On Why Toxic Metal Still Enjoying Strong Global Demand
British scientists have revealed that human breathing causes lead, antimony and copper compounds to form inside medical masks. It reminds of Vladimir Mayakovsky's lines, "as our days entered the water pipe, worked by the slaves of Rome". Which is a typical example of how lead pipes bring about a decline in the population's average life expectancy.
Tests on identifying the risks posed by mask production have become highly relevant during the pandemic. People worldwide need to keep wearing them, Project lead Dr Sarper Sarp of Swansea University says. The research revealed that when submerged in water, all studies samples show high levels of chemical pollutants. The British scientists emphasised that a disposable mask should not be worn severalfold and should be disposed of correctly. It is good to mention that disposable plastic face masks come under Category B waste in some European countries. This means they are processed separately from municipal solid waste and destructed by grinding, compacting or burning in designated areas.
Inhabitants of ancient Rome, of course, did not wear masks. However, in the XIX century, an ingenious theory appeared which explained the fall of the Roman Empire by the widespread use of lead in everyday life. This theory became widely acknowledged and accepted as valid in 1965, propelled by the "Lead Poisoning and the Fall of Rome" article authored by Gilfillan and published in a medical journal.
Lead has been used by humans for thousands of years. It is ubiquitous. The metal is easy to extract and process; it is very malleable, and finally, it is easy to melt. An ingot of lead can be sliced by an ordinary knife. Lead smelting was one of the first metallurgical processes humanity became aware of. The oldest archaeological finds of lead-containing objects are beads dating back to 6400 BCE. Yet, the true popularity came to the metal in ancient Rome.
The former civilisation is believed to be the largest lead producer of the pre-industrial era, with an annual production of 80,000 tonnes. The metal was mined in Central Europe, the Balkans, Greece, Asia Minor, and Spain. In comparison, Dmitri Mendeleev wrote that in the late-19th century, Russia produced only 2-3 tonnes per year whilst consumed about 40,000 tonnes.
|Native lead occurs rarely, but it is found in various rock types - sedimentary, ultramafic intrusive ones, and others. By now, there have been 80 lead-bearing minerals identified. The most notable among them are galena, anglesite, and cerussite.|
The Romans did not only make pipes for water supply systems from this metal. They also added it as lead sugar into wine to improve its taste. Along with water, it was the most popular drink back then, which was actually viewed as a cure for many diseases and actively 'prescribed' by local doctors for therapeutic purposes. Hence, almost all residents of the Roman Empire were poisoned by lead.
Chronic intoxication caused by regular ingestion of heavy metal compounds brings damage to all parts of the brain. It may cause damage to the hematopoietic system and kidney injuries. Lead is a polytropic poison: it affects different body organs and systems, accumulates in bone tissues, and displaces calcium. That is why many modern researchers attribute the health deterioration of the inhabitants of ancient Rome to the everyday use of lead.
Lead was widely used in Russia, too. In 1633 a water supply line with lead pipes was built in the Kremlin. The water which ran through it came from the Vodovzvodnaya Tower. Luckily, in 1737 a decision to dismantle the system was approved. Subsequently, the metal was used to coat the roofs of churches, produce seals for letters and paints, and, following the invention of firearms, to make bullets.
The toxicity of lead is undoubted today. Nonetheless, scientists point out that the chemical element's biological effect and a lack of knowledge about its properties are the primary reasons for overly negative attitudes towards the metal.
Lead is dangerous if ingested directly. Otherwise, if handled correctly, it is perfectly harmless, and moreover, it can protect people from radiation. In addition, it has numerous applications in a variety of industries.
It is known that a large part of the Arctic expedition led by John Franklin, a British explorer, died in 1845-1848 over being poisoned by lead. The haste with which the cans of food had been prepared allowed the metal to leach into the food. Ingestion of lead-contaminated food or drinking water with a high lead content is less harmful to health than inhaling lead dust, fumes or vapours. In areas with complex ore processing plants functioning, lead concentrations in the air are often above the threshold values.
Numerous measures are being taken at enterprises to prevent the inhalation intake of lead by workers. These include practical methods for reducing air dustiness, automation of technological processes and remote control, the use of industry-specific ventilation systems (aspiration, air showers).
In the 20th century, exhaust emissions from car engines caused significant lead pollution because lead additives (tetraethyl lead) were added to motor fuel to increase the octane number. Most countries, including Russia, have since legislated against the use of leaded gasoline, so the problem was solved.
Lead is excellent at absorbing γ-radiation, however. It played a crucial role in eliminating the consequences of the Chernobyl disaster. Rolls of lead sheet and bags filled with lead shot were being dropped onto the burning reactor for several weeks to seal off radiation and prevent the spread of it.
When it became clear that there was no way to avoid people's working at the emergency site, it was decided to use special protective gear. It was basically an 'armoured' suit of lead, consisting of leaded mittens, helmet, protectors for chest and back, and insoles for boots. Such armour was literally made by hand, carved from 3 mm thick plates. Although it weighed 25 to 30 kg, it helped reduce radiation exposure by 1.6 times.
Nowadays, the metal is used as a radiation shield at atomic reactors and in X-ray equipment. There is also a potential for using it as a coolant in future fast-neutron nuclear reactors.
The global output of lead amounts to over 2.5 million tonnes per year. Its compounds and alloys are used in producing a wide range of explosives and missiles and a special liquid for the flotation beneficiation of ores. The heavy metal found use as a cathode material in chemical current sources. There is also use for it in electrical engineering and the chemical industry. Most of the lead production now goes into the manufacture of batteries, particularly lithium ones.