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.
Blood-lead Levels and Lead Poisoning in Emerging Economies
How Low Is Low?

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.