Low Level Lead Exposure and Its Effects on Human Beings: Conference One


The first conference was entitled “Low Level Lead Exposure and Its Effects on Human Beings” and took place at the Royal Institute of British Architects in London from 10-12 May, 1982.  It was organised and sponsored by the CLEAR Charitable Trust.  The conference proceedings were edited by Michael Rutter FRS, Professor of Child Psychiatry at the Institute of Psychiatry and Dr Robin Russell-Jones, Deputy Chairman of CLEAR, the Campaign for Lead Free Air. International experts attended from all over the world including Ellen Silbergeld, Chief Toxics Scientist at the Environmental Defense Fund in Washington DC, who had done ground-breaking work on the biochemical and neurotoxic  effects of lead in animal models; Herb Needleman, Associate Professor of Child Psychiatry and Paediatrics at the Children’s Hospital of Pittsburgh, whose seminal study on the relationship between lead in shed milk, teeth and children’s intelligence and behaviour had revolutionised thinking on a causal link between lead and IQ;

And finally, Clair Patterson who probably deserves to be ranked alongside Albert Einstein as the most famous scientist of the twentieth century. He spent seven years in the late forties and early fifties constructing  a lead-free laboratory that allowed him to measure the very small amounts of lead in two samples: an iron meteorite that represented the base-line year for the age of our solar system and a modern rock sample from the present day. Uranium isotopes 235 and 238 decay to lead isotopes 207 and 206, but there is very little uranium in an iron meteorite so the lead composition represents the primordial lead content of the earth at the birth of the solar system. By contrast, the earth’s crust is abundant in uranium so the lead content is a reflection of the decay of uranium into lead. By knowing the disintegration constants of the two uranium isotopes and by measuring the ratio of the two lead isotopes in these two samples, Patterson was able to calculate the age of the earth and found it to be 4.5 billion years old, an estimate that still stands to this day. He published his findings in the journal Science in January 1955, but hardly anyone knows of his achievement and he never received a Nobel Prize which seems quite extraordinary. (Ref: Patterson C et al. Age of the Earth. Science 1955. 121: 69-75).

I’m now going to quote from a book by Sharon McGrayne “Prometheans in the Lab” which devotes a whole chapter to the life and work of Clair Patterson who died in 1995.

“By 1953, Patterson finally had enough super-clean samples of primordial lead to calculate Earth’s age. He took his precious samples to the mass spectrograph at Argonne National Laboratory, located in the midst of corn fields outside Chicago. As he worked late into the night the laboratory emptied and fell silent. When he finished his experiment  and went outside under Illinois’ star-filled sky, he knew, after 7 years, that meteorites, the Earth and our solar system are 4.5 billion years old.”

When I met Patterson in 1982 I asked him what that felt like. He said “Well, I went outside and I looked up at the stars and then I looked down at the Earth and I said to myself ‘I know how old you are. What’s more I’m the only man in the history of the world who knows how old you are’.  That felt pretty special.”

Once Patterson had his ultra-clean laboratory of course he was then in a position to measure lead levels in preindustrial samples and he was able to show that lead levels in the environment had gone up exponentially since the introduction of leaded gasoline in the 1920’s.  He achieved this by measuring lead levels going back 3,000 years using ice-core samples from Greenland. The graph demonstrates a small blip in lead emissions when the ancient world started mining silver (and therefore lead) from 800 BC and an exponential increase after the introduction of tetraethyl lead into gasoline by the Ethyl Corporation in the US.

Patterson was also able to demonstrate  that modern man was very heavily contaminated with lead. This is illustrated by Patterson’s “Measles Diagram”.

The lead burden of a pre-technological person, as measured in skeletal remains from an ancient burial chamber in Peru is represented by one dot.  A lead-poisoned individual with clinical lead-poisoning is represented by 2,000 dots. And for a typical person living in 20th century America or the UK, their lead burden is represented by 500 dots.  For no other toxin in the the history of mankind has there been such a narrow gap between what is known to be typical and what is known to be toxic.

Finally, the US  National Health and Nutrition Examination Survey (NHANES) monitored the blood lead level in the US population following the introduction of unleaded gasoline into the US from 1976 to 1980 and compared this with the amount of lead being used in gasoline. There was an almost perfect correlation..

Once CLEAR presented their data to the Royal Commision on Environmental Pollution (Ninth report 1983), chaired by Professor Sir Richard Southwood FRS, it was game over and the government opted for lead-free fuel within half an hour of the Royal Commission making their recommendations.

And this is a seriously historic photo taken in 1982.

It shows my late wife Annie, next to the master campaigner and Chairman of CLEARm Des Wilson.  I’m standing next to Ellen Silbergeld. Herb Needleman is on the outside. Clair Patterson is holding my wife’s Russian Blue, Shoo Ling and at the front, are my two children, Joy and Chris, who were there because that is what it was all about really.

In 1981, Clair Patterson wrote this:

“Best scientists lack the comfort of peers.

Their science is always at first incredible

Even though later it teaches more…

Why do they struggle so?

Because in each discovery of new knowledge

Lies an awareness of the beauty and worth of human life

Which enslaves them as guardians of human destiny.”

Patterson’s work was unique because he was the only researcher in the world who had developed an ultra-clean laboratory and a technique – isotope dilution mass spectrometry – that allowed him to measure the incredibly low levels of lead present in pristine or prehistoric samples. This meant that, for almost 30 years, his data was the only reliable data in the world literature and put him so far ahead of his peers that he was operating in his own universe.  In 1982, he gave a key-note address to the conference organised by CLEAR in London.  During the discussion period his findings were challenged by Professor Rutter who was perplexed that noone had replicated Patterson’s findings. This led to one of the great exchanges in the history of science(reproduced verbatim in Lead versus Health. Sources and Effects of Low Level Lead Exposure. Ed Rutter and Russell-Jones pp 30-31).

Patterson: “Let me focus on the blood lead findings reported by Annest and Billick (Chapters 3 and 4).  Their results are not subject to the kind of error to which I referred with respect to the comparison of low natural levels and high levels in urban areas. Their database is reliable just because they apply to people subjected to high lead pollution.  With reasonable precautions you can obtain reliable measurements at those high concentrations of lead. However, this is not always the case.  If you ask for a routine blood lead analysis in a hospital, there may be an error of similar magnitude to that made by many past investigators.

Rutter: As I am sure you would agree that replication constitutes the essence of science….

Patterson: No, I would not.

Rutter: Even if you do not, many scientists would consider replication crucial. Our confidence in science depends upon the ability of different researchers to obtain the same findings if comparable methods are used. You seem to imply that your laboratory measurements are different from those of all others. Is that really so, or have other investigators been able to produce comparable results? Perhaps you could indicate the criteria to be employed in deciding which result to accept and which to reject.

Patterson: Our data derives from isotope dilution mass spectrometry, used under ultra-clean laboratory conditions – a technique that I developed. This is a very powerful and and accurate analytical method for trace amounts of lead. However it is extremely cumbersome, very costly and very time-consuming. As a consequence it can generate only relatively small amounts of data.  After World War 2, as a graduate at the University of Chicago, I was assigned the task of developing this method to measure uranium-lead ages in microscopic materials. Lead contamination constraints imposed by that work were unavoidable. Geological ages of gram quantities of uranium-lead minerals had been determined by macroscopic chemical methods and we had micro-quantities of minerals in rocks that were geologically associated with those macro-ore samples.  Therefore we had to obtain the same ages for the uranium-lead clocks in the microscopic minerals. Contamination of these microscopic systems became immediately apparent by violation of physical laws if we got the wrong geological age. This was a constraint that provided a unique training; it taught me always to exercise great care to control lead contamination while studying the occurences of lead. But the reason why the method is so powerful is that it is the most accurate method for determining very, very tiny quantities of lead. Lead contamination control is a supremely important thing and you must be able to measure very tiny amounts of lead if you are going to control your contamination correctly and reliably.  These two factors are not involved in most of the thousands of laboratories that ordinarily measure lead. Consequently, there are only a very few laboratories in the world where such analyses can be done accurately. There is one at the University of Paris, another at Caltech and one in Denver, Colorado. These few other laboratories that are capable of carrying out reliable studies of lead at ultra low concentrations are studying lead in lunar rock samples or very exotic cosmological debris…. But laboratories that provide most of the official statistics on lead occurences cannot provide accurate and reliable data concerning the occurences of lead in other than urban substances. Even the United States Bureau of Standards cannot yet analyse lead in fish muscle correctly. These are very difficult things – I do not know how to impress upon you the enormous dedication and sophistication that is required to do these things correctly.”

It is interesting that in his determination to impress upon Rutter the importance of excluding lead contamination from his laboratory, Patterson neglects to mention that his uranium-lead samples were being used to determine the age of the earth and of our solar system.

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