NEW YORK--(BUSINESS WIRE)--An estimated 632 million children in 34 low- and middle-income countries (LMICs) have elevated blood lead levels suggestive of lead poisoning, according to a new study published in the March 2021 issue of The Lancet Planetary Health.
The study, a collaborative effort by researchers from Pure Earth, Macquarie University in Sydney, Australia, and the University of Southern California, considerably expands the existing knowledge about blood lead levels in LMICs and underscores the danger for children living in those countries.
Researchers used a threshold blood lead level of 5 micrograms per deciliter (µg/dL), the reference dose at which the U.S. Centers for Disease Control and Prevention recommends action, to evaluate the extent of lead toxicity in children. The systematic review included data published from 520 studies of blood lead levels in 49 low- and middle-income countries.
The U.S. CDC and the World Health Organization have determined there is no safe level of exposure to lead, a potent neurotoxin that irreparably damages the developing brains and nervous systems of young children. Lead exposure also increases the long-term risk of cardiovascular and kidney disease for children and adults, while causing no or subtle outward systems in the early stages. Even very low levels of lead exposure are associated with decreased intelligence, behavioral problems, and learning disabilities, according to numerous studies. Acute high-dose exposures can be fatal for infants and young children.
The study, titled "Blood lead levels in low-income and middle-income countries: a systematic review," is authored by Bret Ericson, Howard Hu, Emily Nash, Greg Ferraro, Julia Sinitsky and Mark Patrick Taylor.
"Lead is one of these major environmental issues that is hiding in plain sight," says Bret Ericson, PhD., the lead author of the study and a New York-based researcher. "Lead poisoning remains a significant issue in low- and middle-income countries. For the countries that we were able to include, the numbers are pretty staggering.”
Slated for release March 10 23:30 GMT in The Lancet Planetary Health, the study represents one of the most comprehensive examinations of blood lead levels in LMICs to date. Additionally, it is being published open access, and the authors have made their data fully available in a downloadable appendix to encourage and support further research and data collection about blood lead levels.
"This is a landmark study because it identifies the extent, magnitude and sources of lead exposure in already disadvantaged global communities. Perhaps most importantly, it draws our attention to the clear and urgent need to address this inequity," says Mark Taylor, FRSN, a co-author and professor, department of Earth and Environmental Sciences, faculty of Science & Engineering, Macquarie University. "Greater effort is required to better manage industrial emissions, the recycling of lead and its unnecessary use particularly in food products and cookware. Ultimately, the goal of this research and future efforts is to ensure that a significant proportion of the world’s next generation are no longer subject to an entirely preventable burden of disease."
Inequalities in lead exposure
While blood lead levels in high-income countries have declined dramatically with the phase-out of leaded gasoline -- dropping from a geometric mean blood lead level of 12.8 µg/dL in the United States in 1976 to one of less than 1 µg/dL by 2016i -- blood lead levels in millions of children living in some LMICs remain persistently elevated, even in the absence of leaded gasoline. These children face exposures to lead from industrial sources, including informal used-lead acid battery recycling, smelting and mining; adulterated foods and spices; ceramics used for cooking; and to a lesser extent, deteriorating lead-based paints, the study finds.
“High-income countries, recognizing lead’s impact on IQ and the importance of intelligence to their knowledge-based economies, have continued to reduce lead exposure. This study’s finding of continued elevated lead exposure among children in low- and middle-income countries underscores a growing global disparity that requires policy makers to take action," says co-author Howard Hu, M.D., Ph.D., Sc.D., professor and Flora L. Thornton Chair in the Department of Preventive Medicine, Keck School of Medicine, University of Southern California.
Study methodology
Researchers limited their study to data collected after 2005 to ensure that background lead levels were not influenced by the use of leaded gasoline, which was almost completely phased out worldwide by 2006. A systematic PubMed review of studies published between Jan. 1, 2010 and Oct. 31, 2019, that reported blood lead levels in the 137 nations classified as LMIC by the World Bank initially yielded 12,695 studies. Of that number, 520 studies, representing 49 countries and more than 1 million people, were found eligible for inclusion. Each included study was assessed for quality based on criteria established by the U.S. Office of Health Assessment and Translation.
Ultimately, background values for blood lead levels in children could be pooled in 34 countries and were used to estimate background distributions for children in those countries. From this data pool, adjusting for bias, the researchers estimated that 632 million children had blood lead levels at or above 5 µg/dL. BLL concentrations for children ranged from a low mean of 1.66 µg/dL in Ethiopia to a high mean of 9.3 µg/dL in Palestine.
"I think there is this idea that because leaded gasoline has been eliminated and we've placed restrictions on lead paint, that lead is an issue of the past," says Emily Nash, regional director for South Asia at Pure Earth and a co-author of the study. "This study makes it very clear that there are ongoing sources of contamination, particularly in LMICs."
Continued use of the study
The study highlights the limited amount of blood lead level data available in LMICs and researchers say, the urgent need for an international registry of blood lead levels. Of the 137 countries in the World Bank country groupings, ultimately only 34 countries had sufficient data on children's blood lead levels published in English and available for analysis.
"Despite our efforts to capture as much data as we could in LMICs, we're barely scratching the surface of the actual extent of the problem," says Nash.
Ericson would like to see the data collected for the study find wider distribution as the basis for an international BLL registry. "An anonymized international registry accessible to researchers and communities around the world would be an amazing research tool that could help inform policy decisions and improve monitoring," said Ericson.
The study published in The Lancet Planetary Health represents an important addition of knowledge to the continuum of increasing awareness about the dangers of lead exposure and the potential for remediation.
Peer-reviewed data and supporting research contained in the study contributed significantly to the findings of the 2020 report, The Toxic Truth: Children's Exposure to Lead Pollution Undermines a Generation of Future Potential, which was produced jointly by UNICEF and Pure Earth. The Toxic Truth detailed children's exposure to lead on a massive and previously unrecognized scale, finding that as many as 800 million children worldwide -- or almost a third of all the children in the world -- suffer from elevated lead levels. The Toxic Truth also incorporated data from the Institute for Health Metrics and Evaluation (IHME) and dozens of other studies. When examining IHME’s data from the same 34 countries examined in this research, both studies arrived at similar numbers of children harmed using different methodologies.
“This research adds to the scientific evidence that a previously unknown wave of lead poisoning has been sweeping through low- and middle-income countries, resulting in a staggering loss of human and economic potential for these children over their lifetimes,” says Richard Fuller, Pure Earth CEO. “What makes this especially urgent is this problem is growing, and the cycle will continue for generations until the sources of lead exposure are removed and no longer poisoning children. The good news is that an initiative to solve this problem at scale has been established.”
Pure Earth, the Clarios Foundation, and UNICEF have launched Protecting Every Child's Potential (PECP), to help prevent children's exposure to lead. PECP draws upon the expertise of its three founding organizations in toxic-site assessment and remediation, sustainable, environmentally sound battery recycling, and children's health and welfare to raise awareness about the dangers of lead exposure from informal and sub-standard used lead-acid battery recycling, adulterated spices, cookware and other products. The PECP is focusing initial efforts on Bangladesh, Georgia, Ghana, and Indonesia, while the Clarios Foundation and Pure Earth are integrating their work already underway in Mexico.
Funding for the study
Work was supported in part by a grant from the United States Agency for International Development and by the International Macquarie University Research Excellence Scholarship.
To access the study, please see:
Blood lead levels in low-income and middle-income countries: a systematic review
Bret Ericson, Howard Hu, Emily Nash, Greg Ferraro, Julia Sinitsky, Mark Patrick Taylor
http://www.thelancet.com/journals/lanplh/article/PIIS2542-5196(20)30278-3/fulltext
i Dignam, Timothy, Rachel B. Kaufmann, Lauren LeStourgeon, and Mary Jean Brown. "Control of Lead Sources in the United States, 1970-2017: Public Health Progress and Current Challenges to Eliminating Lead Exposure." (Journal of Public Health Management and Practice: JPHMP 25, no. Suppl 1 LEAD POISONING PREVENTION, 2019): S13. DOI: 10.1097/PHH.0000000000000889
