A tale of two diesels.

Two different samples of diesel exhaust particles (DEP) have been used by toxicologists interested primarily in cancer/genotoxicity or noncancer--such as pulmonary inflammation and asthma exacerbation--health end points. These are, respectively, a standard reference material, SRM 2975, from a heavy-duty diesel engine, and a sample collected by researchers at the Japanese National Institute for Environmental Studies from an automobile diesel engine. In this issue of Environmental Health Perspectives companion papers appear, by David DeMarini and co-workers and by Pramila Singh and co-workers, characterizing these samples and contrasting their Salmonella mutagenicity and pulmonary toxicity in mice. This commentary is a plea from an atmospheric chemist for more cooperation among toxicologists, analytical chemists, atmospheric chemists, and automotive and combustion engineers to provide a comprehensive assessment of health risks to humans exposed to contemporary diesel emissions and for greater quantities and more diverse types of DEP and ambient samples (i.e., SRMs) that can be shared and exhaustively characterized. This needs to be a continuing process as diesel engines, fuels, and exhaust components evolve in response to control regulations

Pyrazine derivatives in cigarette smoke inhibit hamster oviductal functioning

BACKGROUND: Our past studies have shown that cigarette smoke inhibits oviductal functioning in vivo and in vitro. The goals in this study were to identify pyrazine derivatives in cigarette smoke solutions that inhibit ciliary beat frequency, oocyte pickup rate, and infundibular smooth muscle contraction in the hamster oviduct and to determine their lowest observable adverse effect levels (LOAELs) using in vitro bioassays. METHODS: MS smoke solutions were fractionated using solid phase extraction cartridges and the fractions were both tested on the hamster oviduct in vitro and analyzed by gas chromatography-mass spectrometry to identify individual pyrazine derivatives. Commercial pyrazine standards were purchased, assayed for purity, and tested in dose-response studies on hamster oviducts. The LOAEL and efficacy were determined for each compound in the in vitro bioassays. Statistical significance was determined using the Student's t-Test where p < 0.05. RESULTS: The LOAELs for the most inhibitory pyrazine derivatives in the ciliary beat frequency, oocyte pickup rate, and infundibular smooth muscle contraction assays were as follows: for pyrazine (1 picomolar, 10 picomolar, and 1 nanomolar); for 2-methylpyrazine (1 picomolar, 10 picomolar, and 10 picomolar); and for 2-ethylpyrazine (1 picomolar, 10 picomolar, and 1 picomolar). Six of the seven pyrazine derivatives tested (pyrazine, 2-methylpyrazine, 2-ethylpyrazine, 2-methoxy-3-methylpyrazine, 2,5-dimethylpyrazine, and 2,3,5-trimethylpyrazine) were inhibitory in picomolar or nanomolar doses in all three bioassays, while the seventh derivative, 2,6-dimethylpyrazine, had LOAELs in the nanomolar to micromolar range. CONCLUSION: This work shows that very low doses of pyrazines significantly inhibit proper oviductal functioning, raising questions regarding the safety of these compounds in cigarettes and other consumer products

Studies of the Atmospheric Chemsitry of Energy-Related Volatile Organic Compounds and of their Atmospheric Reaction Products

The focus of this contract was to investigate selected aspects of the atmospheric chemistry of volatile organic compounds (VOCs) emitted into the atmosphere from energy-related sources as well as from biogenic sources. The classes of VOCs studied were polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs, the biogenic VOCs isoprene, 2-methyl-3-buten-2-ol and cis-3-hexen-1-ol, alkenes (including alkenes emitted from vegetation) and their oxygenated atmospheric reaction products, and a series of oxygenated carbonyl and hydroxycarbonyl compounds formed as atmospheric reaction products of aromatic hydrocarbons and other VOCs. Large volume reaction chambers were used to investigate the kinetics and/or products of photolysis and of the gas-phase reactions of these organic compounds with hydroxyl (OH) radicals, nitrate (NO3) radicals, and ozone (O3), using an array of analytical instrumentation to analyze the reactants and products (including gas chromatography, in situ Fourier transform infrared spectroscopy, and direct air sampling atmospheric pressure ionization tandem mass spectrometry). The following studies were carried out. The photolysis rates of 1- and 2-nitronaphthalene and of eleven isomeric methylnitronaphthalenes were measured indoors using blacklamp irradiation and outdoors using natural sunlight. Rate constants were measured for the gas-phase reactions of OH radicals, Cl atoms and NO3 radicals with naphthalene, 1- and 2-methylnaphthalene, 1- and 2-ethylnaphthalene and the ten dimethylnaphthalene isomers. Rate constants were measured for the gas-phase reactions of OH radicals with four unsaturated carbonyls and with a series of hydroxyaldehydes formed as atmospheric reaction products of other VOCs, and for the gas-phase reactions of O3 with a series of cycloalkenes. Products of the gas-phase reactions of OH radicals and O3 with a series of biogenically emitted VOCs were identified and quantified. Ambient atmospheric measurements of the concentrations of a number of PAHs, nitro-PAHs, nitrated polycyclic aromatic compounds and biogenic VOCs were carried out in the Los Angeles air basin. In addition to these laboratory and ambient field studies, two literature reviews of VOC atmospheric chemistry and of the kinetics of the reactions of OH radicals with alkanes were also carried out. This research has been reported in 15 peer-reviewed publications

Heterogeneous reactions of particulate matter-bound PAHs and NPAHs with NO3/N2O5, OH radicals, and O3 under simulated long-range atmospheric transport conditions: reactivity and mutagenicity.

The heterogeneous reactions of ambient particulate matter (PM)-bound polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs (NPAHs) with NO3/N2O5, OH radicals, and O3 were studied in a laboratory photochemical chamber. Ambient PM2.5 and PM10 samples were collected from Beijing, China, and Riverside, California, and exposed under simulated atmospheric long-range transport conditions for O3 and OH and NO3 radicals. Changes in the masses of 23 PAHs and 20 NPAHs, as well as the direct and indirect-acting mutagenicity of the PM (determined using the Salmonella mutagenicity assay with TA98 strain), were measured prior to and after exposure to NO3/N2O5, OH radicals, and O3. In general, O3 exposure resulted in the highest relative degradation of PM-bound PAHs with more than four rings (benzo[a]pyrene was degraded equally well by O3 and NO3/N2O5). However, NPAHs were most effectively formed during the Beijing PM exposure to NO3/N2O5. In ambient air, 2-nitrofluoranthene (2-NF) is formed from the gas-phase NO3 radical- and OH radical-initiated reactions of fluoranthene, and 2-nitropyrene (2-NP) is formed from the gas-phase OH radical-initiated reaction of pyrene. There was no formation of 2-NF or 2-NP in any of the heterogeneous exposures, suggesting that gas-phase formation of NPAHs did not play an important role during chamber exposures. Exposure of Beijing PM to NO3/N2O5 resulted in an increase in direct-acting mutagenic activity which was associated with the formation of mutagenic NPAHs. No NPAH formation was observed in any of the exposures of the Riverside PM. This was likely due to the accumulation of atmospheric degradation products from gas-phase reactions of volatile species onto the surface of PM collected in Riverside prior to exposure in the chamber, thus decreasing the availability of PAHs for reaction

ES&T Guest Comment: Celebrating Bidleman’s 1988 “Atmospheric Processes”

Since its 1988 appearance in ES&T, Terry F. Bidleman’s article, “Atmospheric processes: wet and dry deposition of organic compounds are controlled by their vapor-particle partitioning”, has had a notable impact on the field of contaminant science. The paper has been cited in over 600 journal articles published by authors from every continent. Far from fading into obscurity, the paper’s influence has been remarkably consistent. Citations over the last year match the annual average attained since publication

Heterogeneous Reactions of PM-Bound PAHs and NPAHs with NO₃/N₂O₅, OH Radicals, and O₃ under Simulated Long-Range Atmospheric Transport Conditions: Reactivity and Mutagenicity

The heterogeneous reactions of ambient particulate matter (PM)-bound polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs (NPAHs) with NO₃/N₂O₅, OH radicals, and O₃ were studied in a laboratory photochemical chamber. Ambient PM[subscript 2.5] and PM₁₀ samples were collected from Beijing, China and Riverside, California, and exposed under simulated atmospheric long-range transport conditions for O₃ and OH and NO₃ radicals. Changes in the masses of 23 PAHs and 20 NPAHs, as well as the direct and indirect-acting mutagenicity of the PM (determined using the Salmonella mutagenicity assay with TA98 strain), were measured prior to and after exposure to NO₃/N₂O₅, OH radicals, and O₃. In general, O₃ exposure resulted in the highest relative degradation of PM-bound PAHs with more than four rings (benzo[a]pyrene was degraded equally well by O₃ and NO₃/N₂O₅). However, NPAHs were most effectively formed during the Beijing PM exposure to NO₃/N₂O₅. In ambient air 2-nitrofluoranthene (2-NF) is formed from gas-phase NO₃ radical- and OH radical-initiated reactions of fluoranthene, and 2-nitropyrene (2-NP) is formed from gas-phase OH radical-initiated reaction of pyrene. There was no formation of 2-NF or 2-NP in any of the heterogeneous exposures, suggesting that gas-phase formation of NPAHs did not play an important role during chamber exposures. Exposure of Beijing PM to NO₃/N₂O₅ resulted in an increase in direct-acting mutagenic activity which was associated with the formation of mutagenic NPAHs. No NPAH formation was observed in any of the exposures of the Riverside PM. This was likely due to the accumulation of atmospheric degradation products from gas phase reactions of volatile species onto the surface of PM collected in Riverside prior to exposure in the chamber, thus decreasing the availability of PAHs for reaction

Novel Nitro-PAH Formation from Heterogeneous Reactions of PAHs with NO₂, NO₃/N₂O₅, and OH Radicals: Prediction, Laboratory Studies and Mutagenicity

The heterogeneous reactions of benzo[a]pyrene-d₁₂ (BaP-d₁₂), benzo[k]fluoranthene-d₁₂ (BkF-d₁₂), benzo[ghi]perylene-d₁₂ (BghiP-d₁₂), dibenzo[a,i]pyrene-d₁₄ (DaiP-d₁₄), and dibenzo[a,l]pyrene (DalP) with NO₂, NO₃/N₂O₅, and OH radicals were investigated at room temperature and atmospheric pressure in an indoor Teflon chamber and novel mono NO₂-DaiP, and mono NO₂-DalP products were identified. Quartz fiber filters (QFF) were used as a reaction surface and the filter extracts were analyzed by GC/MS for nitrated-PAHs (NPAHs) and tested in the Salmonella mutagenicity assay, using Salmonella typhimurium strain TA98 (with and without metabolic activation). In parallel to the laboratory experiments, a theoretical study was conducted to rationalize the formation of NPAH isomers based on the thermodynamic stability of OH-PAH intermediates, formed from OH-radical-initiated reactions. NO₂ and NO₃/N₂O₅ were effective oxidizing agents in transforming PAHs to NPAHs, with BaP-d₁₂ being the most readily nitrated. Reaction of BaP-d₁₂, BkF-d₁₂ and BghiP-d₁₂ with NO₂ and NO₃/N₂O₅ resulted in the formation of more than one mono-nitro isomer product, while the reaction of DaiP-d₁₄ and DalP resulted in the formation of only one mono-nitro isomer product. The direct-acting mutagenicity increased the most after NO₃/N₂O₅ exposure, particularly for BkF-d₁₂ in which di-NO₂-BkF-d₁₀ isomers were measured. The deuterium isotope effect study suggested that substitution of deuterium for hydrogen lowered both the direct and indirect acting mutagenicity of NPAHs and may result in an underestimation of the mutagenicity of the novel NPAHs identified in this study.This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by the American Chemical Society and can be found at: http://pubs.acs.org/journal/esthag