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LEAD ABSORPTION - Continued
mile of the smelter, 170 of 172 children (98.8%) had lead levels >404g/100ml; 1 (1.1%) of 89 children in a rural control area 45 miles distant had a lead level >40ug/100ml.
To determine routes of lead intake, lead levels were measured in samples of soil, dust, pottery, and interior paint collected at each home surveyed and in air samples collected at 9 points in the study areas. Results indicated that lead levels in soil, dust, and air were all high close to the smelter and decreased with distance. Levels in paint were nearly identical in all areas. Pottery was used for food handling in only 5 (0.9%) of the 588 homes visited, and there was no dangerous lead release (3). Significant correlations were found between blood lead levels and exposure to lead in air (coefficient of correlation, (r = 0.72)), surface soil (r = 0.59), and interior dust (r = 0.23).
Seven (17.1%) of the 41 children with blood lead levels >80ug/100ml had hematocrits <33%, while 8 (2.1%) of 390 children with blood lead levels of 40-79ug/100ml, and 8 (1.3%) of 616 with levels <400g/100ml were anemic (X2 = 37.04 for >80 vs. <80, p<0.00001). Free erythrocyte protoporphyrin (FEP) levels increased logarithmically with blood lead levels.
To evaluate subclinical neurologic functioning, motor nerve conduction velocities (right peroneal nerve) were measured in blind fashion in 183 5-9 year-old children from the 6 areas near the smelter and in 39 from the control area (4). Data from 17 of these children (7 with blood lead levels >40ug/100ml) were excluded from analysis because of pre-existing neurologic disease, and results from 3 were excluded because data were incomplete or unsatisfactory. The remaining 202 children were all apparently healthy, none had frankly pathologic conduction velocities, and all but 4 fell within 2 standard deviations of agerated means. However, a statistically significant negative correlation was found in these 202 children between conduction velocity and blood lead level (r = -0.38, t = -2.12, p<0.02 by 1-tailed t test). There was a similar correlation between conduction velocity and FEP (r = -0.40).† No significant relationships were noted in this group between conduction velocity and age, sex, or socioeconomic status.
Repeat blood testing in August 1975 by the State of Idaho, Department of Health and Welfare indicated that a significant reduction in lead levels had occurred since the preceding year; the mean blood lead level in 74 children living within 1 mile of the smelter who were tested in both years decreased from 63.5mg/100ml to 47.3ug/100ml (p< 0.001). No children were found in the repeat testing to have blood levels >80ug/100ml; however, 108 (71%) of 153 chil. dren 1-10 years old living within 1 mile of the smelter and 210 (45%) of 471 children living from 1.0-2.5 miles, including several new residents in both areas, had lead levels >40ug/100ml. FEP levels in 1975 among 69 children living within 1 mile of the smelter who were tested in both years averaged 293.1mg/100ml rbc. Extensive monitoring programs under the direction of the State of Idaho are underway and are designed to follow each child until his blood level falls below 40ug/100ml. (Reported by JT Ashley, MD, JA Bax, PhD, JA Mather, MD, State Epidemiologist, IH Von Lindern, MS, and AJ Yankel, MS, Idaho Dept of Health and Welfare; RG Feldman, MD, Dept of Neurology, Boston University School of Medicine, Boston; Toxicology Branch, Clinical Chemistry Div, Bur of Laboratories, and Environmental Hazards Activity, Cancer and Birth Defects Div, Bur of Epidemiology, CDC.) References 1. Medical aspects of childhood lead poisoning. Pediatrics 48:464. 468, 1971 2. MMWR 23(37):323, 1974 3. Klein M, Namer R, Harpur E, et al: Earthenware containers as a source of fatal lead poisoning: Case study and public health considerations. New Engl J Med 283:669-672, 1970 4. Feldman RG, Haddow J, Kopito L, et al: Altered peripheral nerve conduction velocity, chronic lead intoxication in children. Am J Dis Child 125:39-41, 1973