Testosterone proxy In the study on the correlation of high levels of serum calcium with fatal prostate cancer (“Cancer-calcium connection,” SN: 9/27/08, p. 12), were testosterone and vitamin D levels also measured simultaneously? Since low levels of both are related to osteoporosis in men, and testosterone is known to be a fuel of cancer, wasn’t perhaps calcium just a proxy for testosterone? Edward Kausel, Cambridge, Mass. Participants were given vitamin D and calcium supplements as part of the study. But the researchers didn’t measure blood levels of vitamin D, and they acknowledge that these levels vary considerably among individuals and might influence cancer risk. The researchers also didn’t measure testosterone levels. The potential confounders the team accounted for were age, body mass, race and family history of prostate cancer. —Nathan Seppa Biologists gone bad The mercenary pattern identified by David Michaels (“Corporate campaigns manufacture scientific doubt,” SN: 9/27/08, p. 32) is one reason it has been difficult to fight developers who destroy habitat in southern California. They hire accredited biologists who can stand next to an endangered plant and not see it, or do surveys for reptiles in February, nesting birds in October or seasonal migrants in the wrong season. Thus the endangered species that use the habitat are reported not to be there, and the development goes ahead. We call such scientists “biostitutes.” Drew Feldmann, San Bernardino, Calif. Following the yawn The article “Man yawns, best friend follows” (SN: 8/30/08, p. 13) concluded that, “If the study can be replicated, it strongly suggests that dogs may have a primitive empathy capacity.” I like dogs, but before I can jump on the empathetic-canine bandwagon, I need to know if the researchers were aware of and controlled for the following: Dogs (along with many other animals) aren’t comfortable while being stared at, and they aren’t comfortable in the presence of unusual behavior. Dogs, when uncomfortable, often “yawn” to relieve stress. Did these canines show empathy? Or, did they merely show what dog trainers refer to as “stress yawning”? Gretchen Dean, Minneapolis, Minn. If stress were the main factor, then the dogs would probably have yawned during a modified version of the test, in which the person caught the dog’s eye and then silently made a face, but didn’t yawn. When the researcher only made a face, the dogs didn’t yawn.—Susan Milius A global food disaster Sid Perkins reminds us in “Disaster Goes Global” (SN: 8/30/08, p. 16) that in some regions we humans are already consuming close to two-thirds of the land’s biomass. A couple of years ago, a study warned us that at current fishing rates we’ll deplete the ocean’s seafood stocks by 2050 (“Worthless waters,” SN: 11/4/06, p. 291). Yet unless we make efforts to slow the growth of the world population, our numbers will increase by 40 percent in that same time frame. Is my math wrong, or are we going to run out of food? Patricia Leitner, Oakland, Calif. Multistep reactions According to “Disaster Goes Global” (SN: 8/30/08, p. 16), sulfur dioxide reacts with water vapor in the air to produce sulfuric acid. Is this possible? When sulfur dioxide dissolves in water, it produces sulfurous acid, not sulfuric. Industrial production of sulfuric acid requires that sulfur dioxide be further oxidized to give sulfur trioxide, which produces sulfuric acid when dissolved in water. John Myers, San Diego, Calif. The sulfuric acid in volcanic aerosols is the result of not one reaction but a series of reactions involving sulfur dioxide (from the volcano), oxygen (from the atmosphere) and water (from both sources). One of those pathways, as you mention, first creates sulfurous acid that then reacts with oxygen to make sulfuric acid. In the other set of reactions, sulfur dioxide reacts with oxygen to make sulfur trioxide, which then reacts with water to create sulfuric acid. —Sid Perkins