Epidemiologic studies have shown that airborne particulate matter (PM) with a mass median aerodynamic diameter < 10 µm (PM 10 ) is associated with an increase in respiratory-related disease. However, there is a growing consensus that particles < 2.5 µm (PM 2.5 ), including many in the ultrafine (< 0.1 µm) size range, may elicit greater adverse effects. PM is a complex mixture of organic and inorganic compounds; however, those components or properties responsible for biologic effects on the respiratory system have yet to be determined. During the fall and winter of 2000-2001, healthy adult Sprague-Dawley rats were exposed in six separate experiments to filtered air or combined fine (PM 2.5 ) and ultrafine portions of ambient PM in Fresno, California, enhanced approximately 20-fold above outdoor levels. The intent of these studies was to determine if concentrated fine/ultrafine fractions of PM are cytotoxic and/or proinflammatory in the lungs of healthy adult rats. Exposures were for 4 hr/day for 3 consecutive days. The mean mass concentration of particles ranged from 190 to 847 µg/m 3 . PM was enriched primarily with ammonium nitrate, organic and elemental carbon, and metals. Viability of cells recovered by bronchoalveolar lavage (BAL) from rats exposed to concentrated PM was significantly decreased during 4 of 6 weeks, compared with rats exposed to filtered air (p < 0.05). Total numbers of BAL cells were increased during 1 week, and neutrophil numbers were increased during 2 weeks. These observations strongly suggest exposure to enhanced concentrations of ambient fine/ultrafine particles in Fresno is associated with mild, but significant, cellular effects in the lungs of healthy adult rats.
) and the number of farmworkers is estimated to be between 175,000 to 500,000.While the San Joaquin Valley is one of the world's most productive agricultural regions, it is also frequently in violation of U.S. ambient air-quality concentration standards, particularly those for atmospheric particulate matter (PM) (Velasco 2005), which is defined as liquid or solid material such as soil dust or smoke suspended in the air. Particulate levels for the South Coast Air Basin and the Central Valley in California are the highest recorded in the country, exceeding the national ambient air-quality standards for each season of the year. Workers and residents of the San Joaquin Valley are exposed to airborne particulate matter from a broad range of sources including farming practices such as the tilling of dry soil, agricultural burning, crop harvesting and diesel-powered water pumping. Particle emissions include inorganic compounds from soil lofted by, for example, dairy operations and off-road vehicles, or organic matter from animal feed and disturbed, dried manure.The three parameters -size, composition and distribution -for each classification of particles are sufficiently different that each can produce unique health outcomes following inhalation. Epidemiological studies have shown a strong correlation between the exposure of human populations to particulate matter and acute and chronic health effects, including increased deaths due to cardiovascular illness and emergency room visits related to the severity of asthma symptoms (Sheppard same levels of light brown apple moth control as obtained in New Zealand. Many fruit crops in California already receive control measures for native and introduced leafrollers, and these tactics may prove to be effective for light brown apple moth without a great deal of modification.If the New Zealand experience is any indication, adequate control of this leafroller can be achieved more effectively through a vigorous program of biological control and the use of selective insecticides for other pest species. That approach identified a need to introduce natural enemies to attack light brown apple moth through all stages of development. The focus on introductions to address parasitism gaps, especially those targeting the late larval and pupal stages, proved to be highly effective. Further exploration of natural enemies in New Zealand may yield guidance for possible parasitoid importations to North America.As New Zealand has already found, it is unlikely that any one parasitoid will be so specific that it attacks only light brown apple moth. Therefore, any introduction of natural enemies into California must be preceded by a careful cost-benefit analysis. Light brown apple moth is a polyphagous insect, feeding on many plant species, and some native leafrollers may occupy the same niche. The benefit of suppressing populations of light brown apple moth and allowing reduced use of insecticide must outweigh possible adverse impacts on populations of endemic moths and natural enemies. This is an ...
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