Exposures of Workers to Aromatic Hydrocarbons

Exposures to aromatic hydrocarbons are known to produce a number of different effects in humans. Some aromatic hydrocarbon mixtures produce additive effects upon co-exposure, whereas others induce enhanced toxic effects. 

In one study, a group of people who were exposed to a mixture of toluene (2.73) and mixed xylenes (3.15) was compared to a control group that was exposed to the individual solvents alone. Additive effects were noted when exposures were to the mixture versus the individual solvents. Hematology and serum biochemistry did not show any notable changes from exposure to single chemicals versus the mixture. 41  

An immunotoxicology study showed that co-exposure to a mixture of benzene (2.13) and toluene (2.73) resulted in the enhancement of the immunotoxic effects of benzene. The authors surmised that toluene competed with benzene for Phase I metabolizing enzymes, thereby causing benzene concentrations in the body to be higher than if benzene were present alone. 42  

A study of petrochemical workers exposed to a mixture of benzene (2.13), toluene (2.73), and xylene (3.15), each below its TLV (and total VOCs below all three individual TLVs) produced hepatotoxic effects. No reason for the observed effect was offered, but it was concluded that exposure to low level aromatic hydrocarbon mixtures can cause liver damage. 43  

A study on the CNS depressing effects of toluene (2.73), ethylbenzene (3.15), and xylene (3.15), singly and in combinations, showed that CNS effects were increased when exposures were to mixtures. The enhanced effects observed were modest when employees were at rest, but were significantly higher when workers were exercising or performing manual work. The authors attributed the observed effects to pharmacokinetic interactions of the mixture elements. 44  

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