1. Home>
2. Specialties>
3. Psychiatry>
4. Summary and Comment

Very Low Lead Levels Are Pathogenic

Two-year-old children with very low blood lead levels showed mental and psychomotor deficits.

Until recently, the consensus was that neurologic adverse effects were not associated with blood lead levels below a specific threshold. More current data have demonstrated that no cutoff for safety exists, even at very low lead levels (e.g., Journal Watch Psychiatry May 22 2003). Now, researchers have followed 294 mother–infant pairs to examine the relationship of very low blood lead levels (<10 µg/dL) to mental and psychomotor development at ages 12 and 24 months.

Mothers were recruited from maternity hospitals in Mexico City in 1994–1995 and in 1997–1999. Major exclusion criteria were maternal substance-use disorders, multiple pregnancies, maternal use of corticosteroids, prematurity, and low birth weight. Statistical analyses controlled for maternal IQ, birth weight, gender, age, and umbilical-cord lead levels.

Blood lead levels at 12 months were inversely related to psychomotor scores at 24 months. Blood lead levels at age 24 months were inversely correlated with concurrent scores on standardized indices for both mental and psychomotor development. The association with mental development scores was supralinear: The additional deficit when blood lead levels were at or above 5 µg/dL was relatively smaller than the deficit when levels were below 5 µg/dL. The earlier-born cohort had higher blood lead levels, consistent with greater pollution in Mexico City during the 1990s.

Comment: These findings add to accumulating evidence that no lead level is safe and are consistent with other data from children in a wider age range, which showed worse developmental effects from exposure at earlier ages. Environmental specialists need to take these findings into account in establishing standards for emissions from automobiles and other pollution sources.

— Barbara Geller, MD

Published in Journal Watch Psychiatry September 25, 2006

Citation(s):

Téllez-Rojo MM et al. Longitudinal associations between blood lead concentrations lower than 10µg/dL and neurobehavioral development in environmentally exposed children in Mexico City. Pediatrics 2006 Aug; 118:e323-30.

• Original article (Subscription may be required)
• Medline abstract (Free)