Which of the following is TRUE about excess nitrates and/or nitrites in drinking water?

The correct answer encompasses all the provided statements about excess nitrates and/or nitrites in drinking water.

Nitrates and nitrites often originate from agricultural practices, especially the use of fertilizers, as well as from sewage discharges. This contamination can occur via runoff into water supplies, making the initial statement true. Additionally, these compounds are water soluble, which means that they can readily leach through soil and enter groundwater systems, leading to widespread contamination of drinking water sources. This characteristic is particularly concerning in areas with high agricultural activity or inadequate wastewater management.

Moreover, the statement regarding the risk to infants is significant. Infants aged 3 to 6 months are especially vulnerable to methemoglobinemia, commonly known as “blue baby syndrome,” when exposed to high levels of nitrates or nitrites. This condition affects the blood's ability to carry oxygen and can be exacerbated by microbial contamination in the water, increasing the health risks for this age group.

Together, these points demonstrate a comprehensive understanding of the implications of excess nitrates and nitrites in drinking water, confirming that all stated options are accurately reflective of the risks and causes associated with these contaminants.