In the mid 1940's Harrison Brown, of the University of Chicago, assigned a tedious dissertation project to a young Clair Patterson. Geologists then were interested in calculating the age of the earth and Harrison had developed a new method for counting lead isotopes in igneous rocks. Uranium in rocks, over a period of time decays into lead. Scientist knew the exact time taken for this process. By counting the Uranium- lead ratio in a rock, scientists were able to estimate the age of a rock. The process indeed was tedious and Clair Patterson took seven years to complete it. He worked in a very sterile lab, making careful measurements of the lead- Uranium ratios in carefully selected samples of rocks. Patterson worked on meteorites, since it was not possible for him to acquire samples of ancient earth rocks, because earth continuously changes its surface. New rocks are replaced by older ones as the tectonic plates on the earth slowly shift. Since many meteorites are leftover building materials from the early days of the solar system and have not been tainted, determining the age of the rocks would also give us an idea of the age of the earth. During his experiments, Patterson's samples were continuously and unaccountably contaminated with large doses of atmospheric lead, whenever they were exposed to air. He was bothered by this phenomenon, but kept it aside for some other day. Finally in 1953 Patterson announced the age of the earth as 4,550 million years (plus or minus 70 million years) a figure that still stands today.
Patterson now turned his attention to the question of lead in atmosphere. The first thing Patterson realised was that until then, the study of the effects of lead on humans was mostly done by lead additive makers. In one case study, a doctor with no chemical pathology training; recruited volunteers to breathe in or swallow lead in elevated quantities. Their urine and faeces were tested. Unfortunately lead is not excreted as a waste product. Rather it accumulated in bones and blood, and in the tests, neither the blood nor the bones were tested. Lead was given a clean bill of health. As I mentioned in the previous post, tetraethyl lead was used as an additive since 1923. Patterson wanted to compare the atmosphere prior 1923 and that of the present day. It was known that snowfall in places like Greenland accumulates into discrete annual layers. By counting back through these layers and measuring the amount of lead in each, he could work out the global lead concentration at any time in earth's history. What Patterson found was that before 1923 there was almost no lead in the atmosphere and since then the level has slowly climbed. He now made it his life's quest to get lead taken out of gasoline. It would be a challenge; Ethyl (mentioned in the previous post) was a powerful global corporation, with many friends in high places. Patterson suddenly found research funding withdrawn or difficult to acquire. American Petroleum Institute and United states Public health service cancelled a research contract with him. Patterson became a liability to his institution, the school trustees were repeatedly pressed by lead industry officials to shut him up or let him go. Despite all the pressure Patterson never wavered and largely due to his efforts the 'Clean Air Act' 1970 was passed and by 1986 all leaded gasoline was removed in US. I remember using leaded gasoline in India even during 1995, not really sure when it was finally banned. It is said, that there was an 80% reduction in blood lead after the ban. Since Lead always will remain in the body, people alive today have 625 times more lead than people prior 1923. Lead though continues to be added to the air, not by automobile fuel but by other manufacturing processes. I wonder how much lead we have in the paints that we use at home. Clair Patterson died in 1995 and if you have not heard of him before this don't beat yourself. Most geology textbooks don't mention him; some books on the subject of dating of Earth have even misspelt his name. A reviewer of one of this book even thought that Patterson was a woman. I myself had not heard of Patterson until I read Bill Bryson's "A Short History of nearly everything" which inspired me to write this post. Large corporations fight tooth and nail to keep their profitable ventures going. Human life is least of their concerns. Asbestos, Endosulfan, DDT (is still present in bovine milk in India today!) low grade plastics, etc just to name a few. How long before we can all say a no?