We know that lead damages the brain, and that it does so by somehow affecting the release of neurotransmitters at synapses (the process by which neurons pass messages on). Now a new study explains exactly what lead does. Apparently, during the formation of synapses, lead lowers the levels of key proteins involved in neurotransmitter release (synaptophysin and synaptobrevin), and reduces the number of fast-releasing sites. These effects may occur through the inhibition of the NMDA receptor (which produced similar effects), disrupting the release of BDNF. While new synapses are created throughout our lives, there is an explosion of synapse formation during a child's early brain development, explaining why young children’s lead exposure is particularly damaging.
Latest Research News
(2010). Lead Exposure during Synaptogenesis Alters Vesicular Proteins and Impairs Vesicular Release: Potential Role of NMDA Receptor-Dependent BDNF Signaling.
Toxicol. Sci.. 116(1), 249 - 263.
Older news items (pre-2010) brought over from the old website
School-age lead exposures most harmful to IQ
A number of studies have connected higher blood concentration of lead in toddlers with reduced IQ at school age. Now data from two points — children in Cincinnati during the early 1980s; children Rochester, N.Y., during the mid-1990s — has revealed confirmed earlier indications that IQ losses are most predictable from comparisons of a child’s blood-lead level at age 6 compared to the level at age 2, and that the level at age 5-6 is more important than that at age 2 (although that is when most testing is done). Lead-level at age 6 also correlated with reduced brain tissue in certain brain regions in adulthood, especially in those regions relating to judgment, self-control, and mood (and an increased level of criminal behavior).
(2009). Age of Greatest Susceptibility to Childhood Lead Exposure: A New Statistical Approach.
Environmental Health Perspectives.
Children more vulnerable to harmful effects of lead
A study has found that children are more vulnerable to the harmful effects of lead at age 6 than they at younger ages. The study found that children's average blood lead concentrations peaked at 13.9 micrograms of lead per deciliter of blood at age 2, then declined to an average of 7.3 micrograms per deciliter by age 6. For children with the same average blood lead levels through age 6, however, those who received more of their exposure at age 6 had substantially greater decrements in intellectual ability (with lower IQ and reduced volume of gray matter in the prefrontal cortex) than those more heavily exposed at age 2. The Centers for Disease Control and Prevention recommends public health actions be initiated at blood lead levels greater than 10 micrograms per deciliter, despite lower levels being consistently shown to be associated with adverse effects.
The Cincinnati Children's Hospital Medical Center study was presented May 4, 2008, at the annual meeting of the Pediatric Academic Societies in Honolulu.
Early lead exposure impedes later recovery from brain injury
We know that lead exposure in early years can affect the brain. We also know that it increases the risk of various disorders later in life. Now a rat study reveals that animals exposed to lead earlier in life were significantly less able to recover from an induced stroke than those not so exposed. The study only looked at a short time-frame, so it is not yet known if the lead-exposed animals would catch up in their recovery in a longer period of time. There was some recovery in the lead group, but then it leveled off. The control group continued to get better. The findings support the suggestion that lead poisoning impairs neural plasticity.
(2007). Postnatal lead poisoning impairs behavioral recovery following brain damage.
Neurotoxicology. 28(6), 1153 - 1157.
ADHD linked to genetic and environmental interactions
A study of 172 children who were enrolled in a community-based study of low levels of lead exposure has found evidence that increasing lead exposure is linked to impairment on a number of executive functions (impaired in those with ADHD), but that certain genetic and biological factors seemed to predispose an individual to the negative effects of lead exposure. For instance, only children with certain variations of the DRD4 gene seemed vulnerable to lead's adverse effects on attentional flexibility. Boys were more vulnerable to this effect than girls.
The study was presented on May 1, 2006, at the annual Pediatric Academic Societies meeting in San Francisco.
Lead exposure may affect recovery from brain injury
Lead exposure at a young age can hurt the brain's development and cause learning and behavioral problems. Now it seems that it might also affect a child’s ability to recover from brain injury. A new study found young rats exposed to low levels of lead took significantly longer to recover from a brain injury than those animals that weren't lead-exposed, as well as recovering less well.
Dr. Schneider presented the findings Oct. 25, 2004, at the Society for Neuroscience's annual meeting in San Diego.
Environmental damage to brains of children
A new report suggests that the brains of children in many parts of Europe are suffering greater damage from environmental risks than previously recognized. A meeting in Malta of European delegates preparing for a ministerial conference on environment and health, being held in Budapest in June, were given preliminary results from a comprehensive study on environmental threats to children's health, being conducted by the WHO and the University of Udine, Italy. The full report is to be published at the Budapest conference. The findings suggest lead is the single most important damaging chemical for children. In 2001, the estimated percentage of European children in urban areas with elevated blood levels (above 10 micrograms per decilitre) ranged from 0.1% to 30.2%.
Pros and cons of therapy for lead exposure
Lead chelation therapy is widely used to treat lead-exposed children, and is increasingly being used for the treatment of autism in children. However, a rat study has now found that, although the treatment can indeed significantly reduce learning and behavioral problems that result from lead exposure, when rats with no lead in their systems were treated, they showed declines in their learning and behavior that were similar to the rats that were exposed to lead. The findings suggest that lead chelation therapy should only be used, as recommended, for children with at least moderate lead exposure.
(2006). Succimer Chelation Improves Learning, Attention, and Arousal Regulation in Lead-Exposed Rats but Produces Lasting Cognitive Impairment in the Absence of Lead Exposure.
Environmental Health Perspectives. 115(2), 201 - 209.
Workers exposed to lead show more cognitive problems later in life
A follow-up of the 1982 Lead Occupational Study, which assessed the cognitive abilities of 288 lead-exposed and 181 non-exposed male workers in eastern Pennsylvania, has found that among the lead-exposed workers, those with higher cumulative lead had significantly lower cognitive scores. The clearest inverse relationships were between cumulative lead and spatial ability, learning and memory, and overall cognitive score. This linkage was more significant in the older lead-exposed men (55 years and older). Their cognitive scores were significantly different from those of younger lead-exposed men even when the researchers controlled for current blood levels of lead. In other words, even when men no longer worked at the battery plants, their earlier prolonged exposure was enough to matter.
(2009). Association of cumulative lead and neurocognitive function in an occupational cohort.
Neuropsychology. 23(1), 10 - 19.
Reading ability protects brain from lead exposure
Cognitive reserve is a concept that has been chiefly discussed in terms of protecting against age-related cognitive decline and Alzheimer’s, but a new study has found evidence that it can also protect against long-term lead exposure. The study of 112 smelter workers found that the cognitive effects of lead were 2.5 times greater in workers with low reading ability, compared to those with high reading ability (defined as a reading level of 12th grade or higher). Motor speed, however, was comparable in both groups — demonstrating that the nervous system was impaired similarly in both groups.
(2007). Impact of cognitive reserve on the relationship of lead exposure and neurobehavioral performance.
Neurology. 69(5), 470 - 476.
Long-term lead exposure linked to cognitive decline in older adults
A study of nearly a thousand randomly selected Baltimore residents, all between 50 and 70 years old and consequently exposed to higher levels of lead prior to the 1980s when lead was used extensively in commercial products, has revealed higher lead levels in the bone were consistently associated with worse cognitive performance on tests, equivalent to two to six years of aging. Blood lead levels were not associated with a difference in cognitive performance. The study also found bone lead levels were significantly higher in African Americans compared to Caucasians.
(2006). Environmental lead exposure and cognitive function in community-dwelling older adults.
Neurology. 67(9), 1556 - 1562.
Lead exposure leads to brain cell loss and damage years later
A study of 532 former employees of a chemical manufacturing plant who had not been exposed to lead for an average of 18 years has found that the higher their lead levels were, the more likely they were to have smaller brain volumes and greater amounts of brain damage. 36% had white matter lesions. The results confirm earlier findings in this same population that people with occupational lead exposure experience declines in their thinking and memory skills years after their exposure.
(2006). Past adult lead exposure is linked to neurodegeneration measured by brain MRI.
Neurology. 66(10), 1476 - 1484.