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Lead levels in drinking water that are permissible by the Environmental Protection Agency (EPA) may be harmful to patients with kidney disease, a new study suggested.

In about 600,000 people who started dialysis in the U.S. from 2005 to 2017, each 0.01 mg/L increase of lead in drinking water was associated with significantly lower hemoglobin concentrations (0.02 g/dL, 95% CI 0.01-0.02) and an increased use of erythropoietin-stimulating agents, commonly used to treat anemia (0.4%, 95% CI 0.2%-0.6%), reported John Danziger, MD, of Beth Israel Deaconess Medical Center and Harvard Medical School in Boston, and colleagues.

As shown in the team's study online in the the associations were observed at lead levels below the EPA's threshold (0.015 mg/L) that mandates regulatory action. In addition, racial inequities were observed, with significantly higher levels of lead in the drinking water of Black versus white patients.

"Our findings suggest that for those with kidney disease, there is no safe amount of lead in drinking water," the researchers wrote. "While water has generally been considered a minor cause of lead toxicity, increased absorption and decreased excretion in those with kidney disease confer an exaggerated susceptibility."

Children are at increased risk from lead exposure, and the complications of chronic kidney disease (CKD) confer similar susceptibility, the investigators explained. Metabolic conditions prevalent in CKD, such as hypocalcemia, iron deficiency, and malnutrition, increase the proportion of lead absorbed across the gastrointestinal tract. In addition, patients with CKD excrete lead less effectively, resulting in circulating levels that are much higher than in individuals with normal renal function.

In addition to its neurological, cardiovascular, and endocrine effects, lead can also cause significant hematological problems, the researchers noted. Studies have shown that lead interferes with heme biosynthesis, increases red cell destruction, and reduces gastrointestinal iron absorption, and lead toxicity has been linked with lower hemoglobin levels.

The EPA that individuals can take to reduce lead in their drinking water. These include using only cold water for drinking and cooking, running water for a period of time before drinking to help flush away any lead, and cleaning faucet aerators on a regular basis.

Danziger's group analyzed data on 597,968 CKD patients from the U.S Renal Data System, identifying the city of residence for each individual. The researchers assessed water quality for each patient using the , which includes information on lead testing reports for all public community water systems in the U.S. The team calculated the average lead levels in the water for the 5 years preceding dialysis for each patient.

The main outcome measures were hemoglobin concentrations, recorded up to 45 days before patients started dialysis, and use of erythropoietin-stimulating agents. The analysis adjusted for covariates including age, sex, race, body-mass index, estimated glomerular filtration rate, insurance and employment status, diabetes, heart failure, hypertension, cancer, and tobacco use.

The researchers said the findings were similar when the team focused on 208,912 patients with data from the first month of dialysis therapy. Each 0.01 mg/L higher lead concentration was associated with lower hemoglobin (0.05 g/dL, 95% CI 0.04-0.06) and increased use of erythropoietin-stimulating agents (0.3%, 95% CI -0.1% to 0.6%).

The study also found disparities in water quality when examined by race. Although the mean concentrations of lead in water decreased overall during 2005 to 2017, the rate of decrease was slower for Black compared with white patients (0.0001 vs 0.0002 mg/L per year, P<0.001).

"Our findings raise broader concerns about the aging water system infrastructure in the United States," Danziger and co-authors said. "The full extent of lead contamination is unknown, in part due to large numbers of lead lines that remain in service and older household plumbing. In addition, since federal regulations require water systems to non-randomly sample a small proportion of households and report only the 90th percentile of those values, there is no nationally representative measure of water quality at the household level. Accordingly, without accurate estimation of individual levels of exposure, further research is greatly hampered."

Study limitations, the team said, included that alternate sources of drinking water, such as bottled water or filtered water, were not assessed, that calculating the lead exposure of individuals who lived in areas serviced by multiple water systems was difficult, and that the analysis did not take into account other potential source of lead exposure.

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