I have a set of LEGO bricks from Denmark and they were made in the late 1960's; should I be concerned about my son playing with them because of any danger of lead in the product?
No, you should not be concerned about lead. LEGO has always used lead-free colors in their elements, even back in the beginning.
However, not all LEGO-compatible bricks are lead free. For example, Mega Bloks, which are made in China, suffered from the poor quality control that led to massive recalls over lead-tainted products a few years ago.
David Clerk, the magazine's publisher and the executive director of Les Editions Protégez-Vous, said that after consulting with Health Canada, the magazine hired an independent lab in Quebec to perform what he called a "total lead test" on 32 toys, including the Maxi blocks.
Essentially, the process involves scraping off a sample of the toy's plastic, dissolving it in acid and then analyzing the solution.
When the results were returned by a lab, which Clerk said he could not identify because of a confidentiality agreement, a yellow Maxi block was the only toy that exceeded the 600-parts-per-million limit for lead set by Canada and the United States. Blue and red Maxi blocks showed no lead at all.
For confirmation, the magazine tested a second yellow block. It contained 1,180 parts per million of lead, nearly double the initial result.
Wrong. Lego had lead in its bricks up to 1984. The probability of finding lead in Lego bricks exponentially over the years, but there was still a small probability of finding lead in the early 1980s.
Here is one article that covers the topic.