Project at a Glance

Title: Measurement of ambient concentrations of chlorinated dioxins and furans, and polycyclic aromatic hydrocarbons

Principal Investigator / Author(s): Hunt, Gary T

Contractor: ENSR Consulting and Engineering

Contract Number: A932-093

Research Program Area: Health & Exposure

Topic Areas: Agriculture, Health Effects of Air Pollution, Toxic Air Contaminants


A comprehensive program of field sampling and laboratory analyses has been conducted at three (3) locations in California to assess ambient concentrations of a variety of semivolatile organic pollutants of regulatory significance to the California Air Resources Board (CARB). Field sampling campaigns were conducted in Fresno, California during the calendar period December 17, 1990 through January 4, 1991; in Richmond, California during the calendar period January 24 to 25, 1991; and at two (2) separate stations vicinal to "Rice Straw" fields during active "burning" periods. The latter field program was conducted during the October 17 to November 8, 1990 calendar period. State-of-the-art sampling and analyses procedures were employed to determine atmospheric burdens of a variety of toxicotogically significant organics including: Polynuclear Aromatic Hydrocarbons (PAHs), Polychlorinated Dibenzodioxins and Dibenzofurans (PCDDs/PCDFs), nitro-PAHs and oxygenated-PAHs, and mutagenic activity. It is anticipated that this work product will assist the ARB in their continued examination of the distribution and occurrences of PAHs, nitro-PAHs, oxygenated-PAHs, and PCDDs/PCDFs within the State of California. Further, these data will serve to augment the existing database on population exposure to PCDDs/PCDFs and PAHs. PCDDs/PCDFs have been designated as Toxic Air Contaminants (TAC) by ARB in accordance with AB 1807 while PAHs are currently under consideration for listing as Toxic Air Contaminants. The monitoring program made use of three (3) CARB sites and one (1) BAAQMD site as directed by the CARB. These included the Pleasant Grove (CARB) and Colusa County Fairgrounds sites (CARB) situated vicinal to the "Rice Straw" burning region, the Fresno CARB site and a site in Richmond, California owned and operated by the Bay Area Air Quality Management District (BAAQMD). Actual sampling periods were selected by the CARB during each of the aforementioned calendar periods at each of the four-(4) sites. Twelve-hour composite diurnal and nocturnal samples were collected during each session for PAH, nitro-PAH/oxygenated-PAH, and mutagen assay analyses. Twenty-four (24) hour composite samples were collected concurrent with a diurnal/nocturnal pair for PCDDs/PCDFs. The highest concentrations of PAHs, nitro-PAHs/oxygenated-PAHs, PCDDs/PCDFs, as well as mutagen density were observed during the Fresno field program while the lowest concentrations were noted during the "Rice Straw" field program. Atmospheric burdens of PAHs and mutagenic activity during the "Rice Straw" field program are indicative of a rural setting not impacted by open burning of agricultural waste. 'PAHs levels measured during the Fresno field program are indicative of wood combustion emissions. Elevated retene (a chemical signature for the combustion of coniferous woods) concentrations in concert with enhanced nocturnal PAH concentrations suggest strong influences from residential wood burning. The PCDDs/PCDFs concentrations measured during the Fresno program represent some of the highest levels reported to date in the open literature. The PCDDs/PCDFs congener class and isomer specific profiles are indicative of combustion source emissions. The predominant PAHs measured during each of the three (3) field campaigns include naphthalene, 1-methylnaphthalene, 2-methylnaphthalene and biphenyl. Photochemical reactions involving these parent compounds and OH radicals during diurnal periods result in elevated concentrations of 1 -nitronaphthalene, 2-nitronaphthalene and 3-nitrobiphenyl. Mutagenic assay analyses of diurnal samples conducted during the Fresno field program suggest the presence of direct acting mutagenicity. Conversely, mutagenic assay data for nocturnal samples suggest a suppression of this direct-acting mutagenicity with +S9 activation. Nearly equivalent concentrations of the four (4) oxygenated-PAHs were observed in the Fresno samples. The highest concentrations were observed for 9-fluorenone, while the lowest concentrations were observed for pyrene, 3-4 dicarboxylic acid anhydride.

For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753

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