How much lead is really on my hands when soldering?
This fear of lead is largely mis-guided. Yes, there have been reports of children falling ill from eating paint chips with lead in them. But this was made into a big deal because it happened to a child, whose quality of life suffered. But where are the reports of adults with lead-poisoning? Do any of those involve routes other than consuming lead? Why don't people whom are shot with lead bullets get lead poisoning?

The answer is the "consume-ability" of lead (and other metals) by the body. Half of the population has an amalgam of various metals (including mercury) in their mouths in the form of dental fillings. Mercury is extremely toxic; perhaps you've heard of the recent concern over mercury content of fish. Mercury doesn't seem to make anyone sick when it is in fillings however - but it does when eaten. And gold in fact, is even more toxic - but that is also a common tooth filling. However you can eat gold and it won't hurt you... what is going on here?

The process of eating metals is where the problem lies. In our stomachs lies very strong (hydrochloric) digestive acid. This acid breaks down most metals into a "metal salt" form, which IS absorb-able by the body. Once in the metal salt form, the trouble begins. Lead for example, is treated like calcium in the body, so it is stored in the bones.

Gold however, is not dissolve-able by hydrochloric acid, so remains inert. 

There is a process to "rid" of the body of some metal contaminants, called chelation therapy. So if you know you have eaten lead, chelation will remove it from your bones. If it has been 20 years since you ate the lead however, the damage has already been done and chelation will help little.

So unless you've eaten lead, there really is no cause for concern. That said, you should be careful when eating after being near lead. Namely, wash your hands and avoid contaminating your food. Wipe down surfaces (do not use anything acidic) and consider them cleaned.

With toxic mercury in our mouths and deadly gold in our fillings, touching lead should now seem a lot less scary.

P.S. Note that modern solder is lead-free. So-called ROHS solder does not contain any lead at all. Still, eating it is a very bad idea so the same cleanliness guidelines apply. Standard 60/40 rosin-core solder is what this is referring to. Also note that acid-core lead solder, while rare today, may be potentially more hazardous due to the intrinsic acid content.