Which of the following factors does NOT affect outdoor tanning?

The factor that does not affect outdoor tanning is the use of skin care products. While skin care products can enhance the appearance of the skin or provide protection from UV rays, they do not directly influence the tanning process itself. Outdoor tanning primarily depends on environmental factors such as sunlight exposure, which is influenced by the time of year, latitude, and altitude.

Time of year affects the angle and intensity of the sun's rays, with summer months generally providing more direct sunlight, resulting in a higher potential for tanning. Latitude plays a significant role as well; locations closer to the equator receive more intense UV radiation throughout the year compared to those at higher latitudes. Altitude also influences tanning because at higher elevations, the atmosphere is thinner, allowing more UV radiation to reach the surface and potentially increasing tanning rates.

In contrast, while skin care products can offer protection or enhance the tanning experience, they do not impact the natural tanning that occurs from sun exposure. Therefore, they are not a direct factor in the tanning process itself.