[Relationship between fetal lead exposure and birth weight--evaluation using deciduous incisor enamel]

The purpose of this study was to examine the relationship between fetal lead exposure and birth weight, using deciduous incisor enamel as a biomarker and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) for analysis of lead.

We asked dental clinics (n=11) and kindergartens (n=11), mainly in the Tokyo metropolitan area and Miyagi Prefecture, and parents to enroll donors of exfoliate deciduous incisors. Donors who consented to this study voluntarily sent deciduous incisors and questionnaires to the authors between March and October, 2003. The Pb/Ca ratios of inner enamel samples were determined by LA-ICP-MS. The relationship between the lead-to-calcium ratio in the enamel and the birth weight was evaluated by stepwise multiple linear regression analysis.

One hundred forty-one subjects (male, 72; female, 69) were enrolled in this study. The mean Pb/Ca ratio in the enamel was as low as 0.24 mg-Pb/kg-Ca (SD=0.17). Stepwise multiple linear regression analysis extracted the following maternal variables with a positive coefficient with birth weight: gestational age (p < 0.01), weight gain during pregnancy (p < 0.01), prepregnancy BMI (body mass index, p < 0.01), and parity (p < 0.05). Lead concentration in the enamel was significantly negatively associated with birth weight (p < 0.05).

Our study indicated that lead concentration in the enamel was inversely related to birth weight. This association was found in a population of which the mean blood lead level was estimated to be as low as about 1 microg/dl. We concluded that in utero low lead exposure decreased birth weight, within the normal range of birth weight.