Use of lead isotope ratios to identify sources of lead exposure in Alaska Natives.

OBJECTIVES: Although banned nationwide for waterfowl hunting, lead shot is still used for hunting in regions of Alaska. Consumption of birds hunted with lead shot may be a route of human lead exposure in susceptible populations. The Centers for Disease Control and Prevention (CDC) and Alaskan health officials conducted a cross-sectional exposure assessment and used isotope ratios (IR) to test that assumption. STUDY DESIGN: Cross-sectional exposure assessment study. METHODS: We compared isotopic profiles of blood lead in Alaska Native women from Bethel (n = 10) and Barrow (n = 10) to lead shot samples purchased from the respective regions. To evaluate the source of lead for the buckshot, we evaluated IR profiles for lead mineral and ore from a smelter in Torreon, Mexico, a suspected source of origin for the lead. RESULTS: The lead IRs for the blood lead differed significantly from the lead shot IRs (p < 0.001); thus, lead shot is unlikely to be the sole source of lead exposure of public health significance in participants of this study. Overlap in IRs for the lead shot and blood lead existed for 6 (30%) of the women from Bethel and Barrow; however, no correlation was noted between lead levels and the IRs for the blood lead. IR profiles for lead mineral and ore from Mexico were substantially different from the IRs of lead shot from Alaska, confirming that buckshot in this study is unlikely to originate from the Mexican smelter. CONCLUSIONS: Lead shot from the manufacturer in this study does not appear to be the sole source of lead exposure in most participants; nonetheless, lead shot could yet be a potential source of exposure in some populations, possibly those whose diet consists of game hunted with lead shot.

Epidemic parenteral exposure to volatile sulfur-containing compounds at a hemodialysis center.

OBJECTIVE: To determine the cause of acute illness on August 30, 2000, among patients at an outpatient dialysis center (center A). DESIGN: We performed a cohort study of all patients receiving dialysis on August 30, 2000; reviewed dialysis procedures; and analyzed dialysis water samples using microbiologic and chemical assays. SETTING: Dialysis center (center A). PATIENTS: A case-patient was defined as a patient who developed chills within 5 hours after starting hemodialysis at center A on August 30, 2000. RESULTS: Sixteen (36%) of 44 patients at center A met the case definition. All case-patients were hospitalized; 2 died. Besides chills, 15 (94%) of the case-patients experienced nausea; 12 (75%), vomiting; and 4 (25%), fever. Illness was more frequent on the second than the first dialysis shift (16 of 20 vs 0 of 24, P < .001); no other risk factors were identified. The center's water treatment system had received inadequate maintenance and disinfection and a sulfurous odor was noted during sampling of the water from the reverse osmosis (RO) unit. The water had elevated bacterial counts. Volatile sulfur-containing compounds (ie, methanethiol, carbon disulfide, dimethyldisulfide, and sulfur dioxide) were detected by gas chromatography and mass spectrometry in 8 of 12 water samples from the RO unit and in 0 of 28 samples from other areas (P < .001). Results of tests for heavy metals and chloramines were within normal limits. CONCLUSIONS: Parenteral exposure to volatile sulfur-containing compounds, produced under anaerobic conditions in the RO unit, could have caused the outbreak. This investigation demonstrates the importance of appropriate disinfection and maintenance of water treatment systems in hemodialysis centers.

Blood lead levels and risk factors for lead poisoning among children in a Mexican smelting community.

The authors evaluated mean blood lead levels (BLLs) and the prevalence of elevated BLLs in children 1-6 yr of age living in Torreón, Mexico, and assessed risk factors for lead exposure in these children. The study involved a simple random sample of households in the area around a local smelter, as well as a 2-stage cluster sample of neighborhoods and households in the remainder of Torreón. The geometric mean BLL of children in this study (N = 367) was 6.0 microg/dl (95% confidence interval [CI] = 5.2, 6.8) (0.29 microM/l [95% CI = 0.25, 0.33]). Twenty percent of the children had BLLs > or = 10 microg/dl (0.48 microM/l), and 5% had BLLs > or = 20 microg/dl (0.97 microM/l). In multivariate analyses, distance from the smelter, amount of income, and education level of the primary caregiver predicted BLLs. In the environmental risk factor subsample (n = 124), dust and soil lead levels were associated with BLLs and distance from the smelter. BLLs in this study were moderately high, but the levels were lower than those in other smelting communities prior to remediation.

Use of isotope ratios to identify sources contributing to pediatric lead poisoning in Peru.

In 1998, a school-based blood lead level (BLL) survey of 2,510 children, conducted in Lima and Callao, Peru, revealed elevated BLLs in children from 2 Callao schools (mean BLL = 25.6 microg/dl; n = 314) and in children from Callao overall (mean BLL = 15.2 microg/dl; n = 898), compared with children from Lima (mean BLL = 7.1 microg/dl; n = 1,612). Public health officials at Peru's Direccion General de Salud Ambiental (DIGESA) hypothesized that a possible source of the elevated pediatric BLLs observed in Callao was a large depository near the port where mineral concentrates are stored prior to shipment. The U.S. Centers for Disease Control and Prevention worked with DIGESA to identify source(s) that contributed to the pediatric lead poisonings by comparing isotopic profiles of lead in blood, mineral, gasoline, and air filter samples. The lead isotope ratio (IR) observed in mineral samples from the depository in Callao differed from those in gasoline samples from Lima and Callao. The blood lead IRs of children living near the depository were similar to the IRs of the mineral samples and different from the IRs of the gasoline samples, suggesting that lead from the depository-and not gasoline-was the primary source of lead in these children. Lead IR analysis of regional air filter samples supported these findings.