29. Naphthalene Measurement in Ambient Air Using Sorbent Tubes

Charles Perrino, Ira B. Tager
University of California, SPH, Berkeley

Fred Lurmann, Paul Roberts, David Vaughn
Sonoma Tech., Inc, Petaluma

Arantzazu Eiguren-Fernandez, Antonio H. Miguel, Southern California Particle Center and Supersite, Institute of the Environment, University of California, Los Angeles

New measurement techniques have been implemented to characterize airborne naphthalene inside and outside of homes and at schools as part of the Fresno Asthmatic Children’s Environment Study (FACES). Naphthalene was evaluated in 2000 by the International Agency for Research on Cancer and classified as possibly carcinogenic to humans (Group 2B). Recent data indicate that its derivatives have significant health impacts; however it is difficult to collect Nnphthalene efficiently and is often ignored in field sampling programs.

A Chemcomb sampling system containing quartz filters and glass honeycomb denuders coated with XAD-4 resin was used to collect PAH samples at 10 L/min. Naphthalene, present at approximately 10 times the concentration of other measured PAHs, is the most volatile among the 16 US EPA priority PAHs and exhibited breakthrough in the Chemcombs. Consequently, glass sorbent tubes, containing XAD-2 resin were used to collect naphthalene at a lower flow rate to try and maximize collection efficiency. Both the front and back sections of multiple sorbent tubes were analyzed separately: Breakthrough was not observed.

The sorbent tubes were attached to a Micro-Environmental Monitoring System (MEMS), which is capable of collecting 6 samples simultaneously at flow rates between 0.1-10 L/min. A flow rate of 0.2 L/min was used to collect the majority of the sorbent tube samples, which were extracted in methylene chloride and analyzed using a GC-MS with a mass selective detector. Naphthalene levels were measured from August 2002 to February 2003, with 168 samples collected in homes, and 57 samples collected at trailers placed near schools and at a central monitoring site in Fresno. The concentration of naphthalene was highly dependent on location and season, with higher levels found during the colder months. Naphthalene concentrations inside the homes ranged from 0 to 1677 ng/m3 with a mean of 473 ng/m3. Naphthalene concentrations outside the homes and at the outdoor trailer sites ranged from 0 to 910 ng/m3 with a mean of 218 ng/m3.

The performance of the MEMS-based sorbent tubes compared favorably with that of medium volume (113 L/min) Tisch model 1202 PM2.5 samplers which combine both vapor-phase and particle-phase PAHs. An experiment comparing the naphthalene concentrations measured by the two methods was performed in November 2003 on the rooftop of the Keck Laboratory, on the Caltech campus (Pasadena, California). Samples were collected over a three-day period with duplicate samples collected using both methods. A statistical approach for comparing the values from the sorbent tubes and the Tisch system consisted of a Student’s t-test and a two-way ANOVA (F-test). Naphthalene concentrations measured using the two methods were not significantly different. Sampling variability for the Tisch system was about twice that of the sorbent tubes (19% vs 10%). Overall, the average concentration of naphthalene between the two systems was within 6%.