Oxidant air pollutants

This cascading effect may have been best demonstrated from interdisciplinary research addressing the consequences of chronic oxidant air pollution exposure to the mixed conifer forests of the San Bernardino Mountains of Southern California. Miller et al. (76) reported that chronic exposure to oxidant air pollutants resulted in decreased photosynthetic capacity, premature... 

Incomplete oxidation, air pollution from absorber vent operating procedures As no flow... 

Miller, P. R., M. H. McCutchan, and H. P. Milligan. Oxidant air pollution in the Central Vall, Sierra Nevada foothills, and Mineral King Vall of California. Atmos. Environ. 6 623-633, 1972. 

Photochemical Oxidant Air Pollution. A Report of the Air Management Sector Group on the Problem of Photochemical Oxidants and Their Precursors in the Atmosphere. Paris Organisation for Economic Co-operation and Development. 1975. 93 pp. 

TABLE 8-1 Effects of Photochemical-Oxidant Air Pollution Mixtures (in Irradiated Auto Exhaust) and Some Individual Constituents in Single Short (6-h) Exposures ... 

As mentioned previously, decreased voluntary running activity of mice was one of the most sensitive indexes of an effect of ambient photochemical oxidant air pollution or simulated oxidant smog that was produced in the laboratory by irradiating diluted auto-exhaust gases. Whether this effect of the mixtures was due only to ozone or to some other oxidant is not certain. It is plausible to conclude that ozone was the... 

Koontz, C. H. Oxidant air pollution and athletic performance A study in Seattle. Submitted to Department of Preventive Medicine, University of Washington, September 26, 1968. 

McMillan, R. S., D. H. Wiseman, B. Hanes, and P. F. Wehrle. Effect of oxidant air pollution on peak expiratory flow rates in Los Angeles school children. Arch. Environ. Health 18 941-949, 1%9. 

Oxidant air pollutants exist as parts of a complex mixture of gases, many of which may be phytotoxic. However, expect for ambient-air studies and simulated photochemical-oxidant studies, little research was done with pollutant combinations until the classic work of Menser and Heggestad in 1966. It is of interest that Thomas et suggested that sulfur dioxide might lessen the effect of oxidants in causing foliar injury to pinto bean. Middleton et working with ratios of sulfur... 

TABLE 11-28 Economic Estimates of Crop and Vegetation Losses Owing to Oxidant Air Pollutants, United States ... 

Miller, P. R., and A. A. Millecan. Extent of oxidant air pollution damage to some pines and other conifers in California. Plant Dis. Rep. 5S 5S5-S59, 1971. 

Taylor, O. C. (Principal Investigator) Oxidant Air Pollutant Effects on a Western Coniferous Forest Ecosystem. Task C Report Study Site Selection and On-Site Collection of Background Information. EPA-R3-73-043B. Riverside University of California, Statewide Air Pollution Research Center, 1973. (189 pp.J... 

Ecosystems subjected to oxidant air pollutants must be carefully observed and described individually if we are to understand and predict the complex consequences of chronic injury. Woodwell has summarized some of the expected effects of air pollutants on ecosystems elimination of sensitive species and reduction of diversity in numbers of species selective removal of larger overstoiy plants and a favoring of small plants reduction of the standing crop of organic matter, which leads to a reduction of nutrient elements held within the living system and increase in the activity of insect pests and in some diseases that hasten producer mortality. Many other effects can be suggested. 

The purpose of this chapter is to examine in the greatest detail possible the effects of oxidant air pollutants on ecosystems. A project is now going on to study the effects on a mixed-conifer forest ecosystem in southern California, and the planning documents and early results from this study constitute the major source of information for the remainder of this chapter. Other examples of damage to agroecosystems and natural ecosystems are included. 

Since 1968, total-oxidant concentrations have been measured continuously with a Mast ozone meter (calibrated by the California Air Resources Board method) from May through September at Rim Forest-Sky Forest.- The fall, winter, and early spring months have generally been omitted until recently, because synoptic patterns are usually not conducive to oxidant accumulation and transport. For example, average maximal hourly oxidant concentrations ffom October through April 1973 and 1974 stayed below 0.10 ppm those for April were 0.10-0.15 ppm. The main data-collection period coincides with the growing season and thus permits a reasonable estimate of the total annual dose of oxidant air pollution received by vegetation. 

The term ponderosa-Jeffrey type is a general term that includes a mosaic of five subtypes described by McBride on the basis of species dominance. These subtypes are ponderosa pine forest, ponderosa pine-white fir forest, ponderosa pine-Jefh y pine forest, Jeffry pine forest, and Jeffrey pine-white fir forest. The injury by oxidant air pollutants is most intense in the types dominated by ponderosa pine and less intense in the Jeffry pine types. In the field plots of these various types, the average area covered by shrubs is only 3.8% in the ponderosa types, but 26% in the Jeffrey pine types. ... 

TABLE 12-5 Tree Species and Size Composition on a Study Site Affected by Oxidant Air Pollution ... 

Most indirect effects of oxidant air pollutants on primary production and reproduction would be mediated through changes in the physical... 

The effects of oxidant air pollutants on vertebrates can be segregated into direct and indirect categories. Direct effects are clinical and pathologic alterations of tissues that result from exposure to ambient air. Indirect effects result from alterations in numbers or distribution of the plant and animal populations exposed to ambient air. For example, if air pollution eliminates or thins numbers of a susceptible plant species, the food chain of the consumers that feed on it may break down. The result could be a simpler and less stable ecosystem, with fewer plants and animals in species and numbers. 

The clinical and pathologic effects of oxidant air pollutants on domesticated vertebrates have received little study in the laboratory. We have... 

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