N-hexane

Endpoint summary

Description of key information

Two human epidemiological studies were identified for n-hexane (Wang, 1986; Klimisch score =2 and Governa et al., 1987; Klimisch score = 2).

Additional information

In a key epidemiological study researchers evaluated a group of 59 press proofing workers from 16 factories who were employed for at least 2 months (Wang, 1986; Klimisch score =2). All but four of these workers had regular contact with solvents in the process of cleaning the rollers. Two exposure measures using personal air samplers were taken in 14 of the 16 factories. Referent neurological data was also collected from workers and healthy individuals. MCVs were also collected from workers exposed to n-hexane.

The neurological examination identified 15 workers with polyneuropathy and two ashymptomatic workers with abnormal MCVs. All but one of the workers were employed in factories that used solvents with n-hexane concentrations in excess of 50%. 

No association was found with length of employment, statistically significant associations existed between frequency of polyneuropathy and abnormal MCV and n-hexane concentration in the cleaning solvents and between the frequency of polyneuropathy and n-hexane air concentrations. However, a significant reduction in the MCV was found among workers exposed to air concentrations less than 25 ppm, a result that the authors considered to be related to the prolonged exposure due to overtime work.

Governa et al. (1987) investigated the correlation between electrographic changes indicative of polyneuropathy and urinary excretion of metabolites indicative of exposure to n-hexane. Forty workers were randomly chosen from four small shoe factories. All workers handled a type of glue or solvent that contained over 50% n-hexane without protective equipment for about 7 hours/day. All subjects exhibited no more than mild or nonspecific symptoms of polyneuropathy and were free of other known risk factors for nervous system impairment. A urine sample was collected at the end of a shift, and then a neurophysiological examination (MCV, SCV, and associated distal latencies [DL]) was carried out the following day. Reference values were obtained from 41 unexposed individuals. The urinary concentrations n-hexane metabolites were measured in 40 workers, but only those for two of the five n-hexane metabolites were above minimum detection limits (MDLs): 2,5-hexanedione (mean, 6.80 mg/L) and (valerolactone (mean, 3.31 mg/L). A statistically significant dose-response relationship for the electroneuromyography (ENM) scores was found for 2,5 -hexanedione and valerolactone. A threshold value of 7.5 mg/L was closely related to the incidence of abnormalities. Some variation from the relationship was apparent because three workers with lower concentrations of 2.5 -hexanedione (3.0, 3.3, and 4.5 mg/L) displayed ENM changes.