Effect of Physical Exertion on the Biological Monitoring of Exposure to Various Solvents Following Exposure by Inhalation in Human Volunteers: II. n-Hexane

Abstract

This study evaluated the impact of physical exertion on two n-hexane (HEX) exposure indicators in human volunteers exposed under controlled conditions in an inhalation chamber. A group of four volunteers (two women, two men) were exposed to HEX (50 ppm; 176 mg/m ³ ) according to several scenarios involving several periods when volunteers performed either aerobic (AERO), muscular (MUSC), or both AERO/MUSC types of exercise. The target intensities for 30-min exercise periods separated by 15-min rest periods were the following: REST, 50W AERO [time-weighted average intensity including resting period (TWAI): 38W], 50W AERO/MUSC (TWAI: 34W), 100W AERO/MUSC (TWAI: 63W), and 100W AERO (TWAI: 71W) for 7 hr (two 3-hr exposure periods separated by 1 hr without exposure) and 50W MUSC for 3 hr (TWAI: 31W). Alveolar air and urine samples were collected at different time intervals before, during, and after exposure to measure unchanged HEX in expired air (HEX-A) and urinary 2,5-hexanedione (2,5-HD). HEX-A levels during exposures involving AERO activities (TWAI: 38W and 71W) were significantly enhanced (approximately +14%) compared with exposure at rest. MUSC or AERO/MUSC exercises were also associated with higher HEX-A levels but only at some sampling times. In contrast, end-of-exposure (7 hr) urinary 2,5-HD (mean ± SD) was not modified by physical exertion: 4.14 ± 1.51 μmol/L (REST), 4.02 ± 1.52 μmol/L (TWAI 34W), 4.25 ± 1.53 μmol/L (TWAI 38W), 3.73 ± 2.09 μmol/L (TWAI 63W), 3.6 ± 1.34 μmol/L (TWAI 71W) even though a downward trend was observed. Overall, this study showed that HEX kinetics is practically insensitive to moderate variations in workload intensity; only HEX-A levels increased slightly, and urinary 2,5-HD levels remained unchanged despite the fact that all types of physical exercise increased the pulmonary ventilation rate.

Keywords:

• 2,5-HD
• biological monitoring
• human volunteers
• n-hexane
• physical exertion
• workload

ACKNOWLEDGMENTS

The authors wish to thank Ginette Charest-Tardif, Mylène Beaudoin, Véronique Perrault, and Suzanne Paradis for their excellent technical assistance. Financial support from the Institut de recherche Robert-Sauvé en santé et en sécurité du travail is gratefully acknowledged.

Notes

^A Level of intensity during the exercise period.

^B Time-weighted average intensity including intervals without exercise.

^A Two periods of 3 hr separated by 1 hr without exposure.