More good news for those who choose to skip the shampoo: A new study out of the University of Missouri says that dirty hair is better for the ozone. Dirty hair, you see, absorbs seven times the amount of ozone as clean hair, which in turn reduces the exposure to ozone by those with lax hygiene. Okay, so it's kinda confusing, but some of us are feeling a whole lot better about not having showered yet today. [New Scientist]