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Mauricio Hernández-Avila,^1,2 Donald Smith,³ Fernando Meneses,¹ Luz Helena Sanin,¹ and Howard Hu⁴

¹Centro de Investigaciones en Salud Poblacional, Instituto Nacional de Salud Pública, Cuernavaca, Morelos, 62508 Mexico
²Department of Environmental and Occupational Health, The Rollins School of Public Health, Atlanta, GA 30322 USA
³Biology and Environmental Toxicology, University of California, Santa Cruz, CA 95064 USA
⁴Channing Laboratory, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School and Occupational Health Program, Department of Environmental Health, Harvard School of Public Health, Boston, MA 02115 USA

Abstract

There is concern that previously accumulated bone lead stores may constitute an internal source of exposure, particularly during periods of increased bone mineral loss (e.g., pregnancy, lactation, and menopause) . Furthermore, the contribution of lead mobilized from bone to plasma may not be adequately reflected by whole-blood lead levels. This possibility is especially alarming because plasma is the main circulatory compartment of lead that is available to cross cell membranes and deposit in soft tissues. We studied 26 residents of Mexico City who had no history of occupational lead exposure. Two samples of venous blood were collected from each individual. One sample was analyzed by inductively coupled plasma-magnetic sector mass spectrometry for whole-blood lead levels. The other sample was centrifuged to separate plasma, which was then isolated and analyzed for lead content by the same analytical technique. Bone lead levels in the tibia and patella were determined with a spot-source ¹⁰⁹Cd K-X-ray fluorescence instrument. Mean lead concentrations were 0.54 µg/l in plasma, 119 µg/l in whole blood, and 23.27 and 11.71 µg/g bone mineral in the patella and tibia, respectively. The plasma-to-whole-blood lead concentration ratios ranged from 0.27% to 0.70%. Whole-blood lead level was highly correlated with plasma lead level and accounted for 95% of the variability of plasma lead concentrations. Patella and tibia lead levels were also highly correlated with plasma lead levels. The bivariate regression coefficients of patella and tibia on plasma lead were 0.034 (p<0.001) and 0.053 (p<0.001) , respectively. In a multivariate regression model of plasma lead levels that included whole-blood lead, patella lead level remained an independent predictor of plasma lead level (ß = 0.007, p<0.001) . Our data suggest that although whole-blood lead levels are highly correlated with plasma lead levels, lead levels in bone (particularly trabecular bone) exert an additional independent influence on plasma lead levels. It will be important to determine whether the degree of this influence increases during times of heightened bone turnover (e.g., pregnancy and lactation) . Key words: blood, bone, K-X-ray fluorescence, lead, plasma. Environ Health Perspect 106:473-477 (1998) . [Online 6 July 1998]

http://ehpnet1.niehs.nih.gov/docs/1998/106p473-477hernandez-avila/ abstract.html

Address correspondence to M. Hernández-Avila, Instituto Nacional de Salud Pública, Av. Universidad 655, Col. Sta. Ma. Ahuacatitlán, Cuernavaca, Morelos, México, CP 62508.

We are indebted to Doug Woolard for analytical expertise and Gail Fleischaker and Eugenia Fishbein for their research management.

This research was supported by NIEHS P42-ES05947 Project 3, NIEHS Center grant 2 P30 ES00002, NIEHS ES07535, the UC MEXUS program, Consejo Nacional de Ciencia y Tecnologa (CONACyT) grant 4150M9405, and CONSERVA, Department of Federal District, Mexico.

Received 15 August 1997 ; accepted 30 March 1998.