Xylene

Xylene is the most commonly used clearing agent, and the tissue cassette is soaked in xylene three or more times to completely remove the dehydrating agent.

Xylene (CAS 1330-20-7) is generally available as a mixture of o-xylene (CAS 95-47-6), m-xylene (CAS 108-38-3), and p-xylene (106-42-3). These compounds are aromatic hydrocarbons that are principally used as solvents, thinners, and as intermediates or feedstocks for the synthesis of other important commercial chemicals (e.g., plasticizers, perfumes, pharmaceuticals). Xylene is also a component of gasoline. It is a colorless liquid that is sparingly soluble in water. Because of its volatility, it would have a propensity to migrate to the atmosphere following an environmental release and does not pose a hazard to the food web. Human exposure would most likely occur by inhalation, particularly in occupational settings that use it as a solvent. The mechanism of toxicity is most likely a nonspecific narcosis (similar to volatile anesthetic compounds). This narcotic form of toxicity would be anticipated following an acute exposure of humans and/or animals to relatively high levels in air (similar to other petroleum solvents), whereas chronic exposures to lower levels appear to be insignificant. Xylene is not mutagenic and there is no evidence that it would cause cancer in either experimental animals or humans. Clinical management following exposure would consist of moving the victim away from the source and into fresh air (e.g., outdoors). Regulatory standards are available for occupational exposure to xylene. The ecotoxicity of xylene is anticipated to be insignificant.