That's hard to say.
It is certain that lead can cause brain damage, lowering IQs and causing developmental delays, amont other health effects. Very high levels of lead can cause death, such as a child swallowing a lead jewelry charm (as unfortunately happened last year). Recent health studies have demonstrated that even low blood lead levels (below the current level of 10 micrograms per deciliter of blood) can cause signicant health problems, including lowered IQ. The recent consensus is that there is no safe level of lead in the blood.
But how much lead do children get from toys? That's hard to say. There is no reliable way for a parent to know how much lead is in a particular toy. The lead check test kits tell you whether lead is present or not, but don't tell you how much. And it is difficult to assess how much exposure a child gets from handling or mouthing the toy.
Lead exposure is also cumulative, and there are many other sources. Lead is present in homes from historic use in paint. This is probably the most significant source. We also get lead contaminated dust blown into our homes from weathering from homes, bridges, and other structures, and its use in gasoline. Lead is present in drinking water. Lead is found in high levels in some herbal remedies. It is used to stabilize polyvinyl chloride plastic. We also bring lead into the home from occupational exposure and hobbies.
So, what can you do to reduce expoure? The simplest solution is eliminate sources. If you work in a field that may have lead exposure, change your clothes and your shoes before you enter the home. To avoid tracking in lead contaminated dust, use a good welcome mat or take off your shoes. If you have an older home (built before 1978) and have lead paint, keep your paint in good condition. Do not renovate, remodel, sand, etc., without addressing the lead paint. Wash your hands frequently to remove lead dust. Wet wipe surfaces to remove lead dust. And, difficult as it may be, get rid of any recalled toys. You may also want to check other toys for lead.