In an article published on June 29, 2015 by the news provider Yahoo Health, freelance writer Laura Tedesco reports on the safety of reusing plastic food containers. According to Rolf Halden, director of the Center for Environmental Security at the Biodesign Institute, Arizona State University, U.S., the biggest risk of reusing plastic containers is bacterial contamination. Especially if the container is intended for one-time use, it may not be designed for easy cleaning. Restaurant leftovers for instance should be transferred to a glass container, Halden recommends. In terms of chemical leaching, plastic containers with the recycling code 2 (high-density polyethylene, HDPE), 4 (low-density polyethylene, LDPE) or 5 (polypropylene, PP) are safest for reuse, says Daniel Schmitt, associate professor of plastics engineering at the University of Massachusetts Lowell, U.S. These materials typically do not contain plasticizers that could leach into food when the container is heated in the microwave, washed in the dishwasher or left in the sun for a long period of time.
Plastic containers with recycling codes 1 (polyethylene terephthalate, PET), 3 (polyvinyl chloride, PVC), 6 (polystyrene, PS) and 7 (all other plastics such as polycarbonate, PC) are more prone to chemical leaching and less suitable for reuse, Schmitt explains. PVC and PC contain phthalates and bisphenol A (BPA, CAS 80-05-7), respectively, which are of concern due to their endocrine disrupting properties. Some PET containers contain antimony, which has been linked to diarrhea, muscle and joint pain, anemia, and heart problems. PS is made of the monomer styrene, a possible human carcinogen. In general, when reusing food packaging the containers should be used for foods with similar acidity, sugar, fat, and alcohol content to the original food that came in them, Schmitt recommends.
Update: The Food Packaging Forum has developed a fact sheet that explains under which conditions chemicals are more prone to migrate from packaging into food. A separate set of fact sheets published in 2021 also provide an introduction to five common material types used in food packaging along with their material properties that can affect their application, chemical safety, and recycling. One of these focuses specifically on plastic packaging.
Laura Tedesco (June 29, 2015). “Is it safe to reuse plastic food containers?” Yahoo Health
Food Packaging Forum (October 10, 2012). Plastics – plastic food packaging.
Food Packaging Forum (2017). “Fact Sheet: Food Packaging and Human Health.”
Food Packaging Forum (2021). “Fact Sheet: Food Packaging and Recycling.”