Many people hang the iconic tree-shaped air fresheners from their rearview mirror as a way to mask odors in their cars. But you might want to reconsider them if exposure to chemicals is important to you. According to the Natural Resources Defense Council, 86 percent of the air fresheners tested contained phthalates. This chemical -- used in plastic toys and paints -- is used in air fresheners to help "carry" the scent. Thought to be an endocrine disrupter, phthalates should be avoided at all costs. To get a truly clean-smelling car, try filling a tea strainer with charcoal. Charcoal has natural odor-absorbing properties that will help your car smell like nothing at all.