| Abstract
| - The potential health effect, induced by exposure tovolatile organic compounds (VOCs) in ambient air for longperiods, is an important problem. We have investigateda long-term monitoring method for measurement of VOCsin ambient air. Long-term, nonstop sampling periods of4-weeks, 7-days, and 24-h were evaluated simultaneously,using mass flow controllers set to 0.5, 2.0, and 14 mL/min, respectively. Ambient air was drawn through amultisorbent sampling tube packed with Carbotrap C,Carbotrap B, and Carboxen 1000. Adsorbates were introducedinto a GC/MS using a thermal desorption cold trapinjector and determined according to the EPA Method TO-14 list. Concentrations of almost all VOCs estimated bythe 7-day or 4-week sampling method were approximatelyequal to the mean value calculated from the 24-h samplingmethod for each term, except for compounds bearing a vinylgroup such as chloroethene, 1,3-butadiene, and styrene.Concentration variations of CFCs, tetrachloromethane, or 1,1,1-trichloroethane were small, but the other VOCs exhibitedsignificant day-to-day fluctuation reflecting socioeconomicactivities and the direction of wind. As an example, dailyconcentrations of benzene in February and March 1999 rangedfrom 2 to 10 μg/m3 and 1.5−8.6 μg/m3, respectively. Thiswide variation indicates that long-term, nonstop sampling isnecessary for measuring accurate average concentrationsof VOCs in ambient atmospheres.
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