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Singlet oxygen (¹O₂) is a highly reactive species formed through solar irradiation of organic matter in environmental waters. Implicated in a range of reactions, it has proven difficult to quantify its spatial distribution in natural waters. We assessed the microheterogeneous distribution of ¹O₂ in irradiated solutions containing chromophoric dissolved organic matter (CDOM) by using molecular probes of varying hydrophobicity. The apparent ¹O₂ concentrations ([¹O₂][subscript app]), measured by recently developed hydrophobic trap-and-trigger chemiluminescent probe molecules, were orders of magnitude higher than those measured by the conventional hydrophilic probe molecule furfuryl alcohol. The differential [¹O₂][subscript app] values measured by these probes reflect a steep concentration gradient between the CDOM macromolecules and the aqueous phase. A detailed kinetic model based on the data predicts probabilistic ¹O₂ distributions under different solvent conditions.

The aqueous photochemistry of four pharmaceutical compounds detected in surface waters (naproxen, diclofenac, ibuprofen, and clofibric acid) was investigating in purified (Milli-Q) water and in Mississippi River water (MRW). Both direct photolysis and hydroxyl radical-mediated indirect photolysis (using a combination of probe and quencher experiments) were studied. Singlet oxygenation was also investigated for naproxen. Second-order rate constants for reaction with hydroxyl radical were determined using Fenton's reagent. Naproxen was rapidly transformed via direct photolysis in sunlight in both Milli-Q and MRW. The radical quencher isopropyl alcohol (IPA), had a similar effect in both systems, and this effect was interpreted as a reaction of a carboxyl radical intermediate of naproxen. Diclofenac was found to undergo rapid direct photolysis under sunlight, confirming the results of prior studies. Addition of IPA led to more rapid transformation, possibly due to formation of other radical species or photoreduction with IPA serving as the H-source. When irradiated under natural sunlight, slow direct photolysis of clofibric acid is observed in Milli-Q water, and a combination of direct photolysis and radical mediated indirect processes appear responsible for clofibric acid photolysis in MRW. The dominant photochemical loss process for ibuprofen irradiated with a medium pressure Hg-vapor lamp was identified as reaction with photo-generated radicals. These results suggest that photolytic processes are important removal mechanisms for pharmaceutical compounds discharged into sunlit surface waters.[PUBLICATION ABSTRACT]

The photochemical fate of the antimicrobial agent triclosan is presented. Experiments performed in both natural and buffered deionized water show that triclosan rapidly photodegrades by direct photolysis (t½ = 5 h, pH 8, noon summer sunlight, 45°N latitude). Both 2,8‐dichlorodibenzo‐p‐dioxin (2,8‐DCDD) and 2,4‐dichlorophenol (2,4‐DCP) are produced. The 2,8‐DCDD and 2,4‐DCP also are photolabile and, thus, are intermediates. The yields for 2,8‐DCDD and 2,4‐DCP ranged from 3 to 12% depending on the conditions employed. When triclosan is photolyzed in the presence of Suwannee River (GA, USA) fulvic acid, a portion of the initial mass is recovered as insoluble material. Based on experiments in which the formation of insoluble material was monitored with photolysis time, it is postulated that photolysis in natural waters leads to some of the triclosan being coupled to humic matter. Triclosan also reacts rapidly with both singlet oxygen (krxn = 1.07 ± 0.03 × 108 M−1 s−1 in water of pH 10) and hydroxyl radical (k·OH = 5.4 ± 0.3 × 109 M−1 s−1). Indirect photolysis pathways, however, are not expected to be important because of low steady‐state concentrations of reactive oxygen species in natural waters and the efficiency of the direct photolysis of triclosan.

Chronic axial spinal pain is one of the major causes of significant disability and health care costs, with facet joints as one of the proven causes of pain. To provide evidence-based guidance in performing diagnostic and therapeutic facet joint interventions. The methodology utilized included the development of objectives and key questions with utilization of trustworthy standards. The literature pertaining to all aspects of facet joint interventions, was reviewed, with a best evidence synthesis of available literature and utilizing grading for recommendations.Summary of Evidence and Recommendations:Non-interventional diagnosis: • The level of evidence is II in selecting patients for facet joint nerve blocks at least 3 months after onset and failure of conservative management, with strong strength of recommendation for physical examination and clinical assessment. • The level of evidence is IV for accurate diagnosis of facet joint pain with physical examination based on symptoms and signs, with weak strength of recommendation. Imaging: • The level of evidence is I with strong strength of recommendation, for mandatory fluoroscopic or computed tomography (CT) guidance for all facet joint interventions. • The level of evidence is III with weak strength of recommendation for single photon emission computed tomography (SPECT) . • The level of evidence is V with weak strength of recommendation for scintography, magnetic resonance imaging (MRI), and computed tomography (CT) .Interventional Diagnosis:Lumbar Spine: • The level of evidence is I to II with moderate to strong strength of recommendation for lumbar diagnostic facet joint nerve blocks. • Ten relevant diagnostic accuracy studies with 4 of 10 studies utilizing controlled comparative local anesthetics with concordant pain relief criterion standard of ≥80% were included. • The prevalence rates ranged from 27% to 40% with false-positive rates of 27% to 47%, with ≥80% pain relief.Cervical Spine: • The level of evidence is II with moderate strength of recommendation. • Ten relevant diagnostic accuracy studies, 9 of the 10 studies with either controlled comparative local anesthetic blocks or placebo controls with concordant pain relief with a criterion standard of ≥80% were included. • The prevalence and false-positive rates ranged from 29% to 60% and of 27% to 63%, with high variability. Thoracic Spine: • The level of evidence is II with moderate strength of recommendation. • Three relevant diagnostic accuracy studies, with controlled comparative local anesthetic blocks, with concordant pain relief, with a criterion standard of ≥80% were included. • The prevalence varied from 34% to 48%, whereas false-positive rates varied from 42% to 58%.Therapeutic Facet Joint Interventions: Lumbar Spine: • The level of evidence is II with moderate strength of recommendation for lumbar radiofrequency ablation with inclusion of 11 relevant randomized controlled trials (RCTs) with 2 negative studies and 4 studies with long-term improvement. • The level of evidence is II with moderate strength of recommendation for therapeutic lumbar facet joint nerve blocks with inclusion of 3 relevant randomized controlled trials, with long-term improvement. • The level of evidence is IV with weak strength of recommendation for lumbar facet joint intraarticular injections with inclusion of 9 relevant randomized controlled trials, with majority of them showing lack of effectiveness without the use of local anesthetic. Cervical Spine: • The level of evidence is II with moderate strength of recommendation for cervical radiofrequency ablation with inclusion of one randomized controlled trial with positive results and 2 observational studies with long-term improvement. • The level of evidence is II with moderate strength of recommendation for therapeutic cervical facet joint nerve blocks with inclusion of one relevant randomized controlled trial and 3 observational studies, with long-term improvement. • The level of evidence is V with weak strength of recommendation for cervical intraarticular facet joint injections with inclusion of 3 relevant randomized controlled trials, with 2 observational studies, the majority showing lack of effectiveness, whereas one study with 6-month follow-up, showed lack of long-term improvement. Thoracic Spine: • The level of evidence is III with weak to moderate strength of recommendation with emerging evidence for thoracic radiofrequency ablation with inclusion of one relevant randomized controlled trial and 3 observational studies. • The level of evidence is II with moderate strength of recommendation for thoracic therapeutic facet joint nerve blocks with inclusion of 2 randomized controlled trials and one observational study with long-term improvement. • The level of evidence is III with weak to moderate strength of recommendation for thoracic intraarticular facet joint injections with inclusion of one randomized controlled trial with 6 month follow-up, with emerging evidence. Antithrombotic Therapy: • Facet joint interventions are considered as moderate to low risk procedures; consequently, antithrombotic therapy may be continued based on overall general status. Sedation: • The level of evidence is II with moderate strength of recommendation to avoid opioid analgesics during the diagnosis with interventional techniques. • The level of evidence is II with moderate strength of recommendation that moderate sedation may be utilized for patient comfort and to control anxiety for therapeutic facet joint interventions. The limitations of these guidelines include a paucity of high-quality studies in the majority of aspects of diagnosis and therapy. These facet joint intervention guidelines were prepared with a comprehensive review of the literature with methodologic quality assessment with determination of level of evidence and strength of recommendations. Chronic spinal pain, interventional techniques, diagnostic blocks, therapeutic interventions, facet joint nerve blocks, intraarticular injections, radiofrequency neurolysis.