--- topic: "Plastic Food Containers" title: "Storing and Reheating Food in Plastic" order: 1 description: "Heat and fat make plastic containers release more chemicals and particles. What studies show on BPA, phthalates and microwaving, and what to use instead." question: "Is it safe to store and reheat food in plastic containers?" answer: "Heating food in plastic, especially in the microwave, likely raises chemical and particle release; cold storage matters less, and glass is safer for reheating." actions: - "Let hot food cool, then reheat on glass, ceramic or stainless steel, not plastic: microwaving released far more particles than refrigeration [1] and broke down antioxidants in polypropylene packaging [2]." - "Retire old, scratched, stained or cloudy plastic containers, and swap old polycarbonate bottles for stainless steel or glass: a week of use raised students' urinary BPA 69 percent [4]." - "Eat more fresh and less packaged food: three days without canned or plastic-packaged food cut urinary BPA by 66 percent and DEHP metabolites by 53–56 percent in 20 people [3]." cautions: - "Babies and toddlers: do not microwave formula, milk or water in plastic; modelled exposures were highest for infants drinking microwaved water and toddlers eating microwaved dairy from polypropylene containers [1]." - "Estrogen-active chemicals are of most concern in fetal and infant stages [6]." confidence: 3 confidenceNote: "Small human studies show packaging raises BPA and phthalate levels, lab tests show heat raises release, but no study links home container use to disease and microplastic counts are disputed." evidenceSummary: rctCount: 0 observationalCount: 2 metaAnalysisCount: 1 totalParticipants: "97" replicated: true newestStudyYear: 2024 references: - id: "1" pmid: "37343248" title: "Assessing the Release of Microplastics and Nanoplastics from Plastic Containers and Reusable Food Pouches: Implications for Human Health" authors: "Hussain KA, Romanova S, Okur I, et al." year: 2023 journal: "Environ Sci Technol" - id: "2" pmid: "21513311" title: "Microwave heating causes rapid degradation of antioxidants in polypropylene packaging, leading to greatly increased specific migration to food simulants as shown by ESI-MS and GC-MS" authors: "Alin J, Hakkarainen M" year: 2011 journal: "J Agric Food Chem" - id: "3" pmid: "21450549" title: "Food packaging and bisphenol A and bis(2-ethyhexyl) phthalate exposure: findings from a dietary intervention" authors: "Rudel RA, Gray JM, Engel CL, et al." year: 2011 journal: "Environ Health Perspect" - id: "4" pmid: "19750099" title: "Polycarbonate bottle use and urinary bisphenol A concentrations" authors: "Carwile JL, Luu HT, Bassett LS, et al." year: 2009 journal: "Environ Health Perspect" - id: "5" pmid: "21367689" title: "Most plastic products release estrogenic chemicals: a potential health problem that can be solved" authors: "Yang CZ, Yaniger SI, Jordan VC, et al." year: 2011 journal: "Environ Health Perspect" - id: "6" pmid: "24886603" title: "Estrogenic chemicals often leach from BPA-free plastic products that are replacements for BPA-containing polycarbonate products" authors: "Bittner GD, Yang CZ, Stoner MA" year: 2014 journal: "Environ Health" - id: "7" pmid: "24894065" title: "Phthalates and diet: a review of the food monitoring and epidemiology data" authors: "Serrano SE, Braun J, Trasande L, et al." year: 2014 journal: "Environ Health" - id: "8" pmid: "38722707" title: "Correspondence on \"Assessing the Release of Microplastics and Nanoplastics from Plastic Containers and Reusable Food Pouches: Implications for Human Health\"" authors: "Sun Y, Jiao X, Zhang N, et al." year: 2024 journal: "Environ Sci Technol" - id: "9" pmid: "38722646" title: "Rebuttal to Correspondence on \"Assessing the Release of Microplastics and Nanoplastics from Plastic Containers and Reusable Food Pouches: Implications for Human Health\"" authors: "Hussain KA, Romanova S, Okur I, et al." year: 2024 journal: "Environ Sci Technol" - id: "10" pmid: "31380625" title: "Benchmarking the in Vitro Toxicity and Chemical Composition of Plastic Consumer Products" authors: "Zimmermann L, Dierkes G, Ternes TA, et al." year: 2019 journal: "Environ Sci Technol" - id: "11" pmid: "34488348" title: "Plastic Products Leach Chemicals That Induce In Vitro Toxicity under Realistic Use Conditions" authors: "Zimmermann L, Bartosova Z, Braun K, et al." year: 2021 journal: "Environ Sci Technol" - id: "12" pmid: "25775505" title: "Bisphenol S and F: A Systematic Review and Comparison of the Hormonal Activity of Bisphenol A Substitutes" authors: "Rochester JR, Bolden AL" year: 2015 journal: "Environ Health Perspect" --- Plastic containers leak small amounts of chemicals and microscopic particles into food, and heat is the biggest trigger [1][2]. In small human studies, going without packaged food cut urinary BPA by about two-thirds [3], and drinking from polycarbonate bottles raised it by 69 percent [4]. "BPA-free" is not a guarantee, because many replacement plastics still leached estrogen-active chemicals [5][6]. Glass or ceramic is the safer choice for reheating. ## How it works **What leaves plastic.** Containers can release additives such as antioxidants [2], leftover building blocks such as BPA [4], plasticizers such as DEHP [3], and tiny plastic fragments [1]. Diet is a significant route of exposure to phthalates, and in a review of food monitoring data DEHP was consistently high in poultry, cooking oils and cream-based dairy products [7]. See [BPA](/bpa/endocrine-disruptor-and-substitutes) and [phthalates](/phthalates/hormone-disruption-and-health) for what these chemicals do. **Heat is the main trigger.** In one lab study, microwaving commercial microwavable polypropylene packaging broke down its antioxidants (Irgafos 168 and Irganox 1010) and sharply raised migration into fatty food simulants. Conventional heating to the same temperature did not [2]. In another, microwaving released the most micro- and nanoplastics of any scenario, up to 4.22 million microplastic and 2.11 billion nanoplastic particles from one square centimetre of container in 3 minutes. Refrigerated and room-temperature storage released fewer, though still millions to billions over six months, and polyethylene pouches released more than polypropylene containers [1]. Those counts were challenged in a published correspondence and defended in a rebuttal [8][9]. See [reducing microplastic exposure](/microplastics/reducing-exposure). **Which plastic.** The number in the recycling triangle names the resin, not its safety. In lab tests of everyday products, PVC (#3) and polyurethane extracts were the most toxic, PET (#1) and HDPE (#2) caused no or low toxicity, and "bioplastics" made of polylactic acid were not safer. Low-density polyethylene, polystyrene and polypropylene varied [10]. In a second test at 40°C for 10 days, every product released chemicals that triggered baseline toxicity in cells, and LDPE, PVC and polyurethane triggered the most responses [11]. **"BPA-free" is not the end of the story.** Many BPA-free plastics still leached chemicals with estrogen-like activity in cell tests, especially after microwaving, autoclaving or ultraviolet light [5][6]. The common substitutes bisphenol S and F are about as hormonally active as BPA [12]. In one study some resins, such as glycol-modified PET and cyclic olefin polymers, released no detectable activity under any condition tested [6]. **What to do with it.** Use glass or stainless steel for hot, fatty or acidic food. If you keep plastic, use it for cold storage, prefer PET, HDPE or polypropylene, and replace worn pieces. ## The evidence in detail **Human exposure studies.** Rudel and colleagues measured urinary BPA and phthalate metabolites in 20 people from five families who usually ate canned and packaged food. After 3 days of fresh foods that were not canned or packaged in plastic, geometric mean BPA fell from 3.7 to 1.2 ng/mL (a 66 percent drop), DEHP metabolites fell 53 to 56 percent, and the highest values fell 76 percent for BPA and 93 to 96 percent for DEHP metabolites [3]. The study was tiny, urine was pooled into composite samples, and the diet change removed cans and all plastic packaging, so it cannot single out food containers. Carwile and colleagues asked 77 Harvard students to drink most cold beverages from polycarbonate bottles for a week after a one-week washout. Geometric mean urinary BPA rose from 1.2 to 2.0 micrograms per gram of creatinine, a 69 percent increase, and 77 percent among those who reported at least 90 percent compliance [4]. Neither study measured health outcomes, and neither was randomized. **Lab studies of heat.** Hussain and colleagues tested plastic containers and reusable food pouches with water and 3% acetic acid as stand-ins for aqueous and acidic foods. Modelled intakes peaked at 20.3 ng per kg of body weight per day for infants drinking microwaved water and 22.1 ng/kg per day for toddlers consuming microwaved dairy from polypropylene containers. In a cell test, extracted particles killed 77 percent of human embryonic kidney cells at 1,000 micrograms per mL after 48 and 72 hours [1]. That dose is far above the modelled intakes, so it shows a possible hazard, not a real-world dose, and the particle counts themselves were disputed in correspondence [8][9]. Alin and Hakkarainen found that microwave heating degraded the antioxidants in polypropylene packaging, which was not seen with conventional heating at the same temperature, and that migration into a harsh fatty simulant, isooctane, which swelled the plastic, was far higher than into ethanol or aqueous simulants [2]. **Estrogenic activity.** Yang and colleagues exposed MCF-7 breast cancer cells to extracts of commercial plastic resins and products, some after microwaving, ultraviolet light or autoclaving. Almost all samples leached chemicals with detectable estrogenic activity, including products sold as BPA-free, and some BPA-free products had more activity than BPA-containing ones [5]. Bittner and colleagues screened more than 1,000 extracts from 50 BPA-free replacement products with two assays. Items made from acrylic, polystyrene, polyethersulfone and Tritan leached active chemicals, ultraviolet light often increased leaching, and some glycol-modified PET and cyclic olefin items did not [6]. Rochester and Bolden's systematic review of 32 studies, mostly in vitro, found BPS and BPF at the same order of potency as BPA [12]. These are cell and animal findings. They show hormonal activity, not human disease. **Which polymers.** Zimmermann and colleagues extracted 34 products covering eight polymer types: 74 percent triggered at least one end point, including baseline toxicity (62 percent), oxidative stress (41 percent), antiandrogenicity (27 percent) and estrogenicity (12 percent). Most of the 1,411 chemical features could not be identified, and some products caused no toxicity, which shows safer plastics already exist [10]. Their follow-up, with 24 products leached for 10 days at 40°C, found that all induced baseline toxicity, 22 an oxidative stress response and 13 antiandrogenicity, and that most plastic chemicals remain unknown [11]. **Dietary phthalates.** Serrano and colleagues pooled food monitoring studies and estimated daily DEHP intake from a typical diet at 5.7 micrograms per kg for women of reproductive age, 8.1 for adolescents and 42.1 for infants, above the EPA reference dose of 20 for infants, with dairy the largest contributor [7]. These figures cover all dietary sources, not home containers alone. **What conflicts or is missing.** No study has followed people who store and reheat food in plastic and tracked disease. Urinary levels show recent exposure, not harm. Cell assays use doses and conditions unlike a lunch box. The microplastic counts rest on one lab's methods and were disputed [8][9]. And the best human data concern BPA and DEHP, so far less is known about the replacements. **Bottom line (moderate confidence).** Heating raises what leaves plastic, packaged food raises BPA and phthalates in people, and "BPA-free" does not mean estrogen-free. Whether everyday container use harms health is unproven, and avoiding it costs little. **Swaps, ranked by evidence** 1. **Reheat in glass, ceramic or stainless steel, not plastic (strongest).** Independent lab studies agree that heat, especially microwaving, increases release [1][2][5]. 2. **Eat fresh, less canned and plastic-packaged food (human trial, small).** Urinary BPA and DEHP metabolites dropped within 3 days [3]. 3. **Replace old polycarbonate bottles with stainless steel or glass (human study, small).** [4] 4. **If you keep plastic, use PET, HDPE or polypropylene for cold storage and replace worn pieces (cell tests).** PVC and polyurethane were the most toxic in vitro [10][11]. 5. **Relying on a "BPA-free" label alone (weakest).** Substitutes remained estrogen-active [6][12].