A new study helps to reveal why African Americans are more adversely affected by tobacco use:

Researchers found that in African Americans, darker skin specifically that acquired by sun exposure, not genetics is directly linked to smoking frequency and dependence. “African Americans are known to have a more difficult time quitting and suffer from more tobacco-related diseases,” said [study author] Gary King.... Melanin pigments, which determine skin color, bind tightly to nicotine. As a consequence, nicotine and tobacco’s cancer-causing agents tend to linger and accumulate in other melanin-containing tissues like the heart, lungs, liver and brain, potentially putting those organs at increased risk for tobacco-related diseases.

We want to hear what you think about this article. Submit a letter to the editor or write to letters@theatlantic.com.