Lead poisoning is one of common public health problems; the properties of lead and calcium are similar, and if lead is ingested, it will be incorporated into the kidneys, nerve tissue, bone marrow and brain (Wright & Welbourn, 2002). Lead also might interfere with the development of the nervous system, and thus might cause behavior and learning disorders in children. The characteristics of lead poisoning are anemia, irritability, confusion, abdominal pain, and high level of lead in the body might even result in coma and death (Wright & Welbourn, 2002).
Lead is so toxic because it interferes with many enzymes and binds to their sulfhydryl groups. A significant role in lead intoxication belongs to ALAD – delta-aminolaevulinic acid dehydratase (Wright & Welbourn, 2002). This enzyme is important for synthesizing heme, which is the cofactor in hemoglobin. ALAD is inhibited by lead, and it is often used as a biochemical indicator for increased concentration of lead, because unusual activity of this enzyme is easy to determine. Thus, ALAD is involved in the pathogenesis of lead poisoning, and if the activity of erythrocyte ALAD is inhibited, this fact can be used to determine exposure to lead. Thus, ALAD activity is used as a key diagnostic tool in lead toxicology (Wright & Welbourn, 2002).
It has also been determined that there exists genetic susceptibility to lead poisoning (Wright & Welbourn, 2002). Experiments involving the use of special susceptibility markets to environmental toxicants have shows that some individuals might be more vulnerable to lead due to genetic predisposition. Here ALAD also plays a significant role: this enzyme might exist in human body in two polymorphic forms (isozymes) (Wright & Welbourn, 2002). These isozymes affect the differences in bone and blood lead levels (Wright & Welbourn, 2002), thus determining individual susceptibility to lead poisoning.
Onalaja, A. & Claudio, L. (2000). Genetic susceptibility to lead poisoning. Environmental Health Perspectives, 108 (1): 23-44.
Wright, D.A. & Welbourn, P. (2002). Environmental toxicology. Cambridge University Press.