Development of Samplers for Measuring Human Exposure to Ozone

Research Report 63, February 1994

Active and Passive Ozone Samplers Based on a Reaction with a Binary Reagent Jack D. Hackney, Edward L. Avol, William S. Linn, and Karen R. Anderson

A Passive Ozone Sampler Based on a Reaction with Nitrite Petros Koutrakis, Jack M. Wolfson, Arnold Bunyaviroch, and Susan Froelich

A Passive Ozone Sampler Based on a Reaction with Iodide Yukio Yanagisawa

Ozone is a highly reactive gas that is a pervasive air pollutant at ground level. It is a major component of urban smog, forming when emissions from mobile and industrial sources interact with sunlight. Assessing the risk of adverse health effects from such exposures is difficult because only limited data are available on the actual ozone concentrations that people experience. Under the HEI ozone sampler program, three studies were designed to advance the development and testing of personal ozone samplers.

Dr. Hackney and colleagues at Rancho Los Amigos Medical Center designed active and passive samplers based on ozone-induced changes in the intensity of a color formed by a chemical reagent. (Passive samplers depend on the natural diffusion of air and gases to the collection site, and active samplers use a pump to draw air into the device.) Dr. Hackney and associates coated filter papers with a reagent that forms a pink color after ozone exposure. By extracting the reaction product from the paper and measuring the intensity of the colored solution, they determined the amount of ozone that had reacted with the reagent. The investigators also designed a light-tight sample holder to mitigate the reagent\'s sensitivity to light.

Dr. Yanagisawa from the Harvard School of Public Health designed a passive sampler based on ozone oxidizing iodide ion to molecular iodine. The unique feature of this sampler is that as the reaction proceeds on a carbon disk coated with a nylon derivative and potassium iodide, the volatile iodine product stabilizes by forming an electrically charged complex with nylon. The amount of current discharged by the complex then is a measure of the amount of iodine bound to nylon, and thus, the amount of ozone that had reacted with iodide ion to form molecular iodine. In chamber studies, the amount of charged complex formed increased with increasing ozone exposure levels.

Finally, a previously designed passive sampler by Dr. Koutrakis and colleagues at the Harvard School of Public Health was evaluated. The sampler was based on ozone oxidizing nitrite ion, which is coated onto glass fiber filters, to nitrate ion. After extracting the ions from the filters with water, the investigators separated the nitrate ion from the nitrite ion by a process called ion chromatography.