The compound of lead found in old manuscripts that poses the greatest health risk is Lead carbonate (white lead).

- Lead carbonate, commonly known as white lead, was historically used as a pigment in paints and inks found in old manuscripts.
- This compound is highly toxic due to its solubility in acidic environments, such as the human stomach, which facilitates the release of lead ions into the body.
- Once absorbed, lead interferes with multiple physiological systems including the nervous, hematopoietic, and renal systems.

- Unlike lead sulfide, which is relatively insoluble and less bioavailable, lead carbonate readily dissolves, making it more easily absorbed through ingestion or inhalation of dust particles.
- Similarly, lead oxide and lead phosphate have lower solubility and bioavailability compared to lead carbonate.

- The chronic exposure to lead carbonate can lead to lead poisoning (plumbism), with symptoms ranging from abdominal pain, anemia, and nephropathy to severe neurological impairments, especially in children.

Key points:
- Lead carbonate (white lead) is commonly found in old manuscripts as a pigment.
- It has high solubility and bioavailability, making it the most hazardous lead compound in this context.
- Exposure can cause serious systemic toxicity, particularly affecting the nervous system.
- Other lead compounds such as lead sulfide, lead oxide, and lead phosphate are less soluble and pose lower health risks.

Reference: Harrison’s Principles of Internal Medicine, 20th Edition, Volume 2, Chapter 69: Heavy Metal Poisoning / Lead Toxicity