Michael Rosenthal

(9/2018) In last month’s discussion of Emmitsburg drinking water, the point was made that lead was not a contaminant of our local water, a very good thing. Lead is a very toxic material to animals and people, element # 82 on the Periodic Table of Elements. Lead does occur naturally in the earth and has many uses. In 2014 global production was about ten million tons. Among its uses have been plumbing, batteries, bullets, solders, pewters, paint, radiation shielding, and gasoline. Uses of lead have been reducing, due to the recognition of its toxicity. Lead accumulates in soft tissues and bones, and it acts as a neurotoxin, damaging the nervous system and the brain, and interfering with the function of biological enzymes. It is particularly dangerous to children and to those not yet born, both of whom often have life-long health problems from lead exposure.

In nature it rarely is found in elemental form. It is primarily found as lead sulfide, PbS, known as galena. World lead resources are large, exceeding 2 billion tons, and lead is found in many parts of the world, including the United States. Natural concentrations are generally low.

As the world moved toward industrialization, lead demand grew worldwide, and by 1900, the United States led the world in lead production. Major industrial demand was for the use of lead in plumbing and painting. Lead paint was particularly popular. Factory workers in lead production were, however, particularly affected in the late 19th century and early 20th century, enduring physical disorders, including gout and blindness, and also suffering from mental disorders.

In the United States lead was added to gasoline in 1921 in the form of tetraethyl lead, an organometallic compound in which four ethyl groups were bonded to a central lead atom. The purpose of the addition of lead to gasoline was its function as an antiknock agent, allowing automobiles and other motor vehicles to function smoother and quieter. I remember well seeing the notice, contains tetraethyl lead (TEL), on gas pumps as I grew up and continuing until about 2000 when the additive was phased out of gasoline in the United States and the European Union.

Lead paint was common in construction because it had opacity and water resistance. Lead paint was eventually phased out as well. Lead is still used in lead-acid batteries, and aside from disposal concerns, this use poses low threat. However, since lead still has many other industrial applications, care must be taken to protect workers and there must be safe disposal of industrial waste. It would not be a good idea to live next door to a lead battery disposal landfill or near a factory that utilized lead.

Even knowing how dangerous lead can be, lead is still a global issue, since mining, smelting, and battery manufacturing, are common in many countries of the world, and regulation is uneven. Lead enters the human body through inhalation, ingestion, and skin absorption. The most common sources for lead poisoning are through the ingestion of contaminated food or drinking water (remember Flint!), and less commonly by accidental ingestion via soil, dust, or lead-based paint. Leaded gasoline was a major source of lead contamination in soil. You will recall that the Flint, Michigan, lead contamination issue came via water pipes when the water source was changed.

An excellent documentary on the Flint water crisis was shown on Public Television. Its title is "Poisoned Water". If the water is acidic, the lead in the pipes can dissolve into a soluble lead compound, which ends up in household water uses. Hard water forms insoluble layers in the pipes, but soft water and acidic water dissolves lead from the pipes into the water, forming lead bicarbonate, and thus delivers it to the user. Drinking this water over time increases the concentration of toxic lead in the body.

The most dangerous source of lead for children is lead-based paint. Not only does this lead enter a child’s body from day-to-day children’s household activity, but as the paint ages, lead-containing dust enters the environment, and eventually into the human body. Inhalation and smoking also contribute to the body’s increase in lead. The United States banned the use of lead-based paint in residential structures and environments in 1971 and the manufacture of lead-based house paint in 1978. In 1991 the Secretary of the Department of Health and Human Services called lead the "number one environmental threat to the health of children in the United States."

Old lead-based paint is the most significant source of lead exposure in the United States. Lead poisoning can be treated when detected with compounds that react with lead and form new soluble compounds which are then excreted in urine. The mental disorder effect is illustrated by the fact that a statistically significant correlation has been found by researchers between the usage rate of leaded gasoline and violent crime.

Why did it take as long as it did to discontinue to the use of tetraethyl lead? The discovery that TEL improved engine performance made it harder to ban it. At least 17 workers died in 1924, in refineries in New Jersey, but the improvement of fuel effectiveness kept the inclusion of TEL in gasoline. The New York Times editorialized in 1924 that the deaths should not interfere with the production of the more powerful fuel. In 1926 a Surgeon General committee issued a report that concluded there was no real evidence that the sale of TEL was hazardous to human health. The controversy continued for many years, with much evidence being ignored due to the pressures of the lead industry. As Mel Brooks said, "Everything is Show Biz," and the pressures of the lead industry dominated.

A turning point came in the late 1940s and early 1950s when Dr. Clair Cameron Patterson’s studies revealed that lead contamination in the environment dated from the time that TEL became a fuel additive, and he became one of the earliest opponents of its use. The first clinical studies of the toxicity of TEL in humans were published in the 1960s. In the 1970s a researcher found that high lead levels in children correlated with lower school performance. Though the lead industry accused Dr. Patterson of scientific misconduct, he was eventually cleared by a scientific advisory council.

In 1973, the EPA issued regulations to reduce the lead content in leaded gasoline in phases as part of the Clean Air Act, and was supported in court. By 1995 leaded fuel accounted for only 0.6% of United States gasoline sales, and in early 1996 the EPA banned the use of lead in gasoline entirely. Similar bans since implemented in other countries have resulted in the lowering of lead in people’s bloodstreams worldwide.

There is always bound to be a controversy between financial profit and scientifically-based good sense. The good news here is that following the United States decision, many countries have phased out the use of lead in gasoline, including the European Union in 2000. As of 2013, a few countries still sold leaded gasoline, but some of them are in announced phase-outs.

Michael is former chemistry professor at Mount. St. Marys

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