82
Lead207.20
by Amy Thomas
F
rom the fall of the Roman Empire to severely sick factory workers, we have had a long journey with the hazards of lead. It is surely time for the industries using it to find a new route. Another dangerous element, lead (Pb), has been a topic of public health concern due to its damaging effects on the human brain. Although the UK has restricted the unnecessary use of lead, there are still many developing countries that are effected by lead contamination. In 2013, it was thought that lead poisoning caused 853,000 deaths, and recently protesters in America have been drawing attention to the dangerous consequences of lead poisoning in children. Lead is the most commonly used nonferrous (non-iron containing) metal and serves a multitude of purposes in industry. Lead can easily form alloys with other metals as well as undergo chemical reactions that allow the generation of a voltage in batteries. In the past, paint has also contained lead to speed up drying and increase durability; however, governments have since tried to restrict distribution of lead-based paint. Although it is a versatile material for industry, unlike other metals, it has no benefits to the human body. As well as having no biological use, it is highly toxic to bodily systems and can cause irreversible damage in the kidneys, the cardio-vascular system and the reproductive system. Most prominently, lead has neurotoxic effects that are devastating in the developing brains of children. Lead is particularly dangerous to the developing brain due to its interference with cell communication. Complex brain functions like learning and memory are driven by a highly dynamic process known as ‘neuronal plasticity’, literally ‘like plastic’.
www.isciencemag.co.uk
This is where neuronal connections are created, altered and shaped to change the organisation of the brain. Some of the psychological effects of lead poisoning are due to its interference with the special receptors that are involved in brain plasticity; disrupting the finely-controlled communication between the neurons and surrounding cells. Since brain plasticity
is vital for learning and memory, this particular element is not a welcome visitor in our main control room. But, lead also has other weapons in its arsenal for attacking the human body. It can stop the supply of an essential anti-oxidant in our cells, called glutathione, which would normally get rid of vicious reactive-radicals that damage DNA structure and cell membrane. Although we’ve only known about the more detailed neurological effects of lead in recent years, incidents of lead poisoning date back as far as ancient Anatolia. As early as 450-380 BC, Hippocrates documented health defects like gout and abdominal pain following the consumption of contaminated food and wine. Later, it was no surprise that many wealthy Romans also
experienced similar illnesses, considering that Roman cooking utensils, wine urns and plumbing systems were all made with lead. An average Roman’s lead intake was estimated to be around 35 mg/day - 250 mg/day compared with today’s average of 0.3mg/day. Some historians believe that lead poisoning was a prominent cause in the fall of the Roman Empire, although this remains speculation. During the early 20th century, factory inspectors started to notice that more and more women working in the ceramic industry were barren and children were getting severely ill. We now know that lead is particularly toxic to the foetus, disrupting processes involved in neuronal communication during development. Although the government made some changes to the law to reduce the extent of lead damage, Tetraethyllead began to be added to petrol in 1922 as a cheap way of improving engine performance in the USA, UK and China. Not long after, there was an outbreak of acute neuropsychiatric disease in production workers as this particularly dangerous form of lead can pass through the skin. About 80% of workers displayed behavioural changes and five people died within weeks. Despite this, leaded petrol continued to be distributed globally – also damaging catalytic converters in cars. It was only in the late 1970’s, when some governments began to ban lead in petrol, that a 90% reduction in mean blood lead levels was seen. Other countries, including Algeria, Yemen, and Iraq, still use Tetraethyllead in petrol today. Around this time in the 70’s there was also a clamp-down on the use of lead in paints. This was spurred on by research in Australia, highlighting how the widespread use of these lead-based paints through the late 19th century caused neurological disorders and deaths in children. Lead paints were banned, first in Australia in 1914, in the USA in 1978 and not in the UK until 1992! I’m not sure why the phrase ‘crazy-as-apainter’ didn’t catch on as much as ‘madas-a-hatter’ but the consequences of lead poisoning are every bit as potent. Pictures: Helena Spooner, ZoranKrstic (left), Maddy Dench (right)
I, Science
9