Are basal cell carcinoma due to sun damage?

Sometimes: Basal cell carcinoma is often due to sun exposure but also may be due to chemical exposure (ie arsenic) or may be hereditary.

Can be: Bcc can be genetic but most are associated with past sun exposure.

Mostly: Exposure to uv light, not just sun, and genetic susceptibility are instrumental in basal cell carcinoma development.

Sun & basal cell: They are generally due to genetic mutations of the skin cells. The tendency for genetic muations increases with increased sun exposure.

Normally yes: The most common cause of all types of skin cancer is sun exposure. There are rare inherited diseases which lead to skin cancer. Your best prevention is to use good sunscreens and avoid sun exposure during the middle of the day. If you have a spot that won't heal or lasts, then you should see you doctor and perhaps have a biopsy.

Nearly all: A few, perhaps, are not. For example, welders will get them under their chins where the ultraviolet light thrown off by the torch strikes their unprotected skin. We must also not forget tanning beds as a source of basal cell as well as therapeutic uv (puva) used to treat psoriasis. Rare patients with basal cell nevus syndrome get many basal cells, but even then, mostly in sun-exposed areas.