Which of the following inorganics is known to cause illness?

Lead is a well-documented inorganic contaminant that poses significant health risks, particularly when it enters drinking water supplies. It is a toxic metal that can cause various health problems, particularly in children and pregnant women. Exposure to lead can result in developmental delays, reduced IQ, attention problems, and increased risk of behavioral issues in children. In adults, lead exposure can lead to high blood pressure, kidney damage, and reproductive problems.

The concern regarding lead in drinking water is primarily associated with leaded pipes, plumbing fixtures, and lead solder used in piping systems, which can leach lead into the water supply. This is why regulatory bodies enforce strict limits on lead levels in drinking water to safeguard public health.

In contrast, iron, calcium, and sodium are generally not classified as toxic at normal exposure levels encountered in drinking water. While high concentrations of these elements can potentially lead to other health or aesthetic concerns (such as staining or taste issues), they are not associated with the same level of acute health risks as lead. Thus, lead stands out as the inorganic contaminant known to cause significant illness, particularly among vulnerable populations.