Michael B. Rabinowitz

Weight gain and maturity in fetuses exposed to low levels of lead

The relationship between prenatal low-level lead exposure and fetal growth was evaluated in a sample of 4354 pregnancies in which the mean umbilical cord blood lead level was 7.0 micrograms/dl (SD = 3.3; 10th percentile, 3.4 micrograms/dl, 90th percentile, 10.9 micrograms/dl). Higher cord blood lead levels were significantly associated with gestations of slightly longer duration. Comparing infants with cord blood lead levels greater than or equal to 15 micrograms/dl to those with levels less than 5 micrograms/dl, adjusted risk ratios of 1.5 to 2.5 were observed for low birth weight (less than 2500 g) and for fetal growth indices that express birth weight as a function of length of gestation (e.g., small-for-gestational age, intrauterine growth retardation). The 95% confidence intervals of these risk ratios included 1, however, precluding rejection of the null hypothesis of no association. We conclude that the risk of adverse fetal growth is not increased at cord blood lead levels less than 15 micrograms/dl but that modest increases in risk may be associated with levels greater than or equal to 15 micrograms/dl.

Pregnancy hypertension, blood pressure during labor, and blood lead levels.

Pregnancy hypertension, blood pressure during labor, and the umbilical cord blood lead concentration were assessed in 3851 women for whom additional demographic, medical, and personal information was available. Lead levels correlated with both systolic (Pearson r = 0.081, p = 0.0001) and diastolic (r = 0.051, p = 0.002) blood pressures during labor. The incidence of pregnancy hypertension increased with lead level. Multivariate models of pregnancy hypertension and systolic blood pressure as a function of maternal age, parity, hematocrit, ponderal index, race, and diabetes were improved by including lead as a predictor variable. At these observed levels of exposure (mean blood lead, 6.9 +/- 3.3 [SD] micrograms/dl), lead appears to have a small but demonstrable association with pregnancy hypertension and blood pressure at the time of delivery, but not with preeclampsia.

Home refinishing, lead paint, and infant blood lead levels.

We measured the blood lead levels of 249 infants semi-annually from birth to two years of age; we sampled the home paint and recorded any recent home refinishing activity. Mean blood lead from birth to age 2 years did not vary systematically with age but did correlate significantly with the amount of lead in the indoor paint (p less than .01). Refinishing activity in homes with high lead paint was associated with elevations of blood lead averaging 69 per cent.

Stable isotope mass spectrometry in childhood lead poisoning

In order to better understand the relative importance of various sources of lead in childhood lead poisoning, high-precision, isotoperatio, solid-source-mass spectrometry of microgram-sized lead samples was applied to three hospitalized cases in Boston, ranging in age from 1.5 to 14 yr, that had blood-lead levels of 0.7–1.2 μg/g. The lead isotopes in the ambient Boston environment (air, soil, and dust) were also measured.In each case, the isotopic composition (IC) of the childs blood lead was identical with the IC of lead paint taken from the childs residence at a site accessible to the child. Fecal lead samples were also identical to that particular paint. Soil lead IC did not always match the IC of local paints. Paint samples vary widely in their ICs (206/204=17.5–19.4, about 200 times analytical reliability). Dust in homes that never had lead paint contained lead that resembled lead in urban soils. Dust lead IC did not necessarily have the same IC as current automobile lead emissions, but appeared to reflect the long-term accumulation of several sources of urban lead fallout.Limitations and implications of this data are discussed.

Blood lead--tooth lead relationship among Boston children

The amount of lead in deciduous teeth has been used extensively as a marker for infant lead exposure and body burden. Elevated tooth lead levels have been seen in children who had lead poisoning. Also, on a population wide basis tooth lead levels appear to vary according to housing status and presumably lead exposure. This exposure index has been applied using varying techniques in Denmark, and the United Kingdom. Because of the neurotoxicity of lead, the tooth lead levels of retarded and normal children have been compared. Most recently, in research of lead and child development, tooth lead levels have been used as markers of past lead exposure. Despite the widespread use of tooth lead values, very little is known about the exact time course of lead deposition in tooth from blood. This report compares blood lead levels at different ages to tooth lead levels in a group of Boston children.

Lead levels among various deciduous tooth types.

The amount of lead in deciduous teeth has been used extensively as a marker for infant lead exposure and body burden. However, the pattern of lead abundances among the various tooth positions in a childs mouth appears to be non-uniform. Taken together these findings show an apparently inconsistent pattern among the tooth types. These comparisons are complicated by different research groups using different portions of the tooth. This issue is of significance to those who wish to compare the lead burden of children but have available teeth from different positions from the various children. By examining a large number of teeth from two different populations, the authors hope to explore the more universal aspects of any variability among tooth types.

Soil lead-blood lead relationship among Boston children.

Lead contaminated soil has been consistently been found to contribute significantly to childrens risk of blood lead elevation. An association between soil lead and blood lead has been reported for children in Holland, Rochester, New York, Omaha, Nebraska, Christchurch, New Zealand, and Kellogg, Idaho. The authors report on the connection between soil and blood lead levels among a group of Boston children in order to document this pattern of association in a specific setting which may be analogous to other situations of interest. The base population consisted of 11,837 consecutive births at the Boston Hospital for Women between April 1979 and April 1981.

Variability of Blood Lead Concentrations During Infancy

As part of a study of early childhood development, more than 200 children had their blood lead concentrations (PbB) determined semiannually during the first 2 yr of life. These children were selected from 11,837 consecutive births surveyed for umbilical cord PbB at Boston Lying-In Hospital. Candidate subjects were drawn from the highest, lowest, and middle deciles of PbB. The mean PbB was 7.2 +/- 5.3 (standard deviation) micrograms/dl at birth and did not change appreciably with age. However, the average change in an individuals PbB every 6 months was 4 micrograms/dl, which was several fold in excess of the analytical reproducibility. Only 25% of the children in the highest category at birth were in the highest category at 2 yr of age. Approximately 40% of the children remained in their immediately previous PbB tertile category. A stochastic description of these patterns of change fits the data. Our results should caution investigators who might wish to rely on a single determination to categorize children with PbB.

Investigation of unrecognized former secondary lead smelting sites: confirmation by historical sources and elemental ratios in soil.

Twelve suspected former secondary lead smelting sites were investigated. Ten of the sites were confirmed to be former secondary lead smelters or lead works by historical fire insurance maps and contemporaneous metal industry trade directories. At eight sites sampled, the ratio Sb:Pb was closer to ratios from 10 known lead smelting sites than were the As:Pb and Cd:Pb ratios. Data from the 10 known lead smelting sites showed that the Sb:Pb ratio is most characteristic of secondary lead smelting sites. This is because the primary alloy smelted at such sites is antimonial lead. Lead contamination at the eight sites investigated here can be attributed At least in part to the former smelters because of the association between Sb and Pb.

Environmental, demographic, and medical factors related to cord blood lead levels

Blood lead was measured at birth for 11,837 infants in Boston. Extensive maternal demographic, pregnancy, and delivery characteristics were recorded for 4354 of them. For 249 of these, intensive environmental sampling was done. Many medical factors were unrelated to blood lead, including diabetes, venereal diseases, preeclampsia, toxemia, hypertension, age, hematocrit, contraceptive use, presentation, type of delivery, fetal distress, premature rupture of membrane, blood type, gestational age, birthweight, Apgar score, jaundice, and mortality by one month. However, use of tobacco, alcohol, coffee, tea, or marihuana, having had an abortion, receiving welfare and being unmarried, Black, or Hispanic are associated with significantly elevated blood lead. Being college educated, Jewish, younger, and multiparitous are related to lower blood lead levels. Environmental factors covarying with blood lead included dust and soil lead and refinishing activity, but not water, air, or paint lead or traffic density. Many of these predictors are intercorrelated. Simultaneous, step-wise regression models of blood lead ranking these factors are presented. Only 18% of the variance is explainable. Temporal and geographic patterns exist even after taking these maternal and environmental factors into account.