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We determined the secular trend in blood lead levels in a cohort of 321 children born in Mexico City between 1987 and 1992. Blood lead level was measured every 6 months during a 10-year period. We modeled the effect of yearly air lead concentration nested within the calendar year in which the child was born, family use of lead-glazed pottery, socioeconomic status, year in which the child was born, age of the child at the time of blood lead measurement, place of residence, and an indicator variable for subjects with complete or incomplete blood lead values. The yearly mean of air lead of the Valley of Mexico decreased from its highest level of 2.80 microg/m[3] in 1987 to 0.07 microg/m[3] in 2002. The contribution of air lead to blood lead according to year of birth was strongest for subjects born in 1987 and fell to nearly zero for children born in 1992. The geometric mean of the entire cohort rose from 8.4 microg/dL in the first year of life to 10.1 microg/dL in the second and decreased thereafter until it reached 6.4 microg/dL at 10 years of age. Children of families who used lead-glazed ceramics had blood lead levels 18.5% higher than did children of nonusing families. Children who belonged to the lowest socioeconomic levels had blood lead levels 32.2% higher than did those of highest socioeconomic levels. Children who lived in the northeast part of the city had blood lead levels 10.9% higher compared with those who lived in the southwest. [ABSTRACT FROM AUTHOR]

The notion that maternal personality characteristics influence cognitive development in their children has been grounded in stress moderation theory. Maternal personality traits, such as self-esteem, may buffer maternal stressors or lead to improved maternal-child interactions that directly impact neurodevelopment. This can be extended to suggest that maternal personality may serve to attenuate or exacerbate the effects of other neurotoxicants, although this has not been studied directly. We examined whether mothers' self-esteem had a direct or main effect on their children's cognitive outcomes. We also explored the modifying effects of maternal self-esteem on the association between exposure to lead and neurodevelopment in these children. Study participants included 379 mother-child pairs from Mexico City. Data included the Coopersmith Self-Esteem Scale in mothers, children's Bayley's Scale of Infant Development (BSID) scores, and sociodemographic information. Linear regression was used to model the relationship between maternal self-esteem and the Bayley's Mental Development Index (MDI) and Psychomotor Development Index (PDI) scores at age 24 months using models stratified by levels of maternal self-esteem. In adjusted models, each point increase in maternal self-esteem was associated with children having 0.2 higher score on the Bayley's MDI (p=0.04). Similar results were observed using the PDI outcome. Moreover, there was evidence that maternal self-esteem attenuated the negative effects of lead exposure, although the interaction fell short of conventional levels of statistical significance.

Objective: Low-level postnatal lead exposure is associated with poor intellectual development in children, although effects of prenatal exposure are less well studied. We hypothesized that prenatal lead exposure would have a more powerful and lasting impact on child development than postnatal exposure., Design: We used generalized linear mixed models with random intercept and slope to analyze the pattern of lead effect of the cohort from pregnancy through 10 years of age on child IQ from 6 to 10 years. We statistically evaluated dose-response nonlinearity., Participants: A cohort of 175 children, 150 of whom had complete data for all included covariates, attended the National Institute of Perinatology in Mexico City from 1987 through 2002., Evaluations/measurements: We used the Wechsler Intelligence Scale for Children-Revised, Spanish version, to measure IQ. Blood lead (BPb) was measured by a reference laboratory of the Centers for Disease Control and Prevention (CDC) quality assurance program for BPb., Results: Geometric mean BPb during pregnancy was 8.0 microg/dL (range, 1-33 microg/dL), from 1 through 5 years was 9.8 microg/dL (2.8-36.4 microg/dL), and from 6 through 10 years was 6.2 microg/dL (2.2-18.6 microg/dL). IQ at 6-10 years decreased significantly only with increasing natural-log third-trimester BPb (beta=-3.90; 95% confidence interval, -6.45 to -1.36), controlling for other BPb and covariates. The dose-response BPb-IQ function was log-linear, not linear-linear., Conclusions: Lead exposure around 28 weeks gestation is a critical period for later child intellectual development, with lasting and possibly permanent effects. There was no evidence of a threshold; the strongest lead effects on IQ occurred within the first few micrograms of BPb., Relevance to Clinical Practice: Current CDC action limits for children applied to pregnant women permit most lead-associated child IQ decreases measured over the studied BPb range.

The authors determined the secular trend in blood lead levels in a cohort of 91 children born in Mexico City between 1987 and the beginning of 1993. The authors grouped children by calendar year in which they reached 36 mo of age (i.e., 1990-1995), and their blood lead levels were measured every 6 mo during a 66-mo period. The overall geometric mean blood lead level was 8.6 microg/dl (range = 1.0-61.0 microg/dl). A repeated measures analysis of variance revealed a significant downward linear trend in blood lead levels by year (p < .001)--from an estimated marginal geometric mean of 14.2 microg/dl in 1990 to 6.3 microg/dl in 1995. There was also a significant linear age effect (p < .001); blood lead levels generally fell during the 36th-66th mo. Family use of lead-glazed pottery significantly elevated blood lead levels (p = .006), and the effect magnified as age increased (Age x Pottery Interaction [p = .014]). Although the overall downward trend in blood lead levels during the time period described corresponded to a reduction in various sources of lead exposure, there was no alteration in production, distribution, or use of leaded pottery. Currently, use of lead-glazed ceramic pottery is one of the most profound sources of lead exposure in the Mexican population.

We determined the secular trend in blood lead levels in a cohort of 104 children born in Mexico City between 1987 and 1993. We grouped children by the calendar year in which they reached 6 mo of age and measured blood lead levels every 6 mo until they attained 36 mo of age. The overall geometric mean blood lead level was 9.6 microg/dl (range = 1.5-59.5 microg/dl). A repeated measures analysis of variance revealed a highly significant linear trend in blood lead level with year (p < .001); there was a maximum decrease of 7.6 microg/dl between 1989 and 1993. There was a highly significant quadratic age effect (p < .001); blood lead levels rose between 6 and 18 mo of age and decreased thereafter. There was a marginally significant interaction between age of the child and year. Family use of lead-glazed pottery significantly elevated blood lead levels (p = .028). The downward trend in blood lead levels during the time period of study corresponded to the reduction in various sources of lead exposure.

We constructed models of umbilical cord blood lead (PbB), with and without the addition of maternal PbB at delivery and earlier in pregnancy, to determine which factors explaining cord PbB depended upon maternal PbB and which did not. We prospectively studied women of low-to-middle socioeconomic status who lived in the Valley of Mexico from 12 weeks of pregnancy to delivery. We measured maternal venous PbB during pregnancy and at delivery, and umbilical cord PbB (1-38 micrograms/dl, 0.05-1.83 mumol/l). We used multiple regression analyses to model cord PbB and a logit analysis to model the maternal-cord PbB relationship. Older mothers using lead-glazed pottery and canned foods delivered babies with increased cord PbB, while those with occasional alcohol use during pregnancy, high milk intake, and more spontaneous abortions delivered babies with lower cord PbB. Maternal PbB at 36 weeks of pregnancy and at delivery independently explained additional variance in cord PbB, but maternal PbB earlier in pregnancy did not. Some of the effects of lead-glazed pottery, maternal abortions, alcohol use, and canned food use on cord PbB were mediated through maternal PbB. The effects of maternal age and milk intake on cord PbB were independent of their influence on maternal PbB near delivery. Cord PbBs were higher than maternal PbBs at delivery in 33% of the cases, and were predominant in mothers over 30 and those drinking milk less than once per day. Measurable influence of maternal PbB on delivery cord PbB is limited to the four to eight weeks prior to delivery. Many factors suspected of influencing bone lead also control cord PbB, some of them independently of their effect on maternal delivery PbB. Minimizing fetal exposure near the end of pregnancy may require long-term control of maternal lead exposure and good management of pregnancy and diet.