46zilzal
08-22-2007, 06:33 PM
Dr. Aub at Harvard started investigations on the dangers of lead (Pb) poisoning many years ago. After it was taken out of paint and tetra-ethyl lead additives to gasoline as an anti-knock compound, most of the acute poisonings were due to old surfaces which kids would teethe on. For many years acute poisonings were down to almost nothing, as well as chronic exposures.
In the youngster, before the blood-brain barrier is fully intact, ingesting can cause direct toxicity to the brain, and in the growing skeleton it adds to the epiphyseal growth plates in a one to one exchange for bivalent Calcium in the Calcium hydroxyapatite molecule. It causes a characteristic change in the red cells of the blood called basophilic stippling. Once in the peripheral nervous system it can cause peripheral neuropathies characterized by wrist drop.
The major problem with anyone's lead burden in that it is not stable and any shift in the acid/base values of the blood causes this labile fraction to come flooding out all at once, creating serious levels of toxic Pb in the system. Imagine, for example, all the dirt sequestered in the fibers of your carpet that were all released into the air at once in your home. Fairly bad to breathe.
In order to clear the lead burden, chelating agents such as ethylene di-amine tetra-acetic acid (EDTA) are used to capture the bivalent lead. This is used on many heavy metal exposures.
There has not been a serious Pb poisoning outbreak in many year since the ban, but an interesting side note. Gas additives of tetra-ethyl lead, once it goes through the internal combustion engine, come out as inorganic lead. One used to be able to tell which plants were closer to major highways just by evaluating the lead in the leaves. It is so widespread in distribution around the world that when it is no longer found in antarctic core ice samples, they know that point in the ice represented 1929, the year it was added to gasoline.
These importers of unsafe lead painted toys should have severe penalties in re-introducing a problem that was all but solved.
In the youngster, before the blood-brain barrier is fully intact, ingesting can cause direct toxicity to the brain, and in the growing skeleton it adds to the epiphyseal growth plates in a one to one exchange for bivalent Calcium in the Calcium hydroxyapatite molecule. It causes a characteristic change in the red cells of the blood called basophilic stippling. Once in the peripheral nervous system it can cause peripheral neuropathies characterized by wrist drop.
The major problem with anyone's lead burden in that it is not stable and any shift in the acid/base values of the blood causes this labile fraction to come flooding out all at once, creating serious levels of toxic Pb in the system. Imagine, for example, all the dirt sequestered in the fibers of your carpet that were all released into the air at once in your home. Fairly bad to breathe.
In order to clear the lead burden, chelating agents such as ethylene di-amine tetra-acetic acid (EDTA) are used to capture the bivalent lead. This is used on many heavy metal exposures.
There has not been a serious Pb poisoning outbreak in many year since the ban, but an interesting side note. Gas additives of tetra-ethyl lead, once it goes through the internal combustion engine, come out as inorganic lead. One used to be able to tell which plants were closer to major highways just by evaluating the lead in the leaves. It is so widespread in distribution around the world that when it is no longer found in antarctic core ice samples, they know that point in the ice represented 1929, the year it was added to gasoline.
These importers of unsafe lead painted toys should have severe penalties in re-introducing a problem that was all but solved.