Plastic Numbers 1 to 7: Complete Guide to Food Container Symbols and Which Are Safe for Use and Heating

Introduction: Are Plastic Food Containers Safe?

We all use plastic containers daily to store food in the refrigerator, reheat it in the microwave, and transport it to work or school. But have you ever wondered about those small numbers surrounded by a triangle of arrows at the bottom of these containers? These numbers are not random but rather an international classification system that tells you the type of plastic used and how safe it is for food use.

In this comprehensive guide, we will reveal everything you need to know about the seven types of plastic, which ones are safe for repeated use, and which ones should be avoided entirely. We will also explain other symbols found on containers and discuss recent scientific research that has revealed shocking facts about microplastics and their effects on our health.

What Are Plastic Numbers 1 to 7?

The plastic numbering system is called the Resin Identification Code and was developed by the American Plastics Industry Association to help recycling plants sort different types of plastic. The number inside the triangle indicates the type of resin or polymer used to manufacture this plastic. Each type has different properties in terms of durability, heat resistance, and most importantly, its safety for use with food and beverages.

It is important to understand that the presence of the triangle symbol does not necessarily mean that the plastic is recyclable in your area as this depends on local recycling facilities. What matters most for your health is knowing which numbers are safe for food use and which should be avoided.

Number 1: Polyethylene Terephthalate PET or PETE

This is the most common type of plastic and is used to make water bottles, soft drink bottles, peanut butter jars, salad dressings, and vegetable oils. It is characterized by being lightweight, transparent, inexpensive, and easy to recycle.

Is it Safe?

Plastic number 1 is safe for single use only. The problem is that it is designed for single use and reusing it increases the risk of chemical leaching and bacterial growth because it is difficult to clean completely. It may also leach potential carcinogens when exposed to heat.

Important Tip

Do not reuse plastic water bottles, do not leave them in the car under sunlight, and never heat them in the microwave. Use them once then dispose of them in the recycling bin.

Number 2: High Density Polyethylene HDPE

This plastic is strong, durable, and usually opaque. It is used to make milk jugs, detergent containers, shampoo bottles, yogurt containers, and some grocery bags. It is characterized by its high resistance to chemicals.

Is it Safe?

Plastic number 2 is considered one of the safest types of plastic for food use. It has a low risk of chemical leaching and can be reused relatively safely. However, it is preferable not to heat it in the microwave unless it is marked as microwave safe.

Important Tip

This is a good choice for storing food in the refrigerator. Make sure to wash it well between uses and replace it if scratches or discoloration appear.

Number 3: Polyvinyl Chloride PVC

This plastic is used to make clear food wraps, some cooking oil containers, plumbing pipes, and old children's toys. It is characterized by its flexibility and ability to resist oils and fats.

Is it Safe?

Plastic number 3 is dangerous and should be avoided entirely with food. It contains phthalates which are chemicals added to make plastic flexible and these substances are known to cause hormone disruption. Its manufacturing and disposal also produces toxic substances harmful to the environment and health.

Important Tip

Avoid buying food products wrapped in this type of plastic as much as possible. Never use it to store food and never heat it in any way.

Number 4: Low Density Polyethylene LDPE

This plastic is flexible and thin and is used to make grocery bags, bread bags, plastic food wraps, some flexible juice containers, and carpets.

Is it Safe?

Plastic number 4 is relatively safe for food storage and has a low risk of chemical leaching. However, there is an important exception which is plastic food wraps made from this type as studies have shown they contain phthalates that can leach into food especially fatty foods.

Important Tip

Bags and containers made from this type can be reused but avoid heating them. Do not cover hot food with plastic wraps of this type.

Number 5: Polypropylene PP

This is the hero in the world of food plastic. It is used to make yogurt containers, reusable food containers, bottle caps, medicine containers, and some car parts. It is characterized by its high resistance to heat and chemicals.

Is it Safe?

Plastic number 5 is considered the safest for food storage and heating. It can withstand high temperatures up to 110 degrees Celsius and has the lowest risk of chemical leaching. Most containers marked as microwave safe are made from this type.

Important Tip

When buying plastic food containers look for number 5 at the bottom of the container. This is the best choice if you must use plastic. However, even with this type it is preferable to transfer food to a glass container before heating.

Number 6: Polystyrene PS

This is the famous foam or Styrofoam. It is used to make hot coffee cups, restaurant takeout containers, egg cartons, plastic cutlery, and meat trays in supermarkets.

Is it Safe?

Plastic number 6 is dangerous and should be avoided. It can leach styrene which is a substance classified as a possible human carcinogen. Leaching increases significantly when exposed to heat or fatty or acidic foods. It is also difficult to recycle and makes up a large percentage of waste in landfills.

Important Tip

Do not drink hot coffee or tea from foam cups. Never heat food in Styrofoam containers. Transfer food to another container as soon as it arrives from the restaurant.

Number 7: Other

This category includes all types of plastic that do not fall under numbers 1 to 6. It includes polycarbonate, nylon, bioplastic, and others. Found in large 5-gallon water bottles, some baby food containers, sunglasses, and DVDs.

Is it Safe?

Plastic number 7 is concerning because it may contain bisphenol A known as BPA. This substance is a known endocrine disruptor and can mimic the hormone estrogen in the body leading to fertility problems, growth issues, and increased risk of some cancers. Even BPA-free alternatives like BPS and BPF may also be harmful.

Important Tip

Avoid this type as much as possible especially with children. If you have large water bottles of this type do not leave them in a hot place and do not refill them often.

Other Important Symbols on Plastic Containers

In addition to plastic numbers there are other important symbols you should know to use containers safely.

Food Safe Symbol

Appears as a cup and fork and means this container is safe for food contact. This symbol is essential because not all plastic is designed for food use.

Microwave Safe Symbol

Appears as wavy lines or a microwave image and means the container can be used in the microwave. But note this only means the container will not melt and does not necessarily mean it will not leach chemicals.

Freezer Safe Symbol

Appears as a snowflake and means the container can withstand low temperatures in the freezer without cracking or breaking.

Dishwasher Safe Symbol

Appears as dishes with water drops and means the container can withstand high heat and detergents in the dishwasher. If the drops are only at the top this means top rack only.

BPA-Free Symbol

Indicates that the container does not contain bisphenol A. But remember that alternatives may not be completely safe either.

Why Is Heating Plastic in the Microwave Dangerous?

When you heat food in a plastic container in the microwave two dangerous things happen. First is the leaching of chemicals from the plastic into the food and second is the release of very small particles of the plastic itself called microplastics and nanoplastics.

Shocking Discovery from Research

A recent scientific study published in the journal Environmental Science and Technology found that heating a plastic container in the microwave for just 3 minutes can release up to 4.22 million microplastic particles and 2.11 billion nanoplastic particles from each square centimeter of plastic surface. These numbers are amazing and frightening at the same time.

Even Refrigeration Is Not Completely Safe

The same study found that storing food in plastic containers in the refrigerator or at room temperature for more than 6 months can also release millions to billions of microscopic plastic particles.

Children Are Most at Risk

The study calculated that the highest daily dose of microplastics reaches infants who drink milk or water heated in plastic containers. Young children are more susceptible to harm because their bodies are still developing and their immune systems are weaker.

Microplastics and Their Effect on Your Health

Microplastics are very small pieces of plastic less than 5 millimeters in size while nanoplastics are much smaller and can penetrate cell barriers. Recent research has discovered the presence of these particles in places we never imagined before.

Where Have They Found Microplastics?

Recent studies have found microplastics in human brain tissue, heart, lungs, liver, kidneys, blood, urine, breast milk, placenta, and testicles. A study published in 2025 in Nature Medicine found that the concentration of microplastics in the brain was 7 to 30 times higher than in the liver and kidneys.

Potential Health Risks

An important study published in the New England Journal of Medicine in 2024 found that people who had microplastics in their carotid arteries were twice as likely to have a stroke or heart attack or die compared to those without. Chemicals associated with plastic such as BPA and phthalates are known endocrine disruptors meaning they interfere with how hormones work in the body.

Potential Effects Include

Disruption of appetite and metabolism which may lead to obesity, diabetes, and heart disease. Disruption of cell growth regulation which may increase cancer risk. Effects on neurodevelopment which may cause learning and behavior problems. Effects on the reproductive system which may cause early puberty, infertility, and birth defects in males. A 2024 study linked phthalates to more than 100,000 premature deaths annually.

Quick Summary: Which Plastics Are Safe?

Relatively Safe Types

Number 2 HDPE is safe for food storage and can be reused. Number 4 LDPE is safe for storage but avoid food wraps made from it. Number 5 PP is the safest and heat resistant and suitable for microwave.

Types to Avoid

Number 1 PET for single use only and never heat it. Number 3 PVC is dangerous and contains phthalates avoid it completely. Number 6 PS is dangerous and leaches styrene never heat it. Number 7 Other may contain BPA avoid it with food.

Safe Alternatives to Plastic Containers

The best way to protect your health and your family's health is to reduce plastic use as much as possible and replace it with safer alternatives.

Glass Containers

Glass is the best and safest choice. It does not react with food and does not leach any chemicals and can be used in the microwave, oven, freezer, and dishwasher. The only drawback is that it is breakable and heavier. Look for glass containers with silicone or bamboo lids.

Stainless Steel Containers

Stainless steel is an excellent choice especially for transporting food. Very durable and does not react with food and easy to clean. However, it cannot be used in the microwave and you cannot see what is inside.

Ceramic Containers

Ceramic is safe for food and can be used in the microwave and oven. Make sure it is lead-free and made for food use.

Food Grade Silicone

Food-grade silicone is a good and flexible alternative. It can withstand high and low temperatures and does not react with food. Ideal for container lids and baking molds.

Practical Tips for Safe Use

In the Microwave

Always transfer food to a glass or ceramic container before heating. Do not heat food in takeout containers or any plastic container even if it says microwave safe. Use wax paper or paper towels to cover food instead of plastic wraps.

In the Refrigerator

If you use plastic containers choose number 5 PP. Transfer food from takeout containers to appropriate containers as soon as it arrives. Do not store fatty or acidic foods in plastic for long periods.

When Buying

Flip the container and look for the number in the triangle. Choose numbers 2 or 4 or 5 and avoid 3, 6, and 7. Look for the food safe symbol cup and fork. Choose products marked BPA-free.

Container Care

Replace any container with scratches, cracks, or discoloration. Do not use abrasive cleaners with plastic containers. Wash by hand if not designed for the dishwasher. Replace plastic containers every 3 to 5 years even if they look fine.

Frequently Asked Questions

Is All Plastic Marked Microwave Safe Actually Safe?

The microwave safe symbol only means the plastic will not melt in the microwave but does not guarantee that chemicals or microplastics will not leach into food. It is always best to transfer food to a glass container before heating.

Can I Reuse Plastic Water Bottles?

Not recommended. Water bottles are designed for single use and number 1 PET degrades with repeated use and washing which increases the risk of chemical leaching and bacterial growth. Use a reusable water bottle made of stainless steel or glass.

Is BPA-Free Plastic Completely Safe?

Not necessarily. Many companies have replaced BPA with alternatives like BPS and BPF and these alternatives may also be harmful. Studies showed that 70 percent of plastic products release estrogen-like chemicals and the percentage rises to 95 percent when heated.

Is Storing Food in Plastic in the Freezer Safe?

Freezing is less risky than heating but is not risk-free. A study found that frozen food containers release a greater amount of small plastic particles. If you use plastic for freezing choose number 5 and make sure there is a freezer safe symbol.

What About Silicone Bags Are They Safe?

Food grade silicone is generally considered safe. It does not contain BPA or phthalates and does not react with food. Make sure it says food grade or is designated for food.

Are Restaurant Takeout Containers Safe?

Most takeout containers are made from number 5 PP or number 6 PS Styrofoam. Transfer food to another container as soon as it arrives home and never heat it in the same container.

How Do I Dispose of Old Plastic?

Empty and wash containers then place them in the recycling bin if they bear number 1, 2, or 5. Other numbers are difficult to recycle and usually go to landfills. Do not burn plastic because it produces toxic gases.

Conclusion

Plastic is part of our daily lives but not all types are equally safe. Numbers 1 to 7 are not just recycling symbols but your guide to knowing which plastic you can use relatively safely and which should be avoided. The golden rule is that numbers 2, 4, and 5 are relatively safe while numbers 3, 6, and 7 should be avoided with food. But even safe plastic should preferably not be heated in the microwave. The best investment for your health and your family's health is to gradually switch to glass and stainless steel containers. Yes they may be more expensive and heavier but your health is priceless. Start by changing one container at a time and you will find yourself having eliminated most of the plastic in your kitchen within a few months.