This chemical group consists of aromatic hydrocarbons whose molecular structures contain single aromatic rings separated by single chemical bonds or from simple groups containing unsaturated carbon atoms. Included are styrene, vinyltoluene, divinylbenzene, allylbenzene, α‐methyl styrene, phenylacetylene, diphenyl, methylbiphenyl, diphenylmethane, stilbene, and terphenyl. These compounds generally occur as volatile liquids under normal conditions, and possess low vapor pressures, volatility, absorbability, and solubility in aqueous media. Higher molecular weight derivatives are volatile solids. They are primary skin irritants and ocular exposure can cause corneal irritation and damage. Direct aerosol deposition or ingestion and subsequent aspiration can cause pulmonary damage and pneumonitis. They generally have low to moderate acute toxicity and, following repeated exposures, can cause local site‐of contact irritation and systemic toxicity primarily in the nasal cavity, lung, liver, kidney, and bladder. Sensitization reactions are generally not reported. Mixed findings have been reported in genotoxicity studies. These substances generally appear to be carcinogenic in animals, with increase tumor incidences reported in mouse lungs and liver and rat kidney and bladder. These substances can cause acute CNS depression at high exposures but only styrene is reported to produce neurological effects following repeated exposure, specifically toxicity to hearing, color vision, and olfaction. There is some evidence that these substances may produce reproductive and developmental effects. Their environmental fate and disposition are variable, whereas all are demonstrated or expected to be toxic to aquatic organisms.
