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Schizophrenia link to Lead Exposure (Car Exhaust Fumes) February 2004
California scientists have recently released a report in which they claim a link between exposure to lead in the womb and schizophrenia in adulthood.
The discovery is based on a study of blood samples taken from pregnant American women in the 1960s when lead was still widely used in vehicle fuel.
People whose mothers were exposed to high levels of the metal in exhaust fumes were more than twice as likely to develop schizophrenia as adults. (Interestlingly, this ties into other studies that have identified higher risk of schizophrenia for people who live in urban areas (cities) vs. rural areas - because cities obviously have a higher level of cars and related polutants such as leaded fuel exhaust fumes. This doesn't bode well for countries like China and India that have not yet banned Leaded car fuels as has been banned in the US).
A research team, led by Dr. Ezra Susser of Columbia University in New York, released its finding in a report presented here at the annual meeting of the American Association for the Advancement of Science.
It's the first time that any environmental toxin has been related to the later risk of schizophrenia, Susser said.
The discovery was based on a study of blood samples taken from pregnant women in the 1960s, when lead was still widely used in vehicle fuel.
People whose mothers were exposed to high levels of the metal in exhaust fumes were more than twice as likely to develop schizophrenia as adults.
The exposures in this study took place in the 1960s in a built-up area of Southern California, where leaded gasoline powered most vehicles on the state's busy freeways.
In the same study, researchers from New York's Columbia University also found a three times higher rate of schizophrenia among adults whose mothers had flu during the first half of their pregnancy.
The surprising findings were described for the first time at a scientific conference here yesterday.
The results of the study provide the strongest evidence to date that schizophrenia may be caused by toxins or infections that damage the central nervous system under development in the fetus.
"We're not claiming that we know lead or flu is a cause of schizophrenia at this point," said researcher Ezra Susser, head of epidemiology at Columbia's school of public health.
At present, experts do not agree on the exact causes of schizophrenic disorders though there is general agreement that there are genetic influences (that represent 50% to 70% of the factors involved) and environmental factors (such as lead and other toxin exposures, birth complications, etc.) that represent from 30% to 50% of the cause. (for more information see Preventing Schizophrenia)
"But if we could understand even one pathway by which schizophrenia is caused, it would open up a whole new world for understanding and treating this affliction," Susser told a news briefing at the annual meeting here of the American Association for the Advancement of Science.
The study takes advantage of a rare arrangement in the United States, an employer-funded health plan in the region around Oakland, Calif., in the 1960s.
Local workers and their families belonged to a prepaid group medical plan that allowed the Columbia University researchers to test for lead in preserved blood samples taken routinely from expectant mothers between 1959 and 1967. They also had access to medical records up to 1981 for more than 12,000 babies born during that period, out of a total of just over 19,000.
The records revealed 44 cases of what psychiatrists call schizophrenia spectrum disorder, a term spanning full-blown schizophrenia and several closely related brain afflictions.
The researchers measured lead levels in the preserved blood samples taken from the mothers of those 44 cases during their second trimester of pregnancy. They compared those with the archived blood from 75 other women whose children did not develop brain disorders, matched for age and other characteristics. The results were divided into high-lead and low-lead.
The high-lead blood samples were more than twice as likely to include mothers of children who later became schizophrenic.
If the doubling ratio holds up in other samples now being studied from clinics in Boston and Rhode Island, Susser estimates that up to a quarter of the schizophrenia that developed in American urban centres in the 1950s and 1960s could be traced to lead pollution in the womb.
This is the first time an environmental toxin has been linked to later risk of schizophrenia.
'It's a preliminary finding, but an intriguing one. We think that people will now look at a variety of environmental toxins which can disrupt brain development, and see whether they are also related to the risk of schizophrenia.' Dr. Susser told the BBC.
When a babys brain is developing during a crucial period (called synaptogenesis), when the brain cells make many connections to one another, lead may interfere with the growth of nerve cells.
It seems that the cells autodestruct when they should not.
Dr. Susser thinks the same thing is going on (same mechanism) as what
gives rise to foetal alcohol syndrome (foetal = UK spelling. fetal = USA
The suggestion is that cells start to commit suicide when they should not. He believes lead may operate through the same mechanism which some researchers think gives rise to foetal alcohol syndrome.
In this, a baby's brain is damaged prenatally through the mother's consumption of significant amounts of alcohol.
The search is now on for other samples collected during the era of leaded petrol which could confirm the finding.
If it is confirmed, it would have huge implications for the study of schizophrenia, a condition whose origins have baffled researchers for decades.
Abstract of Research: