Since plastic polyethylene was first invented in 1933, it has become the miracle household material. We use it in everything from storing to eating to cooking. We use plastic baby bottles, plastic water bottles, plastic detergent bottles, plastic dishes and cups, plastic … pretty much everything.

All plastics are classified by numerical resin identification numbers, which are usually imprinted on the bottom of every plastic item. Each number from 1 to 7 represents the type of resin used to make that item. Some resins are recyclable; many are not. Some resins contain potentially harmful chemicals; others are safe.

Here’s the lowdown on the plastics you likely use every day in your home:

#1 PET Polyethylene Terephalate – soft drink and water bottles. They’re recyclable, but as this plastic is porous and easily absorbs bacteria, you should use it only once.

#2 HDPE High Density Polyethylene – milk jugs, liquid detergent bottles and shampoo bottles. This plastic is recyclable and transmits no known chemicals.

#3 V or PVC Polyvinyl Chloride – meat wraps, cooking oil bottles and plumbing pipes. It’s not generally recyclable and contains chemicals that release dioxin, a potential carcinogen.

#4 LDPE Low Density Polyethylene – cling wrap, grocery and sandwich bags. This plastic is recyclable but not generally accepted by recyclers. It releases no known chemicals into your food.

#5 PP Polypropylene – cloudy plastic water bottles, yogurt cups and tubs. It’s recyclable, but not generally accepted by recyclers, and releases no known chemicals into your food or water.

#6 PS Polystyrene – disposable coffee cups and clam-shell take-out containers. Polystyrene isn’t recyclable and doesn’t decompose in the landfill for 500 years or more. It can leach styrene, a potential carcinogen.

#7 Other Plastics – baby bottles, reusable water bottles, linings of tin cans and stain-resistant food storage containers. Made with bisphenal A (BPA), which has been linked to heart disease and obesity, they’re not recyclable.

To recap: Plastics #1 aren’t great; #2, #4 and #5 are OK; and, #3, #6 and #7 should be avoided.

Ironically, as common as household plastics are, few studies have been done on the effect of plastics on the long-term health of humans. And since plastics take decades, even hundreds of years, to decompose in the landfill, and are made of oil, a dwindling resource, it would be wise to cut down on the use of plastics in the home.

Much research is being done to engineer a new kind of plastic made from biodegradable materials such as corn, wheat and potatoes instead of petroleum. The new bioplastic is tougher and more durable than polyethylenes, can be recycled into biodiesel liquid fuel and is compostable. Cereplast, a California-based company, is now creating a new “natural” plastic called Biopolvolefin that can be used in consumer electronics, cosmetics, toys and packaging.

Until the new plastic is perfected, here are some ways to safeguard your family:

• Cut down on plastics used in baby bottles and food containers for babies and children under the age of 3.

• Cut down on the use of individual plastic water bottles and use BPA-free personal hydration bottles that can be cleaned and refilled. (Target sells them in pink, blue, purple and green for $9.99.)

• Avoid storing food in cling wrap and never heat cling wrap in the microwave. Also note that when a label says “microwave safe” it really means that it won’t melt when heated; it’s not a guarantee that chemicals won’t leach into your food. Use glass or ceramic containers in the microwave whenever possible.

• Hand wash plastic food storage containers with a non-abrasive sponge or cloth. Throw out old, scratched plastic containers, as they cultivate bacteria.

– Contributed by Mt. Diablo Recycling, Pittsburg