Which contaminants are commonly found in groundwater that can affect potability?

High levels of nitrate are a significant concern in groundwater because they can originate from agricultural runoff, septic systems, and other sources. Elevated nitrate levels can lead to health issues, particularly in infants, as they can cause methemoglobinemia, or "blue baby syndrome," which affects the ability of blood to carry oxygen.

Low amounts of arsenic and radium-228 can indeed be present in some groundwater sources; however, the focus should be on harmful levels of these contaminants. Arsenic is a potent carcinogen, and radium-228 exposure has been linked to an increased risk of bone cancer. While the concern may exist regarding their presence, the phrasing of the choice “low amounts” downplays the potential health risks of these contaminants when they exceed regulatory limits. Thus, while it references relevant contaminants, it does not highlight the significant effects they can have on water quality and human health when found in hazardous levels.

Bacteria are a well-known category of contaminants affecting groundwater quality, but stating "only bacteria" does not encompass the full range of potential contaminants. Groundwater may also be affected by chemicals, heavy metals, and other pathogens.

Finally, while heavy metals can significantly impact water quality, limiting the scope to "heavy metals only