**Core Concept**
Lead poisoning is a type of heavy metal poisoning that occurs due to the accumulation of lead in the body, which can lead to various health issues, including neurological, hematological, and renal problems. The primary sources of lead exposure are environmental and occupational.

**Why the Correct Answer is Right**
Lead poisoning mostly occurs due to the ingestion of lead-contaminated substances, such as lead-based paints, contaminated water, or soil. The lead is absorbed into the bloodstream and distributed to various tissues, where it can cause damage. The body has a limited capacity to excrete lead, and repeated exposure can lead to its accumulation. The kidneys play a crucial role in excreting lead, but prolonged exposure can cause renal damage.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not specified, so it cannot be evaluated.
**Option B:** This option is also not specified, so it cannot be evaluated.
**Option C:** This option is not specified, so it cannot be evaluated.

**Clinical Pearl / High-Yield Fact**
Lead poisoning can be prevented by reducing exposure to lead-contaminated substances. This can be achieved by using lead-free paints, ensuring proper waste disposal, and using personal protective equipment (PPE) when working with lead-containing materials.

**Correct Answer: D. Ingestion of lead-contaminated substances.**