Decoding Plastic Recycling Symbols 1–7 – Identify Materials for Safe Plastic Use

Most people come into contact with plastic products every day yet rarely notice the triangular number marks printed on container bottoms. Numbers 1 through 7 represent an internationally unified classification standard for plastic materials, with each number corresponding to distinct physical properties, heat resistance thresholds and suitable applications. Understanding these symbols is the foundation of safe household plastic use and effectively avoids potential health hazards in daily life.

1 – PET (Polyethylene Terephthalate): Mostly seen on mineral water bottles, soft drink bottles and fruit juice containers. Transparent, lightweight and well-sealed, PET can only withstand temperatures up to around 60°C. Harmful substances may leach out under high heat or prolonged sunlight exposure. It is designed solely for single-use at room temperature. Do not fill it with hot water or hot oil, and avoid long-term repeated use; discard promptly after use.

2 – HDPE (High-Density Polyethylene): A stable rigid plastic used for cooking oil jugs, milk bottles, body wash containers and food storage pails. Hard, acid and alkali resistant, and less prone to bacterial growth, HDPE can be reused for short periods after thorough cleaning. However, its grooved surfaces are hard to sanitize completely, so avoid long-term storage of condiments and edible oils to prevent residual dirt and bacterial buildup.

3 – PVC (Polyvinyl Chloride): Mainly manufactured into industrial pipes, hoses, waterproof construction materials and raincoats. It contains complex additives and has poor heat resistance; toxic substances may release under high temperatures. Never use PVC products to hold food or drinking water, and minimize purchasing daily necessities made of this material.

4 – LDPE (Low-Density Polyethylene): Soft and flexible, LDPE is the raw material for plastic wrap, fresh-keeping bags and soft plastic films. Safe and non-toxic at room temperature with excellent waterproof and moisture-proof performance, it can only tolerate temperatures below 80°C. Do not heat it in microwaves or wrap hot food directly to prevent decomposition and hazardous substance release.

5 – PP (Polypropylene): The safest food-grade plastic for household use and the only plastic approved for microwave heating. Found in food storage containers, lunch boxes, water cups and infant tableware, PP resists temperatures up to 120°C. Chemically stable, oil and acid resistant and non-toxic, it can be cleaned and reused repeatedly, making it the top choice for daily kitchenware.

6 – PS (Polystyrene): Used for rigid cup lids, disposable food containers and foam thermal insulation materials. Lightweight and stable in cold conditions, PS reacts poorly to high heat and grease. It easily generates harmful compounds when holding boiling food, fried dishes or being microwaved. Only use it briefly at room temperature and avoid repeated use.

7 – Other Plastics: Covers composite materials including PC and ABS, applied to large-capacity water bottles, thermos shells, electrical casings and premium daily goods. Compliant food-grade and infant-safe grade No.7 plastics are fully reliable. However, PC material should be kept away from long-term sunlight exposure and repeated high-temperature heating to reduce the risk of undesirable substance leaching; it is completely safe for regular room-temperature use.