In: Chemistry
Ans. The answer depends on the “context of toxicity”.
I. Toluene exhibits higher acute toxicity than benzene: LD50 for toluene is 636 mg/ kg whereas that of benzene is 930 mg /kg. The acute toxicities of toluene are more intense than that of benzene.
Ref: https://books.google.co.in/books?id=e4_S46UcI2AC&pg=PT329&lpg=PT329&dq=Is+toluene+or+benzene+more+toxic+to+humans&source=bl&ots=oxC1oGDcZH&sig=HIOuWTu80yuugVHOGtOaQR55KfE&hl=en&sa=X&ved=0ahUKEwjwy_HEsujXAhWINI8KHVp8DtYQ6AEISTAF#v=onepage&q=Is%20toluene%20or%20benzene%20more%20toxic%20to%20humans&f=false
II. Benzene is carcinogenic: The carcinogenic effects of benzene are well established. The toluene does not exhibit carcinogenic effects in long-term exposure. The products of benzene metabolism (benzoxide, epoxides, etc.) may react with DNA and cause genotoxicity. Moreover, these products are retained in the body for prolonged period as their excretion is not readily facilitated due to their relatively greater hydrophobic nature.
The products of toluene metabolism (benzoic acid, cresols, etc.) are more hydrophobic and are readily excreted when compared to that of the products of benzene metabolisms. Moreover, the carcinogenic effects of toluene are still not well established.
Therefore, when chronic exposure is considered, benzene is more toxic than benzene.