Jan. 22, 2003 -- Exposure to even low levels of lead may have potentially hazardous effects on the kidneys and speed the progression of kidney failure, according to a new study. Experts say the finding should raise awareness about the negative health effects of environmental exposure to lead.
Although low-level lead exposure has been linked to age-related kidney decline in the past, researchers say this study is the first to show strong evidence of a cause-and-effect relationship between the two.
The current study, published in the Jan. 23 issue of TheNew England Journal of Medicine, shows that persistent exposure to low levels of lead may increase the risk of kidney failure in non-diabetic people with chronic kidney disease. But treatment with chelation therapy can counter some of these effects and slow the development of kidney failure in people at risk.
In the study, researchers followed 202 people in Taiwan whose kidneys were unable to function properly and no history of lead exposure for 24 months. After this observation period, 64 patients who had an elevated (high-normal) body lead burden (an indicator of long-term exposure to lead) were divided into two groups that either received chelation therapy or a placebo treatment for three months, followed by repeat chelation therapy as needed for an additional 24 months.
By the end of the study, researchers found the progression of kidney failure was much slower in patients who received chelation therapy compared with those who got the placebo. Patients who received chelation also had improvements in kidney function. The average total body lead burden and blood lead level also decreased among those in the chelation group.
Those improvements in kidney function after the initial chelation therapy persisted for at least 24 months.
Researchers say the exact mechanism behind the benefits of chelation therapy on kidney function is unknown, but the treatment involves using agents that bind to lead and make it easier for the body to eliminate, usually through urine.
Researcher Ja-Liang Lin, MD, of the division of nephrology and clinical toxicology at Gung Memorial Hospital in Taipei, Taiwan, and colleagues say the average blood lead level of the participants was similar to that found in a recent nationwide survey in Taiwan and within the range reported for the general population in Europe and the U.S..
They say their results show that even small increases in lead exposure, as measured by body lead burden, can negatively affect kidney function, even if blood lead levels (which reflect only the amount of lead currently circulating in the body) are within normal levels.
In an editorial that accompanies the study, Philip A. Marsden, MD, of St. Michael's Hospital in Toronto, Canada, says the study should be commended for raising the awareness of doctors, governments, and patients about the importance of environmental exposure to lead as either a cause or consequence of kidney disease.