McDonald's has finally announced procedures for returning the cadmium-tainted Shrek glasses it recalled on Friday after word leaked out prematurely that the recall was in the works.  (You can read about the hurry-up recall here.)

Starting Wednesday, consumers can bring the glasses to any McDonalds and get a $3-per-glass refund. The company says it's paying a premium - the glasses had been sold since last month for $1.99 or $2.49 apiece - to cover the cost of sales taxes, and is not requiring a receipt.  Click here to read about the recall at a McDonald's  website.

You might want to wrap them before taking them to the restaurant, and wash your hands carefully afterward. Although McDonald's and the Consumer Product Safety Commission have both emphasized that the recall was "precautionary," the glasses do pose some risk of exposure to a heavy metal that can have long-term toxic effects, according to Don Mays, senior director of product safety for Consumers Union.

"It can cause renal cancer, so you want to limit your exposure," Mays told me.  Mays also says there is evidence that exposure - at some level - can cause developmental damage.

How much risk do the glasses pose?   The answers to that are unclear. Cadmium shows up elsewhere in the environment - it's in foods such as oysters and potatoes, for instance, says Consumers Union toxicologist Urvashi Rangan. But no one is saying how much exposure you'd get, say, from licking your fingers after holding a Shrek glass - or even how that might compare with the cadmium ingested from eating an order of fries. (One point of comparison: Rangan says a whole potato, with skin, contains about 12 parts-per-billion of cadmium. The limit for cadmium in toys is 75 parts-per-million.)

Nor are toxic chemicals likely to be your biggest risk from eating those fries - but that's a subject for another day.

McDonald's likes one statement so much that it repeats it five times on its recall website: "CPSC has said the glassware is not toxic."  The CPSC's recall notice says, "McDonald's is asking consumers to immediately stop using the glass out of an abundance of caution."

But CPSC is plainly treading a fine line.  Asked for clarification, agency spokesman Alex Filip explained: "It's not toxic exposure. There's no immediate kind of issue. You don't pick up a Shrek glass and get sick."

Filip says the amount of cadmium on the glasses is far below the amount in Chinese-made cadmium jewelry that was recalled earlier this year and had been sold at dollar storesClaire's Boutiques,  and Walmart. "When you ingest them, you're going to ingest toxic levels," Filip says. Adding to that risk is that cadmium, like other heavy metals, "sticks in the body for a long time."

So, until then, the CPSC's announcement says only that "long term exposure to cadmium can cause adverse health effects." And McDonald's is stressing that its recall of 12 million glasses does not amount to an admission of violating any existing standards:

A key distinction legally is that the Consumer Product Safety Improvement Act of 2008 set that strict limit on cadmium in toys - 75 parts-per-million - "but glasses aren't toys," Mays says.

Mays and many others continue to ask about the role of ARC International, the French glassware manufacturer that CPSC says made the Shrek glasses at its plant in Millville, N.J., about 50 miles south of Philadelphia.

"Even though they may have been made in New Jersey," Mays says, "the question is: Where did they get their raw materials? Where did they get their paint and dyes?"

So far, ARC officials have not returned phone calls, and McDonald's is saying very little.

"The paint was made in France," McDonald's spokeswoman Ashlee Yingling told me.

Were the glasses painted in Millville?

"That's a question for ARC," Yingling says. "I don't know the answer to that."