Toxicity and Fate of Heavy Metals with Particular Reference to Developing Foetus

Heavy metals especially lead, mercury, cadmium, arsenic and chromium are well known for causing birth defects. Although, the mother may be unaffected and unaware of the contamination, infants exposed to such agents in-utero may have a number of side effects as these substances readily move across the placental barrier. Heavy metals are dangerous because they have the tendency to bioaccumulate in biological organisms over a period of time. The foetus and newborns are much more sensitive to the effects at low levels of metal exposure and this is mainly due to body weight being less and higher rate of food consumption rate, higher gastrointestinal absorption rate, less effective renal excretion, and a less effective blood-brain barrier. On the other hand, lead is tightly bound to red blood cells, thereby enhancing the transfer from maternal circulation through the placenta to the foetus. Placental transfer begins as early as the twelfth week of gestation. Arsenic is found in drinking water and is a potent toxicant but scanty research has been done on its effect on maternal health. Chromium (Cr6+) accumulates in placenta and impairs foetal development in the placenta. Therefore, the fertile population should prevent themselves from exposure to chemicals, drugs and other environmental agents.