Why should sodium hexametaphosphate be handled with caution?

Sodium hexametaphosphate should be handled with caution primarily because it can cause physical injury due to its particulate form. While the statement about it being "very sharp" might not be entirely accurate in the sense of traditional cutting tools, it emphasizes the need for care when handling any powdery substance. When fine particles are present, they can become airborne, potentially leading to inhalation or contact with sensitive skin and eyes. Therefore, appropriate protective measures like gloves, masks, and goggles are recommended to minimize any risk of irritation or injury.

The other options reflect concerns that are not typically associated with sodium hexametaphosphate. For instance, it is not classified as highly toxic nor does it typically release harmful fumes. Additionally, while it can cause irritation in contact with certain surfaces or materials, it does not have the physical properties of being sharp enough to cut like a blade. Understanding these aspects of the substance is crucial for ensuring safe handling practices.