Plasticizer migration is when chemical additives that make plastics flexible slowly leak out of the material over time. Think of it like oil seeping out of a sponge—these chemicals don’t stay locked in place and can move into whatever touches the plastic, whether that’s food, your skin, or even the air around you.
Plasticizers are essentially the “softening agents” of the plastic world. Without them, materials like PVC would be rigid and brittle, like a hard plastic pipe. With plasticizers added, that same material becomes flexible enough to make things like shower curtains, food wrap, or medical tubing.
The problem is these chemicals aren’t chemically bonded to the plastic—they’re just mixed in. This means they can escape, especially when the plastic gets warm, old, or comes into contact with certain substances.
How Does Plasticizer Migrate
Plasticizers escape from plastic through three main pathways: they evaporate into the air, dissolve into liquids, or transfer directly to other solids they touch.
Volatilization (Gas Phase Migration)
Volatilization occurs when plasticizers evaporate directly from the plastic surface into the surrounding air. It’s like how water slowly evaporates from a wet towel—except these chemicals are evaporating from what looks like solid plastic.
Heat accelerates this process dramatically. Leave a plastic item in a hot car, and the plasticizers will volatilize much faster than at room temperature. This is why the inside of your car might develop that “new car smell” or why old plastic items sometimes have a distinct chemical odor.
You’ve probably noticed this with vinyl shower curtains. That strong plastic smell when you first hang a new curtain? That’s plasticizers volatilizing into your bathroom air.
Extraction (Liquid Migration)
Extraction happens when plasticizers dissolve into liquids that contact the plastic. Fatty foods and oils are particularly good at pulling plasticizers out of plastic packaging—it’s why storing olive oil in certain plastic bottles can be problematic.
This migration type is especially concerning with food packaging. When plastic wrap touches cheese or meat, the fats in these foods can literally extract plasticizers from the wrap and absorb them.
Water can also extract plasticizers, though usually more slowly than oils. However, hot water speeds up the process significantly, which is why microwaving food in certain plastics or running plastic items through the dishwasher can increase migration rates.
Solid-to-Solid Migration (Contact Migration)
Contact migration occurs when plasticizers move directly from one solid material to another through direct contact. It’s like how a marker can bleed through paper—the chemicals move from one surface to the other without any liquid or air involved.
This type often happens in stacked products or when different materials are stored together. For instance, if you wrap leftovers in plastic wrap and it sits against other food items in your fridge, plasticizers can migrate directly into those foods.
The migration rate depends on how compatible the materials are. Plasticizers move more easily into materials with similar chemical properties, which is why they migrate readily into other plastics or fatty substances.
Why is Plasticizer Migration Bad
Plasticizer migration creates several serious problems that affect both human health and product quality:
- Health risks from chemical exposure: Many plasticizers, particularly phthalates, are endocrine disruptors that can interfere with hormone function. They’ve been linked to developmental issues in children, fertility problems, and certain cancers.
- Food contamination: When plasticizers migrate into food, you’re essentially eating chemicals that were never meant to be consumed. This is especially concerning with fatty foods that absorb plasticizers more readily.
- Product degradation: As plasticizers leave, the plastic becomes brittle and cracks. That flexible vinyl becomes hard and breaks easily, rendering products useless long before they should fail.
- Environmental pollution: Migrated plasticizers don’t just disappear—they accumulate in soil, water, and air. These chemicals persist in the environment and can affect wildlife and ecosystems.
- Indoor air quality issues: Volatilized plasticizers contribute to poor indoor air quality. They’re part of what researchers call “sick building syndrome,” where people experience health symptoms from chemical exposure in buildings.
- Contamination of other materials: Plasticizers can migrate into and damage other products, leaving stains, causing discoloration, or making materials sticky and degraded.
How to Remove Plasticizer Migration
While you can’t completely reverse plasticizer migration that’s already occurred, you can minimize future migration and reduce exposure:
- Replace old plastic items: Older plastics have had more time to degrade and typically have higher migration rates. Replace aging plastic food containers, especially those showing signs of wear.
- Use barrier layers: Place parchment paper or aluminum foil between plastic wrap and food. This physical barrier prevents direct contact and reduces migration into your food.
- Control temperature: Store plastic items in cool, dry places away from heat sources. Never microwave food in plastic containers unless they’re specifically labeled microwave-safe.
- Choose plasticizer-free alternatives: Look for products labeled “phthalate-free” or “BPA-free.” Better yet, switch to glass, stainless steel, or ceramic containers for food storage.
- Improve ventilation: In spaces with many plastic items, increase air circulation to dilute and remove volatilized plasticizers. Open windows regularly and use exhaust fans.
- Clean surfaces regularly: Wipe down plastic items with mild soap and water to remove surface plasticizers. This won’t stop migration but can reduce the amount available to transfer.
- Limit contact time: Don’t store food in plastic for extended periods. Transfer items to non-plastic containers for long-term storage, especially for fatty foods and liquids.
- Select appropriate plastics: When you must use plastic, choose types with lower migration rates. Polyethylene and polypropylene generally have less plasticizer migration than PVC.
FAQs
What foods absorb the most plasticizers?
Fatty foods like cheese, meat, oils, and butter absorb plasticizers most readily. The chemical structure of fats makes them particularly good at extracting these chemicals from plastic packaging, which is why these foods should ideally be stored in glass or other non-plastic containers.
Can you smell plasticizer migration?
Yes, you often can smell it—that “new plastic” or “vinyl” smell is actually plasticizers volatilizing into the air. If a plastic item has a strong chemical odor, it’s actively releasing plasticizers, and you should ensure good ventilation.
Are all plasticizers harmful?
Not all plasticizers are equally harmful, but many common ones like phthalates have known health risks. Newer bio-based plasticizers are being developed as safer alternatives, though research on their long-term effects is still ongoing.
How long does plasticizer migration continue?
Migration continues throughout the entire lifespan of the plastic product, though it typically starts fast and slows over time. A plastic item can continue releasing plasticizers for years or even decades, though the rate decreases as the plasticizer content depletes.
Can washing plastic remove plasticizers?
Washing can remove some surface plasticizers but won’t stop migration from within the material. Hot water and harsh detergents can actually increase migration rates, so use cool water and mild soap when cleaning plastic items you’ll continue using.
Which plastics have the most plasticizers?
Flexible PVC (polyvinyl chloride) contains the highest levels of plasticizers, often 30-40% by weight. Soft, bendable plastics like shower curtains, plastic wrap, and vinyl flooring typically have more plasticizers than rigid plastics.