Flip over a plastic container and you’ll see a small number inside a triangle. That number is the resin code. Three of those numbers get flagged for safety concerns more than any others.
This guide answers the question directly. We’ll name the three plastics, explain why each one raises concerns, and show you what a reputable plastic molding service recommends instead. Whether you’re a shopper checking a water bottle or a product designer specing resin for a molded part, the answers are the same.
Here’s what you’ll find in the sections ahead:
The three plastics most commonly flagged as unsafe are:
Each one is fine for certain industrial uses. They are generally avoided in food contact, children’s products, and medical applications.
Most plastic safety concerns come back to three resin codes: #3, #6, and #7. Here’s a quick look at each one and where you’ll run into them.
| Resin Code | Plastic | Common Products | Main Concern |
| #3 | PVC (Polyvinyl Chloride) | Pipes, flooring, shrink wrap, some medical tubing | Phthalates and chlorine-based additives |
| #6 | Polystyrene (PS) | Foam cups, clamshell takeout containers, plastic cutlery | Styrene migration into hot or fatty foods |
| #7 | Polycarbonate (PC) | Water bottles, clear food storage, some baby bottles | BPA content |
You’ll find the resin code stamped inside a small triangle on the bottom of most plastic products. The numbers come from ASTM International’s D7611 standard, which defines seven resin categories.
One important note: “unsafe” depends on the application. A PVC drain pipe is not the same risk as a PVC food wrap. Heat, contact type, and what the part touches all matter.
Black plastics also deserve a mention. They’re often made from recycled electronics and can carry flame retardants or heavy metals. We steer clients away from black resins for any food- or skin-contact part.
When a client asks us to quote a food-contact part, these three resins trigger an automatic material review in our shop. We flag them early so you don’t have to rework the design later.
PVC is one of the most widely used plastics in the world. You’ll find it in water pipes, vinyl flooring, shrink wrap, window frames, and some medical tubing. It’s cheap, durable, and easy to mold.
The problem is the chemistry. PVC is built on a chlorine backbone and almost always needs added softeners called phthalates to make it flexible. Older formulations also used lead-based stabilizers. Both can migrate out of the plastic over time.
Risk shows up in two places:
PVC is still a solid choice for the right job. Cold-water pipes, electrical insulation, and non-contact industrial parts are all fine uses. Regulators have pushed back on the risky applications. The EU has restricted several phthalates in consumer PVC under REACH, and the U.S. Consumer Product Safety Commission limits them in children’s toys.
In our shop we do run PVC for industrial parts. We flag it for any product that will touch food, skin, or a child’s mouth.
Most people know polystyrene as foam coffee cups and clamshell takeout boxes. It also shows up as rigid plastic in cutlery, yogurt lids, and CD cases. The foam version is called EPS (expanded polystyrene).
The main concern is a chemical called styrene. Small amounts can migrate out of the plastic and into whatever it’s holding. The National Toxicology Program lists styrene as “reasonably anticipated to be a human carcinogen.”
Two things make the risk worse:
Regulators have taken notice. New York, New Jersey, Maine, Washington, and dozens of cities have banned or restricted EPS foam in food service. More states review similar rules each year.
Polystyrene also has manufacturing downsides. It’s brittle, cracks under stress, and holds up poorly against oils and solvents. Even setting aside the health concerns, it’s a weak pick for most durable molded parts.
Polycarbonate is the clear, tough plastic that made reusable water bottles popular in the first place. It’s strong, heat-resistant, and optically clear. You’ll still see it in eyewear lenses, electronics housings, safety shields, and automotive parts.
The concern is a building-block chemical called BPA (bisphenol A). Polycarbonate is made by linking BPA molecules together. Small amounts can leach out, especially when the plastic is heated, scratched, or aging. BPA is an endocrine disruptor, meaning it can mimic hormones in the body.
That’s why baby bottles, sippy cups, and most reusable water bottles moved away from polycarbonate over the last 15 years. The FDA banned BPA in baby bottles and sippy cups in 2012.
One source of confusion: the #7 code is a catch-all for “other.” Not every #7 plastic is polycarbonate. Bio-based plastics and newer copolyesters also get labeled #7.
Safer clear alternatives include:
For clients who need a clear, tough resin for a consumer product, we typically recommend Tritan or a similar BPA-free copolyester instead of polycarbonate.
Knowing what to avoid is only half the answer. Here’s what to use instead for food, medical, and everyday consumer products.
Here’s a side-by-side look at what to swap:
| Avoid | Safer Swap | Typical Use |
| PVC (#3) | HDPE or PP | Food packaging, children’s products |
| Polystyrene (#6) | PP or PLA | Takeout containers, cutlery, cups |
| Polycarbonate (#7) | Tritan copolyester | Reusable water bottles, clear food storage |
| PVC medical tubing | Medical-grade TPE | Flexible tubing, skin-contact devices |
We run most of these safer resins in production, including PP, ABS, TPU, and TPE. If you’re choosing a material for a molded part, we can walk you through which one fits your end use, budget, and volume.
Resin choice is the first real decision in any molded-part project. Pick the wrong material and the mold, the tolerances, and the end-use performance all suffer. Pick the right one and the rest of the project gets easier.
A good plastic molding service runs a material review before anything gets cut. That review usually covers:
Custom plastic injection molding is where that review pays off. The right resin, matched to the right part geometry and run size, sets up everything downstream.
When you reach out, it helps to have a few things ready:
Freeform Polymers has run plastic molding out of North Logan, Utah since 2011. We’re ISO 9001:2015 certified, and every quote we send includes a material review from our engineering team. If a resin raises a safety flag for your application, we’ll tell you before the mold gets built.
Ready to spec the right resin for your product? Contact us and request a quote from our team or stop by our North Logan shop today!
