Polypropylene Food Container (#5 PP)

Polypropylene (PP, recycling code #5) is one of the most widely used food contact plastics globally, found in yogurt containers, deli containers, ketchup bottles, take-out containers, and reusable food storage containers. It does not use bisphenols or phthalate plasticizers in its basic polymerization process, and regulatory agencies including the FDA and EFSA have cleared it as a food contact material for a broad range of applications.

Studies comparing plastic types for estrogenic activity have generally ranked polypropylene on the lower end of concern, though some research has found that certain commercial PP formulations contain additives that do show estrogenic activity in cell assays. The heterogeneity between PP products is real — the base polymer may be consistent, but the specific additive package (antioxidants, UV stabilizers, slip agents) varies by manufacturer and is not typically disclosed.

The conditions that increase PP leaching are the same as for other plastics: heat, fatty food contact, and surface degradation. Microwaving fatty foods in PP containers is the combination most likely to produce measurable migration. Several studies have found that microwaving fatty foods in polypropylene containers (including those labeled 'microwave safe') produces detectable compound migration into food. The 'microwave safe' designation indicates the container will not melt or warp, not that migration is absent.

For cold storage of non-fatty foods — raw vegetables, leftover soups, dry goods — PP is a reasonable choice among plastics. For households transitioning away from plastic and making prioritization decisions, the highest-impact substitutions are: stop microwaving in any plastic container, switch to glass or stainless for fatty food storage, and replace scratched or worn containers first. Polypropylene in good condition at cold temperatures represents a lower risk than older or high-heat plastic use.