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Old debate on lead rekindled

TOXIC ICE: “Geochemist Clair Patterson demonstrated that over the last few centuries, the levels of lead in the ice cores of the Arctic and Antarctic had gone up a hundredfold.” File photo shows icebergs on the Antarctic Peninsula.   | Photo Credit: STRINGER

>Noodles laced with lead have made the news. But humans have been imbibing lead with their food and drink for over 2,000 years. Lead is an abundant, easily accessible metal that has been in use for millennia. The Romans used lead extensively in cooking vessels, water pipes, and as an alloy in their silver coins. Annual production in the Roman Empire amounted to 80,000 tonnes. Grape juice boiled in lead vessels was added to wine and other dishes, all of which meant that Romans guzzled lead in substantial quantities throughout their lives. This happened despite the fact that Greco-Roman physicians knew that lead was highly toxic; they had vividly described the symptoms of lead poisoning. Some historians speculate that the collapse of the Roman Empire was brought on by lead poisoning.

The wordwide annual production of lead today amounts to 50 lakh tonnes; it is used in solder, paint and even food colouring. By now, lead has accumulated in significant quantities in human bodies and the environment. But the major culprit in the spread of lead is the anti-knock additive to the automobile fuel, tetraethyl lead (TEL). The history of how TEL was unnecessarily thrust on humanity and the biosphere makes a riveting story.

Push for TEL and opposition

TEL was first synthesised in Germany in the mid-19th century, but never put to use, being highly toxic. It was resurrected by the American automobile, oil and chemical industry as an anti-knock agent in the early 1920s. By then it had been widely acknowledged that mixing alcohol with petroleum could effectively serve the same purpose, with Scientific American reporting on April 13, 1918: “It is now definitely established that alcohol can be blended with gasoline to produce a suitable motor fuel.” By 1920, a U.S. Naval Committee had concluded that alcohol-gasoline blends “withstand high compression without producing knock.” But alcohol cannot be patented and cannot bring large profits to companies. So, all discussion of its potential was deliberately suppressed, and TEL pushed with vigour.

This push met with much opposition because there were many deaths and serious injuries in plants manufacturing TEL. As a result, several U.S. states banned its use. Many distinguished medical scientists opposed it. In response, the U.S. Surgeon-General convened a meeting in 1925 that, in turn, appointed a committee. This committee reported that there was no existing evidence of the ill-effects of long-term exposure to lead in the atmosphere on human health, but also pointed out that this was because there had been no research on the topic, and such research needed to be initiated urgently. Industry happily funded a pliant medical scientist, Robert Kehoe. For the next 40 years, the Surgeon-General and Kehoe undertook forceful advocacy of TEL. Many noted scientists remained unconvinced, but Kehoe challenged them to show clear evidence of the ill-effects of TEL. An important element of Kehoe’s claim of the absence of ill-effects of TEL was that the natural levels of lead in human blood were as high as 0.2-0.4 ppm. Notably, toxic effects of lead appear at just slightly higher blood levels of 0.5-0.8 ppm. Since Kehoe monopolised the research, it was impossible for the many doubters to produce counter-evidence.

The logjam was broken in the 1960s when a brilliant young geochemist, Clair Patterson, entered the scene. Patterson was working on iron meteorites to determine the age of our earth, for which it was essential to determine the levels of lead in the meteorites accurately. But this proved incredibly difficult, for Patterson discovered that the whole environment was so polluted by lead that it was well-nigh impossible to set up a lead-free laboratory. Finally, Patterson succeeded, and in 1956 determined the earth’s age to be 4.56 billion years, an estimate that continues to be accepted to this date. Patterson was then stimulated to look into the issue of lead in natural and human-impacted environments. Surprised by the closeness of the ranges of presumed natural and toxic lead levels in human blood, he began to examine the levels of a series of elements in the non-living environment and the biosphere. Patterson showed that living organisms preferentially take up useful elements such as calcium and actively exclude toxic ones such as barium from the same group.

This led to his second major contribution to science in the form of the concept of biopurification. According to this principle, natural concentrations of harmful elements in human body should be far lower than levels that are toxic, and that Kehoe’s claim of natural levels of lead in human blood being as high as 0.2-0.4 ppm was very much suspect.

Rising levels of lead

Patterson then systematically investigated levels of lead in rocks, rivers and sea water, ocean sediments, the atmosphere and the biosphere. He demonstrated that over the last few centuries, the levels of lead in the remains of marine organisms incorporated in sediments had gone up a hundredfold. He took ice cores from the Arctic and Antarctic and demonstrated a similar increase. The obvious conclusion was that the prevailing levels of lead in the human body were a result of pollution, and were not natural levels at all, as Kehoe had been claiming so far. Patterson provided clinching evidence of this when human teeth and bones from ancient burials turned out to have just one-thousandth the amount of lead as teeth and bones of modern-day humans.

Summarising his work, Patterson published a ground-breaking paper in 1965 that destroyed all of Kehoe’s unsustainable claims. The scientific, especially the medical research, community that had been mutely witnessing the unacknowledged ill-effects of lead pollution was immediately convinced. After sidelining his work and oil companies cutting off his funding, the U.S. government was finally forced to ban TEL a full 20 years after the publication of his paper.

But this chemical, thrust upon the world only because it is patentable, continues to bring in profits to its manufacturers from across the world, including India’s neighbours, Afghanistan and Myanmar, who still use it as an automobile fuel additive. Indeed, as Larry Summers, then a vice-president of the World Bank, and later Secretary of Treasury under Bill Clinton, had written in his notorious memo of 1991: “The measurements of the costs of health impairing pollution depends on the foregone earnings from increased morbidity and mortality. From this point of view, a given amount of health impairing pollution should be done in the country with the lowest cost, which will be the country with the lowest wages. I think the economic logic behind dumping a load of toxic waste in the lowest wage country is impeccable and we should face up to that.” Perhaps India, too, is acting today on this “impeccable” logic, to the evident detriment of its environment and the quality of life of its people.

(Madhav Gadgil is D.D. Kosambi Visiting Research Professor, Goa University.)


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Printable version | Oct 14, 2021 5:26:58 AM | https://www.thehindu.com/opinion/op-ed/Old-debate-on-lead-rekindled/article10887690.ece

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