In recent decades, the United States has dramatically decreased childhood lead exposures and associated risks. According to the Centers for Disease Control and Prevention (CDC), the geometric mean of lead found in the blood of children in the U.S. dropped from 15 μg/dL between 1976 and 1980 to 1.3 μg/dL between 2007 and 2010; mean levels were higher because of the nature of such log-normally distributed data.
However, in many parts of the world lead is a ubiquitous contaminant that presents significant ongoing occupational public health concerns. In fact, new studies have demonstrated that lead may be much more dangerous than we previously believed. LEAD TOXICITY The toxicology of lead in the human body involves neurological, neurobehavioral, developmental, gastrointestinal, hematologic, renal, cardiovascular, immunological, and skeletal effects. Similar to some of the effects of other metal exposures, the main mechanisms of lead toxicity are enzyme inhibition, protein binding, mimicry (when lead substitutes for iron and calcium in cellular transportation and reactions), production of reactive oxygen species, and aberrant DNA manifestation. (Several of the resources listed below contain additional information about the effects of lead exposure.)
In general, children are especially sensitive to the effects of lead exposure at doses that do not typically produce effects in adults. According to a study that appeared in the journal Brain, this sensitivity is due to several factors: a child’s gastrointestinal tract absorbs more ingested lead than an adult’s; a child’s brain is more easily accessed by systemic circulation of lead, especially at age five or younger; and a child’s developing nervous system is far more vulnerable to the toxic effects of lead.
The most prominent outcome of lead poisoning in children is neurotoxicity with the loss of associated IQ. As discussed in a paper that appeared last year in BioMed Research International, such effects include increased behavioral problems, perhaps related to impaired decision-making ability because of decreased attention span as well as reduced processing speed, language, visual-spatial, and motor skills.
No safe blood-lead level for young children has been identified by CDC. Previously, CDC determined that 10 μg/dL was a “level of concern.” However, new studies demonstrated that lead is dangerous at lower levels to the nervous system of children. In 2010, a World Health Organization (WHO) publication emphasized that the adverse effects of lead start at levels lower than 10 μg/dL, and the rate of response, from a dose-response perspective, is more pronounced at lower levels of exposure.
In 2012, CDC published a “reference value” for lead in blood at 5 μg/dL, replacing the 10 μg/dL level of concern. This reference value is not necessarily an action level; it represents the 97.5 percentile of the distribution of lead in the blood of children who are one to five years of age currently living in the U.S. As discussed in the WHO publication, some scientists have suggested that a lower blood-lead level, perhaps 2 μg/dL, should require follow-up and an assessment by health professionals.

Is there a threshold for the adverse effects of lead in children? This question will remain a focus of scientific discussion for a long time. Neurobehavioral parameters in children are difficult to measure, and past levels of lead exposure and body lead burden are only indirectly quantifiable through blood testing. We should also consider that a non-threshold dose-response is atypical for non-cancer endpoints of toxicity.

Though lead toxicity in children obviously occurs at much lower levels of exposure than was previously believed, the absence of recommended action levels for lead in children’s blood introduces uncertainty into risk management policies. This is especially true in developing countries where the reduction of childhood lead exposure requires country-specific and cost-effective approaches. LEAD IN DEVELOPING COUNTRIES An AIHA reference document regarding lead in developing countries published in June 2014 focused on occupational and environmental lead exposures and risks in the former Soviet Union, a largely unfamiliar region for most scientists and experts working in the field of childhood lead poisoning. In certain areas of the immense territories between Europe and Asia, the extent of childhood lead exposure is astonishing. For example, a report sponsored by the Russian government in 1997 concluded that 10 million urban Russian citizens are affected by lead contamination in soil. The report also suggested that 44 percent of children in the urban Russian population suffer from behavioral and learning issues caused by lead poisoning.
During our own 2003 study in Kazakhstan, we found that lead poisoning was a significant problem across various areas of the country, but particularly among children in the city of Shymkent, where the largest lead smelter in the region was located. The smelter was built in the 1930s and continued to operate until 2012. More than 66 percent of the children tested in Shymkent had blood-lead levels above 10 μg/dL, and two boys living near the smelter were found to have blood-lead levels of more than 100 μg/dL. In the surrounding 10-square-kilometer area, lead in the soil exceeded 1,000 mg/kg, and lead-in-air levels ranged from 1 to 8 μg/m3, depending on distance and direction from the smelter. Densely populated areas close to the smelter administrative center were contaminated not only by lead, but also by arsenic, cadmium, and other metals in consistent ratios. Based on our estimation, approximately 60,000 pre-school children in the city were seriously affected by lead exposure annually.
More than 10 years after our discovery of the environmental lead catastrophe in Shymkent, efforts continued to help children in the city, but multiple barriers prevented direct action. In 2008, an international team, including the authors of this article, developed a feasibility study for comprehensive soil remediation. Four years later, after intense international pressure, the lead smelter in Shymkent was shut down, but the government did not take steps to implement the cleanup process and blamed lack of progress on the economy. Although news organizations such as Al-Jazeera publicized the story, international organizations were unsuccessful in drawing enough attention to the problem to protect the population. It was not financially possible to relocate the affected children because of the large number of affected families living in direct proximity to the smelter.
We are continuing to educate parents and teachers on precautionary behavior in contaminated environments, but these actions can only partly decrease exposure and risks. Even children with extremely high blood-lead levels and acute health issues were unable to receive medical intervention because there was no accepted treatment protocol. Chelation therapy was not permitted because of potential side effects.
It is likely that the situation in Shymkent is typical of many other regions of the former Soviet Union. The Blacksmith Institute, a nonprofit that seeks to address pollution in low- and middle-income countries, investigated Balkhash City, in the Karaganda region of Kazakhstan, where the largest British-owned copper smelter operates. The average soil level of lead in residential areas was 1,626 mg/kg (SD 1,098 mg/kg). According to the EPA’s Integrated Exposure Uptake Biokinetic (IEUBK) model, 87 percent of the children living in such conditions would probably have blood-lead levels higher than 10 μg/dL.
In areas of Kazakhstan where we performed surveys, including the largest cities at the time, about 19 percent of children had blood-lead levels higher than 10 μg/dL. If an action level were established at 5 μg/dL, more than 63 percent of these children could require medical attention due to lead exposure. At the same time, the 97.5 percentile of lead in blood of studied children in Kazakhstan is 33.8 μg/dL, or 18.5 μg/dL if the Shymkent zone is excluded. These results suggest that the blood-lead levels adopted in the U.S. may not be practical for developing countries. Specific strategies are needed for gradual reduction of the level of concern for emerging economies. These strategies must be based on monetary resources and other practicalities, but they must also take into account the immediate human suffering and serious economic consequences of childhood lead poisoning.
RESOURCES
BioMed Research International: “Pb Neurotoxicity: Neuropsychological Effects of Lead Toxicity” (2014).
Brain: “Lead Neurotoxicity in Children: Basic Mechanisms and Clinical Correlates” (Jan. 2003).
Bulletin of South Kazakhstan State Pharmaceutical Academy: “Application of a Bio-kinetic Model (IEUBK) to Estimate the Effectiveness of Different Soil Remediation Scenarios for Lead Contamination in Shymkent, Kazakhstan” (2012). 
Cassarett and Doull’s Toxicology: The Basic Science of Poisons (2008).
CDC, Morbidity and Mortality Weekly Report: “Blood Lead Levels in Children Aged 1–5 years—United States, 1999–2010” (April 2013).
CDC, Morbidity and Mortality Weekly Report: “Interpreting and Managing Blood Lead Levels <10 μg/dL in Children and Reducing Childhood Exposures to Lead” (Nov. 2007). 
Ethnicity and Disease: “N-Acetyl-Cysteine Protects Against DNA Damage Associated with Lead Toxicity in HepG2 Cells” (2010).
Journal of Medical Toxicology: “Medical toxicology case presentations: to chelate or not to chelate, is that the question?” (Dec. 2013).
The Lancet: “Enzyme Inhibition by Lead Under Normal Urban Conditions” (Jan. 1970). 
Neurotoxicology: “Lead-Protein Interaction as a Basis for Lead Toxicity” (1993). 
REFIA: Report on the Lead Contamination of Environment in Russian Federation and Its Impact on Public Health, 1997.
Toxicology and Applied Pharmacology: “Molecular and Ionic Mimicry and the Transport of Toxic Metals” (May 2005).
Xenobiotica: “Are Free Radicals Involved in Lead Poisoning?” (Aug. 1991). 
WHO: “Childhood Lead Poisoning” (2010).
BY ANDREY KORCHEVSKIY, JAMES RASMUSON, AND ERIC RASMUSON
Blood-lead Levels and Lead Poisoning in Emerging Economies
How Low Is Low?​
In areas of Kazakhstan where we performed surveys, about 19 percent of children had blood-lead levels higher than 10 μg/dL.

Other sources of lead exposure have contributed to elevated levels of lead in the blood of Kazakhstan children. Lead paint is widespread and, according to some new data, its use is growing. In addition, we discovered a significant presence of lead in toys and tableware. Lead in gasoline apparently has been banned in Kazakhstan and other countries of the region, although some leaded gasoline may have been used there illegally.

WHAT TO DO, AND WHAT NOT TO DO
Developing countries need increased international attention on the subject of occupational and environmental lead contamination. International expertise in this area is abundant, and the increasing awareness on “green” topics presents new opportunities to discuss the issues surrounding lead exposures and associated risks.

Many international foundations are interested in resolving environmental and public health issues in developing countries. Considering Russia’s strained relationships with its neighbors, helping countries clean up the affected zones could be a way to build bridges between societies.

The extent of the lead problem in countries of the former Soviet Union suggests that it would be beneficial for public health policymakers, and perhaps occupational and environmental health organizations such as AIHA, to determine a meaningful action level value with respect to children’s blood-lead levels. The CDC’s reference value is probably out of reach for many developing regions, unless it is interpreted as a recommended, eventual reduction of 10 µg/dL to 5 µg/dL. The target level may have to be adjusted to local situations and economies. Without a target action-level for blood lead in children, it is difficult or even impossible to establish goals related to environmental remediation, biological monitoring, and education or relocation of affected populations. As a start, we recommend establishing a blood-lead level target of 5 µg/dL with the possibility of gradually decreasing this level as countries progress in their lead poisoning prevention systems.

AIHA’s reference document addresses the issues of lead poisoning prevention and treatment. Medical treatment associated with lead poisoning is extremely important for children in post-Soviet countries. However, treatment approaches remain controversial, because, as far as we know, chelation therapy is not permitted there for children with any level of blood lead, even when suffering severe encephalopathy. Medical professionals should be educated in the use of chelation therapy to treat acute cases of lead poisoning, especially when, as the CDC recently emphasized, there is a tendency to use this term fraudulently in Internet advertisements. Currently, CDC recommends chelation therapy for levels of lead in blood higher than 45 µg/dL, with consideration of such treatment at lower levels, based on the results of medical testing, down to 25 µg/dL. New methods of treatment for children with lower levels of lead in blood would be helpful, but their development will require intensive scientific studies, rigorous testing, and regulatory approval. In any event, removal of lead-poisoned children from the source of the lead always remains the most important goal. ​

The international community should consider all necessary steps to reduce lead contamination in the environment. Given the apparent growth of lead-based paint utilization in the former Soviet Union and other countries, a ban on lead in paint (above an appropriate lead concentration standard) should be a worldwide priority. 

The problems associated with childhood lead poisoning in developing countries are of special interest for industrial hygienists in the U.S. Because of social responsibility standards, those issues should be assessed and known for employees of international companies. Companies working in areas where children may have elevated baseline blood-lead levels should work to reduce lead emissions, should educate their staff in methods to prevent further environmental contamination, and as responsible corporate citizens, should offer help and community education to reduce risks. New research on lead exposure in adults may require reduction of workplace air and worker blood-lead standards. In the occupational environment, measures to further diminish lead exposure represent best practices and will also result in reduction in related household exposures.  

ANDREY KORCHEVSKIY, PhD, CIH, is director of research and development with Chemistry & Industrial Hygiene, Inc., in Wheat Ridge, Colo. He can be reached at akorchevskiy@c-ih.com.

JAMES RASMUSON, PhD, CIH, DABT, is senior scientist and CEO at Chemistry & Industrial Hygiene, Inc. He can be reached at jim@c-ih.com.

ERIC RASMUSON, CIH, is president at Chemistry & Industrial Hygiene, Inc. He can be reached at erasmuson@c-ih.com.

Editor’s note: This article is sponsored by the AIHA International Affairs Committee ​(IAC) as part of its mission to promote the best industrial hygiene practices and standards worldwide. The article is based on the reference document “Community/Child Lead Exposure in Developing and Emerging Economies: A Case Study of Lead Contamination in Eastern Europe/the Caucasus/Central Asia​” (PDF) adopted by the AIHA Board of Directors on June 1, 2014. A discussion of this document and the AIHA policy on lead poisoning prevention is expected during a session at AIHce 2015 in Salt lake City, Utah.