I think there is more misinformation than information about the risk of lead. Yes, lead in paint is an issue. But a far larger issue was the lead in gasoline up until the mid-70's. Spewed out the exhaust, it settled on soil and roofs. I'll bet if you tested the soil underneath a downspout of an old house in Brooklyn, you'd be shocked at the amount of lead you'd find.

The current practice for vegetable gardens in New York City is to remove the current soil and replace it with less tainted soil. That's how bad the lead pollution from gasoline was. Imagine living in that environment. Thank God for the EPA.

As far as lead paint in the interior of houses goes, painting over the lead paint is an adequate remedy. For exteriors, I don't know what the best solution is. Painting over is better than doing nothing, but by now any older house has probably been repainted once.

I don't want to know what is under the downspout of my 1910 Brooklyn based Victorian Home. In fact we don't even run water down them any more due to clogs and tree roots.

I grow nothing edible within 25 feet of the foundation. However I do grow most annual vegetables in raised beds consisting of outside soil and compost.

Few years back (1984) we had a house fire and replaced the wood painted siding with unstained ceder shingles, and sanded down the foundation and repainted it.

Where conducive to sunflowers I grew them around the foundation, supposedly they are good at pulling heavy metals out of the soil. Haven't grown much anymore, no space ;p

Your lead exposure must be from ingested lead, simply because there is some lead in your soil does not mean much because you would need to eat a lot of that soil to beome exposed. Few plants will uptake lead from soil, there are some that will, but none of our foods will. With foods your largest concern would be what is on the outside, the soil still attached, but washing well will eliminate that potential exposure.
You can very easily limit your exposure to lead but there are numerous other things that are more difficult that we do not even know what problems they cause that people use with no regard to the potential problems. Many of the pesticides people use frequently have been found to cause major health problems in people, and apparently the regulators do not care.

I would add to kimmsr's excellent explanation that it is not necessary to 'eat' large amounts of contaminated soil as you would normally think of eating. It is actually referred to by risk assessors as passive ingestion, including dust and dirt on your hands transferred while eating, chewing fingernails, etc.; the aforementioned dirt adhered to vegetables; and airborne dust that sticks to the inside of the mouth while breathing and is ingested. Most of this passive exposure is invisible tiny particles.

It's estimated a person passively ingests about 200 mg of soil and dust per day, children 400.

Assuming you don't grow veggies there, the risk from the strip of lead-contaminated soil around the foundations of old houses is averaged with the rest of the yard which is typically lower. CDC and EPA have lots of informative web pages and brochures on this, but I think it doesn't require 25 ft. distance, but more like 5 ft. Lead dust tends to not travel far from where it falls.

While the lead ban in paints was mandated in 1978, I doubt that many house paints were lead pigmented even many years prior to that. I remember the label on some oil based exterior paint I used in 1958 that was titanium oxide pigmented. I couldn't guarantee TOTAL purity from lead then OR now.

There was considerable concern for this when community gardens were becoming popular on now-vacant lots in cities (where old buildings had been removed) and when edible landscaping became popular often with edibles grown close to walls of older houses.

IF I remember correctly (and it would need careful rechecking) it was determined that an abundant addition of organic matter to the soil tied up the lead and made it far less available to the plants growing in it.

That said, certain plants (I forget which) uptake lead abundantly and some are used to extract contaminant lead from soil (some such plants have their ashes sent to lead founderies for proper disposal and lead recovery).

I read a few interesting blogs about lead paint and gardening - some good tips here. If you type in 'garden' in the search a few different posts come up about how to prep soil, how to wash the veggies if they were grown near lead dust, etc.

Here is a link that might be useful: Blog about lead and gardening