Prof. Dr. Shyam P Lohani
We are well aware that heavy metal toxicity is still contributing considerably to the global burden of disease. The scientific community is advocating for the ban on the use of such metals in many of the products in daily use. Although there is no standard definition assigning metals as heavy metals, most heavy metals have a high atomic number, atomic weight and specific gravity greater than 5.0. Heavy metals include metalloids, transition metals, basic metals, lanthanides, and actinides. Among many heavy metals, elemental mercury, bismuth, and lead are toxic metals with relatively high density and less commonly, iron, copper, zinc, aluminum, beryllium, cobalt, manganese, and arsenic may also be considered heavy metals.
Amid growing concern of heavy metal toxicities last month, Nepal celebrated international lead poisoning prevention week (ILPPW) of action from 20 to 26 October 2019 with a series of awareness campaigns, seminars, and workshops throughout the country. The 2019 ILPPW aimed at increasing awareness among the public about the detrimental effects of lead in human health, called for the promotion of actions to address human health effects of lead exposure, especially for children, and urging further actions to eliminate lead in paint through regulatory action at country level.
Lead exposure contributes to 0.6 per cent of the global burden of disease or 14 million disability-adjusted life years (DALY) which accounts to 74 per cent of cardiovascular diseases, 21 per cent of idiopathic developmental intellectual disability and 5 per cent chronic kidney disease (Weidema and Fintke, 2018). The Institute of Health Metrics and Evaluation (IHME) in 2017 estimated that 1.06 million deaths were attributed to lead exposure (IHME, 2017). The highest burden due to lead exposure is in low and middle-income countries, according to the World Health Organisation (WHO, 2019).
Lead has been mined for more than 6,000 years and the metal itself and its compounds are used throughout history. This easily worked and corrosion-resistant metal has been used in pipes, pewter, and paint since Roman times. Lead is still widely used for car batteries, pigments, ammunition, cable sheathing, lead crystal glass, radiation protection, jewelry, cosmetics, and solders. It has also been used in lead glazes for pottery, as an insecticide, hair dyes and as an anti-knocking additive in petrol. All such uses have been banned, replaced or discouraged in many countries in recent times. Lead has no known biological role and it has an accumulative property and can cause serious health problems.
Since 26 December 1999, only unleaded gasoline has been distributed in Nepal. It is expected that the present problem of lead exposure in Nepal is mainly from lead-painted toys, furniture, walls, lead-contaminated foods, and inhalation of lead mixed air as well as from occupational exposure.
Children younger than 6 years are especially vulnerable to lead poisoning affecting their mental as well as physical development. At very high levels, lead poisoning can be fatal if untreated. Lead-based paint and lead-contaminated dust in older buildings are the most common sources of lead exposure in children. Adults who work in battery industries, home renovation works and auto repair shops might be exposed to lead. The main route of exposure of lead is either ingestion or inhalation and once absorbed, lead is distributed to many organs from the brain, kidney to liver and bones. The human body mainly stores lead in teeth and bones and accumulates over time. The remobilisation of lead from bones during pregnancy exposes the fetus. Undernourished children are more susceptible to absorb more lead because other nutrients such as calcium and iron are lacking. Thus, children at higher risk of lead poisoning are from the economically disadvantaged population.
Lead toxicity is one of the most common preventable causes of neurological morbidity from an environmental toxin. It is ubiquitous and produces insidious hazards with the potential of causing irreversible effects on human health. It primarily affects central nervous, hematopoietic, hepatic and renal systems producing serious consequences. Acute toxicity primarily occurs with occupational exposure and is relatively uncommon while chronic toxicity is much more common. Lead poisoning occurs when lead builds up in the body over the months or years. Even small amounts of lead can cause serious health problems and many of those effects are irreversible.
At high levels, lead can affect the brain and central nervous system to cause convulsions, coma and even death. In particular, lead can cause developmental disorders in children resulting in reduced intelligent quotient, behavioral changes such as reduced attention span, antisocial behavior, and thus reduced educational achievement. Lead exposure also causes anemia, hypertension, immunotoxicity, and reproductive toxicity. Both the neurological and behavioral effects are irreversible.
Several studies conducted over different periods and in different parts of the country have shown elevated levels lead in children. Similarly, time-series studies conducted on lead in paint found that most of the paints, especially enamel paints, then available in the Nepalese market contained high levels of lead, well above the Nepalese government set standard of lead in paints, i.e. 90 ppm.
The Government of Nepal has set standard limiting lead in paints imported and produced in Nepal to ninety parts per million (90 ppm) or ninety milligrams per liter (90 milligrams per litre) effective from 20 June 2015, and mandated label paints can with lead content and protective precautionary measures to prevent occupational exposure. The above endeavour by the government is expected to abate the lead exposure to children and occupational workers up to some extent. Since the enactment of standard, the Ministry of Education, Science and Technology has published notice to use only lead paint containing less than 90 ppm for the use in all community and institutional schools.
Now, it is time for all stakeholders from governmental to non-governmental organisations to private and retailers to distributors to the manufacturers of paint to abide by the set standards and raise awareness for the abatement of human lead exposure. It is also called upon to all health professionals involved in prevention to treatment of lead poisoning for seriously taking up this preventable public health problem to making our children lead-safe.
(Prof. Lohani is the Clinical Director of the Nepal Drug and Poison Information Centre and can be reached at firstname.lastname@example.org)
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