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Photooxidation products resulting from volatile organic compounds (VOCs) reacting with sunlight are important contributors to gas-phase air pollution. We characterized the product-weighted mutagenic potencies (rev m3mgC–1h–1) in SalmonellaTA100 of atmospheres resulting from the hydroxyl radical (OH)-initiated photochemical oxidation of 11 C4or C5alkenes or dienes in the presence of nitric oxide (NO) and from the ozonolysis of four VOCs without NO (isoprene; 1,3-pentadiene; 1,4-pentadiene; and 1,3-butadiene). Irradiated atmospheres from precursors with a single C═C bond (3-methyl-1-butene, 2-methyl-1-butene, cis/trans-2-pentene, 2-methyl-2-butene, 1-butene, and 1-pentene) had low potencies (<5), whereas linear dienes with terminal C═C bonds had high potencies (50–65). Dienes with a branched structure (isoprene) or internal C═C bonds (1,3-pentadiene) had intermediate potencies (15–20). No VOCs were mutagenic without photochemical oxidation. VOCs+O3in the dark produced less mutagenic atmospheres than photochemistry in the presence of NO. Atmospheres induced primarily C to T and C to A mutations, the main base substitutions in nonsmoker lung cancer. Atmospheres from the photooxidation of isoprene and 1,3-pentadiene also induced GG to TT, the signature mutation of peroxyacetyl nitrate. Five molecular compositions identified by Chemical Ionization Mass Spectrometry (CIMS), most containing nitrogen, correlated (r= 0.76–0.85) with the mutagenic potencies of irradiated atmospheres; most had a likely nitrate functional group. Assessment of the mutagenicity of emitted VOCs should consider VOC photooxidation products, especially dienes with terminal C═C bonds, as these products likely contribute to overall health effects from ambient air pollution.

Achieving a reversible decrease of metabolism and other physiological processes in the whole organism, as occurs in animals that experience torpor or hibernation, could contribute to increased survival after serious injury. Using a Bayesian network tool with transcriptomic data and chemical structure similarity assessments, we predicted that the Alzheimer’s disease drug donepezil (DNP) could be a promising candidate for a small molecule drug that might induce a torpor-like state. This was confirmed in a screening study with Xenopus laevistadpoles, a nonhibernator whole animal model. To improve the therapeutic performance of the drug and minimize its toxicity, we encapsulated DNP in a nanoemulsion formulated with low-toxicity materials. This formulation is composed of emulsified droplets <200 nm in diameter that contain 1.250 mM DNP, representing ≥95% encapsulation efficiency. The DNP nanoemulsion induced comparable torpor-like effects to those produced by the free drug in tadpoles, as indicated by reduced swimming motion, cardiac beating frequency, and oxygen consumption, but with an improved biodistribution. Use of the nanoemulsion resulted in a more controlled increase of DNP concentration in the whole organism compared to free DNP, and to a higher concentration in the brain, which reduced DNP toxicity and enabled induction of a longer torpor-like state that was fully reversible. These studies also demonstrate the potential use of Xenopustadpoles as a high-throughput in vivo screen to assess the efficacy, biodistribution, and toxicity of drug-loaded nanocarriers.

Highly oxygenated molecules (HOMs) are a class of compounds associated with secondary organic aerosols exhibiting high oxygen to carbon (O:C) ratios and often originating from the oxidation of biogenic compounds. Here, the photooxidation and ozonolysis of isoprene were examined under a range of conditions to identify HOM tracers for aged isoprene aerosol. The HOM tracers were identified as silylated derivatives by gas chromatography–mass spectrometry and by detecting their parent compounds by liquid chromatography–high resolution mass spectrometry. In addition to the previously observed methyltetrols and 2-methylglyceric acid, seven tracer compounds were identified, including 2-methyltartronic acid (MTtA), 2-methylerythronic acid (2MeTrA), 3-methylerythronic acid (3MeTrA), 2-methylthreonic acid (2MTrA), 3-methylthreonic acid (3MTrA), erythro-methyltartaric acid (e-MTA), and threo-methyltartaric acid (t-MTA). The molecular structures were confirmed with authentic standards synthesized in the laboratory. The presence of some of these HOMs in the gas and particle phases simultaneously provides evidence of their gas/particle partitioning. To determine the contributions of aged isoprene products to ambient aerosols, we analyzed ambient PM2.5samples collected in the southeastern United States in summer 2003 and at two European monitoring stations located in Zielonka and Godów (Poland). Our findings show that methyltartaric acids (MTA) and 2- and 3-methylthreonic acids (and their stereoisomers) are representative of aged isoprene aerosol because they occur both in the laboratory chamber aerosol obtained and in ambient PM2.5. On the basis of gas chromatography–mass spectrometry (GC-MS) analysis, their concentrations were found to range from 0.04 ng for 3-methylthreonic acid to 6.3 ng m–3for methyltartaric acid at the southeast site in Duke Forest, NC, USA.

Secondary organic aerosol (SOA) can affect the atmospheric radiation balance through absorbing light at shorter visible and UV wavelengths. However, the composition and optical properties of light-absorbing SOA is poorly understood. In this work, SOA filter samples were collected during individual chamber experiments conducted with three biogenic and eight aromatic volatile organic compound (VOC) precursors in the presence of NOXand H2O2. Compared with the SOA generated using the aromatic precursors, biogenic SOA generally exhibits negligible light absorption above 350 nm; the aromatic SOA generated in the presence of NOXshows stronger light absorption than that generated with H2O2. Fifteen nitroaromatic compound (NAC) chemical formulas were identified and quantified in SOA samples. Their contributions to the light absorption of sample extracts were also estimated. On average, the m-cresol/NOXSOA sample has the highest mass contribution from NACs (10.4 ± 6.74%, w/w), followed by naphthalene/NOX(6.41 ± 2.08%) and benzene/NOX(5.81 ± 3.82%) SOA. The average contributions of NACs to total light absorption were at least two times greater than their average mass contributions at 365 and 400 nm, revealing the potential use of chromophoric NACs as brown carbon (BrC) tracers in source apportionment and air quality modeling studies.

Environmental context Sesquiterpenes, chemicals emitted by terrestrial vegetation, are oxidised in the ambient atmosphere leading to the formation of secondary organic aerosol. Although secondary organic aerosol can have significant effects on air quality from local to global scales, considerable gaps remain in our understanding of their various sources and formation mechanisms. We report studies on the oxidation of sesquiterpenes aimed at improving aerosol parameterisation for these reactions for incorporation into future air quality models. Abstract A series of sesquiterpenes (SQT) were individually oxidised under a range of conditions, including irradiation in the presence of NOx, reactions with O3 or reactions with NO3 radicals. Experiments were conducted in either static mode to observe temporal evolution of reactants and products or in dynamic mode to ensure adequate collection of aerosol at reasonably low reactant concentrations. Although some measurements of gas-phase products have been made, the focus of this work has been particle phase analysis. To identify individual products, filter samples were extracted, derivatised and analysed using gas chromatography mass spectrometry techniques. The results indicate that secondary organic aerosol (SOA) is readily formed from SQT oxidation. The high reactivity of these systems and generally high conversion into SOA products gives rise to high SOA levels. SOA yields (ratio of SOA formed to hydrocarbon reacted) averaged 0.53 for ozonolysis, 0.55 for photooxidation and 1.19 for NO3 reactions. In select experiments, SOA was also analysed for the organic matter/organic carbon (OM/OC) ratio, and the effective enthalpy of vaporisation (ΔHvapeff). The OM/OC ranged from 1.8 for ozonolysis and photooxidation reactions to 1.6 for NO3 reactions, similar to that from SOA generated in monoterpene systems. ΔHvapeff was measured for β-caryophyllene–NOx, β-caryophyllene–O3, β-caryophyllene–NO3, α-humulene–NOx and α-farnesene–NOx systems and found to be 43.9, 41.1, 44.9, 48.2 and 27.7kJmol-1. Aerosol yields and products identified in this study are generally in good agreement with results from several studies. A detailed examination of the chamber aerosol for the presence of chemical tracer compounds was undertaken. Only β-caryophyllinic acid, observed mainly under β-caryophyllene photooxidation and ozonolysis experiments, was detected in ambient aerosol. Chemical analysis yielded compounds having oxygen and nitrogen moieties present, which indicates continued evolution of the particles over time and presents high dependence on the SQT–oxidant system studied. This study suggests that SOA from laboratory ozonolysis experiments may adequately represent ambient aerosol in areas with SQT emissions.

AbstractChemical tracer methods for determining contributions to primary organic aerosol (POA) are fairly well established, whereas similar techniques for secondary organic aerosol (SOA), inherently complicated by time-dependent atmospheric processes, are only beginning to be studied. Laboratory chamber experiments provide insights into the precursors of SOA, but field data must be used to test the approaches. This study investigates primary and secondary sources of organic carbon (OC) and determines their mass contribution to particulate matter 2.5 µm or less in aerodynamic diameter (PM2.5) in Southeastern Aerosol Research and Characterization (SEARCH) network samples. Filter samples were taken during 20 24-hr periods between May and August 2005 at SEARCH sites in Atlanta, GA (JST); Birmingham, AL (BHM); Centerville, AL (CTR); and Pensacola, FL (PNS) and analyzed for organic tracers by gas chromatography-mass spectrometry. Contribution to primary OC was made using a chemical mass balance method and to secondary OC using a mass fraction method. Aerosol masses were reconstructed from the contributions of POA, SOA, elemental carbon, inorganic ions (sulfate [SO42−], nitrate [NO3−], ammonium [NH4+]), metals, and metal oxides and compared with the measured PM2.5. From the analysis, OC contributions from seven primary sources and four secondary sources were determined. The major primary sources of carbon were from wood combustion, diesel and gasoline exhaust, and meat cooking; major secondary sources were from isoprene and monoterpenes with minor contributions from toluene and β-caryophyllene SOA. Mass concentrations at the four sites were determined using source-specific organic mass (OM)-to-OC ratios and gave values in the range of 12–42 µg m−3. Reconstructed masses at three of the sites (JST, CTR, PNS) ranged from 87 to 91% of the measured PM2.5mass. The reconstructed mass at the BHM site exceeded the measured mass by approximately 25%. The difference between the reconstructed and measured PM2.5mass for nonindustrial areas is consistent with not including aerosol liquid water or other sources of organic aerosol.

In the present study, we have characterized in detail the MS2 and MS3 fragmentation behaviors, using electrospray ionization (ESI) in the negative ion mode, of previously identified sulfated isoprene secondary organic aerosol compounds, including 2‐methyltetrols, 2‐methylglyceric acid, 2‐methyltetrol mononitrate derivatives, glyoxal and methylglyoxal. A major fragmentation pathway for the deprotonated molecules of the sulfate esters of 2‐methyltetrols and 2‐methylglyceric acid and of the sulfate derivatives of glyoxal and methylglyoxal is the formation of the bisulfate [HSO4]− anion, while the deprotonated sulfate esters of 2‐methyltetrol mononitrate derivatives preferentially fragment through loss of nitric acid. Rational interpretation of MS2, MS3 and accurate mass data led to the structural characterization of unknown polar compounds in K‐puszta fine aerosol as organosulfate derivatives of photooxidation products of unsaturated fatty acids, i.e. 2‐hydroxy‐1,4‐butanedialdehyde, 4,5‐ and 2,3‐dihydroxypentanoic acids, and 2‐hydroxyglutaric acid, and of α‐pinene, i.e. 3‐hydroxyglutaric acid. The deprotonated molecules of the sulfated hydroxyacids, 2‐methylglyceric acid, 4,5‐ and 2,3‐dihydroxypentanoic acid, and 2‐ and 3‐hydroxyglutaric acids, showed in addition to the [HSO4]− ion (m/z 97) neutral losses of water, CO2 and/or SO3, features that are characteristic of humic‐like substances. The polar organosulfates characterized in the present work are of climatic relevance because they may contribute to the hydrophilic properties of fine ambient aerosol. In addition, these compounds probably serve as ambient tracer compounds for the occurrence of secondary organic aerosol formation under acidic conditions. Copyright © 2007 John Wiley & Sons, Ltd.

AbstractOrganic carbon (OC) was measured semicontinuously in laboratory experiments of steady-state secondary organic aerosol formed by hydrocarbon + nitrogen oxide irradiations. Examination of the mass of carbon measured on the filter for various sample volumes reveals a systematic offset that is not observed when performing an instrumental blank. These findings suggest that simple subtraction of instrumental blanks determined as the standard analysis without sample collection (i.e., by cycling the pump and valves yet filtering zero liters of air followed by routine chemical analysis) from measured concentrations may be inadequate. This may be especially true for samples collected through the filtration of small air volumes wherein the influence of the systematic offset is greatest. All of the experiments show that filtering a larger volume of air minimizes the influence of contributions from the systematic offset. Application of these results to measurements of ambient concentrations of carbonaceous aerosol suggests a need for collection of sufficient carbon mass to minimize the relative influence of the offset signal.

The effects of various halide salt and inorganic acid pretreatments on the photocatalytic destruction of toluene were examined to determine the source of activity enhancements seen previously with HCl pretreatments. Pretreatments with chloride salts (NaCl, KCl) are found to have little influence on photocatalyst activity, suggesting that the presence of an acid is needed. Acid pretreatments either increase (sulfuric, nitric, phosphoric) or decrease (hydrobromic, hydroiodic, and perchloric) the catalyst activity. These results indicate that acidification alone is not responsible for the observed changes in catalyst activity and that both protons and anions influence photocatalyst behavior.

Substituted-ethane diphosphonic acids are an interesting moiety of organic acids because they display particularly favorable chemical characteristics toward the selective dissolution of metal oxides. In recent years, these systems have been studied to develop a cradle-to-grave process for the decontamination of ferrous metals typical of the nuclear power industry. This paper expands the understanding of this system to the dissolution of ferrous oxides found on corroded metals of nuclear facilities.It is found that pure iron oxides such as magnetite (Fe3O4) and hematite (Fe2O3) dissolved quickly (<1 h) using 0.5 M 1-hydroxyethane-1,1-diphosphonic acid (HEDPA) and a strong reducing agent; the oxides with slower kinetics are the spinel structures, such as the nickel ferrites (NiOFe2O3), which dissolved very slowly in the foregoing solution. These results were confirmed in bench-scale tests on actual carbon steel and radioactively contaminated stainless steel samples. The decontamination of actual stainless steel from a nuclear reactor vessel required high concentrations of both HEDPA and reducing agent. Methods for treating the spent HEDPA solution are discussed.

We produced experimental intravitreal fibrin clots in rabbits that had previous gas compression of the vitreous or intact vitreous. Twenty-four hours after production of fibrin, the eyes were injected with 25 μg of tissue plasminogen activator or physiologic irrigation solution. In the gas compression group (n = 11), all tissue plasminogen activator-treated eyes cleared within six hours of injection; complete clearing was not seen until six days in the physiologic irrigation solution-treated eyes (n = 9). A similar response was seen in the intact vitreous group. No evidence of toxicity was observed as measured by slit-lamp biomicroscopy, intraocular pressure, corneal thickness, electroretinography, or histopathologic examination.

• Background: Standardized echography is routinely utilized to assess uveal melanomas. Echographic pseudoextension is defined as normal structures mimicking intrascleral or extrascleral extension of tumor on echography. • Methods: The records of 151 consecutive uveal melanoma patients evaluated with standardized echography over a 6-year period (1986–1991) were reviewed to identify those in which pseudoextension or true extension was diagnosed. • Results: Fourteen (9%) cases of pseudoextension were noted, with causes including juxtapapillary tumor location (seven cases), extraocular muscle insertion (five cases), vortex ampullae (one case), and post-brachytherapy changes (one case). Clinical, echographic, and/or histopathologic follow-up confirmed absence of true extension. Six (4%) cases of true extrascleral extension were identified and confirmed histopathologically. • Conclusion: Differentiating extraocular tumor extension from pseudoextension is critical, and use of standardized A-scan and contact B-scan echography is integral in this assessment.

• Methanol ingestion can lead to visual impairment, central nervous system dysfunction, or death. The extent of ocular involvement has been difficult to determine because the toxicity is restricted to humans and nonhuman primates due to species differences in methanol metabolism. A rodent model of methanol toxicity recently developed by us was used to evaluate retinal dysfunction in methanol poisoning. Formic acidemia and visual toxic reactions developed in methanol-intoxicated rats. Electroretinographic analysis indicated a significant early deficit in b-wave amplitude followed by a temporally delayed, lesser reduction in a-wave amplitude. Histologic evaluation of the eyes 60 hours after methanol administration revealed generalized retinal edema and vacuolation in the photoreceptors and retinal pigment epithelium. Ultrastructural examination showed swelling and disruption of the mitochondria in photoreceptor inner segments, optic nerve, and the retinal pigment epithelium. These studies document direct retinal involvement in this nonprimate model of methanol toxicity.

• High-resolution contact B-scan echographic imaging of the ciliary body and peripheral retina was performed on five eyes with anterior hyaloidal fibrovascular proliferation and media opacity by means of a wide (58°) scanning arc. This technique determined the circumferential and anteroposterior extent of peripheral traction retinal detachment associated with anterior hyaloidal fibrovascular proliferation, which correlated highly with findings at subsequent vitrectomy. Final visual acuity of 20/400 or better was achieved in the two eyes (50%) with more limited peripheral traction detachment. In the presence of media opacity, anterior echographic imaging may allow early detection of traction retinal detachment associated with anterior hyaloidal fibrovascular proliferation and may be useful in characterizing the severity of this condition.

Formic acid is the toxic metabolite in methanol poisoning. Permanent visual damage in methanol-intoxicated humans and nonhuman primates has been associated with prolonged exposures (>24 hr) to blood formate concentrations in excess of 7 mM; however, little information is available on the toxicity associated with chronic low-level or repeated exposure to methanol. The present studies compared the effects on retinal function and structure of rapidly increasing formate concentrations typical of acute methanol intoxication with low-level plateau formate concentrations more likely to be generated by subacute or chronic methanol exposure. Rats that accumulated formate concentrations of 8–15 mMdeveloped metabolic acidosis, retinal dysfunction, and retinal histopathologic changes. Retinal dysfunction was measured as reductions in thea- andb-waves of the electroretinogram that occurred coincident with blood formate accumulation. Histopathologic studies revealed vacuolation in the retinal pigment epithelium and photoreceptor inner segments. Rats exposed to formate concentrations ranging from 4 to 6 mMfor 48 hr showed evidence of retinal dysfunction in the absence of metabolic acidosis and retinal histopathology. These data indicate that formic acid generated from methanol oxidation acts as a direct retinal toxin. Formate-induced retinal dysfunction in methanol-intoxicated rats can be produced by steadily increasing concentrations of formate and importantly can also be produced by prolonged exposure to lower concentrations of formate. Our findings substantiate evidence based on clinical case reports and a small number of epidemiological studies and support the hypothesis that the visual system toxicity produced by acute, subacute, or chronic methanol poisoning share a common mechanism.

• Titanium retinal tacks were implanted through the formed vitreous into the posterior retinas of rabbits and evaluated by electroretinographic testing and by light microscopy at intervals after implantation. Tritiated thymidine autoradiography was used to evaluate the proliferation of ocular tissues in response to tack insertion. Within one month after implantation, the retinal tacks were surrounded by scar tissue produced by the proliferation of retinal glial cells and choroidal and scleral connective tissue cells. The tissue response was focal and there was no excessive fibrous tissue or vascular proliferation or any indication of iris neovascularization for six months. The observations of firm retinal adherence and low tissue reactivity suggest that titanium tacks can be used to secure the retina during retinal attachment surgery and can remain permanently in the eye.

• Thirteen members of a family presumed to be harboring the gene for autosomal dominant vitreoretinochoroidopathy were examined. In four affected members, electro-oculography demonstrated marked reduction of the Arden ratio (range, 1.1 to 1.5; normal, ≥1.8), despite electroretinographic evidence of mildly affected rod function and normal cone function. These findings suggested that a diffuse disturbance of the photoreceptor-pigment epithelium complex may have been present prior to widespread loss of photoreceptor function in the affected members of this family. As in previously described families, the pattern of inheritance appeared consistent with autosomal dominance.

• Visualization of the position of an episcleral plaque in relation to the underlying choroidal melanoma during the early radiation treatment period reconfirms accurate plaque location and may help assure optimal treatment. We used high-resolution B-scan echography to confirm the position of the episcleral plaque in 16 consecutive cases of choroidal melanoma. The technique is most useful for well-defined tumors as small as 3 mm in height whose anterior border does not extend beyond the ora serrata.