Editor's note: In light of today's news about the toy recall, Dr. Sanjay Gupta answers five questions about lead and its affect on children.

Q: What is lead poisoning?

Dr. Gupta: Lead is a highly toxic metal that can be found primarily in lead-based paint and soil. Lead poisoning occurs when there is a toxic level in your body. Lead itslef has no function in the body, but can mimic other metals, which are important in the body such as calcium and zinc. While children and adults can both suffer from lead poisoning, it's far more common in children because their developing bodies can absorb more lead, and be more affected by it. Lead poisoning is sometimes confused with porphyria (think Madness of King Gerorge) but they are in fact different problems.

Q: How do you get it? Only by ingesting lead?

Dr. Gupta: You can get lead poisoning by eating, breathing or swallowing too much of it. You can breathe, especially during renovations, in dust containing lead. You can also eat soil or paint chips containing the toxic metal. Other lead sources are drinking water, food, ceramics, home remedies and other cosmetics. Substantial lead amounts can be found in old lead-based paint, household dust and soil.

Q: We often see children with pencils in their mouths-how much lead does it take to make a child sick?

Dr. Gupta: Well, interestingly lead pencils don't really contain lead. They contain non-toxic graphite, a form of carbon. It's hard to say exactly how much is too much because we're talking about microscopic amounts here. But, here is one way of looking at it. According to the U.S. Consumer Product Safety Commission, if a child ate a lead-based paint chip one-tenth of a square inch (that's the size of the tip of a pencil eraser) each day for 2 to 4 weeks, that kid could test with dangerously high levels of lead. In a blood test, 10 micrograms per deciliter or above is considered dangerous for anyone, but especially in kids age six years or younger.

Q: What does lead poisoning do to you?

Dr. Gupta: When it comes to the effects of lead poisoining, the list is long.

In adults, the list includes difficulties during pregnancy, reproductive problems, high blood pressure, nerve disorders, muscle and joint paint, memory and concentration problems.

Kids' brains and nervous systems are especially sensitive to lead. In children, lead poisoning can lead to developmental delays, damage to the brain and nervous system and even behavioral problems such as ADHD -- just to name a few.

Q: If untreated, what are worst case consequences?

Dr. Gupta: A major problem with lead poisoning is that there are no obvious symptoms until the case is far gone. So, cases often go undiagnosed. At very high levels, lead poisoning leads to seizures, coma and even death.

If parents are concerned, they should ask their doctor to perform a lead test on their children. A lead test is not mandatory, but is often performed by pediatricians. Here is something that I learned while investigating this story: the CDC recommends that all children be screened for blood lead levels once per year, especially between the ages of 6 months and 6 years.

For more information about lead poisoning, please visit the Centers for Disease Control and Prevention.