Remaking Chocolate - And other news from science and technology. By William Saletan

From this article:

Smoking increases male sterility. A study indicates that chronic smokers’ sperm are 75 percent less fertile than nonsmokers’ sperm, and the more you smoke, the less fertile your sperm are. The causal route implies that smoking probably reduces female fertility, too.

Smoking may lower intelligence. In a small study of men, smoking 1) correlated with lower IQ scores, verbal reasoning, and spatial reasoning; and 2) correlated more strongly with low mental proficiency (verbal reasoning, math reasoning, short-term memory) than drinking did. The authors suspect smoking impairs blood and oxygen flow to the brain.