Review of benzene neurotoxicity
DIMITRIADIS E.A.

Following acute inhalation of benzene in relatively high concentrations¹⁶, factory workers exhibited symptoms of neurotoxicity. These symptoms reported to occur at levels ranging from 250 to 3000 ppm included headache, vertigo and dizziness. Exposure to higher concentrations of benzene [20.000 ppm (mg/m³)] for five to ten minutes can result in death¹.

Neurological findings on lethal exposures are similar to those reported on non-lethal exposures to benzene. These symptoms are similar to the consequences of exposure to multiple organic solvents, including benzene, and are reversible when solvents are removed¹². Chronic exposure to benzene and toluene was studied in121 factory workers exposed to benzene for 2 to 9 years¹⁰. Air concentration of benzene was 6-15 ppm and toluene vapors did not exceed the 5 ppm level.

Seventy-four of the workers examined complained of frequent headaches, became tired easily, had difficulty sleeping and complained of memory loss.

Acute neurotoxic effects of exposure to benzene conducted in test animals and people are numbness, anesthesia, downfall of central nervous system, breath cessation, loss of conciousness and death^3,18.

Chronic studies on animals after being exposedto benzene for a short term have shown peripheral neuropathy and mild toxic encephalopathy.

Herregods et al (1984)⁷ detected transverse myelitis in a young man exposed daily to benzene as he worked in a drug and chemical substances warehouse. Diagnosis of transverse myelitis is consistent with an acute spinal cord transaction having an impact on grey and white matter.

Baslo and Aksoy (1982)³ directed neurological tests on eight patients with a history of chronic exposure to benzene who were working in a shoe factory detected with aplastiv anemia (leukaemia).

Epidimiological studies on various teams of workeras exposed to benzene have shown statistically significant changes in peripheral velocity, neurological function (sensory and motor neurological conduction velocity and electromyographical abnormalities), changes which had existed from months to years.

Epidemiological studies have also shown a statitistically significant increase in nervous behavior on workers exposed to benzene for many years.

Some other dysfunctions included: fatigue, irritability and memory impairment, changes of personality or mood (sentinental aberration, reduced impulsiveness, control and motivation) and also mental function impairment (reduced concentration, memory and learning ability).

Among problems caused by organic solvents, the most important disturbances mentioned are characterized by irreparable damage to brain, memory (insanity) and structure of CNS^7,8.

By contrast, figures supplied for the stabilization of the dose level used in neurotoxic studies are extremely few. Neurological outcomes regarding benzene that cannot be defined by NOAEL have been recorded in both animals and humans.

Doses used in neurotoxic studies were high and duration of exposure was very brief. Maximum exposure to benzene was four weeks⁷. It is worth nothing that researches at the workplace have not used low levels of benzene.

Kahn and Muzyka (1973)¹⁰ reported complaintsfrom factory workers for neurotoxicity when exposed to 6-16 ppm. However, their study failed to provide an objective assessment, therefore, it is considered inadequate. Other studies on humans involved exposure to high doses of benzene. No remarks have been made to animals yet. Hematological studies have demonstrated that these results are unworthy of further attention.

Key words: Benzene, neurotoxicity.