Effect of Physical Exertion on the Biological Monitoring of Exposure to Various Solvents Following Exposure by Inhalation in Human Volunteers: III. Styrene

Abstract

This study evaluated the impact of different work load intensities on biological indicators of styrene exposure. Four adult Caucasian men, aged 20 to 44 years, were recruited. Groups of 2-4 volunteers were exposed to 20 ppm of styrene in an exposure chamber according to scenarios involving either aerobic, muscular, or both types of physical exercise for 3 or 7 hr. The target intensities for each 30-min exercise period-interspaced with 15 min at rest-were the following: REST, 38 watts AERO (time-weighted average intensity), 34 watts AERO/MUSC, 49 watts AERO/MUSC, and 54 watts AERO for 7 hr and 22 watts MUSC for 3 hr. End-exhaled air samples were collected at 15 time points during and after 7-hr exposures for the determination of styrene concentrations. Urine samples were collected before the start of exposure, after the first 3 hr of exposure, and at the end of exposure for the determination of mandelic acid (MA) and phenylglyoxilic acid (PGA) concentrations. Compared with exposure at rest, styrene in alveolar air increased by a factor up to 1.7, while the sum of urinary MA and PGA increased by a factor ranging from 1.2 to 3.5, depending on the exposure scenario. Concentrations of biological indicators of styrene fluctuated with physical exertion and were correlated with the magnitude of the physical activity and pulmonary ventilation. Despite the physical exertion effect, urinary concentrations of styrene metabolites after a single-day exposure remain below the current biological exposure index value recommended by ACGIH; therefore, no additional health risk is expected. However, results shows that work load intensities must be considered in the interpretation of biological monitoring data and in the evaluation of the health risk associated with styrene exposure.

Ethanol toxicokinetics resulting from inhalation exposure in human volunteers and toxicokinetic modeling

“…2-fold in men and 3-fold in women) of BLE measured at the end of the exercise compared to the values measured at rest. The impact of exercise (50 W) is similar to that observed for other solvents (toluene, styrene, acetone and trichloroethylene) (Nadeau et al, 2006;Tardif et al, 2007a;Truchon et al, 2009). Additionally, a difference between women and men for the ratio BLE (50 W)/BLE (rest) was observed.…”

“…It is well known that the impact of physical activity can in some cases enhance the rate of absorption of certain solvents (Nadeau et al, 2006;Tardif et al, 2007b;Truchon et al, 2009). This increased absorption is mainly due to certain physiological changes associated with effort such as increased cardiac output and increased pulmonary ventilation.…”

Chemical-Specific Adjustment Factors for Intraspecies Variability of Acetone Toxicokinetics Using a Probabilistic Approach

“…Factors that have been shown to modify the kinetics of inhaled organic solvents in humans include among others; age, gender, physical exercise, and metabolism. 26,[40][41][42][43] Variability may also be due to lack of knowledge, i.e. uncertainty.…”

“…Physical activity has been shown to alter the toxicokinetics of a large number of volatiles. 26,37,40,55 An increase in workload increases pulmonary ventilation and cardiac output. 37 The cardiac output is also redistributed, with active muscles, fat and skin receiving relatively larger portions of the blood flow whereas the blood flow to liver, gastrointestinal tract and kidneys decreases.…”

“…37 The cardiac output is also redistributed, with active muscles, fat and skin receiving relatively larger portions of the blood flow whereas the blood flow to liver, gastrointestinal tract and kidneys decreases. 37,40 The metabolism can thus be affected indirectly by the decrease in blood flow to liver. Elimination of solvents by exhalation may be increased by an increase in ventilation.…”