Blood lead level considered "safe" by the U.S. Centers for Disease Control: 10 µg/dL
Blood lead level shown to have a negative impact on intellectual functioning: 5-9.9 µg/dL
Child IQ at these levels: 4.9 points lower
Did you follow that? If it's a little early in the day (or, um, the year) for you to be thinking in mathematical terms, allow me to translate into plain English: A study (pdf) published last week demonstrates that children with lifetime blood lead levels between 5 and 10 micrograms scored, on average, about 5 points lower on standard IQ tests at age 6. Since the CDC considers anything below 10 micrograms to be normal, the study concludes that children's intellectual functioning is impaired even at low blood lead levels. In case you're wondering, the study included measures to adjust for maternal IQ and other factors that might affect a child's IQ.
If you've been holding out because that recalled toy is little Suzy's favorite and she doesn't put it in her mouth anyway, I'd say this study is a pretty good sign that it's time to let it go. The more research we see, the more it looks like any lead exposure is too much lead exposure.