide manufacturers of articles from recycled plastics with CFSAN's initial thoughts on the important issues that need to be addressed during the evaluation of a recycling process to produce material suitable for food contact. Before discussing the "Points" and the developments following their release, it seems useful to first outline the current regulatory framework for the use of recycled plastics in contact with food.

Rader et al.; Plastics, Rubber, and Paper Recycling ACS Symposium Series; American Chemical Society: Washington, DC, 1995.


32. KUZNESOF & VANDERVEER

Food-Contact Applications

Figure 1. Composition of municipal solid waste (181 million tons, 1992).


391

392


Regulatory Framework


FDA's primary responsibility under the Federal Food, Drug, and Cosmetic Act is to ensure that the products it regulates are wholesome, safe, and effective. Furthermore, the National Environmental Policy Act requires that FDA assess the impact of new food-packaging materials on the environment (4). Although FDA supports recycling and the broader societal goal of diverting material from the solid waste stream, it can only do so when it is in harmony with FDA's mission to protect the public health. No federal regulations presently exist that explicitly address the use of postconsumer recycled plastics for food-contact applications. The regulations for indirect food additives in Title 21 of the United States Code of Federal Regulations (21 CFR), Part 175 (Adhesives and Components of Coatings), Part 177 (Polymers), Part 178 (Adjuvants, Production Aids, and Sanitizers), and the requirements specified in Section 174.5 relating to Good Manufacturing Practice are applicable, however. In particular, Section 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." Thus, manufacturers of food-contact articles made from recycled plastic must ensure that the recycled material, like virgin material, is of suitable purity and meets all existing specifications for the virgin material. And it must be remembered that compliance with regulations extends to any adjuvants, such as antioxidants, colorants, or antistatic agents, that have been incorporated into polymer resins. In addition to actively working over the past three years to improve the guidance to the industry for evaluating the technology for recycling plastics into foodcontact articles (5,(5), CFS A N personnel have also been considering whether there is a need to establish any new regulations that would explicitly apply to the use of recycled plastics for food-contact articles. In the interim, industry is urged to continue its consultations with the agency in order to satisfy FDA's concerns regarding the safe use of recycled plastics. FDA wishes to continue to be responsive to industry requests for guidance and opinions on specific applications of recycled plastics. Some of these applications and opinions will be discussed below. Because these opinions have been based on the "Points," it is appropriate now to consider that document at greater length. Points to Consider The "Points" begins with a brief discussion of the basic types of plastic recycling including recycling of pre-consumer industrial scrap and salvage and some specific concerns relevant to each. Re-use of containers, which pertains to source reduction, is also discussed. This is followed by a description of an approach for estimating the maximum level of a chemical contaminant in the recycled material that would be acceptable and would not compromise the public health. Finally, an experimental protocol is suggested by which analytical chemistry data can be developed for evaluating the adequacy of a recycling process to remove chemical contaminants.



32.

KUZNESOF & VANDERVEER


393

Post-consumer recycling processes can be classified as either physical or chemical reprocessing. Physical reprocessing involves grinding, melting, and reforming plastic packaging material. The basic polymer is not chemically altered. Before the polymer is melted and reformed, the ground, flaked, or pelletized resin is washed to remove contaminants. The wash step is a critical part of physical reprocessing, and many companies engaged in evaluating physical reprocessing methods regard their wash procedures and washing agents as proprietary information. Processors should avoid using substances that are not regulated for food contact, as these substances may become incorporated into the polymer resin and subsequently migrate into food at concentrations that may render the food adulterated. Different resins may also require different reforming conditions, such as different processing temperatures, the use of vacuum stripping, or other procedures that could influence contaminant levels and affect the polymer properties and functionality of the recycled material. Scientists at the Chicagobased National Center for Food Safety and Technology (NCFST), a consortium of government (FDA), industry, and academia dedicated to cooperative research in food safety and technology, have also been exploring various aspects of the cleanup of physically processed recycled plastics (7). Some of this work involving recycled PETE was presented at the August, 1994, National Meeting of the American Chemical Society (Komolprasert, V . , and Lawson, A . , in press; Komolprasert, V . , et al., in press). Recyclers must be able to demonstrate that potential contaminant levels in the reformed plastic can be sufficiently reduced to ensure that the resulting packaging will not adulterate food. Production of a resin with the desired qualities, however, may require the addition of antioxidants, processing aids, or other adjuvants to the recycled resin. The type and total amount of additives must be in compliance with existing regulations. Recycled resins that require new additives or amounts of additives in excess of what is currently regulated may require an amendment to the food additive regulations via the petition process. Physical reprocessing presents some unique problems that may make it inappropriate for the production of food-contact articles, particularly if the recycler has little or no control over the quality of the feedstock entering the recycling facility. If effective source control can be established, however, the problem of commingling post-consumer plastic food-contact materials with other post-consumer plastics that may be made of unregulated resin or that may contain unregulated adjuvants can be minimized or eliminated. Source control is an important element of Good Manufacturing Practice. Additionally, the development of sorting procedures that result in the reprocessing of only a single characteristic container, e.g., a PETE soda bottle, adds additional assurance that the recycled article is suitable for food contact. Chemical reprocessing may involve depolymerization of the used packaging material with subsequent regeneration and purification of resulting monomers or oligomers. These materials are then repolymerized and the regenerated polymer is formed into new packaging. Regenerated monomer, polymer, or both may be blended with virgin polymer. The regeneration process may involve a variety of



394


monomer/polymer purification steps, such as distillation, crystallization, and additional chemical reaction, in addition to washings. The primary goal of chemical reprocessing is the regeneration of purified starting materials. The use of additional adjuvants must be in compliance with regulations. Compared with physically reprocessed recycled plastics, it is considerably simpler to demonstrate that chemically reprocessed material is of suitable purity for its intended use. However, chemical reprocessing does not appear to be cost effective. Hence, there has been considerable industry interest of late in developing physical reprocessing technology that can provide the necessary assurance that the recycled material is indeed "of suitable purity." The meaning of "suitable purity" has been linked in the "Points" to the establishment of an acceptable upper-limit of dietary exposure to chemical contaminants from recycled material. Therefore, the residual concentration of a contaminant in the plastic that corresponds to the dietary exposure limit needs to be determined. The "Points" discussed the potential risk to consumersfromacute exposure and chronic (long-term) exposure to chemical contaminants migrating into food from recycled packaging. Because the concentrations of contaminants in recycled plastic are expected to be extremely low, acute exposures would be too low to manifest acute toxicological effects. The possibility was considered, however, that traces of carcinogenic substances (or any other substances that may constitute a chronic health hazard) could be carried through multiple recyclings to establish very low steady-state concentrations in the recycled material over the long term. Therefore, the possibility that a consumer could be exposed to low concentrations of a particular carcinogen over a long period of time had to be addressed. Consideration was given to the question of carcinogenic risk in a probabilistic way rather than on a compound-by-compound basis. The principles used were those that formed the basis for FDA's 1993 proposal to establish a "Threshold of Regulation" (T/R) for substances purposely used in the manufacture of foodcontact articles (8,9). The T/R proposal would sanction the use of food additives in packaging materials for which the probable exposure to a consumer is expected to be sufficiently low as to constitute negligible risk; such use would not require a food additive petition. The "Points" stated that "Preliminary thinking" in CFS A N suggested that exposure to a contaminant at 1 part per billion (ppb) in the daily diet, the samefigurethat was being considered for the T/R policy, could be considered a negligiblerisk.Subsequently, FDA proposed 0.5 ppb of the daily diet as the exposure level for negligible risk (8). This is the exposure that CFSAN's Office of Premarket Approval now also considers appropriate in assessing recycling applications. Illustrations of calculations and assumptions used to determine the maximum residual level of a contaminant in recycled plastic that would contribute no more than 1 ppb to the diet are given in the "Points." The calculations are easily adapted to an exposure of 0.5 ppb. The ability of a particular recycling process to reduce contaminant levels in plastic containers or packaging to levels below those corresponding to a dietary exposure of 0.5 ppb should be demonstrated. A scheme for doing this involving


32.



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analytical studies with surrogate contaminants was elaborated in the "Points." In summary, consumer misuse could be simulated by exposing plastic packaging, either in container form or as flaked or ground resin, to selected surrogate contaminants. Following this exposure, the containers or resin would be subjected to the recycling process. Analysis of the resin for the surrogates would demonstrate the efficacy of the recycling process. According to the "Points," the selection of surrogate contaminants should attempt to bracket a variety of chemical and physical properties. It is suggested that the surrogates 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 substance. Other selection criteria are being evaluated by NCFST and by the plastics industry. To date, CFSAN's Office of Premarket Approval has reviewed data on surrogate contaminant analyses from several companies for evaluating the recycling of PETE. The surrogates that have been used are listed in Table I along with the results of the analyses. Some surrogates have proved difficult or unsuitable. For example, disodium monomethylarsonate (crabgrass killer) has been tested as a surrogate contaminant for PETE. Analysis for arsenic using atomic absorption spectroscopy is apparently confounded by the presence of antimony in PETE; antimony-containing catalysts are used in the manufacture of PETE. Orffo-cresol, which is known to significantly swell PETE and was suggested in the "Points," may actually dissolve PETE under the conditions of the study protocol; it is no longer recommended. Gasoline, motor oil, and kerosene would initially appear to be appropriate choices as surrogates. Analytical difficulties in achieving adequately low detection limits, however, preclude their further recommendation. The detection limits for the other surrogates listed in Table I were low enough for a reasonable assessment of the data. The "Points" also considered the possibility that a proposed recycling process may fail the surrogate challenge, i.e., it would not reduce contaminant levels in the recycled polymer below the acceptable limit corresponding to a dietary exposure of 0.5 ppb. It is important to keep in mind, however, that an estimation of dietary exposure to a surrogate contaminant based only on the determination of its concentration in the recycled polymer assumes that all of the contaminant (100%) migrates from the package to the food. This is a highly conservative assumption. The relevant point with respect to food safety, therefore, is not how much contaminant is in the plastic packaging material, but rather how much migrates into food during thetimeof food contact. This can be assessed by performing migration studies of the type typically recommended to support a food additive petition for regulating a new packaging material or polymer adjuvant (10). (Copies are available from the Office of Premarket Approval, HFS-200, CFSAN, FDA, 200 C Street, SW, Washington, DC 20204.) In addition to migration studies, other factors that can be used to lower the exposure estimate include blending virgin with recycled resin, improving source controls, restricting uses for recycled material, or using a functional barrier for certain applications (see below).


396


Table I: Surrogate Contaminants for Evaluation of Recycled PETE Surrogate

Spiking Level

gasoline* cupric acetoarsenite chlordane lindane* diazinon motor oil toluene* chloroform* carbaryl malathion "chromium salt" lead oxide kerosene lead sulfate cadmium acetate

neat at use conc. at use cone. 2% aqueous emulsion 1 % aqueous solution * neat 1635 ppm 1256 ppm 1000 ppm 1000 ppm 1000 ppm (as Cr) 1000 ppm (as Pb) 1000 ppm 293 ppm (as Pb) 268 ppm


b

6

c

0

04

0

6

e f

e f

d

d

d

d

d

d

d

Pre-Process Level in Resin

Post-Process LeveP in Resin fin Extract]

670 ppm not reported not reported 281 ppm 100 ppm 24,600 ppm 404 ppm 899 ppm 0.356 ppm 247 ppm 51.2 ppm (as Cr) 152 ppm (as Pb) < 2.5 ppm 189 ppm (as Pb) not reported

< 5 ppm < 25 ppb < 0.5 ppm < 25 ppb [< 10 ppb] < 10 ppb < 25 ppm < 100 ppb [< 10 ppb] < 50 ppb [< 10 ppb] [< 20 ppb] [< 0.05 ppb] [< 5 ppb (as Cr)] [< lppb(asPb)] [< 1.0 ppm] [< 10 ppb (asPb)] < 10 ppb (as Cd)

'Plastic samples were extracted with 8% ethanol for 10 days at 120°F. Levels reported in brackets are from 10-day extracts. Surrogate was used in more than one study. The highest reported levels are listed. Samples spiked by filling bottles with surrogate. Samples spiked by blending surrogates into pellets. 'Chemical reprocessing mixture spiked with surrogate. Samples spiked by soaking flaked plastic in surrogate. c

d

f

The Plastics Recycling Task Force (PRTF), an ad hoc industry group formed under the joint auspices of the National Food Processors Association (NFPA) and the Society of the Plastics Industry (SPI), in March, 1992, submitted to CFSAN for comment a draft document entitled "Guidelines for the Safe Use of Recycled Plastics for Food Packaging Applications" (11). The PRTF also recommended the surrogate contaminant approach for challenging a recycling process. In addition, a plan was presented that would call for migration studies to be conducted to assess the amount of contaminant that would actually be expected to migrate into food should the analysis of residual contaminant in the polymer be above the acceptable limit based on 100% migration. The March 19, 1994, Technical Highlights newsletter published by NFPA announced completion of PRTF work on recycled HDPE for food packaging and claimed development of analytical methodology with a detection limit of at least 0.3 parts per million (ppm) for all surrogates, corresponding to a dietary exposure of 0.5 ppb. Migration Principles and Functional Barriers The use of recycled material as a nonfood-contact layer of a multilayer food package would appear to be an excellent application for recycled plastics. Risk




397


from contaminant migration into food would be expected to be negligible provided that the recycled resin is separated from the food by an effective barrier constructed of regulated virgin resin or other appropriate material, e.g., aluminum foil. Chemists at CFSAN (6) have recently addressed the question of migration of contaminants from recycled plastics into food through theoretical calculations based on principles of diffusion in polymers (12). They have shown that it is possible to calculate for a given polymer the maximum acceptable concentration of a contaminant that would result in a dietary exposure considered to be of negligible risk. Furthermore, they have applied the diffusion model to a two-layer construction with recycled polymer as die nonfood-contact layer and have shown how to estimate the minimum thickness of a virgin food-contact layer that would serve as a functional barrier. In thefirstinstance, it was assumed that the food package consists of a monolayer of 100% recycled material in which any contaminant is homogeneously distributed (Figure 2a) and that the diffusion of the contaminant into the food obeys Fick's law. This means that the amount of migration into food can be expressed as

M, = 2C (Dt/n)

112

0

( 1 )

where M< is the amount of a substance migrating from a unit surface area of package (/ig/cm ), D is the diffusion coefficient (cm /s) - assumed to be concentration-independent, C is the concentration 0*g/cm ) of the contaminant in the polymer at zero time, and t is time (s). The general assumptions behind equation 1 are 1) the concentration of migrant in the polymer does not significantly change during food-contact time and 2) the food is an infinite sink with no resistance to mass transfer (i.e., there will be no partitioning effects to inhibit migration from polymer to food). Begley and Hollifield (6) point out that equation 1 has been shown in numerous studies to be useful in predicting migration from food packaging to food. 2

2

3

0

The two-layer or laminate package was modeled by Begley and Hollifield in terms of the pseudo-membrane problem (12), which assumes afixedconcentration (CJ on one side of the membrane (i.e., at the virgin polymer/recycle layer interface) of thickness / and a zero concentration on the other side (in the food). See Figure 2b. The solution to the problem, which assumes the food to be an infinite sink for the migrant, is given by equation 2.

(-1)' '

1/2

6

^

rf

2

exp

2

-n n Dt\]

I

2


(2)


398


Figure 2. Migration of contaminants from recycled plastic into food for (a) monolayer and (b) multilayer packaging structures, where / is the thickness of a layer of virgin plastic.



399


Equation 2 is highly complex. To simplify matters, Begley and Hollifield defined a unitless variable, T, for the purpose of providing a general perspective on the diffusion rate for a contaminant through the virgin layer into the food: (3)

2


X = Dt/l .

It can be seen from equation 2 that the larger r is, the faster will a contaminant cross the virgin layer into the food. Solving equation 2 for 0.1 predicts that at most 1 % of the initial contaminant concentration at the recycle/virgin interface will move across the virgin layer. For r = 0.6, diffusion will be rapid and approximately 45% of the migrant will migrate into the food. At values of T above 0.6, the magnitude of migration is predicted to approach that of the monolayer package. (For values of r greater than 0.6, the migration from a laminated package, calculated by using equation 2, may exceed the calculated migration from a monolayer package. At high values of r, the assumption that C is a constant is no longer valid.) c

To evaluate contaminant migration from a food package by using the above models and thereby determine whether an initial contaminant level will be acceptable in terms of the 0.5-ppb exposure benchmark, the diffusion coefficient for the contaminant in the polymer must be known for the maximum temperature conditions to which the polymer will be subjected during food contact (e.g., refrigerated conditions, retort conditions). Combining diffusion coefficients with expected time of food contact for a given temperature and using FDA's basic assumption that 10 grams of food contacts 1 square inch of packaging surface (or 1.55 g/cm ), Begley and Hollifield calculated the extent of migration to food that could be expected for different initial contaminant levels in a set of four polymers. Their calculations for a 2-mil (0.051 mm) thick monolayer package for 30 days of food contact are presented graphically in Figure 3 for PETE, polystyrene (PS), p o l y v i n y l chloride) (PVC), and LDPE. (Migration predicted by using equation 1 is independent of monolayer thickness. However, dividing equation 1 on both sides by / gives 2

Af can then be plotted as a function of C for various values of r (i.e., D) where / and t arefixed.)With fixed t and /, D was varied around lxlO" cm /s to obtain the different lines for each value of r. For example, for D = 3.5xl0" cm /s, r = 0.35. The horizontal lines represent those concentrations in the food corresponding to a dietary intake of 1 ppb. The different concentrations are a result of the differing proportions in which the polymers are used for food packaging (10). Thus, for r = 0.15, if the initial concentration of a contaminant in PETE were to exceed 13 jig/cm? (9 jxg/g), the predicted dietary exposure t

c

12

2

12


2

400


would exceed 1 ppb. Similarly, in order not to exceed an exposure of 0.5 ppb, the initial contaminant level should not exceed about 7 pig/cm . 3


The graph in Figure 4 for the laminate structure was constructed by using the same values of T, i.e., t, D, and /, as were used for the monolayer. The ordinate represents the migration expected through the virgin layer into the food for a given concentration in the recycled layer. For a 2-mil thick virgin PETE layer, the calculations indicate that the concentration of contaminant in the recycled layer could be as high as 200 jig/cm (r = 0.15) before migration would result in a dietary exposure of 1 ppb. This is 15 times the level of contamination calculated for the monolayer package, 13 /xg/cm . Such large differences should not lead to a conclusion that highly contaminated recycled resins are suitable for food packaging. The intentional use of highly contaminated materials would not be considered good manufacturing practice (GMP). The modeling, however, is clearly useful in providing guidance and insight for evaluating a particular recycling process. CFSAN's Chemistry Review Branch has already used this approach in evaluating the suitability of several recycled resins for food-packaging applications. 3

3

FDA Opinions The early requests for agency opinions on specific applications for post-consumer recycled polymers were the easiest to consider in a favorable light. The principal issue was and is the likelihood and magnitude of potential consumer exposure to contaminants. Those applications for which the food-/package-contact time is extremely short (e.g., some fast-food-service applications), the temperature of the food in contact with recycled material is room temperature or lower (e.g., produce trays in supermarkets), the ratio of a unit surface area of food-contact material to the mass of food contacting the area is extremely small (e.g., large shipping crates used for grapefruit), or the contact of packaging material with nonedible portions of foods (e.g., shells of eggs and skins of bananas) are not expected to result in exposures to contaminants that would compromise public health. Among those submissions that CFS A N has favorably reviewed are four based on surrogate contaminant analyses for chemically reprocessed PETE soda bottles. One of the PETE submissions pertained to its use as a nonfood-contact layer in a laminate structure. In addition, a number of favorable opinions for physically reprocessed polymer have been given to date (Table II). Some were based solely on the considerations mentioned above relating to short contact times, low temperatures during food/package contact, etc. Others were based on theoretical calculations using equation 2 above, or on migration studies demonstrating an effective barrier under the proposed conditions of use. Migration data submitted for a multilayer package construction supported a conclusion that a 1-mil thick virgin food-contact layer of PETE would serve as a functional barrier to contaminants from a recycled PETE layer for up to 1 year with filling and storage




0

10

401


20 30 40 Contaminant concentration in recycled layer (jig/cm )

50

3

Figure 3. Migration from a monolayer package, predicted by using equation 1 (from Ref. 6, with permission).

Contaminant concentration in recycled layer (p,g/cm ) 3

Figure 4. Migration from a two-layer package, predicted by using equation 2 (from Ref. 6, with permission).


60

402



Table II. Physically Reprocessed Plastics — Favorable Opinions Polymer*

Application

PETE PETE PETE PETE PE and PP

berry baskets deli foods deli and bakery foods all botdes shipping containers for meat, poultry, and seafood; harvesting crates grocery bags airline snack boxes retail meat and poultry trays produce trays egg cartons

PE PS PS PS PS

'PETE = polyethylene terephthalate; PE = polyethylene; PP = polypropylene; PS = polystyrene. temperatures not exceeding room temperature. Theoretical modeling has also shown that a 1-mil virgin PETE layer can be an effective barrier for up to 1 year even for products that are hot-filled or pasteurized above 66°C (150°F). Calculations for polystyrene for a 2-week food-contact time at room temperature also predict a 1-mil virgin layer to be a barrier. Currently, CFSAN has several additional requests for evaluation that are under review. It is expected that most of the submissions during the next few years will be concerned with physically reprocessed polymers because of the unfavorable economics for chemical reprocessing. Summary and Conclusions FDA has a positive outlook on plastics recycling for many types of foodpackaging and other food-contact applications. In attempting to be responsive to requests from the food and food-packaging industries for guidance in this area, CFSAN developed the "Points" and is now considering whether proposing any new regulations would be beneficial to the industry and to consumers. During the past 3 years, CFSAN personnel have met with industry representatives, including the PRTF, on a number of occasions to discuss approaches to encourage the proper use of post-consumer recycled plastic for food-contact applications. The "Points" describes the rationale, based on the probabilistic approach that led to the agency's Threshold of Regulation proposal, for establishing an acceptable upper limit of potential dietary exposure to contaminants in recycled plastic. This is now set at 0.5 ppb of the daily diet. The "Points" also introduces the concept



32.



403

of using surrogate contaminants for assessing the efficiency of a recycling process to remove contaminants and highlights good source control of materials and consumer education as major factors contributing to the successful use of recycled plastic for food-contact applications. CFSAN personnel have demonstrated the utility of calculations based on Fick's Law for evaluating contaminant migration from recycled polymers into food, and scientists at NCFST are making progress in their work on surrogate contaminant analysis and are assessing the effectiveness of various steps in a recycling process to remove contaminants while maintaining the functionality of the recycled material. An update of the "Points," which would include more discussion on functional barriers and would reflect the change from 1 ppb to 0.5 ppb of dietary exposure for a contaminant, is being contemplated. The agency will continue to consider additional requests for food-contact uses of recycled polymers on a case-by-case basis. The industry must still meet its burden to ensure that recycled plastic is, as the CFR requires, "of a purity suitable for its intended use." Literature Cited 1. 2. 3. 4.

Anon. Consum. Rep. 1994, 59, 91-101. Lampo, R.; Finney, D. ASTM Standardization News 1993, 22, 36-45. Anon. Mod. Plast. 1994, 71, 73ff. Hoffmann, B.L.; Nowell, L.H. Food Drug Cosmet. Law J. 1990, 45, 615621. 5. Thorsheim, H.R.; Armstrong, D.J. CHEMTECH. 1993, 23(8), 55-58. 6. Begley, T.H.; Hollifield, H.C. Food Technol. 1993, 47(11), 109-112. 7. Komolprasert, V . ; Lawson, A. "Effect of Aqueous-Based Washing on Removal of Hydrocarbons from Recycled Polyethylene Terephthalate (PETE)," Proceedings of the Annual Meeting of the Society of Plastics Engineers, May 1-5,1994; Society of Plastics Engineers: San Francisco, CA, 1994; 3, 2206-2209. 8. U.S. Food and Drug Administration. Fed. Regist. October 12, 1993, 58 (195), 52719-52729. 9. Rulis, A . M . In Risk Assessment in Setting National Priorities; Bonin, J.; Stevenson, D., Eds.; Plenum Publishing Corp.: New York, NY, 1989, pp 271-278. 10. U.S. Food and Drug Administration. Recommendations for Chemistry Data for Indirect Food Additive Petitions; Office of Premarket Approval: Washington, DC, 1988. 11. National Food Processors Asssociation (NFPA) and Science in the Public Interest (SPI). Letters of March 17, 1992, from the Law Offices of Keller and Heckman, Washington, DC, to Director, Division of Food and Color Additives, CFSAN, FDA; NFPA and SPI: Washington, DC, 1992. 12. Crank, J., The Mathematics of Diffusion, 2nd Ed.; Oxford Press: London, 1975. RECEIVED July 24,

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Recycled Plastics for Food-Contact Applications - ACS Symposium

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