Unfortunately in our current world, many of us live in environments where our kids are in fact getting some lead exposure. Lead does not break down or fade away with time. It remains in the environment and we are stuck dealing with bad habits from the past.
When we get the lead results, the best news is <2 or undetectable. In past years the public health department's lead prevention program would get involved if the level was over 10 but as of 2016 the standards have changed. Now, NO measurable level is considered okay. If there is some lead showing up, we want to figure out where it is coming from and keep that level from getting higher. If your child in San Francisco has any elevated lead level the city will send out a public health nurse to help you explore your environment and see if they can figure out the source.