Not too long ago, but in ancient times as far as my kids are concerned, the big yellow arches served food in clamshells. Readers younger than 20 won’t remember these, but they were actually small polystyrene (foam) boxes.

McDonald’s used to snuggle its Big Macs and other burgers in these foam clamshells as if they were fine cut-glass vases. With fast food’s far reach, McDonald’s became the largest single user of polystyrene foam, selling to 22 million customers each day.

At the end of the 1980s, a decade when excess was celebrated, four cities in the U.S. (Berkeley being the only California city) banned McDonald’s from using polystyrene foam in their cities. There was pushback and redirection by McDonald’s, but by late 1990, Mickey D’s bucked under the pressure of the masses and changed its ways.

At the time, because there was pending legislation in 49 of 50 states, all the fast food chains followed suit, banning polystyrene and switching to paper packaging. Even the U.S. Park Service and the Coast Guard had banned foam containers.

That was the end, right?

Unfortunately, no. Less than 20 years later, we have forgotten the lessons learned from the efforts that led to an almost total elimination of polystyrene from touching our foods.

Polystyrene, as we most commonly see it, is expanded polystyrene, or EPS. A blowing agent is added to polystyrene pellets to make it moldable. Unfortunately, EPS is manufactured from refined petroleum and derived from styrene, which is a known neurotoxin. The manufacturing process produces several wastes, such as ethylene and benzene, which are known to the EPA to cause cancer. EPS foam reacts and leaches chemicals when it comes in contact with hot foods (like take-out, hot chocolate and coffee), acid foods (like lemon and orange), those with Vitamin A and anything that is microwaved. Do I need to go on?!

And yet, we continue to see EPS foam cups, EPS foam meat trays and EPS foam take-out boxes. California alone produces more than 400,000 tons of it. Even our children, in Tracy’s schools, are exposed to this toxic material when they eat school lunches on EPS foam food trays.

If you can get past the chemicals leaching into our food, many in the industry will say that EPS can be recycled. In fact, if you see a Number 6 on the bottom, it can recycled. However, most cities don’t, because of the cost.

EPS has a negative scrap value, at about $3,000 a ton, compared with glass, which is about $89 a ton. Tracy does recycle EPS foam but, for some unknown reason, doesn’t advertise it. The solid waste Web site specifically tells residents it shouldn’t be added to the blue toter.

Chemists are looking at adding microbes to polystyrene to make it more biodegradeable, but it’s a very bad deal right now. The simple fact is, if you are using EPS foam and not recycling it, it will end up in the landfill.

In fact, sadly, those 22 million containers a day thrown out by McDonald’s consumers are still in the landfills. Most experts say it will take hundreds or a thousand years for EPS foam to break down — long past the lives of our children’s great-grandchildren.

If you haven’t already guessed it, I avoid EPS foam at all costs. In our house, the ubiquitous polystyrene is called “bad styrofoam.” My kids don’t ask for hot chocolate in foam cups or smoothies from Jamba Juice. They roll their eyes (causing some teenage angst) when I decline to bring home take-out in foam boxes and ask the restaurant for another choice.

For a change: Recycle your foam meat trays, foam egg cartons and foam coffee cups.

To make a difference: Don’t buy foam cups or plates for your events. Buy eggs that are in cardboard containers.

To make a stand: Avoid polystyrene at all costs, for your health and that of the planet. If you refuse to use it, businesses will get the hint!

• Christina D.B. Frankel is a 20-year Tracy resident, architect and mother of three. Her column, Living Green, runs twice-monthly in the Tracy Press. She can be reached at cdfrankel@sbcglobal.net.