There is a toxic substance in your house, most likely seeping into yours and your children's hormonal systems.

Chemicals from it have been linked to obesity, early puberty, increased cancer risk and reduced fertility. And yet, many of us unknowingly continue to eat and drink from items that contain it.

The substance is Bisphenol A, or BPA, an ingredient in polycarbonate plastics. BPA chemicals have been found in plastic food wrapping, plastic containers and feeding bottles, and the resin that lines food cans.

They contain endocrine disrupters, synthetic chemicals that when absorbed into the body either mimic or block hormones and disrupt the body's normal functions, and they are facing a ban in the U.S., and have already been banned in Canada.

Research has shown that BPA leaches from these products and has been found in a large percentage of people in developed countries, including in urine and blood and in amniotic fluid, placenta, umbilical cord blood and breast milk.

What can consumers do to protect their health and avoid BPA?

Plastics are typically classified by a number from #1 to #7, each number representing a different type of resin. That number is usually imprinted on the bottom of the container, in a recycling triangle with the number in the middle.

Plastics to avoid are #3 PVC, #6 PS, and #7 PC:

- #3 polyvinyl chloride (PVC) is often used in cling wraps for meats, as they contain phthalates that interfere with hormonal development.

During the manufacture and incineration of PVC, dioxin is released, a potent carcinogen and hormone disruptor.

- #6 extruded polystyrene (PS), commonly known as Styrofoam, is used in takeout containers and cups, disposable plastic cutlery. It can leach styrene (a possible human carcinogen) into food, as well as disrupt hormones or affect reproduction.

- #7 polycarbonate (PC) is found in baby bottles, 5 gallon water bottles, water cooler bottles and the epoxy linings of tin food cans. It is composed of a hormone-disrupting chemical called bisphenol A, which has been linked to cancer and obesity.

It is important to note that not all #7 plastics are polycarbonate containing BPA.

You can usually tell a BPA plastic because it is translucent and rigid. The safer alternative, polylactic acid (PLA) plastics - a corn-based polymer - is biodegradable and is cloudy and more pliable.

Safer plastics to use are #2 HDPE, #4 LDPE and #5 PP.

#1 PET and PLA (polyclactide) plastics are also fine for single use. PLA plastics are made from renewable resources such as corn, potatoes, and sugar cane and can be composted.

Still not sure of what type of plastic you are using and don't want to check all your items?

A practical way to keep your family safe is to follow these tips:

- Never heat food or drink in plastic unless the directions specifically say that the plastic is microwave safe. Personally, I never heat anything in plastic, no matter what the directions say - I just transfer my food to a microwave-safe dish such as pyrex.

- Microwave-safe plastic wrap should be placed loosely over food so that steam can escape, and should not directly touch your food.

- Have your tank water tested and once you are assured that it is potable, drink directly from your tank, and fill a reusable water bottle.

It's better for you and better for the environment.

- Having a picnic or other event and really want disposable dishes and utensils? Buy biodegrable PLA picnic ware and compost it afterwards. It's available locally!

For more information on BPA and safe plastics, visit the National Geographic site, www.thegreenguide.com or Health Canada at www.hc-sc.gc.ca.

Laura Semos is the education officer at Consumer Affairs.