Christmas trees, or rather what's under them, are often a worry among small children who write letters, make wishes, and hope for Santa Clause to bring them tons of toys and presents on his annual December sleigh ride around the globe. And the biggest worry among parents is that their children will not be satisfied with the gifts that Santa brings them.

But while moms, dads, and children for decades have worried about what's under the tree, scientists in the 1960s and '70s were more concerned with one particular item on the list. Tinsel, the shiny, paper-like decoration that families draped around their trees each Christmas contained lead at the time, putting the health and safety of young boys and girls in danger.

"Scientists started to realize that this type of tinsel put children at risk for lead poisoning," Chemical and Engineering News Senior Editor Carmen Drahl said in the video.

Tinsel, derived from the French word, “estincelle,” for spark or sparkle, was originally hung as thin strips of silver on Christmas trees in Germany to reflect the warmth of candle lights. Silver, though, was eventually replaced by the early 1900s with other metals, such as copper and aluminum, which did not wear as easily. But the use of these also went down because of their flammable nature and shortages of metal during World War I, according to C&EN News.

Manufacturers soon replaced this with lead, mixing the heavy metal with other metals into an alloy component that continued to make the Christmas decor shine. But when scientists in the early 1960s realized the risk of lead poisoning from tinsel, the Food and Drug Administration began placing regulations on the distribution of the product up until 1972, when manufacturers agreed to stop using lead and find an alternative component. It also placed a ban on lead-based tinsel imports from foreign countries. All production of lead-based tinsel stopped or was expected to stop starting Jan. 1, 1972, though the decision to stop production was not immediately told before or after to the public.

"There was never any effort to hide it," then-Director Malcolm "Mac" Jensen of the FDA's Bureau of Product Safety told The Associated Press in November 1972. "The decision was made internally not to publicize it because we feared that many people preferring the lead variety would stockpile it."

The Food and Drug Administration, the Centers for Disease Control and Prevention, and the National Institute of Environmental Health Sciences did not return calls to Medical Daily for comment.

Exposure to lead is a serious issue, particularly among small children, as it affects almost every system of the body and puts them at higher risk than adults for numerous problems, including disturbances in muscle growth, kidney and nervous system damage, and even seizures, periods of unconsciousness and in extreme cases, death, according to Kids Health.

"High levels of lead can be fatal," said Patty Davis, a spokesperson for the U.S. Consumer Product Safety Commission, told Medical Daily. "There can also be learning problems, behaviroral problems."

The Centers for Disease Control and Prevention estimates that approximately half a million American children between one and five have a blood level of 5 micrograms per deciliter, the point at which health officials urge medical and public action to be taken in treating the child. There is currently no safe blood level for lead.

Tinsel today, though, is relatively safer than its obsolete-lead based predecessor, much of it consisting of polyvinyl chloride, a plastic polymer coated with a thin coating of metal, such as aluminum to make it sparkle. Tinsel, according to Davis, can also consist of mylar, a polyester film.

UPDATE: This article was updated to include a quote by Patty Davis, a spokesperson for the U.S. Consumer Product Safety Commision.