Distribution of dearomatised white spirit in brain, blood, and fat tissue after repeated exposure of rats

Petroleum products with low content of aromatics have been increasingly use d during the past years. This study investigates tissue disposition of dear omatised white spirit. In addition, brain neurotransmitter concentrations w ere measured. Male rats were exposed by inhalation to 0, 400 (2.29 mg/l), o r 800 p.p.m. (4.58 mg/l) of dearomatised white spirit, 6 hr/day, 5 days/wee k up to 3 weeks. Five rats from each group were sacrificed immediately afte r the exposure for 1, 2, or 3 weeks and 2, 4, 6, or 24 hr after the end of 3 weeks' exposure. After 3 weeks of exposure the concentration of total whi te spirit was 1.5 and 5.6 mg/kg in blood; 7.1 and 17.1 mg/kg in brain; 432 and 1452 mg/kg in fat tissue at the exposure levels of 400 and 800 p.p.m., respectively. The concentrations of n-nonane, n-decane, n-undecane, and tot al white spirit in blood and brain were not affected by the duration of exp osure. Two hours after the end of exposure the n-decane concentration decre ased to about 25% in blood and 50% in brain. A similar pattern of eliminati on was also observed for n-nonane, n-undecane and total white spirit in blo od and brain. In fat tissue the concentrations of n-nonane, n-decane, n-und ecane, and total white spirit increased during the 3 weeks of exposure. The time to reach steady-state concentrations is longer than 3 weeks. After th e 3 weeks' exposure the fat tissue concentration of n-nonane, n-decane, n-u ndecane, and total white spirit decreased very slowly compared with the rat e of decrease in blood and brain suggesting that long-lasting redistributio n from fat to brain may occur. One week of exposure at 800 p.p.m. caused a statistically significant increase in whole brain dopamine concentration wh ile the noradrenaline concentration was unaffected. Exposure at both exposu re levels for 1 week caused a statistically significantly decreased concent ration of 5-hydroxytryptamine in whole brain. The reduction was related to the exposure concentration. These changes in neurotransmitter concentration s were normalised after 2 and 3 weeks' exposure. In conclusion, after 3 wee ks of exposure the fat:brain:blood concentration coefficients for total whi te spirit were approximately 250:3:1, and redistribution from fat to brain is possible. As total white spirit behaved similarly to the n-alkanes in bl ood, brain, and fat tissue, we suggest that the non-n-alkane white spirit c omponents possess toxicokinetic properties similar to the n-alkanes.