Plastic by the Numbers: What Codes #1 Through #7 Mean for Your Health

Georden Jones, Founder, The Peer Review · Last updated: September 2, 2026

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The Short Answer

The little triangle stamped on the bottom of a plastic container was never designed to tell you anything about safety. The Society of the Plastics Industry created the seven-number system in 1988 purely to help recycling sorters separate resin types on a conveyor belt, and the number itself carries no toxicology information at all [1]. That said, the seven resins do not carry equal risk, and the differences track two things: what chemicals are built into or added to the polymer, and what condition the plastic is in when it touches your food, water, or air. HDPE (#2), LDPE (#4), and PP (#5) are the resins with the lowest documented leaching risk and no endocrine-disrupting additives built into the base polymer [2][3]. PVC (#3) relies on phthalate plasticizers linked to endocrine disruption, PS (#6) releases styrene, classified by IARC as probably carcinogenic, when it contacts heat or fat, and PC and other #7 resins historically relied on BPA, another confirmed endocrine disruptor now being phased out of food contact use in the EU [4][5][6]. PET (#1), the water-bottle resin, sits in the middle: low risk for a single cold use, but its antimony catalyst leaches measurably more once the bottle is heated, in a hot car or during reuse [7][8]. Every resin, regardless of number, sheds microplastic and nanoplastic particles through ordinary mechanical wear and heat, and that cross-cutting exposure is now associated with cardiovascular harm in a way the older, additive-specific concerns are not [9][10]. Because the risk profile splits so sharply by resin type and by how the plastic is used, this page earns a Mixed Signals rating: the number matters, but only once you know what it stands for.

Quick Answer: which plastic numbers are lower-risk?

• Lower-risk for food and drink: #2 (HDPE), #4 (LDPE), #5 (PP), with no endocrine-disrupting additives in the base resin and low leaching at room temperature [2][3].
• Higher-risk: #3 (PVC, phthalates), #6 (PS, styrene), #7 (PC/BPA and unidentified blends) [4][5][6].
• Middle case: #1 (PET), fine cold and single-use, but leaches more antimony once heated or reused [7][8].
• Cuts across all seven: heat, acidity, sunlight, and mechanical wear all increase leaching and microplastic shedding, regardless of resin number [9][11][12].
• Evidence Rating: Mixed Signals. Individual additives like phthalates and BPA have Strong Consensus endocrine-disruption data behind them; whether ambient microplastic/nanoplastic exposure itself causes disease is Not Enough to Say, despite a real and growing association [9][10][13].

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Table of Contents

• Identify: What the Recycling Triangle Numbers Mean
• Where Each Resin Shows Up
• How Plastic Chemicals and Particles Enter Your Body
• Investigate: Risk by Resin, #1 Through #7
• The Microplastics Problem Cuts Across All Seven
• What Canada, the US, and the EU Require
• Inform: What This Means for You
• Improve: How to Lower Your Plastic Exposure Without Panicking
• FAQ
• The Bottom Line
• References

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Identify: What the Recycling Triangle Numbers Mean

Every number 1 through 7 inside the chasing-arrows triangle is a Resin Identification Code, a system the Society of the Plastics Industry introduced in 1988 for exactly one purpose: helping recycling facilities sort incoming plastic by polymer type, since different resins have to be melted and reprocessed separately [1]. It was never a safety rating, never a toxicity scale, and the number climbing from 1 to 7 does not mean the plastic gets more dangerous. #7 in particular is simply “everything that didn’t fit the first six categories,” which is why it covers both resins with real documented concern, like polycarbonate, and comparatively inert newer bioplastics under a single digit [1].

The seven codes are: #1 PET (polyethylene terephthalate), #2 HDPE (high-density polyethylene), #3 PVC (polyvinyl chloride), #4 LDPE (low-density polyethylene), #5 PP (polypropylene), #6 PS (polystyrene), and #7 Other, a catch-all that includes polycarbonate, Tritan copolyester, acrylic, nylon, and various bioplastics. What determines whether a given piece of plastic leaches something worth worrying about is a combination of three things: whether the base polymer or its additives contain a known endocrine disruptor or carcinogen, what temperature and chemistry (fat, acid, alcohol) the plastic is exposed to, and how worn, scratched, or aged the item is [2][11][12]. The number is a useful shorthand for the first factor only, and this page walks through what each one means.

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Where Each Resin Shows Up

• #1 PET: water and soda bottles, peanut butter and salad dressing jars, most clear single-use beverage containers [7][8].
• #2 HDPE: milk jugs, detergent and shampoo bottles, most opaque household bottles [2].
• #3 PVC: some plastic cling wraps (particularly older or non-US formulations), plumbing pipe, vinyl flooring, blister packaging, and, historically, some teething toys and children’s items before phthalate restrictions tightened [4][14].
• #4 LDPE: bread bags, squeeze bottles, some cling films, the soft plastic that wraps produce [3].
• #5 PP: yogurt tubs, bottle caps, drinking straws, medicine bottles, and most “microwave-safe” reusable containers and baby-food tubs sold today [2][11].
• #6 PS: foam coffee cups, foam clamshell takeout containers, disposable cutlery, packing peanuts, and rigid clear cups and lids [5][15].
• #7 Other: reusable polycarbonate water bottles and 5-gallon office cooler jugs (especially older stock), the epoxy lining inside food and beverage cans, DVDs, sunglasses lenses, and newer BPA-substitute resins like Tritan used in many current “BPA-free” bottles [6][16][17].

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How Plastic Chemicals and Particles Enter Your Body

Plastic does not release its additives or shed particles under all conditions equally. Four specific triggers, well documented across the resins covered below, do most of the work [7][9][11][12]:

• Heat drives leaching up sharply, across nearly every resin. PET left in a hot car or reused after repeated dishwasher cycles releases measurably more antimony than the same bottle at room temperature; a study heating PET samples to 80°C for 48 hours saw antimony levels climb from roughly 0.2 μg/L to as high as 9.7 μg/L, above the drinking-water benchmark of 5–6 μg/L [7][8]. Polypropylene shows the same pattern: a 2025 study testing PP containers found zero endocrine-disrupting chemicals at refrigerator temperatures, but measurable DEHP, DBP, BBP, BPA, and nonylphenol once the water reached 40–100°C [11].
• Acidic and fatty foods pull chemicals out of plastic faster than water does. Styrene migration from polystyrene rises with both heat and fat content, and citrus juice or tomato sauce accelerates the same breakdown, which is why hot, oily takeout in a foam container is a worse combination than cold water in the same cup [5][15].
• UV exposure and general aging make plastic leach and shed more, not less, over time. Sunlight and repeated wear break down the polymer’s surface structure, which is part of why a scratched, cloudy, or sun-exposed plastic item is a higher-leaching item than a fresh one, independent of resin number [12].
• Mechanical wear and heat together are the main driver of microplastic and nanoplastic shedding, the exposure route covered in its own section below. A single 2023 study found that microwaving polypropylene baby-food containers for three minutes released as many as 4.22 million microplastic and 2.11 billion nanoplastic particles per square centimetre of container surface, far more than refrigeration or room-temperature storage of the same container [9].

Once released, the exposure reaches the body mainly through ingestion (eating or drinking what leached into food or water) and, for airborne dust and fibres, inhalation; skin contact is a comparatively minor route for most plastic exposure outside of specific product categories like flexible PVC medical tubing [7][9][12].

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Investigate: Risk by Resin, #1 Through #7

#1 PET: low risk cold, higher risk heated or reused. PET itself is not the concern; the catalyst used to manufacture it, antimony trioxide, is, and it remains in the finished bottle at roughly 100–300 mg/kg, meaning a one-litre bottle can contain 3–9 mg of antimony [7]. At room temperature, migration into the water is minimal and stays well under safety thresholds. Heat changes that: studies storing PET bottles at 50–80°C for extended periods measured antimony increases of 2 to 90 times baseline, in some cases approaching or exceeding the EPA’s 6 ppb drinking-water standard [7][8]. Antimony trioxide itself is classified by IARC as not classifiable as to carcinogenicity in humans (Group 3), so the concern here is General Consensus around avoiding heat exposure, not a settled carcinogenicity finding [7].

#2 HDPE: the lowest-concern resin in common use. HDPE is chemically stable, does not require phthalate plasticizers or BPA to function, and shows consistently low leaching across the available testing [2]. It is the resin most consumer-safety guides point to as a default safer choice, alongside LDPE and PP [2][3].

#3 PVC: phthalate plasticizers with Strong Consensus endocrine-disruption evidence. Rigid PVC is fairly inert, but flexible PVC, the kind used in some cling wraps, blister packs, and older children’s products, needs plasticizers to stay soft, and DEHP has historically been the most common one [4][14]. DEHP is classified by IARC as possibly carcinogenic to humans (Group 2B) and is listed under California’s Proposition 65 for both cancer and reproductive toxicity [4][18]. The endocrine evidence is substantial: DEHP exposure is associated with disrupted glucose and lipid metabolism in children, reproductive effects, and the ability to cross the placental barrier during pregnancy [14][19]. Both the EU and US restrict DEHP and related phthalates in children’s toys and childcare articles, covered in the regulatory table below [14][20].

#4 LDPE: similar low-concern profile to HDPE. LDPE does not require the same additive packages as PVC or PS, and available data shows low migration under normal use [3]. Its main practical downside is recyclability rather than health, since soft plastic film is harder for most municipal programs to process than rigid HDPE or PET.

#5 PP: solid at room temperature, more complicated once heated. Polypropylene has a high melting point (160–170°C) and has long been considered one of the more food-safe resins, which is why it dominates today’s “microwave-safe” container and baby-food-tub market [2][11]. Two 2025 findings complicate the “microwave-safe” label without overturning it entirely: a Scientific Reports study found measurable endocrine-disrupting chemical migration at 40–100°C, though levels stayed below EU and FDA regulatory limits, and a 2024 systematic review from the European Food Safety Authority concluded microplastics are released from food-contact materials mainly through mechanical wear during normal use [11][21]. Separately, the 2023 Nebraska study on microwaved PP baby-food containers found particle release in the millions to billions per square centimetre under heat specifically, not under refrigeration [9]. Read together, PP earns a real Mixed Signals verdict: low concern cold, real open questions once heated.

#6 PS: styrene leaching that regulators and IARC do not fully agree on. Polystyrene, especially the expanded foam form, releases styrene when it contacts heat, fat, or acid, and IARC updated its classification of styrene to Group 2A, probably carcinogenic to humans, in 2019 [5][15]. The FDA and EFSA still consider polystyrene food-service items acceptable, arguing the calculated acceptable daily intake for styrene is thousands of times higher than what people consume from food packaging [5]. That gap between IARC’s hazard classification and the regulators’ exposure-based risk assessment is a genuine, unresolved tension rather than a case of one side being simply wrong, and it is why hot coffee in a foam cup and oily takeout in a foam clamshell are the specific combinations worth avoiding even under the current permissive rules [5][15].

#7 Other: dominated historically by BPA, now a mixed bag of substitutes. The catch-all #7 category has long been associated with polycarbonate, the rigid, clear plastic used in older reusable water bottles, 5-gallon cooler jugs, and pre-2012 baby bottles, all of which relied on BPA [6][16]. BPA mimics estrogen and is linked to reproductive, developmental, and metabolic effects in laboratory studies [6]. The FDA banned BPA specifically from baby bottles and sippy cups in 2012, though notably in response to an industry petition after manufacturers had already voluntarily abandoned it in that category, not as a broader safety reversal, and the ban did not extend to other food packaging, water bottles, or can linings [16][22]. Many current “BPA-free” #7 products substitute Tritan copolyester or other bisphenols such as BPS; some research on these substitutes suggests similar estrogenic activity to BPA itself, which makes their long-term safety Not Enough to Say rather than a settled improvement [6][17].

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The Microplastics Problem Cuts Across All Seven

Every resin above sheds microscopic fragments through ordinary wear, heat, and friction, regardless of what number is stamped on it, and this exposure route is now drawing more research attention than any single additive [9][11][12]. Microplastics and nanoplastics have been detected in human blood, placenta, lungs, and breast milk, entering primarily through ingestion and inhalation [10][13]. The most striking recent data point comes from a 2024 study published in the *New England Journal of Medicine*, which found microplastics and nanoplastics embedded in carotid artery plaque in a majority of surgical patients tested, and those patients had a meaningfully higher rate of heart attack, stroke, or death over roughly three years of follow-up compared to patients without detectable particles in their plaque [10]. Proposed mechanisms include oxidative stress, mitochondrial dysfunction, and chronic low-grade inflammation from the particles themselves [10][13].

It is important to be precise about what this evidence does and does not show. The NEJM study is an association, not proof that the particles caused the cardiovascular events, and a 2025 systematic review concluded that microplastics are “suspected,” not confirmed, to affect human digestive, reproductive, and respiratory health, with causation not yet established [11][13]. That combination, biologically plausible mechanisms, a real and growing association in human tissue, and no confirmed causal pathway, is exactly what earns this exposure route a Not Enough to Say verdict rather than either dismissal or alarm.

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What Canada, the US, and the EU Require

Requirement	Canada	United States	European Union
BPA in food contact materials generally	Not restricted outside baby bottles; Health Canada maintains current BPA exposure levels are safe [23]	Not restricted outside baby bottles and infant formula packaging [16][22]	Banned as of January 20, 2025 (Regulation 2024/3190), with transition periods of 18–48 months by product category, fully phased out by 2028 [6]
BPA in baby bottles / sippy cups	Banned since 2010 under the Canada Consumer Product Safety Act	Banned as of December 2012 (industry-petition-driven) [16]	Banned, and now folded into the broader 2025 bisphenol ban [6]
DEHP and related phthalates in toys/childcare articles	Limited to 1,000 mg/kg (0.1%) in soft vinyl for children under 4, under the Phthalates Regulations (SOR/2016-188) [20]	Banned above 0.1% in children’s toys and childcare articles since 2008 (CPSIA) [14]	Restricted above 0.1% by weight under REACH Annex XVII, entries 51 and 52, since 2020 [24]
DEHP cancer/reproductive listing	Assessed under CEPA as toxic; no consumer warning label requirement	Listed under California Proposition 65 for cancer (since 1988) and reproductive/developmental toxicity (since 2003); no federal equivalent [18]	Classified as a substance of very high concern under REACH
Polystyrene foodservice items (foam cups, clamshells)	Not federally restricted; some provincial/municipal bans	Not federally restricted; numerous state and city-level foam foodservice bans	Expanded and extruded polystyrene food containers and cups banned under the 2021 Single-Use Plastics Directive
Pre-market safety review for food-contact plastics	Post-market notification model; Health Canada can act after the fact	FDA pre-market clearance for new food-contact substances, but legacy resins are largely grandfathered	European Food Safety Authority pre-market opinion required for new food-contact substances

The clearest pattern here: the EU is consistently the most precautionary, with the broadest BPA ban of the three and the only foam-foodservice ban that applies nationwide rather than by patchwork. The US sits in the middle, with meaningful federal action on phthalates in children’s products but a narrow, baby-bottle-only BPA rule and no federal foam ban, leaving that gap to states and cities. Canada is the most permissive on BPA specifically, restricting it only where children’s direct exposure is highest, while matching the US fairly closely on phthalates in children’s products.

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Inform: What This Means for You

• The number on the bottom of a container tells you the polymer, not the safety level. #2, #4, and #5 are the resins with the cleanest leaching profile at room temperature; #3, #6, and #7 carry the most additive-related concern [2][4][5][6].
• Heat is the single biggest lever across every resin. The same PET bottle, PP container, or PS cup that is low-risk cold becomes measurably higher-risk once it is microwaved, dishwashed repeatedly, or left somewhere hot [7][9][11].
• “Microwave-safe” describes structural stability, not zero chemical migration. PP holds its shape in a microwave; that is a different claim than “releases nothing,” and 2025 testing found it does release measurable amounts of several regulated chemicals under heat, even if current levels stay under regulatory limits [11].
• “BPA-free” is not the same as “additive-free.” Many BPA-free #7 products substitute other bisphenols or Tritan copolyester, some of which show similar estrogenic activity in early research, making this a case of Not Enough to Say rather than solved [6][17].
• Microplastic and nanoplastic exposure happens regardless of which resin you choose, through ordinary wear and heat, and it is the one plastic-related health question where the science is moving fastest and remains the least settled [9][10][13].

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Improve: How to Lower Your Plastic Exposure Without Panicking

1. Never microwave or add boiling liquid to any plastic, including containers labeled microwave-safe. Transfer food to glass or ceramic first; this single habit addresses the heat-driven leaching and particle-shedding risk across nearly every resin covered above [9][11].
2. Default to #2, #4, and #5 for food storage, and treat #3, #6, and #7 as the ones to actively avoid for food and drink when a choice is available [2][3][4][5][6].
3. Don’t leave PET water bottles in a hot car, and don’t reuse single-use PET bottles indefinitely. Antimony leaching rises sharply with heat and repeated use, which single-use bottles were never designed for [7][8].
4. Retire scratched, cloudy, or visibly aged plastic containers, since surface degradation from wear and UV exposure increases both chemical migration and microplastic shedding, independent of resin type [12].
5. Keep hot, fatty, or acidic food out of foam containers and cling wrap contact, the specific combination that pulls the most styrene and phthalates out of PS and PVC [5][14][15].
6. When you want to eliminate plastic contact with hot liquid entirely, use glass or stainless steel (see Glass and Stainless Steel) rather than hunting for a “safer” hot-use plastic, since none of the seven resins is designed to be chemically inert under heat.

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FAQ

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The Bottom Line

The recycling triangle was built to sort plastic for recycling, not to rank it for safety, and once you separate the two, the seven resins split clearly by risk [1]. HDPE (#2), LDPE (#4), and PP (#5) are the lowest-concern choices for food and drink at room temperature, while PVC (#3) carries Strong Consensus phthalate endocrine-disruption evidence, PS (#6) leaches styrene that IARC classifies as probably carcinogenic under heat and fat exposure, and PC and other #7 resins are built around BPA or its substitutes, whose long-term safety is still being worked out [2][4][5][6]. PET (#1) is a genuine middle case: fine cold and once, riskier heated or reused [7][8]. Underneath all of that, every resin sheds microplastic and nanoplastic particles through ordinary heat and wear, and that cross-cutting exposure, now linked to cardiovascular findings but not yet proven causal, is the open question worth watching most closely [9][10][13]. Skip the microwave with any plastic, default to #2, #4, and #5 for storage, and reach for glass or stainless for anything hot, and you have addressed nearly everything the evidence supports worrying about.

Stay curious, stay critical.
Georden

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References

1. “Get to Know Plastic Resin Codes.” Pertachem.
2. “Is HDPE Food Safe? Guide to Food Grade Polyethylene (#2).” Shobeir Shimi.
3. “Safety assessment of a process to recycle post-consumer HDPE closures into food contact closures.” PMC.
4. “Early-life exposure to di(2-ethyl-hexyl) phthalate: Role in children with endocrine disorders.” PMC.
5. “Assessment of the impact of the IARC Monograph Vol. 121 on the safety of styrene (FCM No 193) for its use in plastic food contact materials.” PMC.
6. “Commission adopts ban of Bisphenol A in food contact materials.” European Commission Food Safety.
7. “Effects of storage time and temperature on the antimony and some trace element release from polyethylene terephthalate (PET) into bottled drinking water.” PMC.
8. “Antimony in Polyethylene Terephthalate-Bottled Beverages: The Migration Puzzle.” PMC.
9. Hussain, K.A. et al. “Assessing the Release of Microplastics and Nanoplastics from Plastic Containers and Reusable Food Pouches: Implications for Human Health.” Environmental Science & Technology, 2023.
10. “Microplastics and Nanoplastics in Atheromas and Cardiovascular Events.” New England Journal of Medicine.
11. “Cooking food in microwavable plastic containers: in situ formation of a new chemical substance and increased migration of polypropylene polymers.” ScienceDirect.
12. “A Fast and Automated Strategy for the Identification and Risk Assessment of Unknown Substances in Plastic Food Contact Materials: Recycled LDPE as a Proof-of-Concept.” PMC.
13. “Microplastic and nanoplastic pollution and associated potential disease risks.” The Lancet Planetary Health.
14. “Regulatory framework of phthalates and two common alternatives: A review of European Union legislation.” ScienceDirect.
15. “Can You Microwave Styrofoam? Safety Guide.” Styrofoam World.
16. “Federal Ban on BPA in Baby Bottles Offers Limited Protections.” NRDC.
17. “Are ‘BPA-Free’ Plastics Actually Safe for Babies? What Science Says.” Americord Registry.
18. “Di(2-ethylhexyl)phthalate (DEHP).” California Proposition 65 Warnings Website (OEHHA).
19. “Endocrine Disruption: Structural Interactions of Androgen Receptor against Di(2-ethylhexyl) Phthalate and Its Metabolites.” PMC.
20. “Phthalates Regulations (SOR/2016-188).” Justice Laws Website, Government of Canada.
21. “Molded Fiber Food Packaging with PFAS: Is It Safe and Compostable?” Imperial Dade.
22. “BPA: FDA Bans Endocrine-Disrupting Chemical from Baby Bottles and Sippy Cups.” TIME.
23. “Bisphenol A (BPA) in Canadians.” Health Canada.
24. “REACH Annex XVII Substances List: An Overview.” ComplianceGate.

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Georden Jones is the founder of The Peer Review. Read the full story.