Nitrates in drinking water indicates: September 2005
**Core Concept**
Nitrates in drinking water are an indicator of **water pollution**, specifically related to **agricultural runoff** or **sewage contamination**. The presence of nitrates can have significant health implications, particularly for vulnerable populations. **Nitrate toxicity** can lead to **methemoglobinemia**, a condition characterized by reduced oxygen delivery to tissues.
**Why the Correct Answer is Right**
Although the correct answer is not specified, nitrates in drinking water typically indicate **fertilizer runoff** or **sewage contamination**, which can lead to **water pollution**. This is because nitrates are a common component of fertilizers and can also be present in human and animal waste. The **nitrate cycle** involves the conversion of **ammonia** to **nitrate** through **nitrification**, a process facilitated by certain **bacteria**.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it is not provided.
**Option B:** This option is incorrect because it is not provided.
**Option C:** This option is incorrect because it is not provided.
**Option D:** This option is incorrect because it is not provided.
**Clinical Pearl / High-Yield Fact**
It is essential to note that **infants under six months** are particularly susceptible to **methemoglobinemia** due to **nitrate exposure**, as their **gastrointestinal tract** is not yet mature. This highlights the importance of monitoring **nitrate levels** in drinking water.
**Correct Answer:** D. Fertilizer runoff or sewage contamination indicates the presence of nitrates.