Long-term exposure to which of the following is linked to an increased risk of developing melanoma?

The association between long-term exposure to ultraviolet (UV) sunlight and an increased risk of developing melanoma is well-established in scientific literature. UV radiation from the sun is a known carcinogen that can damage the DNA in skin cells. This damage, if it accumulates over time, can lead to mutations and ultimately the development of skin cancers, including melanoma. People who spend excessive time in the sun without proper protection, such as sunscreen or protective clothing, are particularly at risk.

The other options provided—household dust, indoor heating, and seawater—do not have a significant connection to the incidence of melanoma. While indoor heating and household dust may present other health concerns, they are not related to skin cancer risks. Likewise, while seawater is often mentioned in the context of skin issues due to salt and microbes, it does not carry the same risk factor for melanoma as UV exposure does. Thus, long-term exposure to ultraviolet sunlight stands out as the primary factor linked to increased melanoma risk.