| Dietary Lead Intakes for Mother/Child Pairs and Relevance to Pharmacokinetic Models
Brian L. Gulson,
1,2
Kathryn R. Mahaffey,
3
C. William Jameson,
4
Montserrat Vidal,
1,2
Alistair J. Law,
2
Karen J. Mizon,
1,2
Andrew J. M. Smith,
5
and Michael J. Korsch
2
1
Graduate School of the Environment, Macquarie University, Sydney, Australia
2
CSIRO Division of Exploration and Mining, North Ryde, Australia
3
U.S. Environmental Protection Agency/National Center for Environmental Assessment, Cincinnati, OH 45268 USA
4
National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709 USA
5
CSIRO Division of Mathematical and Information Science, Macquarie University, Sydney, Australia Abstract
Blood and environmental samples, including a quarterly 6-day duplicate diet, for nine mother/child pairs from Eastern Europe have been monitored for 12 to >24 months with high precision stable lead isotope analysis to evaluate the changes that occur when the subjects moved from one environment (Eastern Europe) to another with different stable lead isotopes (Australia) . The children were between 6 and 11 years of age and the mothers were between 29 and 37 years of age. These data were compared with an Australian control mother/child pair, aged 31 and 6 years, respectively. A rationale for undertaking this study of mother/child pairs was to evaluate if there were differences in the patterns and clearance rates of lead from blood in children compared with their mothers. Blood lead concentrations ranged from 2.1 to 3.9 µg/dl in the children and between 1.8 and 4.5 µg/dl in the mothers, but the mean of differences between each mother and her child did not differ significantly from zero. Duplicate diets contained from 2.4 to 31.8 µg Pb/kg diet ; the mean ± standard deviation was 5.5 ± 2.1 µg Pb/kg and total daily dietary intakes ranged from 1.6 to 21.3 µg/day. Mean daily dietary intakes relative to body weight showed that the intake for children was approximately double that for the mothers (0.218 vs. 0.113 µg Pb/kg body weight/day) . The correlations between blood lead concentration and mean daily dietary intake either relative to body weight or total dietary intake did not reach statistical significance (p>0.05) . Estimation of the lead coming from skeletal (endogenous) sources relative to the contribution from environmental (exogenous) sources ranges from 8 to 70% for the mothers and 12 to 66% for the children. The difference between mothers and children is not statistically significant (p = 0.28) . The children do not appear to achieve the Australian lead isotopic profile at a faster rate than their mothers. These data provide evidence that the absorption or uptake of lead from dietary sources is similar in adult females and children of the age in this study. In spite of lower bone lead and faster bone remodeling and recycling in children compared with adult females, we see no differences between the mothers and their children in overall contribution of tissue lead to blood lead. Results from this study suggest that fractional absorption of ingested lead by children 6-11 years of age is comparable with absorption patterns observed among adult females in the 29-37-year-old age range. Because pharmacokinetic models apply a 40-50% absorption even for 7-year-old children, further investigations on fractional absorption of ingested lead by young children are warranted. Further investigations are especially needed in younger children than those who were subjects in the current study, particularly children in the 1-3-year-old age range. In addition, the effect of nutritional status and patterns of food intake on children's lead absorption require investigation, particularly given the increased prevalence of marginal nutritional status among low-income populations that are at increased risk of elevated blood lead levels. Key words : child, diet, lead isotopes, models, mother. Environ Health Perspect 105:1334-1342 (1997) .
Address correspondence to B.L. Gulson, Graduate School of the Environment, Macquarie University, Sydney NSW 2109 Australia. We thank Mary Salter for phlebotomy ; the participants in this study ; John Eisman for numerous discussions ; Yvonne Markowski, Flora Vigors, Nelly Cadiz, and Ian Campbell of the Department of Immigration, Local Government and Ethnic Affairs, for assistance in making contact and initiating introductions with the families ; David Johnson from the NSW Environmental Protection Authority for the high volume air filter samples ; Jeff Davis for collection of the gasoline samples ; and Nicole Patison for reviewing an earlier version of this manuscript. This research was largely funded by NIEHS through contract NOI-ES-05292, Biokinetics of Lead in Human Pregnancy. The following discussion represents the individual professional views of the investigators and should not be interpreted as the official position or policy of the U.S. Environmental Protection Agency. Received 19 March 1997 ; accepted 11 July 1997.
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