By: Phil Fellin
In several contracts, methods were developed to determine airborne volatile organic compounds (VOCs) in indoor environments and in the personal breathing zone. Passive sampling devices (PSDs) were developed to evaluate indoor airborne concentrations and personal exposures to VOCs in the National Survey of Indoor VOCs (754 homes), and in Multi-media Exposure Pilot Studies (94 subjects). The use of PSDs proved to be a key factor in the studies success. The monitors are small, light-weight, make no noise, and are generally unobtrusive, making the respondent burden, or the impact on participants, relatively low compared to active samplers.
The Priority Substances List 1 (PSL1), first promulgated in the late 1980s, and consultation with other Health Canada groups was used to develop the target list VOCs for study. PSD development required evaluation of analytical methods, extraction recoveries, and sampling rates for each VOC in test atmosphere chambers and in field situations. Subsequently, a second list of compounds, PSL2, containing additional compounds was developed under CEPA. It was necessary to assess on the occurrence of these compounds indoors. Due to their advantages, the use of PSDs for this activity was highly desirable. However, PSL2 substances include several classes of compounds with significantly different properties including volatility, polarity and molecular weight that affect the sampling, extraction and analysis characteristics. Since the initial Multi-media study indicated that inhalation potentially represented the primary route of exposure for many VOC, it was important to develop methods for reliable measurement of the PSL2 substances including:
- examination of several methods of analysis and optimization of procedures for the new compounds (testing of analytical columns, and optimization of conditions for new and old target VOCs).
- evaluation of different solvents, combinations of solvents and extraction conditions for the recovery of new target VOCs from PSDs. The need for simplicity and compatibility with previous studies suggesting the use of the existing 3M OVM PSDs as the sampling method of choice.
- evaluation of sampling rates for the PSL2 VOCs with the current and possibly new (same body but different sorbents) PSDs in test atmospheres and in typical indoor environments. Suitable generation methods were developed for each compounds at conditions including temperatures rangeing from 10 ?C to 35 ?C, relative humidity from 10% to 90%, air velocity from .05 to 4 m/s, airborne concentrations of composite mixtures of VOCs simultaneously (detection limit to 2 ?g/m3), and the presence of typical indoor and outdoor co-pollutants including the primary criteria pollutants; O3 (10 to 120 ?g/m3), SO2 (5 to 150 ?g/m3) and NO2 (5 to 250 ?g/m3).
Because of our experience with method development and the availability of test atmosphere generation systems, we were awarded many sole-source contracts by Health Canada to develop PSDs to determine airborne VOCs for multi-media studies.
The laboratory is accredited by CALA to ISO/IEC 17025 for specific tests on the scope of accreditation.