[Factors related to the blood lead level in children 6 to 30 months old in the Prospective Lead Study in Mexico City]. / Factores relacionados con el nivel de plomo en sangre en niños de 6 a 30 meses de edad en el Estudio Prospectivo de Plomo en la Ciudad de México.

A majority of the sample of children (N = 160-121, ages 6-30 months) from the Mexico City Prospective Lead Study exceeds the lowest limit action level (10 micrograms/dl) of the Centers for Disease Control standards for childhood lead exposure. Over one-third of the sample at 18 months and 24 months exceeds the action level (15 micrograms/dl) for aggressive intervention. Diet plays an important role in regulating early childhood blood lead levels. Fresh milk and breast feeding are associated with lower lead levels, but extended breast feeding is related to elevated lead levels. Low income and poor maternal education are associated with higher lead concentration in children. Child consumption of canned milk and juice, up to this date, is associated with elevated child lead levels. Canned products sealed with lead are disappearing from Mexican markets. Efforts to improve childhood nutrition and poverty may be expected to have the additional benefit of lowering lead levels of Mexican children.

Prenatal and postnatal blood lead level and head circumference in children to three years: preliminary results from the Mexico City Prospective Lead Study.

Multiple regression modeling was used to explore the relationship between prenatal and postnatal blood lead levels and child head circumference in the first three years of life. Maternal blood lead at 36 weeks of pregnancy and cord blood lead were found to be inversely related to 6 month and 18 month head circumference, respectively. Child 12 month blood lead was inversely related to 36 month head circumference. Limitations of the data set and the statistical techniques were discussed, as were the interpretations of the findings.

[Sources of lead in pregnant women in the Valley of Mexico]. / Fuentes de plomo en embarazadas de la Cuenca de México.

Lead levels in samples of the groups at highest risk to the effects of lead exposure, pregnant women and their infants, are higher than levels known to produce developmental retardation in children in a considerable proportion of the sample tested in Mexico City. Modeling of prenatal factors predicting maternal lead during pregnancy shows the strong effect of the use of low-temperature ceramics on lead level. The data also suggests an important contribution from air lead. The downward trend in lead exposure in pregnant women in the Valley of Mexico over the last 10 years, concurrent with downward trends in air lead is encouraging. However, reducing the manufacture and use of leaded pottery could produce a significant further reduction of lead exposure with a modest program of public education, government regulation and subsidization of lead free pottery.

[Evaluation of the potential risk of perinatal exposure to lead in the Valle de Mexico]. / Evaluacion del riesgo potencial de la exposicion perinatal al plomo en el Valle de Mexico.

PIP: Lead exposure even at low levels has adverse effects for the central nervous system (CNS), but pregnant women, neonates, lactating infants, and preschool and school age children are most susceptible to it. In rats anatomical alterations included swelling in the mitochondria of renal duct cells (at 26 mcg/dl); biochemical effects involved marked reduction of cytochrome content in the cerebral cortex (36 mcg/dl); and physiological effects were induced at the level of 30-50 mcg/dl. Central nervous system effects entailed persistent decrease of visual acuity (65 mcg/dl at birth and 7 mcg/dl 90 days later), the increase of the latency of primary and secondary components of evoked visual responses during the prenatal and adult period (65 mcg/dl and 7 mcg/dl on days 21 and 90 after birth, respectively). 30 and even 20 mcg/dl of lead in the blood produced nerve conductivity deficits. A study of 425 children with lead poisoning showed a 39% rate of mental retardation and convulsions impervious to treatment. Lead levels within a range of 10-25 mcg/dl reduced the score on the mental development inventory by 4-8 points. The population of the Valley of Mexico numbers 15-20 million with 50% of Mexico's industry. A who investigation indicated blood levels of an average of 22.5 mcg/dl in a group of school teachers, the highest in 10 major population centers in the world. Blood levels in 405 pregnant women in Mexico City averaged 20.3 mcg/dl, and the sample from the umbilical cord of fetuses showed 13.6 mcg/dl. Another study disclosed blood levels of 16 mcg/dl in mothers and 13 mcg/dl in their offspring. The most probable sources of lead are: leaded gasoline, secondary recapture of lead for making batteries, use of paints, ceramics used for storing and cooking food, lead seal of milk containers, and consumption of food contaminated with lead.^ieng