Lead exposure is known to have undesirable effects on the kidney both in adults as well as children. Despite the elimination of lead from gasoline and paint it was discovered that most Americans still have detectable lead levels in the blood. The mean blood lead levels in the 12-to-19-year-olds were 1.5 micrograms per deciliter in 1991 to 1994 and 1.1 micrograms per deciliter from 1999 to 2000, researchers say.The U.S. Centers for Disease Control and Prevention (CDC) had established that minimum dose of 10 microgram per deciliter of blood was lethal to health.But recently researchers from Johns Hopkins Children’s Center have found that levels much lower than that could have detrimental effets.The study was published in the Jan. 11 issue of Archives of Internal Medicine. The main sources of lead exposure include lead paint, folk remedies, glazed pottery, soil and drinking water in some urban areas with older housing.The study urges the need to minimize these sources of lead exposure. 769 healthy children and teens in ages of 12 to 20 were enrolled, of which more than 99 percent had lead levels below 10, with an average level of 1.5 micrograms per deciliter. Those with lead levels in the upper quarter of the normal range appeared to have worse kidney function than children with lower lead levels. Kidney function is defined by the speed with which the kidneys filter the blood. Those with lead levels above 2.9 had a kidney filtration rate 6.6 units (milliliters of blood filtered per minute and adjusted for body size) lower than children whose lead levels were below 1 microgram per deciliter. Researchers also found that for each twofold increase in the amount of lead in the blood, the kidney’s filtration capacity dropped by 2.3 units in males and by 3.3 in females. The link between higher lead levels and worse kidney function persisted even after investigators eliminated high blood pressure — less than 5 percent of those in the study had it — as a possible factor affecting kidney status.
The experiment emphasized on the fact that previous studies on the level of lead that could be lethal could have been mislead by the tests adopted to measure kidney fuction. kidney function is measured by estimating the kidneys’ filtering capacity, called glomerular filtration rate (GFR), using two tests: a standard creatinine test, which measures the speed with which the kidneys filter out creatinine from the blood, and a newer test that measures how fast the kidneys filter out the protein cystatin C. Cystatin C is believed to be a more accurate gauge because, unlike creatinine, which can fluctuate depending on muscle mass and other factors, its levels are more stable. Indeed, the differences in kidney function were far more pronounced when the researchers looked at cystatin C and not as significant when they applied the standard creatinine test. The previous studies were done using creatinine test which is responsible for the large variation in test results.
The findings of the study is important because this slightly decreased kidney function found in healthy children, could spell more kidney trouble down the road as these children get older or if they acquire additional risk factors for kidney disease, such as high blood pressure and diabetes,” says Susan Furth, M.D. Ph.D., senior investigator on the study and a pediatric nephrologist at Hopkins Children’s.
