No Amount of Lead in the Blood Is Safe, Researchers Say
By Matt McMillen
WebMD Health News
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Reviewed by Louise Chang, MD
Aug. 20, 2012 -- New evidence that links low levels of lead in the blood to an increased risk of gout suggests that currently acceptable levels of lead exposure are too high.
In a study published in Annals of Internal Medicine, researchers report that the risk of gout is apparently elevated even among adults whose blood lead levels are several times less than what the CDC considers acceptable.
"The point here is that there is no such thing as a safe lead level," says researcher Eswar Krishnan, MD, an assistant professor at Stanford University School of Medicine.
But, Krishnan tells WebMD, such risk factors cannot explain every case. So he went looking for others. A review of the medical literature pointed him toward lead.
Krishnan says it's been known for some time that lead in the blood at concentrations greater than 80 micrograms per deciliter (mcg/dL), or eight times the acceptable level, is associated with hyperuricemia and gout. But he says that his own findings concerning much lower levels were unexpected.
"I honestly was expecting a negative result or an unimpressive one," he says. "What we found was very surprising."
Studying the Lead/Gout Link
For the study, Krishnan and his colleagues used data from two recent National Health and Nutrition Examination Surveys, which are conducted annually by the CDC. They focused on men and women over the age of 40 who had no kidney disease. In all, they examined the records of more than 6,000 adults from around the United States.
While most adults have blood lead levels below 10 mcg/dL -- the acceptable level supported by the CDC -- the researchers found that people with blood lead levels as low as 1.2 mcg/dL seemed to have an increased risk of gout.
The risk remained after they adjusted the data to account for differences in age, gender, race, diet, and a variety of health measures. In the study, those with the highest level of lead measured about 4 mcg/dL. Their risk appeared to be about three-and-a-half times that of those with the lowest levels of lead in their blood.
The risk of hyperuricemia -- a common forerunner of gout -- also rose significantly.
Although this study could not prove cause and effect, the research methods were able to uncover the strong link between lead and gout.
More Research Needed on Both Risk and Treatments
Ashwini Sehgal, MD, who wrote an editorial that accompanies Krishnan's study, also found the results surprising. And, like Krishnan, he says more research needs to be done before we fully understand the risks and what to do about them.
"We don't yet know the best way to use this information, so we can't make any real recommendations," says Sehgal, a kidney specialist and associate professor of medicine at Case Western Reserve University in Cleveland.
He says the most common ways people are exposed to lead is through jobs such as mining, smelting, and battery manufacturing. Hobbies that involve soldering may also put people at risk, though that risk can be reduced by wearing a mask and working in well-ventilated spaces. Krishnan says smokers have higher blood lead levels, another good reason to quit.
If you have gout and are worried about lead exposure, Sehgal advises discussing your occupational exposure history with your doctor.
Krishnan says a blood lead test might be a good idea if a patient has gout without any of the known risk factors, such as obesity and hypertension. The problem, he says, is what to do if a patient's blood levels are found to be high.
"We don't yet know the best way to get the lead out," says Krishnan. "We don't have a very good, evidence-based treatment for that."
Krishnan says he hopes his study will encourage further research into lead's impact as well as into therapies to reduce risky levels of lead in the blood. While he recognizes that lead exposure can't be completely eradicated, better efforts need to be made to control it.
"Clinically speaking, we should not be tolerating lead," says Krishnan.
SOURCES: Krishnan, E. Annals of Internal Medicine, Aug. 20, 2012. Sehgal, A. Annals of Internal Medicine, Aug. 20, 2012. News release, Annals of Internal Medicine. Eswar Krishnan, MD, assistant professor, Stanford University School of Medicine, Palo Alto, Calif. Ashwini Sehgal, MD, associate professor of medicine, Case Western Reserve University, Cleveland, Ohio. CDC: "Adult Blood Lead Epidemiology and Surveillance (ABLES) Interactive Database." American College of Rheumatology: "Gout."
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