Lead exposure causes diminished IQ, delayed language development, reading difficulty, memory loss, abnormal social engagement, antisocial behavior, and ADHD.
Over the years, the CDC criteria to be diagnosed with childhood lead poisoning has changed from a BLL above 40mcg/dL in the 1970s, to a BLL of less than 10mcg/dL in 1991, and then to a BLL of less than 5mcg/dL in 2012. These changes were made because some population studies demonstrated adverse health effects on children with these low BLLs. Lead poisoning originates from the exposure to a lead-contaminated environment. This contamination is most frequently in the form of lead-based paint. A child will become lead poisoned from ingesting chips of lead paint (pica), by inhaling lead dust, or by ingesting soil or water contaminated by lead. Once in the human body, lead quickly becomes absorbed by bone. When children’s lead levels are analyzed sequentially over time, the typical peak is at 18 months of age. This is because children around that age are crawling on the floor to explore their environment which, if contaminated by lead dust or lead paint chips, increases risk of ingesting lead-contaminated paint or dust. After 18 months of age, children are walking (rather than crawling)—and thus off the floor—when exploring their environment. As a result, they are not as readily exposed to lead paint chips from which they can be poisoned. Thus, on average, children older than 18 months are less likely to have elevated BLL and children who had elevated BLL from a prior exposure will see their levels decline. However, patients who engage in pica or who continue live in a lead-contaminated environment will continue to be exposed to lead perpetuating lead poisoning.
Significant developmental issues that could be attributed to lead poisoning started to manifest themselves as early as 22 months of age. As is typical of lead poisoning in children, deficits continue to become worse. Neuropsychological diagnoses can include developmental delays, speech delay (including language skills below normal and articulation disorders), cognitive abilities below normal, emotional status below age appropriate, as well as lowered social status.
Acute and chronic lead exposure is damaging to the central nervous system, especially to the brain which is quickly growing and developing from the in utero period to two years of age. As already mentioned, this is the typical age of maximum exposure to lead due to children crawling in a lead-filled environment and ingesting paint chips and/or lead dust. The effects of lead on the central nervous system in children can be extensive and progressive, even after the lead burden is gone.