Print edition: 
It's bad enough that about 12 million potentially toxic "Shrek" drinking glasses were recalled by McDonald's last week.
But what should really get people's alarm bells ringing is the fact that nobody seems to know, or is willing to say publicly, how the carcinogenic metal cadmium got into paint used to depict Shrek, Donkey and other characters.
Worse, federal law allows cadmium to be in a product marketed to children as long as the product isn't a toy, raising questions as to how many other goods may be out there that also pose a health risk.
"We're still trying to figure out whether this is just the tip of the iceberg," said Rachel Weintraub, director of product safety for the Consumer Federation of America. "All we know is that the company that made the glasses for McDonald's makes a lot of products for a lot of clients."
Cadmium has been linked to a variety of serious ailments, including kidney and liver damage. The U.S. Centers for Disease Control and Prevention ranks it as the seventh-most-hazardous substance in the environment.
But the Consumer Product Safety Commission, which orchestrated the McDonald's recall, bans use of cadmium only on the surface of kids' toys. Other uses are not explicitly prohibited.
Cadmium is typically added to paint to create bright reds and yellows. Some manufacturers have used it as a substitute for lead. Earlier this year, federal authorities said they were particularly alarmed by cadmium-tainted kids' jewelry made in China.
"There's definitely a lack of rules when it comes to cadmium," said Robert Hopkins, a partner at the law firm Duane Morris who specializes in product-safety issues. "The regulations for cadmium now only focus on toys."
And is a "Shrek" drinking glass a toy?
"It's not a toy," said Alex Filip, a spokesman for the Consumer Product Safety Commission. "McDonald's didn't have to recall the glasses."
For that reason, he praised the restaurant chain for being "a good corporate citizen that puts its customers first."
McDonald's started offering $3 refunds Wednesday, even though the glasses cost $1.99 with a food purchase and $2.49 without. The company said it wanted to ensure that people were compensated for any taxes paid or for the inconvenience of returning tainted glasses.
Still, questions abound.
First and foremost, how did cadmium get into the paint? The glasses were apparently manufactured in Millville, N.J., by Arc International North America. Did the paint come from there or from somewhere else?
"The real story here is the supply chain," said Weintraub at the Consumer Federation of America. "If the paint came from elsewhere, there's no telling how many other manufacturers may have used it."
Filip at the product safety commission said government officials haven't delved into the source of the paint. "Our primary concern was getting the glasses out of the chain of commerce," he said.
Arc International North America knows where it got the paint. But no one at the company returned repeated calls for comment.
The company is a subsidiary of France's Arc International, which describes itself as a world leader in glassware and tableware. Its brands include Pyrex, Luminarc and Arcoroc.
Fred Dohn, Arc International's chief executive for North America, said in a statement that all of the company's products "meet the highest standards of quality and safety." He said Arc viewed the recall "as an internal decision by McDonald's."
Lisa Howard, a McDonald's spokeswoman, said by e-mail that the paint came from France. But she declined to say whether it was produced by Arc or by a subcontractor, or whether the ingredients for the paint also originated in France.
Nor did Howard address whether the cadmium was incorporated in the paint deliberately or by accident. Europe has banned use of cadmium in most electrical and electronic goods, and there's been talk of a blanket ban on cadmium in all products.
