A continuing challenge in occupational hygiene is that of accurately estimating a worker's long-term exposure to the multitude of airborne chemicals found in the workplace and surrounding community. Hence, the development of new methods that will permit more effective sampling of contaminants in the workplace is essential to ensure that accurate exposure assessments are completed. Evacuated canisters have been used for many years to collect ambient air samples for gases and vapors. With the development of a new flow control device, interest in using evacuated canisters for personal breathing zone sampling as an alternative to sorbent samplers has increased. A capillary flow controller was recently designed to provide a very low flow rate, permitting a sample to be collected over an extended period of time with the use of a small portable canister. Initial research focused on the development of the capillary canister and the evaluation of its ability to collect a representative sample. Recent studies indicate that representative samples can be effectively collected at extremely low flow rates ranging from 0.05 to 1.0 ImL/min in small (300 mL) evacuated canisters.
The specific aims of this proposal are to: 1. Test the applicability of the capillary-canister in a variety of air sampling environments, including indoor air and factory environments, 2. Examine the correlation between different exposure assessment scenarios, such as the collection of multiple 8-hour samples versus a single 40-hour sample, 3. Quantify the bias associated with the diminishing flow rate through extensive computer simulations and validate the mathematical model through comparison with measured data. In summary, we hope to demonstrate that this new innovative sampling system collects accurate and representative air samples in a cost effective manner, with verified overall uncertainties that are well within acceptable guidelines. A validated capillary-canister device will equip industrial hygienists with the ability to extend personal sampling times beyond what is currently obtained and to sample a broader range of chemicals simultaneously. ? ?
