The Short Answer
If you have to use a disposable plastic bag, Ziploc is the best option available.
Recent independent testing found that Ziploc was the only major brand that did not contain detectable levels of PFAS ("forever chemicals"). Generic and store brands from Target, Walmart, and others failed this test, showing high levels of organic fluorine.
However, "clean plastic" is still plastic. While Ziploc bags are free from BPA and phthalates, we strongly recommend you avoid heating them. Microwave "safe" labels only mean the plastic won't melt—not that it won't leach chemicals into your food.
Why This Matters
For decades, we worried about BPA in hard plastics. Now, the concern has shifted to PFAS (per- and polyfluoroalkyl substances), which are often used in food packaging to make it grease-resistant.
PFAS are linked to hormone disruption, immune system suppression, and cancer. Finding out that most sandwich bags contain these chemicals is a massive red flag for lunchboxes everywhere. The fact that Ziploc appears to be manufacturing their bags without these chemicals is a significant win for the brand.
But the new frontier of risk is microplastics. A 2025 class-action lawsuit and emerging studies suggest that when plastic is stressed—by the high heat of a microwave or the freezing cold of a freezer—it sheds millions of microscopic plastic particles directly into your food.
What's Actually In Ziploc Bags
SC Johnson (the parent company) is transparent about their materials compared to competitors.
- Polyethylene (LDPE/LLDPE) — The main body of the bag. It is generally considered one of the "safer" plastics (Resin Code #4) because it uses fewer additives than PVC or Polycarbonate. What Plastic Containers Are Safe For Food
- Polypropylene (PP) — Often used for the zipper mechanism to provide the "snap" closure.
- Dye — Used in the color-coded "Smart Zip" seals (the pink and blue lines).
What is NOT in them:
- BPA — Ziploc bags are BPA-free.
- Phthalates — They do not use phthalate plasticizers to make the bags soft (LDPE is naturally flexible).
- Dioxins — SC Johnson confirms their bags are dioxin-free and do not create dioxins unless burned at 1500°F.
What to Look For
Green Flags:
- Brand Name Matters — In this specific category, the name brand (Ziploc) consistently outperforms store brands in safety tests.
- Platinum Silicone — If you want to heat food, look for platinum silicone bags like Stasher. Are Silicone Storage Bags Safe
Red Flags:
- "Microwave Safe" Labels — Ignore them. This label is a durability claim, not a health guarantee. Heating plastic accelerates chemical migration. Are Plastic Storage Bags Microwave Safe
- Store Brands — "Great Value" (Walmart), "Up & Up" (Target), and "Boulder" bags all tested positive for PFAS markers in 2024.
- Cloudy or Old Bags — If a bag looks scratched or cloudy, the plastic is degrading. Throw it out.
The Best Options
If you need disposable bags, buy the real thing. If you want to cook or heat food, switch to silicone.
| Brand | Product | Verdict | Why |
|---|---|---|---|
| Ziploc | Standard Storage Bags | ✅ | Passed PFAS testing; BPA-free. |
| Stasher | Silicone Bags | ✅ | Heat-safe; no microplastics; reusable. |
| Store Brands | Generic Sandwich Bags | 🚫 | 81% failed PFAS purity tests. |
| Hefty | Slider Bags | ⚠️ | Mixed testing results; exercise caution. |
The Bottom Line
1. Buy Ziploc, not generic. It is the only brand proven to be PFAS-free in recent independent labs.
2. Keep them cool. Use them for sandwiches, snacks, and room-temp storage.
3. Never microwave them. Transfer food to a glass container or plate before heating. Is Safe To Microwave Food In Plastic
FAQ
Can I put Ziploc bags in the microwave?
No. While the company says they are "microwave safe" for defrosting, heating plastic dramatically increases the release of microplastics and chemical additives into your food. Use glass for heating.
Do Ziploc bags contain BPA?
No. Ziploc bags are made from polyethylene, which does not require Bisphenol-A (BPA) in its manufacturing. They have been BPA-free for many years.
Can I recycle Ziploc bags?
Yes, but not at home. You cannot put them in your curbside bin because they jam recycling machines. You must take them to store drop-off locations (often at grocery stores) that accept plastic film. They must be clean and dry.
Are Ziploc bags safe for sous vide?
We don't recommend it. While many people do it, sous vide involves heating plastic in contact with food for long periods. Even at lower temperatures, this increases the risk of leaching. Use food-grade silicone bags designed for high heat instead.