Cumene-Mechanism of toxicity

Cumene is a common name for isopropylbenzene, an organic compound. Cumene is a volatile colorless liquid at room temperature with a characteristic sharp, penetrating, aromatic odor. It is insoluble in water but is soluble in alcohol and many other organic solvents. Cumene is structurally a member of the alkyl aromatic family of hydrocarbons, which also includes toluene (methylbenzene) and ethylbenzene.Cumene can be found in crude oil, refined fuels, and is a part of processed highoctane gasoline.

Health hazard

Cumene is manufactured by reacting benzene with propylene at elevated temperature and pressure in the presence of a catalyst. It is considered an environmental pollutant because it is a natural component of petroleum and is present in tobacco smoke. Cumene vapor can be absorbed by the respiratory tract. Sufficiently high levels of exposure to cumene causes central nervous system (CNS) depression leading to death, internal bleeding of numerous organs, as well as irritation of the eyes and respiratory system, skin, and mucous membranes. Cumene is a high production volume chemical.

Uses

Around 98% of cumene is used in the production of phenol and its coproduct, acetone, using cumene hydroperoxide as chemical intermediate. However, the demand for cumene is largely dependent on the performance of phenol’s derivatives, which have resulted in healthy growth rates in demand for cumene. It is also used as a starting material in the production of acetophenone, α-methylstyrene, diisopropylbenzene, and dicumylperoxide. Cumene is used as a thinner for paints, lacquers, and enamels. It is also used in the manufacture of acetophenone, methylstyrene, and other chemicals commonly found in home cleaning products. Minor uses of cumene include as a constituent of some petroleum-based solvents, such as naphtha; in gasoline blending diesel fuel and highoctane aviation fuel; and as a raw material for peroxides and oxidation catalysts such as polymerization catalysts for acrylic and polyester-type resins. It is also a good solvent for fats and resins and has been suggested as a replacement for benzene in many of its industrial applications.

Environmental Fate

Cumene is released into the environment as a result of production and processing from petroleum refining and the evaporation and combustion of petroleum products. Cumene also occurs in a variety of natural substances including essential oils from plants and foodstuffs. When released to soil, cumene is expected to biodegrade and may volatilize from the soil surface. Cumene is expected to have low mobility based on its estimated adsorption coefficient (Koc) of 820. Based on Henry’s law constant of 0.0115 atm m³ mol^-1, cumene volatilization from moist soil surfaces is expected to be an important environmental fate and it may volatilize from dry soil surfaces based on its vapor pressure. Cumene is expected to strongly adsorb to soils and is not expected to leach to groundwater.

When released into the atmosphere, a vapor pressure of 4.5 mmHg at 25°C indicates that cumene exists solely as a vapor in the ambient atmosphere. Cumene in the vapor phase reacts with photochemically generated hydroxyl radicals. The reaction of cumene in the vapor phase with ozone has an estimated half-life of 2.5 days. Cumene may also react with ozone radicals found in the atmosphere but not at an environmentally important rate.

Mechanism of toxicity 

CNS depression is the most commonly reported toxic effect and sensitive end point of exposure to cumene. It is characterized in animals by narcosis, decreased motor activity, incoordination, prostration, and impaired gait and reflexes to stimuli. The exact mechanism has not been discovered but it is believed to involve the similarity with which cumene is lipidsoluble and not water-soluble, for nerve tissue due to its high lipid content. Signs of CNS depression occurred in most of the available studies on acute and subchronic inhalation of cumene. Some of these studies showed that the CNS depressant effects occurred during exposure and shortly thereafter and the effects disappeared within 24 h. This is consistent with the rapid absorption and excretion of cumene shown in pharmacokinetic studies. 

Cumene also causes sensory irritation at neurotoxic concentrations. Some other studies on respiratory rate inhibition (RD50) showed that the sensory irritation of cumene and related alkylbenzenes compounds is caused by a physical interaction with a receptor protein in a lipid layer, rather than by a chemical interaction.

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