Moderately raised blood lead levels in children

Area of Science:

• Environmental Health
• Neuroscience
• Pediatrics

Background:

• High blood lead levels are definitively linked to cognitive deficits and hyperactivity.
• Recent research explores the impact of moderate lead levels (20-40 microgram/100 ml) on behavior and cognition.
• Previous epidemiological studies have not established a clear relationship between moderate lead levels and behavioral or cognitive impairments.

Purpose of the Study:

• To review the evidence on the relationship between moderate blood lead levels and cognitive/behavioral outcomes in children.
• To assess the methodological limitations of existing studies, particularly those using chelation techniques.
• To consider the influence of socio-economic factors and potential interactions with lead exposure.

Main Methods:

• Review of epidemiological studies investigating moderate blood lead levels and cognitive/behavioral phenomena.
• Analysis of studies employing chelation techniques, noting methodological weaknesses.
• Consideration of socio-economic factors and their impact on intelligence and behavior.

Main Results:

• Epidemiological studies generally fail to demonstrate a clear link between moderate lead levels and overactivity or reduced performance on standard tests.
• Published chelation studies have been hampered by methodological flaws.
• Socio-economic factors are strongly associated with measured intelligence and behavior.

Conclusions:

• Socio-economic factors are the primary consideration for preventative measures related to cognitive and behavioral development.
• The possibility remains that more sensitive tests could reveal subtle cognitive impairments in children with moderately elevated lead levels.
• An interaction between lead exposure and individual host resistance may influence outcomes.