ABSTRACT
A follow-up study of slow cortical potentials in children with elevated blood lead (PbB) histories was conducted two years after initial evaluation. An age x PbB interaction was again observed wherein slow wave (SW) voltage varied as a linear function of PbB with the slope of the function dependent on age. The linear relationship of SW voltage and PbB was significant using either original PbB values, (14-55 micrograms/dl), follow-up values (11-39 micrograms/dl), or the mean of the two PbB values. No evidence of a threshold for this effect was observed. The similarity of results obtained at initial and follow-up assessments suggests that the observed alterations in CNS function are persistent, despite a significant decrease in mean PbB across time. The observed change in SW voltage at PbB levels previously considered to be harmless suggests the need to reconsider the currently accepted 30 micrograms/dl threshold for undue lead absorption in children.
Subject(s)
Cerebral Cortex/drug effects , Electroencephalography , Lead Poisoning/physiopathology , Child , Child, Preschool , Female , Follow-Up Studies , Humans , Intelligence Tests , Lead/blood , Male , Socioeconomic FactorsABSTRACT
This study explored the effects of age and PbB upon EEG power spectra and various measures of hemispheric laterality in children, aged 13-75 months, watching a display (cartoon). The following are the principle conclusions: (1) The delta- and theta-band amplitude decreased with age. (2) When only bilaterally synchronized EEG between P3 and P4 was considered, the amplitude of P3 was estimated as greater than P4 in all frequency bands and for all ages. Previous reports have not shown lateral EEG dominance in children below 75 months. (3) When lateral dominance measures consider only the relationship between synchronized EEG at P3 and P4, bilateral communality in the delta band increased with age. (4) Increased PbB generally produced an increase in the relative amplitude of synchronized EEG between P3 and P4 in all frequency bands. This was true for PbB levels well below 15 micrograms/dl, among the lowest level PbB effects previously reported. No clinical or behavioral effects of PbB values have been reported below 15 micrograms/dl. It appears to be theoretically and practically important to understand the functional significance of bilaterally synchronized activity. The signal processing of the CNS can be explored using these methods. Greater understanding of these data would help define the extent and etiology of PbB effects on the CNS
