(Forbes.com)In February 2006, a 4-year-old boy in Minneapolis, Minn., accidentally swallowed a small heart-shaped locket that had broken off of an eight-inch long bracelet. In most circumstances, the locket would have passed through the boy's system or been removed in a medical procedure. But this wasn't "most circumstances." The silver-colored locket contained a high concentration of lead. The boy died.

The bracelets were given away with the purchase of children's shoes in major shoe stores across the country from May 2004 until a few weeks after the boy's death. After the boy's death, the U.S. Consumer Product Safety Commission recalled more than 1 million toys containing potentially dangerous levels of the chemical. In the years since, major product recalls on everything from pet food to baby formula have amplified consumer safety concerns about chemicals toxins. Nearly three years after the boy's death in Minneapolis, children's toys remain near the top of the list of consumer safety concerns.

And rightfully so. One of every three toys tested in a study of 1,500 popular children's toys contained potentially harmful levels of lead, arsenic, mercury and other dangerous chemicals, according to findings released earlier this month by the Ecology Center, an Ann Arbor, Mich.-based consumer safety organization. Most of the toys tested positive for only one of the chemicals. As a result, the study graded the products according to contamination levels for each specific chemical. The toys with the highest contamination level for at least one of the chemicals earned the ignominious honor of being included on the Ecology Center's list of the year's "worst toys."

"The goal is to give people a list of ingredients for the different chemicals these toys contain, which can't be found anywhere else," said Mike Shriberg, the Ecology Center's policy director. "Parents can make their own decisions about what they think is safe for their children. We're just giving them the information."

Depending on exposure levels, all of the chemicals assessed in the study have been linked with equally serious health issues. Arsenic has been linked to cancer, blood disorders and damage to fetal development. Cadmium can cause serious harm to the kidneys and lung. Bromine, a chemical widely used in flame retardants, has been linked to birth defects and reproductive problems. The list goes on and has a lot to say about children's jewelry — nearly all of it bad.

In Pictures: 14 Very Toxic Toys

"Toxins were five times as likely to be found in jewelry as any other category of children's products," said Shriberg.

Fifteen per cent of the jewelry tested (compared to 3 per cent of other products) had lead levels above 600 parts per million (ppm).

Take Disney's Hannah Montana two-heart necklace, which is loaded with so much lead that it earned a prominent spot on the "worst toys" list. In the study, researchers used a handheld X-ray device to test the toys for lead, cadmium, chlorine, arsenic, bromine and mercury, which have been recognized by regulatory agencies as potentially dangerous in high concentrations.

Although a new federal law, the U.S. Consumer Product Safety Modernization Act, set to take effect in February 2009 will limit lead content to 600 parts per million in all children's products, roughly 3.5 per cent of the toys tested (like the Hannah Montana bracelet) had concentrations of lead that exceeded the 600 ppm legal limit.

The impending U.S. law will also set limits on the amount of arsenic, cadmium, mercury and other potentially unsafe chemicals allowed in children's products. Cadmium will be capped at 75 ppm, arsenic at 25 ppm and mercury at 60 ppm. More than 1 per cent of the toys tested positive for levels of arsenic and mercury, which is well in excess of the limits mandated by the looming federal legislation.

The good news: Things are getting better.

Roughly 21 per cent of all the products tested in the study did not contain potentially unsafe chemicals. Toys like the Autobot Classic Series: Red Alert, Hot Shot Transformers and Hasbro's Luke Skywalker & R2-D2 Star Wars figures qualified for the coveted "best toys" list, which includes more than 300 toys that did not contain even trace amounts of concerning chemicals.

"When you see these toys sitting on the shelf, there is no way to determine which products are made with toxic chemicals and which aren't," said Shriberg. "They cost the same amount and look the same. It really shows that manufacturers have no excuse for making toys with dangerous chemicals."