Many home test kits used for testing lead levels in consumer products are often unreliable, the U.S. Consumer Product Safety Commission said Monday.

The CPSC conducted a trial involving a total of 104 test kits and found that 56 failed to detect lead. Another two kits said lead was present when in fact there was none.

What is lead?
Lead is a soft metal used in many products. It can be found in contaminated soil or water, old paint, inexpensive jewelry and other consumer items, such as blinds and leaded crystal.

"Based on the study, consumers should not use lead test kits to evaluate consumer products for potential lead hazards," the CPSC said in a release.

High amounts of lead can harm the nervous system, kidneys and other major organs. Anemia, a decline in red blood cells, can occur, as well as damage to the nervous system that may impair mental function. At worst, lead poisoning can cause seizures or death.

Lead kits fail to detect low lead concentrations

The CPSC said the most common types of lead testing kits fail to detect low lead concentrations commonly found in jewelry and vinyl products. Safety officials also warned iron, tin, dirt and paint colours can skew the results.

The CPSC said consumers using home testing kits have identified high lead levels in some products. But when the same products were tested in a lab, the goods were found to be safe.

"This is another indication of the poor reliability of the kits for this purpose," the CPSC said. "Testing by a qualified laboratory and trained personnel is the only way to accurately assess the potential risk posed by a consumer product that may contain lead."

In recent months, U.S. and Canadian officials have issued a series of recalls of made-in-China toys for safety problems involving lead levels.