Pollutants & the brain: Research reports

Lead

March 2008

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 at the annual meeting of the Pediatric Academic Societies in Honolulu.
http://www.physorg.com/news129129066.html
http://www.eurekalert.org/pub_releases/2008-05/cchm-cmv050108.php

December 2007

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.
The report appeared in the November issue of NeuroToxicology.  Full reference
http://www.eurekalert.org/pub_releases/2007-12/tju-jnf120307.php

July 2007

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 12^th grade or higher). Motor speed, however, was comparable in both groups — demonstrating that the nervous system was impaired similarly in both groups.
The study was published in the July 31 issue of Neurology. Full reference
http://www.eurekalert.org/pub_releases/2007-07/aaon-rap072407.php

December 2006

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.
The findings were reported online 30 October in Environmental Health Perspectives. Full reference
http://www.eurekalert.org/pub_releases/2006-12/cuns-csr121306.htm

September 2006

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.
The study was published online on September 13 in Neurology. Full reference
http://www.eurekalert.org/pub_releases/2006-09/aaon-lle091306.htm

May 2006

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.
The study was published in the May 23 issue of Neurology. Full reference
http://www.eurekalert.org/pub_releases/2006-05/aaon-lel051806.htm

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, at the annual Pediatric Academic Societies meeting in San Francisco.
http://www.eurekalert.org/pub_releases/2006-05/cchm-sla042606.htm

October 2004

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.
http://www.eurekalert.org/pub_releases/2004-10/tju-jnf102404.htm

March 2004

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%.
http://news.bbc.co.uk/1/hi/sci/tech/3568939.stm

Chemicals

April 2008

How chronic exposure to solvents can impair the brain

Chronic occupational exposure to organic solvents, found in materials such as paints, printing and dry cleaning agents, has been linked to long-term cognitive impairment, but chronic solvent-induced encephalopathy (CSE) is still a controversial diagnosis. An imaging study of 10 CSE patients who had been exposed to solvents and had mild to severe cognitive impairment, 10 participants who had been exposed to solvents but had no CSE symptoms, and 11 participants who were not exposed to solvents and had no symptoms, has now found impairment in the frontal-striatal-thalamic (FST) circuitry of CSE patients. The disturbances are predictive of the clinical findings — impaired psychomotor speed and attention — and were also linked to exposure severity.
The study was published online April 15 in Annals of Neurology.  Full reference
http://www.eurekalert.org/pub_releases/2008-04/w-dib041508.php

April 2005

Chemical in clear plastics can impair learning

A rat study has found that low doses of the environmental contaminant bisphenol–A (BPA), widely used to make many plastics found in food storage containers (including feeding bottles for infants), inhibit estrogen–induction of synaptic connections in the hippocampus, suggesting implications for children's learning ability. Also, when the ability to make estrogen is impaired, as in old age, exposure to BPA could adversely affect hippocampal function and contribute to age–related neurodegenerative diseases such as Alzheimer's disease, in which hippocampal function is impaired. The doses were below the current U.S. Environmental Protection Agency reference daily limit for human exposure.
The study was available online 24 February in Environmental Health Perspectives. Full reference
http://www.eurekalert.org/pub_releases/2005-04/yu-cpi041205.htm

PCB

November 2001

Pollutants affect babies' brains

It appears that exposure to polychlorinated biphenyls (PCBs) in a mother's blood and breast milk can hinder the development of a baby's brain before and after birth. Although PCBs are now banned, these chemicals were once widely used in industry as coolants and lubricants and are still being leaked into the environment from old electrical equipment.
The report appeared in a recent issue of The Lancet. Full reference
http://news.bbc.co.uk/hi/english/health/newsid_1644000/1644446.stm

June 2001

PCB-laden fish may affect adult verbal memory

The dangers of PCBs (once widely used as electrical insulators and lubricants and in paints and varnishes) have long been known, and assumed to apply chiefly to children and developing fetuses. A long-term study of those who eat the PCB-laden fish from Lake Michigan suggests for the first time that high levels of PCB may cause problems learning and remembering new verbal information in adults. In particular, those with high blood PCB levels had difficulties recalling a story told just 30 minutes earlier, and were less likely than their less-exposed peers to cluster words given orally into categories based on their meaning to boost recall.
The study is on line and appeared in print in the June issue of Environmental Health Perspectives, a journal of the National Institutes of Health. Full reference
http://www.eurekalert.org/pub_releases/2001-06/UoIa-Hcot-0406101.htm
http://ehpnet1.niehs.nih.gov/docs/2001/109-6/toc.html