A recent study published in Food and Chemical Toxicology suggests that lead, cadmium, and mercury have varying negative effects on human brain development and cognition.

Contaminated water and food are the main sources of lead, cadmium, and mercury in the human body. The metals are well known to affect brain development and cognition with long-term, low-level exposure, but the present study sought to define the differences among their neurotoxic effects at different stages of brain development.

For the study, different doses of low-level lead, cadmium, and mercury were administered to Sprague-Dawley rats via drinking water during the critical stage of brain development, late stage, and after maturation. The findings showed that exposure to the toxic heavy metals decreased the density of memory- and learning-related dendritic spines in the hippocampus during the critical period of brain development, resulting in hippocampus-dependent spatial memory deficits. During the late phase of brain development, only the density of learning-related dendritic spines was reduced and higher doses of the metals were required to cause an effect, which led to hippocampus-independent spatial memory abnormalities.

However, exposure to lead, cadmium, and mercury after brain maturation revealed no significant change in dendritic spines or cognitive function. The study’s authors recommend focusing on mitigating exposure to lead, cadmium, and mercury from water or food during early brain development as much as possible.