Which contaminant has been linked to cognitive disorders in children drinking contaminated water?

Lead has been widely studied and documented as a contaminant that can have serious adverse effects on cognitive development in children. When children are exposed to lead, especially during critical periods of development, it can interfere with their brain development and lead to a range of cognitive disorders. Research consistently shows that even low levels of lead exposure can lead to decreased IQ, attention problems, and other learning disabilities.

In contrast, while nitrates, arsenic, and mercury can also pose health risks, their direct link to cognitive disorders in children is not as clearly defined as that of lead. Nitrates primarily affect oxygen transport in blood, arsenic is associated with various health issues including cancer but not prominently with cognitive disorders, and mercury can affect the nervous system mainly with a focus on neurological development but does not have as robust a link to cognitive decline specifically in drinking water compared to lead.