Establishing Relevant Ozone Standards to Protect Vegetation and Human Health: Exposure/Dose-Response Considerations

Abstract

Vegetation EffectsAlthough understanding the effects of specific levels of doses is important when attempting to link exposures with the potential for air pollutant effects, little is known about the concentration, and in some cases, the form of the pollulant that enlers the organism. The sensitivity of vegetation as a function of time of day or period of growth, as well as soil conditions may result in plants being exposed to high 0, concentrations with little resultant injury or damage, while more moderate levels of 0, exposures result in injury. 7 Because not enough is known to quantify the links between exposure and dosage, for standard setting purposes researchers and policymakers have focused on describing the relationships between exposure characteristics and plant response. Until further information is available on actual dosages received by vegetation and their resulting effects, the focus will continue to be on exposure. Relating Important Components of Ozone Exposure to Ambient CondllionsCopyright 1993 -Air & Waste Management Association . Because 0, is an omnipresent air r,lIutant that affects both human health and vegetation, I, the U.S. Environmental Protection Agency (EPA) has established both primary and secondary standards; the primary standard reflects an interest in protecting human health and the secondary, the public's welfare. For 0" both the primary and the secondary standards are the same. The federal standard for 0, is attained when the expected number of days per year with maximum hourly average concentrations above 0.12 ppm is equal to or less than 1. The potenlial for air pollution to affect an organism is dependent upon such characteristics as the pollutant's concentration, length of eXposure, time between exposures, uptake rate and sensitivity of the target organism. 1 The use of the current form and level of the federal 0, standard assumes that successful attainment of the standard will result in protection from those 0, exposure patterns responsible for human health and vegetation effects. However, research results indicate that the current form of the standard may not be protective enough for either human health',' or vegetation. 5 •• This paper discusses (1) those components of 0, exposure that may be most important in affecting vegetation and human health, (2) the strengths and weaknesses of applying alternative forms of the 0, standard to protect vegetation and human health, and (3) future research efforts designed to link experimental effects results and their associated 0, exposures with actual ambient exposures. ImplicationsSerious discussion is taking place concerning the application of a new National Ambient Air Quality Standard for ozone in the fonn of a daily maximum 8-hour average concentration for the protection of human health. Controlled human exposure work supports the suggestion that concentration may be more important than exposure duration and ventilation rates. The results suggest that an extended-period average index, such as the daily maximum 8-hour average ...

Characteristics of Urban Ground-Level Ozone in Korea

“…During all the multiple-day O 3 episodes, a high-pressure system called the North Pacific High dominated Korea. This is quite typical in Korea during the summer season, and brings a hot and humid air mass.…”

“…Multiple-day episodes during the specified period were also investigated. 3 measurements are taken at a height between 7 and 15 m. Once the data have been quality assured, the information is then transferred to the Air Quality Management Bureau (AQMB) of KMOE. Each monitor in the AQMB database has a discrete number identifying the city and the city monitor number.…”

“…[1][2][3][4] Accordingly, it has become the focus of increased national concern in Korea. Over the last two decades, Korea has experienced a rapid growth in urbanization, industrialization, and the number of motor vehicles.…”

The Application of Exposure-Based Criteria in Developing Alternative Primary Ambient Ozone Standards

“…9 Consideration of cumulative exposure indices, rather than multi-hour averages, also has been suggested. 4 The current National Ambient Air Quality Standard for ozone specifies an hourly concentration (0.12 ppm) and a permissible rate of exceedance, which is not more than one day per year on average at each ozone monitoring location, where the averaging time is three years. It takes no account of the magnitude, duration, or geographical extent of exceedances.…”

“…The effects of ozone on a person depend upon individual sensitivity, ozone co ncentratio n, vol ume of ai r breathed per minute, duration of exposure, and, particularly, concentration. 4 In recent multi-hour exposure studies, changes in respiratory physiology occurred following 6.6 hours exposure to ozone at concentrations at and below the federal NAAQS, 5 and decrements in forced…”