Study finds byproducts in recycled food packaging warrant review

Understanding the risks posed by nonintentionally added substances (NIAS) in recycled polyolefin materials used as food contact materials (FCMs) in packaging is necessary to safeguard public and environmental health, according to a recently published study.

Researchers at Iowa State University recently highlighted the necessity of monitoring NIAS contaminants and aligning them with regulations to limit the use of potentially harmful additives in plastics.

NIAS are not added into polymers to impart technical benefits but often are byproducts of degradation or manufacturing or are created during consumer use. More monitoring would enhance the safe recycling and disposal of plastic, which is key to building a more circular economy. Properly evaluated, reusing plastics also reduces environmental waste and landfill accumulation.

Food packaging is one of the most important sectors of the plastic industry, comprising almost 40 percent of the total plastic demand. According to the U.S. Environmental Protection Agency, 14.5 million tons of plastic containers and packaging were produced in the USA in 2018, yet the proportion of this material that is being recycled has held steady or even declined over the past few years.

It is important to consider the potential health and environmental impacts of these compounds and to monitor their concentrations in virgin and postconsumer recycled (PCR) polymers. The U.S. Food & Drug Administration and other authorities have set guidelines for manufacturers to test and ensure the safety of recycled plastics used in food packaging.

Currently, plastic waste derived from food and nonfood applications is not differentiated and small concentrations of nonfood-grade materials potentially could be commingled into reclamation streams unintentionally. The presence of unintentional materials requires more scientific research. Understanding the identity and level of these chemicals and their potential harm is needed if they are to be used for direct food contact.

The Iowa State University study was supported by the Institute for the Advancement of Food and Nutrition Sciences (IAFNS). IAFNS’ Food Packaging Safety and Sustainability Committee—one of 12 full scientific committees at IAFNS—is a leader in promoting sustainability that relies on new scientific research. To ensure packaging companies and food companies avoid unintended chemical substitutions and other contaminants from reclaimed material streams requires careful science. By working across sectors in a sustainable way focused on public health, safe, high-quality food packaging can be explored.

The scientists identified 61 different compounds in virgin and PCR polyolefin samples grouped as hydrocarbons, aldehydes, alcohols, phthalates, carboxylic acids, per-and polyfluoroalkyl substances (PFAS), ketones and amines. Overall, nine substances were detected in the virgin polyethylene samples, while 52 components were detected in the recycled polyolefin samples. Most of the compounds detected can be attributed to degradation products, process additives or food additives.

The detection of hydrocarbons, polycyclic aromatic hydrocarbons (PAHs) and other potentially harmful substances in recycled polyolefins raises concerns about exposure to these compounds resulting from the use and disposal of plastic food contact products. The Cramer classification system was used to assess the threshold of toxicological concern associated with the detected compounds. The PCR sample showed a slightly higher proportion of Cramer Class III compounds (48.08 percent) than the virgin sample (44.44 percent), indicating higher potential for risk. (The Cramer classification system classifies chemicals into one of three classes (I – low, II – intermediate and III – high) reflecting the probability of low, moderate and high toxicity). This method can provide an initial assessment of a chemical’s potential toxicity and help identify any structural features that may contribute to its toxicity based on molecular structure and functional groups.

Virgin polymer is made from new raw materials, whereas PCR polymer had a previous service life where it could have been exposed to a wider variety of chemicals or conditions of use. For example, if the recycled materials were previously used in food packaging, they could have been exposed to food-contact materials that contain some of the compounds identified in the screening experiments. Also, the recycling process itself could introduce or concentrate certain compounds in the recycled polymer.

The new research underscores the importance of implementing effective monitoring and developing best practices. This will reduce the use of potentially harmful additives in plastic manufacturing and ensure the safe recycling of plastic as efforts build toward a circular economy. According to the European Union, “The circular economy is a model of production and consumption, which involves sharing, leasing, reusing, repairing, refurbishing and recycling existing materials and products as long as possible. In this way, the life cycle of products is extended. In practice, it implies reducing waste to a minimum.” The use of PCR polymers in food-contact materials can facilitate achieving a circular economy by reducing environmental waste and landfill accumulation.

The study also underscores the importance of implementing effective control measures to reduce reliance on potentially harmful or questionable additives in plastic manufacturing and to ensure the safe recycling and disposal of plastic waste. Further research is necessary to combine chemical and toxicological data to determine the origin (impurities, byproducts, etc.) and compliance of these compounds. Additionally, understanding migration kinetics of these chemicals from the different sources of postconsumer plastics is critical to understanding exposure risk under various conditions of use as food contact materials.

This study provides critical understanding of the safety and potential risks associated with using PCR polyolefins from different sources in food-contact applications.

According to the study authors, “Overall, the presence of these compounds in polyolefins emphasizes the need for better understanding of the potential risks associated with the production, use and disposal of plastic products.”

Wendelyn Jones, Ph.D., is executive director of the Institute for the Advancement of Food and Nutrition Sciences (IAFNS), a nonprofit organization that pools funding from industry collaborators and advances science through in-kind and financial contributions from public and private sector participants. More information is available here.