By Dr. Colin Michie FRCPCH
Our environments sometimes contain invisible threats to our health. Poisoning by a heavy metal – lead – still causes health problems in the Caribbean region. There is probably no safe exposure level for lead. Any level of lead can poison the growing brain – pregnant women and children particularly are at risk. Poisoning is not often suspected.
Lead has been an ancient part of human cultures; it is a common metal in the crust of our fragile planet. A miraculous, adaptable, soft material, used for coins, ornaments, sinkers, slingshots, decorative enamels on pots and recently colouring for plastics. Roman water pipes made from lead – “plumbum” – gave rise to the term “plumbing”. Cosmetics used lead salts to give a smooth white colour, popular for centuries in Egypt, Japan and Venice.
Lead was thought to cause illnesses in potters, miners, painters and drinkers over centuries. It was a common contaminant in early Caribbean rums – lead poisoning in the West Indies was suspected of causing dry gripes. “Worms” or condensers made of lead were used in most estate rum stills. Contaminated rum slowly and steadily poisoned slaves, sailors and soldiers alike.
Despite wide suspicions about toxicity, lead’s marvels and applications diversified. Lead in domestic paints prevented mildew, being toxic to fungi. Old paint flakes create fine particles, so lead paints persist for generations in the dusts of homes. These paints have been banned in many countries, but not all. Tetraethyllead introduced a century ago to control fuel combustion then released many thousand tons of tiny particles of lead into the atmosphere. Banning leaded fuel reduced new contamination, but inherited, heritage lead remains, deposited along our highways and urban pavements. Lead is used to make some artisanal dutchy pots, glaze Mexican cookware and colour plastic; this may leach into many environments and our foods. Exposure to lead can be a problem in battery manufacture and recycling, on shooting ranges and around some mine workings.
Children ingest more soil and dust than adults. This habit increases their chances of lead exposure. Some children and adults including pregnant mothers selectively eat paint flakes – pica – this can cause poisoning. Food plants such as leafy or root vegetables, and several herbs, extract the metal from contaminated soils: these crops increase our lead intakes. Water supplies can become contaminated from lead pipework, as in Flint, Michigan. High lead levels in some tobacco and cannabis will increase lead intakes when smoked. E-cigarettes have also been found to release lead into the lungs from their heating elements and some of their liquids.
Lead follows similar paths to calcium in the body. In adults, 90% of lead is found in the skeleton and teeth, showing as white lines on X-rays. Lead exposure contributes to early tooth loss, but toxicity involves all organs, damaging blood vessel linings and cell energy supplies. Within nerves, lead slows conduction and promotes inflammation, causing tremors, poor balance, delayed reaction times, muscle weakness, dizziness, slurred speech, headaches and poor memory. At high concentrations, paralysis and seizures develop – plumbism or saturnism. Bone marrow poisoning leads to anaemia. Fertility is reduced in men and women. Vessel damage raises blood pressures, delivers cardiac disorders, strokes and kidney damage.
In children, lead poisoning happens at lower exposures – baby teeth analyses can estimate exposure during foetal and neonatal life. Lead levels are linked to a child’s intelligence quotient. High lead levels can reduce hearing and cause irritability, along with poor concentration and learning in school. Over time, it increases risks of wheezing and allergic asthma. This variety of symptoms makes lead poisoning difficult to diagnose.
Lead poisoning is more troublesome in those deficient in iron, zinc and protective vitamins. A large Chinese study suggests it is more frequent in poorer communities. Specific medications can remove lead by binding strongly to it – the process of chelation, which carries lead away, mostly in the urine. Under expert supervision chelation removes lead from brain and bone. Regrettably, these treatments often have side-effects; they cannot always repair existing neurological or kidney damage.
History shows communities respond slowly to news of lead poisoning, despite layers of regulations and messaging. It is important to remain aware of lead in order to exclude possible contamination around us. Testing and monitoring of waste sites, paints, battery recycling and imported products on our islands will protect human capital. Children may be protected by ensuring they wash their hands often; cleaning their toys and play areas is useful in limiting dust ingestions. Their intellectual potentials must be protected! Varied plant-based diets delivering vitamins and flavonoids are beneficial. Some probiotics might reduce lead uptake, as may algae such as chlorella and spirulina, although evidence of their benefits is still being studied.
Lead poisoning is a knotty mix of legacy and contemporary challenges: Can you help?
Useful resources: gov.uk/government/publications/lead-properties-incident-management-and-toxicology/lead-toxicological-overview
gov.uk/government/publications/lead-poisoning-advice-for-the-public-and-healthcare-professionals/lead-information-for-the-public
who.int/news/item/18-10-2024-global-call-to-action-on-lead-poisoning-prevention
Dr. Colin Michie specializes in paediatrics, nutrition, and immunology. Michie has worked in the UK, southern Africa and Gaza as a paediatrician and educator and was the associate Academic Dean for the American University of the Caribbean Medical School in Sint Maarten a few years ago.
