In June, McDonald's recalled its promotional Shrek glass with "an abundance of caution" after trace levels of the heavy metal cadmium were found on the glass' painted decal.

More than 12 million glasses were sold to consumers, and the quick-service giant was praised for its handling of the recall.

The drinking glass issue, however, will not go away.

The Associated Press conducted laboratory testing on drinking glasses featuring pop culture icons such as Superman and Wonder Woman, concluding they exceed federal limits for lead by up to 1,000 times.

At the center of the concern is the decorative enamel on Superhero and "Wizard of Oz" glass sets made in China and purchased at Warner Brothers Studios in Burbank, Calif. Levels of lead were between 16 and 30 percent, exponentially exceeding the federal limit on children's products, which is 0.03 percent.

These same glasses also contained high levels of cadmium, the source of the McDonald's recall. However, there are no federal limits on cadmium in design surfaces.

Other tests commissioned by the AP involved Burger King and McDonald's glasses specifically, and included small but notable amounts of lead or cadmium.

The AP testing and investigation was in direct response to the Shrek recall, as federal regulators continue to express concern over toxic metals transferring from children's hands to their mouths.

The AP notes that the study shows the contamination in glassware is more widespread than the McDonald's Shrek instance. Lead's presence, in particular, has raised many questions since it had been banned in China, where many of the glass manufacturers are located.

Thirteen new glasses and 22 old glasses were tested in total, including collectibles from the late 1960s through 2007, mostly from quick-service restaurant promotions. A Disney "Goofy" glass distributed by McDonald's, and three "Return of the Jedi" glasses sold through Burger King were tested, both shedding lead traces.

Both companies released statements to the AP, noting that these glasses met federal safety standards at the time of their release.

The AP's testing was conducted by ToyTestingLab, out of Rhode Island.

Coca-Cola's voluntary withdrawal

Also, one of the glasses tested came from the Coca-Cola store, and included as much cadmium as levels found on the "Shrek" glasses. The amounts are not deemed a health hazard under federal guidelines, however, Coca-Cola issued a voluntary withdrawal of the glasses on Nov. 21.

The company will withdraw 22,000 sets of themed drinking glasses for quality reasons, including a glass that resembles a can of Coca-Cola.

The company released the following statement about its decision: "While recent tests indicated some cadmium in the decoration on the outside of the glass, the low levels detected do not pose a safety hazard or health threat. The Coca-Cola Company has an unwavering commitment to quality, and at times we may withdraw products from the market for quality reasons, even if there is no safety concern or legal requirement to do so."

The glasses have been on the market since March. For instructions on how to return the glasses, visit the company's website.