Lead exposure in childrenBMJ 2022; 377 doi: https://doi.org/10.1136/bmj-2020-063950 (Published 07 April 2022) Cite this as: BMJ 2022;377:e063950
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We read with great interest the article of Roberts et al (1). As the authors state, in high-income countries the successful phasing out of leaded gasoline in most countries, together with other lead control measures, has resulted in a significant decline in population-level blood lead concentrations (2). However, developmental disabilities among children are increasing (3) and the results of several studies are consistent with an association between lead exposure and these disorders (4).
The decline in lead exposure has been observed during the same period when the increase in developmental disabilities has been noted. This raises the doubt that lead could not contribute to the increase of these disabilities. However, there could be a possible explanation; even if lead emissions are declined the exposure to this toxicant could be greater for greater ease of being transported into the environment by ultrafine particulate (UFP), the latter increased considerably due to the use of new combustion technologies. Furthermore, lead transported by UFP can reach the brain bypassing the blood circulation. In this way, blood lead levels could be within normal limits not reflecting its presence in the brain.
The unification of East and West Germany in 1990 resulted in sharp decreases in emissions of major air pollutants except for the UFP. The number concentration of UFP increased by 115% between 1991 and 1998. The ratio of these UFPs to total suspended particulate (TSP) also increased by more than 500%, indicating a dramatic change in the size distribution of airborne particles (5).
New technologies used for reducing the emission of pollutants could have caused a secondary increase in UFP emission. Using transmission electron microscopy, researchers noted that UFP commonly adheres to the surface of larger coal fly ash (CFA) particles (6,7). The adherence of small particles onto larger particles may play a role in the observed increase of UFP concentration in Erfurt because large particles are expected to be removed more efficiently by common HVAC pleated filters thus increasing the number of UFP emissions.
Furthermore, for example, new coal-fired power plants are equipped with selective catalytic reduction (SCR) unit, electrostatic precipitator (ESP), and wet flue gas desulfurization (WFGD) unit to reduce the emission of pollutants. SCR may affect the emission characteristics of particulate matter due to NH3 slip during denitrification. The operation of SCR with an NH3 injection leads to an increase in UFP emission levels at the ESP outlet due to the formation of (NH4)2SO4 and NH4HSO4 aerosols (8).
On average, the UFP number concentrations contribute more than 90% of the total particle number concentrations in the urban atmosphere and about 70% - 80% in the suburban atmosphere. Close to a major road, the total particle number concentrations may consist of 95% of UFP (9).
Trace metals (Pb, Hg, As, and Ca) are found in greater abundance in the UFP than in the fine aerosol (10). UFP can reach the brain either through circulation or by direct translocation along the olfactory nerve into the olfactory bulb, after depositing on the olfactory mucosa of the nasal region (11).
In conclusion, the reduction of lead exposure could have been counteracted by the use of new combustion technologies that increase the emission of pollutants capable of facilitating the transport of this toxicant.
1) David J Roberts, 1 Sally M Bradberry, 2 Frances Butcher, 1 Araceli Busby3. Lead exposure in children. BMJ 2022;377:e063950 http://dx.doi.org/10.1136/bmj-2020-063950. Published: 07 April 2022
2) WHO. Lead poisoning. 11 October 2021.
3) Durkin MS. Increasing Prevalence of Developmental Disabilities Among Children in the US: A Sign of Progress? Pediatrics. 2019 Oct;144(4):e20192005 DOI: 10.1542/peds.2019-2005. PMID: 31558575.
4) Delgado CF, Ullery MA, Jordan M, Duclos C, Rajagopalan S, Scott K. Lead Exposure and Developmental Disabilities in Preschool-Aged Children. J Public Health Manag Pract. 2018 Mar/Apr;24(2):e10-e17 DOI: 10.1097/PHH.0000000000000556. PMID: 28257404.
5) S Ebelt, M Brauer, J Cyrys, T Tuch, WG Kreyling, et al. Air Quality in Postunification Erfurt, East Germany: Associating Changes in Pollutant Concentrations with Changes in Emissions. Environmental Health Perspectives. Vol.109, N. 4, April 2001.
6) Yuanzhi C, Shah N, Huggins F et al. (2005) Transmission electron microscopy investigation of ultrafine coal fly ash. Environ Sci Technol; 39: 1144–51.
7) Hicks JB, McCarthy SA, Mezei G, Sayes CM. PM1 particles at coal- and gas-fired power plant work areas. Ann Occup Hyg. 2012 Mar;56(2):182-93. DOI: 10.1093/annhyg/mer085. Epub 2011 Nov 29. PMID: 22127876.
8) T Cheng, C. Zheng, L Yang, H Wu, H Fan. Effect of selective catalytic reduction denitrification on fine particulate matter emission characteristics. Fuel. Volume 238, 15 February 2019, Pages 18-25. DOI.org/10.1016/j.fuel.2018.10.086.
9) Hussein, T. et al. Particle size characterization and the indoor-to-outdoor relationship of atmospheric aerosols in Helsinki. 2004. Scandinavian Journal of Work, Environment & Health, 30, 54-62.
10) University of Rochester-EPA Excellence PM Center. Ultrafine Particles: Characterization Health Effects and Pathophysiological Mechanisms. Progress Report Year 4. July 2003.
11) Oberdörster, G. et al. Translocation of inhaled ultrafine particles to the brain. Inhalation Toxicology. Inhal Toxicol. 2004 Jun;16(6-7):437-45.
Competing interests: No competing interests
Re: Lead exposure in children
I read with great interest the recent paper in The BMJ by Roberts, et al, titled 'Lead exposure in children' and congratulate the authors on bringing together an impressive summary of lead exposure and poisoning in the UK. I do question whether it is relevant to say that exposure in the UK is 'likely to be similar' to the USA and France. The USA are celebrating 30 years of lead poisoning prevention programmes and France started to limit lead in paint in 1909. The UK could have a worse lead exposure problem than those countries.
A recent Unicef report titled "The Toxic Truth", quoting data from the Institute for Health Metrics and Evaluation, estimates that there are around 214,000 (186,117 - 281,542) children in the UK with blood lead concentrations above 5 µg Pb/dL (The UK public health intervention level). This broadly matches the numbers reported in the USA.
Roberts describes interventions and communications that can be implemented once an elevated lead exposure has been identified in children. There are also cheap and simple initiatives that could be put in place to prevent lead exposure at a population level. These include:
a) Check all homes for lead paint on sale or rent and, if found, provide information on how to manage the risk
b) Place leaflets in professional and DIY stores, that stock paint and abrasives used in decorating, explaining how to deal with lead paint safely
c) Communicate to GPs and carers reminding them to consider lead exposure as a potential cause for many non-specific presentations including miscarriage, pre-term birth, low birth weight, problem behaviours, ADHD, developmental intellectual disability, delayed puberty, coronary heart disease and kidney disease.
These measures, together with simple changes in behaviour, and screening for elevated blood lead concentrations, would be a good start at improving the lives of many UK children that are diminished in length and quality through lead exposure.
HSA Lead Exposure Public Health Intervention and Surveillance Steering Group (LEPHIS)
The Lead Exposure and Poisoning Prevention (LEAPP) Alliance aims to influence health and housing policy leaders to do more to manage lead exposure in the UK. (leappalliance.org.uk)
Competing interests: No competing interests