Sand is not a different physical form than that which causes cancer. (See: toxic silicosis) Often it's dosage that leads to concern. A typical walk on the beach will not result in cancer from sand exposure.
This is incorrect. Sand is larger, rounded, particles. Toxic silicosis is caused by small (like 10um) particles. The physical form is what makes it possible to inhale one and walk on the other.
The chemical form is identical.