There has been a renewed interest recently in the effects of low doses of lead especially in children (see this question, for example: Is lead exposure responsible for the rise and fall of violent crime in the US?). Or this (slightly overblown) report about the continuing sale of lead additives to a small group of countries.
But there are several significant sources of lead exposure. Lead paint was once common in homes and toys, lead plumbing contributed significantly, several foodstuffs and especially canned products with lead-solder and many industrial sources all add to lead exposure.
There is essentially no argument that lead is dangerous. But Booker and North in their 2007 book Scared to Death (a sustained rant arguing the modern world has dramatically overreacted to safety and environmental concerns) argue that lead from petrol was not a major contribution to blood-lead levels. For example, they claim:
...epidemiologists published a study based on lead levels in maternal blood samples in south Wales. These had shown a fall of around 20% during a period when there had been no change in petrol sales in the area or in air lead levels. The researchers concluded that 'petrol lead was at most a minor contributor to blood lead.'
[the article referred to is here but paywalled]
One of the authors had previously argued that:
we will probably never know the relevance of petrol lead to blood lead despite the confidence expressed by many commentators.
Blood-lead levels were falling at significant rates (see this 1996 BMJ article) before the bans on lead in petrol (which were driven as much by the incompatibility with catalytic converters as the lead exposure argument).
Most commentators today seem to assume that petrol was the major contributor to lower lead in the environment and in people. The consensus view is summed up well by this quote from an editorial in the Bulletin of the World Health Organisation in 2002:
The use of lead as a petrol additive has been a catastrophe for public health. Leaded petrol has caused more exposure to lead than any other source worldwide. By contaminating air, dust, soil, drinking- water and food crops, it has caused harmfully high human blood lead levels around the world, especially in children
But do we have any clear evidence that this is true? Was petrol the big source of lead in our bodies or was it only a minor one, less important, for example, than banning leaded paint?