Chemical characteristics, leaching, and stability of the ubiquitous tire rubber-derived toxicant 6PPD-quinone

We here report chemical characteristics relevant to the fate and transport of the recently discovered environmental toxicant 6PPD-quinone (2-((4-methylpentan-2-yl)amino)-5-(phenylamino)cyclohexa-2,5-diene-1,4-dione or "6PPDQ"). 6PPDQ is a transformation product of the tire rubber antioxidant 6PPD that is ubiquitous in roadway environments, including atmospheric particulate matter, soils, runoff, and receiving waters, after dispersal from tire rubber use and wear on roadways. The aqueous solubility and octanol-water partitioning coefficient (i.e. log KOW) for 6PPDQ were measured to be 38 ± 10 μg L-1 and 4.30 ± 0.02, respectively. Within the context of analytical measurement and laboratory processing, sorption to various laboratory materials was evaluated, indicating that glass was largely inert but loss of 6PPDQ to other materials was common. Aqueous leaching simulations from tire tread wear particles (TWPs) indicated short term release of ∼5.2 μg 6PPDQ per gram TWP over 6 h under flow-through conditions. Aqueous stability tests observed a slight-to-moderate loss of 6PPDQ over 47 days (26 ± 3% loss) for pH 5, 7 and 9. These measured physicochemical properties suggest that 6PPDQ is generally poorly soluble but fairly stable over short time periods in simple aqueous systems. 6PPDQ can also leach readily from TWPs for subsequent environmental transport, posing high potential for adverse effects in local aquatic environments.

Transformation Products of Tire Rubber Antioxidant 6PPD in Heterogeneous Gas-Phase Ozonation: Identification and Environmental Occurrence

6PPD, a tire rubber antioxidant, poses substantial ecological risks because it can form a highly toxic quinone transformation product (TP), 6PPD-quinone (6PPDQ), during exposure to gas-phase ozone. Important data gaps exist regarding the structures, reaction mechanisms, and environmental occurrence of TPs from 6PPD ozonation. To address these data gaps, gas-phase ozonation of 6PPD was conducted over 24-168 h and ozonation TPs were characterized using high-resolution mass spectrometry. The probable structures were proposed for 23 TPs with 5 subsequently standard-verified. Consistent with prior findings, 6PPDQ (C18H22N2O2) was one of the major TPs in 6PPD ozonation (∼1 to 19% yield). Notably, 6PPDQ was not observed during ozonation of 6QDI (N-(1,3-dimethylbutyl)-N'-phenyl-p-quinonediimine), indicating that 6PPDQ formation does not proceed through 6QDI or associated 6QDI TPs. Other major 6PPD TPs included multiple C18H22N2O and C18H22N2O2 isomers, with presumptive N-oxide, N,N'-dioxide, and orthoquinone structures. Standard-verified TPs were quantified in roadway-impacted environmental samples, with total concentrations of 130 ± 3.2 μg/g in methanol extracts of tire tread wear particles (TWPs), 34 ± 4 μg/g-TWP in aqueous TWP leachates, 2700 ± 1500 ng/L in roadway runoff, and 1900 ± 1200 ng/L in roadway-impacted creeks. These data demonstrate that 6PPD TPs are likely an important and ubiquitous class of contaminants in roadway-impacted environments.

Screening p-Phenylenediamine Antioxidants, Their Transformation Products, and Industrial Chemical Additives in Crumb Rubber and Elastomeric Consumer Products

Recently, roadway releases of N,N'-substituted p-phenylenediamine (PPD) antioxidants and their transformation products (TPs) received significant attention due to the highly toxic 6PPD-quinone. However, the occurrence of PPDs and TPs in recycled tire rubber products remains uncharacterized. Here, we analyzed tire wear particles (TWPs), recycled rubber doormats, and turf-field crumb rubbers for seven PPD antioxidants, five PPD-quinones (PPDQs), and five other 6PPD TPs using liquid chromatography-tandem mass spectrometry. PPD antioxidants, PPDQs, and other TPs were present in all samples with chemical profiles dominated by 6PPD, DTPD, DPPD, and their corresponding PPDQs. Interestingly, the individual [PPDQ]/[PPD] and [TP]/[PPD] ratios significantly increased as total concentrations of the PPD-derived chemical decreased, indicating that TPs (including PPDQs) dominated the PPD-derived compounds with increased environmental weathering. Furthermore, we quantified 15 other industrial rubber additives (including bonding agents, vulcanization accelerators, benzotriazole and benzothiazole derivatives, and diphenylamine antioxidants), observing that PPD-derived chemical concentrations were 0.5-6 times higher than these often-studied additives. We also screened various other elastomeric consumer products, consistently detecting PPD-derived compounds in lab stoppers, sneaker soles, and rubber garden hose samples. These data emphasize that PPD antioxidants, PPDQs, and related TPs are important, previously overlooked contaminant classes in tire rubbers and elastomeric consumer products.

Application of Nucleotide-Based Kinetic Modeling Approaches to Predict Antibiotic Resistance Gene Degradation during UV- and Chlorine-Based Wastewater Disinfection Processes: From Bench- to Full-Scale

This study investigated antibiotic resistance gene (ARG) degradation kinetics in wastewaters during bench- and full-scale treatment with UV light and chlorine─with the latter maintained as free available chlorine (FAC) in low-ammonia wastewater and converted into monochloramine (NH₂Cl) in high-ammonia wastewater. Twenty-three 142-1509 bp segments (i.e., amplicons) of seven ARGs (blt, mecA, vanA, tet(A), ampC, bla_NDM, bla_KPC) and the 16S rRNA gene from antibiotic resistant bacteria (ARB) strains Bacillus subtilis, Staphylococcus aureus, Enterococcus faecium, Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae were monitored as disinfection targets by qPCR. Rate constants for ARG and 16S rRNA gene amplicon degradation by UV, FAC, and NH₂Cl were measured in phosphate buffer and used to expand and validate several recently developed approaches to predict DNA segment degradation rate constants based solely on their nucleotide contents, which were then applied to model ARG degradation during bench-scale treatment in buffer and wastewater matrixes. Kinetics of extracellular and intracellular ARG degradation by UV and FAC were well predicted up to ∼1-2-log₁₀ elimination, although with decreasing accuracy at higher levels for intracellular genes, while NH₂Cl yielded minimal degradation under all conditions (agreeing with predictions). ARB inactivation kinetics varied substantially across strains, with intracellular gene degradation lagging cell inactivation in each case. ARG degradation levels observed during full-scale disinfection at two wastewater treatment facilities were consistent with bench-scale measurements and predictions, where UV provided ∼1-log₁₀ ARG degradation, and chlorination of high-ammonia wastewater (dominated by NH₂Cl) yielded minimal ARG degradation.

Reactivity of Viral Nucleic Acids with Chlorine and the Impact of Virus Encapsidation

Free chlorine disinfection is widely applied to inactivate viruses by reacting with their biomolecules, which include nucleic acids, proteins, and lipids. Knowing the reactivities of viral genomes with free chlorine and the protection that encapsidation provides would ultimately help predict virus susceptibility to the disinfectant. The relative reactivities of different viral genome types and the impact of viral higher order structure with free chlorine are poorly characterized. Here, we studied the reactivity of viral genomes representing four genome types from virus particles with diverse structures, namely, (+)ssRNA (MS2), dsRNA (φ6), ssDNA (φX174), and dsDNA (T3) with free chlorine. We compared the reactivities of these viral nucleic acids when they were suspended in phosphate buffer solutions (naked forms) and when they were in the native virus particles (encapsidated forms). The reactivities of nucleic acids were tracked by polymerase chain reaction (PCR)-based assays. The naked dsDNA of T3 was the least reactive with free chlorine, with an average second order rate constant normalized by the number of bases in the measured regions (in M^-1 s^-1 b^-1) that was 34×, 65×, and 189× lower than those of the dsRNA of φ6, ssRNA of MS2, and ssDNA of φX174, respectively. Moreover, different regions in the ssRNA genome of MS2 and the dsRNA genome of φ6 exhibited statistically different reaction kinetics. The genomes within virus particles reacted slower than the naked genomes overall, but the extent of these differences varied among the four viruses. The results on viral nucleic acid reactivity help explain different susceptibilities of viruses to inactivation by free chlorine and also provide a valuable comparison of the susceptibilities of different nucleic acids to oxidants.

Degradation and deactivation of plasmid-encoded antibiotic resistance genes during exposure to ozone and chlorine

Degradation and deactivation kinetics of an antibiotic resistance gene (ARG) by ozone (O₃) and free available chlorine (FAC) were investigated in phosphate-buffered solutions at pH 7 for O₃ (in the presence of tert‑butanol), and pH 6.8 or 8.1 for FAC. We used a plasmid (pUC19)-encoded ampicillin resistance gene (amp^R) in both extracellular (e-) and intracellular (i-) forms. The second-order rate constant (k_O3) for degradation of 2686 base pair (bp) long e-pUC19 toward O₃, which was determined by quantitative polymerase chain reaction assay, was calculated to be ~2 × 10⁵ M^-1s^-1. The deactivation rate constants of e-pUC19 by O₃ measured with various recipient E. coli strains were within a factor of 2 compared with the degradation rate constant for e-pUC19. The degradation/deactivation kinetics of i-pUC19 were similar to those of e-pUC19, indicating only a minor influence of cellular components on O₃ reactivity toward i-pUC19. For FAC, the degradation and deactivation rates of e-pUC19 were decreased in the presence of tert‑butanol, implying involvement of direct FAC as well as some radical (e.g., ^•OH) reactions. The degradation rates of e-amp^R segments by direct FAC reaction could be explained by a previously-reported two-step sequential reaction model, in which the rate constants increased linearly with e-amp^R segment length. The deactivation rate constants of e-pUC19 during exposure to FAC were variable by a factor of up to 4.3 for the different recipient strains, revealing the role of DNA repair in the observed deactivation efficiencies. The degradation/deactivation of e-pUC19 were significantly faster at pH 6.8 than at pH 8.1 owing to pH-dependent FAC speciation variation, whereas i-pUC19 kinetics exhibited much smaller dependence on pH, demonstrating intracellular plasmid DNA reactions with FAC occurred at cytoplasmic pH (~7.5). Our results are useful for predicting and/or measuring the degradation/deactivation efficiency of plasmid-encoded ARGs by water treatment with ozonation and chlorination.

Evaluation of hydroxyl radical and reactive chlorine species generation from the superoxide/hypochlorous acid reaction as the basis for a novel advanced oxidation process

The reaction of hypochlorous acid (HOCl) with superoxide radical (O₂^•-) - a source of hydroxyl radical (HO^•) and various reactive chlorine species (RCS) - was investigated as the basis for a novel non-photochemical advanced oxidation process (AOP). Moderately stable (t_1/2 ~ minutes) aqueous O₂^•- stocks were prepared by several approaches at pH>12 and either (a) added directly to aqueous free available chlorine (FAC; i.e., HOCl/OCl^-) at circumneutral pH, or (b) premixed with alkaline FAC and then acidified to pH 7, to degrade various organic probe compounds via in situ generated HO^• and RCS. Radical production was optimal at [HO₂^•/O₂^•-]₀/[FAC]₀ ~ 2, with ~0.8 mol HO^• formed/mol FAC consumed, and HO^• and RCS exposures reaching ~5×10^-10 and ~10^-9 M×s, respectively. Similar trends were observed in natural waters and organic matter-amended phosphate buffer containing up to 5 mgC/L of dissolved organic carbon. Direct formation of oxyhalides, trihalomethanes (THMs), and haloacetic acids (HAAs), was minimal, though THM and HAA formation was moderately enhanced during post-chlorination of O₂^•-/FAC-treated solutions. This process could provide a beneficial addition to the range of available AOPs due to its high radical exposures, simplicity, rapid time-scales, potential for on-site O₂^•- generation, and widespread accessibility of FAC and other reagents.

Degradation Kinetics of Antibiotic Resistance Gene mecA of Methicillin-Resistant Staphylococcus aureus (MRSA) during Water Disinfection with Chlorine, Ozone, and Ultraviolet Light

Degradation kinetics of antibiotic resistance genes (ARGs) by free available chlorine (FAC), ozone (O₃), and UV₂₅₄ light (UV) were investigated in phosphate buffered solutions at pH 7 using a chromosomal ARG (mecA) of methicillin-resistant Staphylococcus aureus (MRSA). For FAC, the degradation rates of extracellular mecA (extra-mecA) were accelerated with increasing FAC exposure, which could be explained by a two-step FAC reaction model. The degradation of extra-mecA by O₃ followed second-order reaction kinetics. The degradation of extra-mecA by UV exhibited tailing kinetics, which could be described by a newly proposed kinetic model considering cyclobutane pyrimidine dimer (CPD) formation, its photoreversal, and irreversible (6-4) photoproduct formation. Measured rate constants for extra-mecA increased linearly with amplicon length for FAC and O₃, or with number of intrastrand pyrimidine doublets for UV, which enabled prediction of degradation rate constants of extra-mecA amplicons based on sequence length and/or composition. In comparison to those of extra-mecA, the observed degradation rates of intracellular mecA (intra-mecA) were faster for FAC and O₃ at low oxidant exposures but significantly slower at high exposures for FAC and UV. Differences in observed extra- and intracellular kinetics could be due to decreased DNA recovery efficiency and/or the presence of MRSA aggregates protected from disinfectants.

Rapid determination of trace haloacetic acids in water and wastewater using non-suppressed ion chromatography with electrospray ionization-tandem mass spectrometry

A simple and rapid method employing non-suppressed ion chromatography with electrospray ionization tandem mass spectrometry has been developed for the direct determination of trace-level haloacetic acids (HAAs) in water samples. Using 70/30 (v/v) acetonitrile/1 M aqueous methylamine as the mobile phase, three IC columns - AS16, AS18 and AS24 from Thermo-Scientific - were tested, respectively, with the AS16 column exhibiting the best overall performance with respect to resolution and retention time. To assess the effects of mobile phase composition on retention time of HAAs, the AS16 column was further tested using (i) different proportions of acetonitrile to aqueous methylamine, (ii) different proportions of acetonitrile to aqueous solution at fixed methylamine concentrations, and (iii) different concentrations of methylamine at fixed proportions of acetonitrile to aqueous solution. With a low proportion of aqueous solution, van der Waals and/or hydrogen-bonding interactions appeared to play an important role in governing HAA retention, i.e., HAAs with relatively higher apparent logK_ow* caused by elevated solvent _s^spK_a exhibited longer retention times; whereas with a high proportion of aqueous solution, ionic interactions appeared to dominate retention of HAAs, with the more polarizable HAAs exhibiting longer retention times. Using 70/30 (v/v) acetonitrile/1 M aqueous methylamine, the method detection limits were in the range of 0.090-0.216 μg/L for the 11 selected chloro-, bromo- and iodoacetic acids. Finally, this method was applied to monitor HAAs yields in laboratory chlorination experiments and to determine concentrations of HAAs in tap water and wastewater effluent samples.

A ubiquitous tire rubber-derived chemical induces acute mortality in coho salmon

In U.S. Pacific Northwest coho salmon (Oncorhynchus kisutch), stormwater exposure annually causes unexplained acute mortality when adult salmon migrate to urban creeks to reproduce. By investigating this phenomenon, we identified a highly toxic quinone transformation product of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), a globally ubiquitous tire rubber antioxidant. Retrospective analysis of representative roadway runoff and stormwater-affected creeks of the U.S. West Coast indicated widespread occurrence of 6PPD-quinone (<0.3 to 19 micrograms per liter) at toxic concentrations (median lethal concentration of 0.8 ± 0.16 micrograms per liter). These results reveal unanticipated risks of 6PPD antioxidants to an aquatic species and imply toxicological relevance for dissipated tire rubber residues.

Degradation and deactivation of a plasmid-encoded extracellular antibiotic resistance gene during separate and combined exposures to UV254 and radicals

This study investigated the degradation and deactivation of an extracellular ampicillin resistance gene (amp^R) encoded in plasmid pUC19 during exposure to UV₂₅₄, ^•OH (generated by UV_>290/H₂O₂), and combined exposure to UV₂₅₄ and ^•OH (and/or SO₄^•-) using UV₂₅₄/H₂O₂ and UV₂₅₄/S₂O₈^2-. The degradation rates of amp^R measured by quantitative polymerase chain reaction increased with increasing target amplicon length (192-851 bps). The rate constants for the degradation of pUC19 (2686 bps) were calculated as 0.26 cm²/mJ for UV₂₅₄ and 1.5 × 10¹¹ M^-1s^-1 for ^•OH, based on the degradation rates of amp^R amplicons and assuming an equal sensitivity of DNA damage across the entire plasmid. DNA repair-proficient Escherichia coli (E. coli) AB1157 strain (wild-type) and its repair-deficient mutants including AB1886 (uvrA^-), AB2463 (recA^-), AB2480 (uvrA^-, recA^-), and DH5α (recA^-, endA^-) were applied as recipient cells in gene transformation assays. Results suggested that the elimination efficiency of transforming activity during UV₂₅₄ and ^•OH exposure was dependent on the type of DNA repair genes in recipient E. coli strains. Losses of transforming activity were slower than the degradation of pUC19 by a factor of up to ∼5 (for E. coli DH5α), highlighting the importance of DNA repair in recipient cells. The degradation rates of amp^R amplicons were much larger (by a factor of ∼4) in UV₂₅₄/H₂O₂ and UV₂₅₄/S₂O₈^2- than UV₂₅₄ direct photolysis, indicating the significant contribution of ^•OH and SO₄^•- to the gene degradation. Not only UV₂₅₄ and SO₄^•-, but also ^•OH contributed to the degradation of amp^R during UV₂₅₄/S₂O₈^2-, which was attributed to the conversion of SO₄^•- to ^•OH and a 10-fold larger reactivity of ^•OH towards amp^R as compared to SO₄^•-. However, the enhanced gene degradation by radicals did not lead to a faster elimination of gene transforming activity during UV₂₅₄/H₂O₂ and UV₂₅₄/S₂O₈^2-, suggesting that UV₂₅₄- and radical-induced DNA damage were not additive in their contributions to losses of gene transforming activity. Wastewater effluent organic matter (EfOM) accelerated the degradation of amp^R during UV₂₅₄ irradiation by means of reactive species production through indirect photolysis reactions, whereas EfOM mainly acted as a radical scavenger during UV₂₅₄/H₂O₂ and UV₂₅₄/S₂O₈^2- treatments.

Degradation and Deactivation of Bacterial Antibiotic Resistance Genes during Exposure to Free Chlorine, Monochloramine, Chlorine Dioxide, Ozone, Ultraviolet Light, and Hydroxyl Radical

This work investigated degradation (measured by qPCR) and biological deactivation (measured by culture-based natural transformation) of extra- and intracellular antibiotic resistance genes (eARGs and iARGs) by free available chlorine (FAC), NH₂Cl, O₃, ClO₂, and UV light (254 nm), and of eARGs by ^•OH, using a chromosomal ARG ( blt) of multidrug-resistant Bacillus subtilis 1A189. Rate constants for degradation of four 266-1017 bp amplicons adjacent to or encompassing the acfA mutation enabling blt overexpression increased in proportion to #AT+GC bps/amplicon, or in proportion to #5'-GG-3' or 5'-TT-3' doublets/amplicon, with respective values ranging from 0.59 to 2.3 (×10¹¹ M^-1 s^-1) for ^•OH, 1.8-6.9 (×10⁴ M^-1 s^-1) for O₃, 3.9-9.2 (×10³ M^-1 s^-1) for FAC, 0.35-1.2(×10¹ M^-1 s^-1) for ClO₂, and 2.0-8.8 (×10^-2 cm²/mJ) for UV at pH 7, and from 1.7-4.4 M^-1 s^-1 for NH₂Cl at pH 8. For FAC, NH₂Cl, O₃, ClO₂, and UV, ARG deactivation paralleled degradation of amplicons approximating a ∼800-1000 bp acfA-flanking sequence required for natural transformation in B. subtilis, whereas deactivation outpaced degradation for ^•OH. At practical disinfectant exposures, eARGs and iARGs were ≥90% degraded/deactivated by FAC, O₃, and UV, but recalcitrant to NH₂Cl and ClO₂. iARG degradation/ deactivation always lagged cell inactivation. These findings provide a quantitative framework for evaluating ARG fate during disinfection/oxidation, and support using qPCR as a proxy for tracking ARG deactivation under carefully selected circumstances.

Characterization of disinfection byproduct formation and associated changes to dissolved organic matter during solar photolysis of free available chlorine

Solar irradiation of chlorine-containing waters enhances inactivation of chlorine-resistant pathogens (e.g., Cryptosporidium oocysts), through in situ formation of ozone, hydroxyl radical, and other reactive species during photolysis of free available chlorine (FAC) at UVB-UVA wavelengths of solar light (290-400 nm). However, corresponding effects on regulated disinfection byproduct (DBP) formation and associated dissolved organic matter (DOM) properties remain unclear. In this work, when compared to dark chlorination, sunlight-driven FAC photolysis over a range of conditions was found to yield higher DBP levels, depletion of DOM chromophores and fluorophores, preferential removal of phenolic groups versus carboxylic acid groups, and degradation of larger humic substances to smaller molecular weight compounds. Control experiments showed that increased DBP levels were not due to direct DOM photolysis and subsequent dark reactions with FAC, but to co-exposure of DOM to FAC and reactive species (e.g., O₃, HO^•, Cl^•, Cl₂^•-, ClO^•) generated by FAC photolysis. Because solar chlorine photolysis can enable inactivation of chlorine-resistant pathogens at far lower CT_FAC values than chlorination alone, the increases in DBP formation inherent to this approach can likely be offset to some extent by the ability to operate at significantly decreased CT_FAC. Nonetheless, these findings demonstrate that applications of solar chlorine photolysis will require careful attention to potential impacts on DBP formation.

Sunlight-mediated inactivation of health-relevant microorganisms in water: a review of mechanisms and modeling approaches

Health-relevant microorganisms present in natural surface waters and engineered treatment systems that are exposed to sunlight can be inactivated by a complex set of interacting mechanisms. The net impact of sunlight depends on the solar spectral irradiance, the susceptibility of the specific microorganism to each mechanism, and the water quality; inactivation rates can vary by orders of magnitude depending on the organism and environmental conditions. Natural organic matter (NOM) has a large influence, as it can attenuate radiation and thus decrease inactivation by endogenous mechanisms. Simultaneously NOM sensitizes the formation of reactive intermediates that can damage microorganisms via exogenous mechanisms. To accurately predict inactivation and design engineered systems that enhance solar inactivation, it is necessary to model these processes, although some details are not yet sufficiently well understood. In this critical review, we summarize the photo-physics, -chemistry, and -biology that underpin sunlight-mediated inactivation, as well as the targets of damage and cellular responses to sunlight exposure. Viruses that are not susceptible to exogenous inactivation are only inactivated if UVB wavelengths (280-320 nm) are present, such as in very clear, open waters or in containers that are transparent to UVB. Bacteria are susceptible to slightly longer wavelengths. Some viruses and bacteria (especially Gram-positive) are susceptible to exogenous inactivation, which can be initiated by visible as well as UV wavelengths. We review approaches to model sunlight-mediated inactivation and illustrate how the environmental conditions can dramatically shift the inactivation rate of organisms. The implications of this mechanistic understanding of solar inactivation are discussed for a range of applications, including recreational water quality, natural treatment systems, solar disinfection of drinking water (SODIS), and enhanced inactivation via the use of sensitizers and photocatalysts. Finally, priorities for future research are identified that will further our understanding of the key role that sunlight disinfection plays in natural systems and the potential to enhance this process in engineered systems.

Inactivation efficiency of plasmid-encoded antibiotic resistance genes during water treatment with chlorine, UV, and UV/H2O2

This study assessed the inactivation efficiency of plasmid-encoded antibiotic resistance genes (ARGs) both in extracellular form (e-ARG) and present within Escherichia coli (intracellular form, i-ARG) during water treatment with chlorine, UV (254 nm), and UV/H₂O₂. A quantitative real-time PCR (qPCR) method was used to quantify the ARG damage to amp^R (850 bp) and kan^R (806 bp) amplicons, both of which are located in the pUC4K plasmid. The plate count and flow cytometry methods were also used to determine the bacterial inactivation parameters, such as culturability and membrane damage, respectively. In the first part of the study, the kinetics of E. coli inactivation and ARG damage were determined in phosphate buffered solutions. The ARG damage occurred much more slowly than E. coli inactivation in all cases. To achieve 4-log reduction of ARG concentration at pH 7, the required chlorine exposure and UV fluence were 33-72 (mg × min)/L for chlorine and 50-130 mJ/cm² for UV and UV/H₂O₂. After increasing pH from 7 to 8, the rates of ARG damage decreased for chlorine, while they did not vary for UV and UV/H₂O₂. The i-ARGs mostly showed lower rates of damage compared to the e-ARGs due to the protective roles of cellular components against oxidants and UV. The contribution of OH radicals to i-ARG damage was negligible in UV/H₂O₂ due to significant OH radical scavenging by cellular components. In all cases, the ARG damage rates were similar for amp^R versus kan^R, except for the chlorination of e-ARGs, in which the damage to amp^R occurred faster than that to kan^R. Chlorine and UV dose-dependent ARG inactivation levels determined in a wastewater effluent matrix could be reasonably explained by the kinetic data obtained from the phosphate buffered solutions and the expected oxidant (chlorine and OH radicals) demands by water matrix components. These results can be useful in optimizing chlorine and UV-based disinfection systems to achieve ARG inactivation.

Ferrate(VI) oxidation of β-lactam antibiotics: reaction kinetics, antibacterial activity changes, and transformation products

Oxidation of β-lactam antibiotics by aqueous ferrate(VI) was investigated to determine reaction kinetics, reaction sites, antibacterial activity changes, and transformation products. Apparent second-order rate constants (kapp) were determined in the pH range 6.0-9.5 for the reaction of ferrate(VI) with penicillins (amoxicillin, ampicillin, cloxacillin, and penicillin G), a cephalosporin (cephalexin), and several model compounds. Ferrate(VI) shows an appreciable reactivity toward the selected β-lactams (kapp for pH 7 = 110-770 M(-1) s(-1)). The pH-dependent kapp could be well explained by considering species-specific reactions between ferrate(VI) and the β-lactams (with reactions occurring at thioether, amine, and/or phenol groups). On the basis of the kinetic results, the thioether is the main reaction site for cloxacillin and penicillin G. In addition to the thioether, the amine is a reaction site for ampicillin and cephalexin, and amine and phenol are reaction sites for amoxicillin. HPLC/MS analysis showed that the thioether of β-lactams was transformed to stereoisomeric (R)- and (S)-sulfoxides and then to a sulfone. Quantitative microbiological assay of ferrate(VI)-treated β-lactam solutions indicated that transformation products resulting from the oxidation of cephalexin exhibited diminished, but non-negligible residual activity (i.e., ∼24% as potent as the parent compound). For the other β-lactams, the transformation products showed much lower (<5%) antibacterial potencies compared to the parent compounds. Overall, ferrate(VI) oxidation appears to be effective as a means of lowering the antibacterial activities of β-lactams, although alternative approaches may be necessary to achieve complete elimination of cephalosporin activities.

Sunlight-driven photochemical halogenation of dissolved organic matter in seawater: a natural abiotic source of organobromine and organoiodine

Reactions of dissolved organic matter (DOM) with photochemically generated reactive halogen species (RHS) may represent an important natural source of organohalogens within surface seawaters. However, investigation of such processes has been limited by difficulties in quantifying low dissolved organohalogen concentrations in the presence of background inorganic halides. In this work, sequential solid phase extraction (SPE) and silver-form cation exchange filtration were utilized to desalt and preconcentrate seawater DOM prior to nonspecific organohalogen analysis by ICP-MS. Using this approach, native organobromine and organoiodine contents were found to range from 3.2-6.4 × 10(-4) mol Br/mol C and 1.1-3.8 × 10(-4) mol I/mol C (or 19-160 nmol Br L(-1) and 6-36 nmol I L(-1)) within a wide variety of natural seawater samples, compared with 0.6-1.2 × 10(-4) mol Br/mol C and 0.6-1.1 × 10(-5) mol I/mol C in terrestrial natural organic matter (NOM) isolates. Together with a chemical probe method specific for RHS, the SPE+ICP-MS approach was also employed to demonstrate formation of nanomolar levels of organobromine and organoiodine during simulated and natural solar irradiation of DOM in artificial and natural seawaters. In a typical experiment, the organobromine content of 2.1 × 10(-4) mol C L(-1) (2.5 mg C L(-1)) of Suwannee River NOM in artificial seawater increased by 69% (from 5.9 × 10(-5) to 1.0 × 10(-4) mol Br/mol C) during exposure to 24 h of simulated sunlight. Increasing I(-) concentrations (up to 2.0 × 10(-7) mol L(-1)) promoted increases of up to 460% in organoiodine content (from 8.5 × 10(-6) to 4.8 × 10(-5) mol I/mol C) at the expense of organobromine formation under the same conditions. The results reported herein suggest that sunlight-driven reactions of RHS with DOM may play a significant role in marine bromine and iodine cycling.

Enhanced inactivation of Bacillus subtilis spores during solar photolysis of free available chlorine

Aqueous free available chlorine (FAC) can be photolyzed by sunlight and/or artificial UV light to generate various reactive oxygen species, including HO(•) and O((3)P). The influence of this chemistry on inactivation of chlorine-resistant microorganisms was investigated using Bacillus subtilis endospores as model microbial agents and simulated and natural solar radiation as light sources. Irradiation of FAC solutions markedly enhanced inactivation of B. subtilis spores in 10 mM phosphate buffer; increasing inactivation rate constants by as much as 600%, shortening inactivation curve lag phase by up to 73% and lowering CTs required for 2 log10 inactivation by as much as 71% at pH 8.0 and 10 °C. Similar results were observed at pH 7.4 and 10 °C in two drinking water samples with respective DOC concentrations and alkalinities of 0.6 and 1.2 mg C/L and 81.8 and 17.1 mg/L as CaCO3. Solar radiation alone did not inactivate B. subtilis spores under the conditions investigated. A variety of experimental data indicate that the observed enhancements in spore inactivation can be attributed to the concomitant attack of spores by HO(•) and O3, the latter of which was found to accumulate to micromolar concentrations during simulated solar irradiation of 10 mM phosphate buffer (pH 8, 10 °C) containing [FAC]0 = 8 mg/L as Cl2.

Transformation of beta-lactam antibacterial agents during aqueous ozonation: reaction pathways and quantitative bioassay of biologically-active oxidation products

Reactions of ozone (O3) with the beta-lactam antibiotics penicillin G (PG) and cephalexin (CP) have previously been found to yield products retaining antibacterial activities. These products are unequivocally identified here as the stereoisomeric (R)-sulfoxides of each parent molecule and characterized by a combination of chemical analysis and an antibacterial activity assay. PG-(R)-sulfoxide, which is approximately 15% as potent as PG itself, is formed in approximately 55% yield, whereas CP-(R)-sulfoxide, which is 83% as active as CP, is formed with a maximum 34% yield. PG-(R)-sulfoxide is recalcitrant toward further oxidation by O3, but readily transformed by hydroxyl radical (HO*) (kHO*,app"=7.4x10(9) M(-1) s(-1), pH 7), resulting in quantitative elimination of its antibacterial activity. In contrast, CP-(R)-sulfoxide is degraded by both O3 and HO* (kO3,app"=2.6x10(4) M(-1) s(-1) and kHO*,app"= 7.6x10(9) M(-1) s(-1), pH 7), leading to quantitative elimination of its antibacterial activity. During ozonation of a secondary municipal wastewater effluent sample (pH 8.1, CDOC=4.0 mg/L, [alkalinity]=3.6 mM as HCO3-) spiked with [PG]0=1 microM, PG-(R)-sulfoxide yields did not exceed 0.15 microM for O3 doses up to 100 microM (4.8 mg/L), but reached 0.47 microM with 10-mM t-BuOH added as a HO* scavenger. In contrast, CP-(R)-sulfoxide yields did not exceed 0.1 microM for the same wastewater spiked with [CP]0=1 microM in either the presence or absence of t-BuOH, indicating that CP-(R)-sulfoxide transformation is governed primarily by direct reaction with O3. These findings suggest that, for a given degree of parent compound transformation, PG-(R)-sulfoxide yields would likely be greatest during ozonation of wastewaters characterized by low O3 demands and high HO* scavenging rates, whereas CP-(R)-sulfoxide yields would be less matrix-dependent. In general, complete deactivation of penicillins during wastewater treatment will likely require higher O3 exposures than necessary for deactivation of cephalosporins.

Oxidation of antibacterial compounds by ozone and hydroxyl radical: elimination of biological activity during aqueous ozonation processes

A wide variety of antibacterial compounds is rapidly oxidized by 03 and hydroxyl radical (*OH) during aqueous ozonation. Quantitative microbiological assays have been developed here or adapted from existing methods and utilized to measure the resulting changes in antibacterial potencies during O3 and *OH treatment of 13 antibacterial molecules (roxithromycin, azithromycin, tylosin, ciprofloxacin, enrofloxacin, penicillin G, cephalexin, sulfamethoxazole, trimethoprim, lincomycin,tetracycline, vancomycin, and amikacin) from 9 structural classes (macrolides, fluoroquinolones, beta-lactams, sulfonamides, dihydrofolate reductase inhibitors, lincosamides, tetracyclines, glycopeptides, and aminoglycosides), as well as the biocide triclosan. Potency measurements were determined from dose-response relationships obtained by exposing Escherichia coli or Bacillus subtilis reference strains to treated samples of each antibacterial compound via broth micro- or macrodilution assays and related to the measured residual concentrations of parent antibacterial in each sample. Data obtained from these experiments show that O3 and *OH reactions lead in nearly all cases to stoichiometric elimination of antibacterial activity (i.e., loss of 1 mole equivalent of potency per mole of parent compound consumed). The beta-lactams penicillin G (PG) and cephalexin (CP) represent the only clear exceptions, as bioassay measurements indicate that biologically active products may be formed in the reactions of these two compounds with both O3 and *OH. The active product(s) generated in the direct reaction of O3 with PG appear(s) to be recalcitrant to further transformation by O3, though any biologically active products formed in the reactions of CP with O3, or of either PG or CP with *OH, are apparently deactivated by further reactions with O3 or *OH, respectively. Thus, with few exceptions, it can be expected that municipal wastewater ozonation will generally yield sufficient structural modification of antibacterial molecules to eliminate their antibacterial activities, whether oxidation results from selective reactions with O3 or from relatively nonselective reactions with incidentally produced OH.

Ozonation of source-separated urine for resource recovery and waste minimization: process modeling, reaction chemistry, and operational considerations

Bench-scale, semibatch experiments were performed to examine physical-chemical constraints on ozone (O3) absorption and micropollutant oxidation during ozonation of source-separated hydrolyzed urine and the concentrate and diluate streams produced via electrodialysis of hydrolyzed urine. O3 consumption by each matrix was found to occur within a fast pseudo-first-order kinetic regime. Critical constraints on micropollutant oxidation were found through mass transfer modeling to be (i) micropollutant diffusion from the bulk solution into the gas-liquid interfacial film for compounds recalcitrant toward O3 (i.e., k"O3,app < or = 10(3) M(-1) s(-1)), and (ii) aqueous-phase mixing for compounds highly reactive toward O3 (i.e., k"O3,app > 10(3) M(-1) s(-1)). Homogeneous chemical reaction modeling indicated that aqueous reaction chemistry is significantly influenced bythe degree to which incidentally produced hydroxyl radicals are consumed by NH3 in each matrix, in terms of (a) micropollutant oxidation efficiencies, and (b) potential yields of oxidation byproducts. On the basis of the experimental data reported here, per capita energy requirements were estimated for treatment of source-separated urine via (1) ozonation, (2) ozonation with postelectrodialysis, and (3) electrodialysis with postozonation. These estimates indicate that scenario (1) would likely be less energy efficient than ozonation of municipal wastewater effluent in achieving equivalent reductions in urine-derived micropollutant loads, whereas scenarios (2 and 3) could be more efficient than equivalent centralized wastewater treatment strategies in achieving equivalent levels of urine-derived nutrient and micropollutant attenuation. Furthermore, experimental and model data suggest that urine ozonation efficiency may be substantially improved by optimizing aqueous-phase mixing and specific gas-liquid interfacial area.

Kinetics of triclosan oxidation by aqueous ozone and consequent loss of antibacterial activity: relevance to municipal wastewater ozonation

Oxidation of the antimicrobial agent triclosan by aqueous ozone (O(3)) was investigated to determine associated reaction kinetics, reaction site(s), and consequent changes in antibacterial activity of triclosan. Specific second-order rate constants, k(O(3)), were determined for reaction of O(3) with each of triclosan's acid-base species. The value of k(O(3)) determined for neutral triclosan was 1.3(+/-0.1)x10(3)M(-1)s(-1), while that measured for anionic triclosan was 5.1(+/-0.1)x10(8)M(-1)s(-1). Consequently, triclosan reacts very rapidly with O(3) at circumneutral pH (the pH-dependent, apparent second-order rate constant, K(app,O(3)) , is 3.8x10(7)M(-1)s(-1) at pH 7). The pH-dependence of K(app,O(3)) and comparison of triclosan reactivity toward O(3) with that of other phenolic compounds indicates that O(3) reacts initially with triclosan at the latter's phenol moiety. k(O(3)) values for neutral and anionic triclosan were successfully related to phenol ring substituent effects via Brown-Okamoto correlation with other substituted phenols, consistent with electrophilic attack of the triclosan phenol ring. Biological assay of O(3)-treated triclosan solutions indicates that reaction with O(3) yields efficient elimination of triclosan's antibacterial activity. In order to evaluate the applicability of these observations to actual wastewaters, triclosan oxidation was also investigated during ozonation of effluent samples from two conventional wastewater treatment plants. Nearly 100% triclosan depletion was achieved for a 4 mg/L(8.3x10(-5)mol/L)O(3) dose applied to a wastewater containing 7.5 mg/L of DOC, and approximately 58% triclosan depletion for dosage of 6 mg/L(1.3x10(-4)mol/L)O(3) to a wastewater containing 12.4 mg/L of DOC. At O(3) doses greater than 1mg/L(2.1x10(-5)mol/L), hydroxyl radical reactions accounted for <35% of observed triclosan losses in these wastewaters, indicating that triclosan oxidation was due primarily to the direct triclosan-O(3) reaction. Thus, ozonation appears to present an effective means of eliminating triclosan's antibacterial activity during wastewater treatment.

Aqueous chlorination of the antibacterial agent trimethoprim: reaction kinetics and pathways

Trimethoprim (TMP), one of the antibacterials most frequently detected in municipal wastewaters and surface waters, reacts readily with free available chlorine (i.e., HOCl) at pH values between 3 and 9 (e.g., the pH-dependent apparent second-order rate constant, k''(app)=5.6 x 10(1)M(-1)s(-1), at pH 7). Solution pH significantly affects the rate of TMP reaction with HOCl. The reaction kinetics in reagent water systems can be well described by a second-order kinetic model incorporating speciation of both reactants and accounting for acid-mediated halogenation of TMP's 3,4,5-trimethoxybenzyl moiety. Studies with the substructure model compounds 2,4-diamino-5-methylpyrimidine and 3,4,5-trimethoxytoluene show that TMP reacts with HOCl primarily via its 3,4,5-trimethoxybenzyl moiety at acidic pH, and with its 2,4-diaminopyrimidinyl moiety at circumneutral and alkaline pH. LC/MS product analyses indicate that the TMP structure is not substantially degraded upon reactions with HOCl. Instead, a wide variety of (multi)chlorinated and hydroxylated products are formed. Experiments with real drinking water and wastewater matrixes confirmed that substantial TMP transformation can be expected for conditions typical of wastewater and drinking water chlorination.

Kinetics and mechanistic aspects of As(III) oxidation by aqueous chlorine, chloramines, and ozone: relevance to drinking water treatment

Kinetics and mechanisms of As(III) oxidation by free available chlorine (FAC-the sum of HOCl and OCl-), ozone (O3), and monochloramine (NH2Cl) were investigated in buffered reagent solutions. Each reaction was found to be first order in oxidant and in As(III), with 1:1 stoichiometry. FAC-As(III) and O3-As(III) reactions were extremely fast, with pH-dependent, apparent second-order rate constants, k''app, of 2.6 (+/- 0.1) x 10(5) M(-1) s(-1) and 1.5 (+/- 0.1) x 10(6) M(-1) s(-1) at pH 7, whereas the NH2Cl-As(III) reaction was relatively slow (k''app = 4.3 (+/- 1.7) x 10(-1) M(-1) s(-1) at pH 7). Experiments conducted in real water samples spiked with 50 microg/L As(III) (6.7 x 10(-7) M) showed that a 0.1 mg/L Cl2 (1.4 x 10-6 M) dose as FAC was sufficient to achieve depletion of As(III) to <1 microg/L As(III) within 10 s of oxidant addition to waters containing negligible NH3 concentrations and DOC concentrations <2 mg-C/L. Even in a water containing 1 mg-N/L (7.1 x 10(-5) M) as NH3, >75% As(III) oxidation could be achieved within 10 s of dosing 1-2 mg/L Cl2 (1.4-2.8 x 10(-5) M) as FAC. As(III) residuals remaining in NH3-containing waters 10 s after dosing FAC were slowly oxidized (t1/2 > or = 4 h) in the presence of NH2Cl formed by the FAC-NH3 reaction. Ozonation was sufficient to yield >99% depletion of 50 microg/L As(III) within 10 s of dosing 0.25 mg/L O3 (5.2 x 10(-6) M) to real waters containing <2 mg-C/L of DOC, while 0.8 mg/L O3 (1.7 x 10(-5) M) was sufficientfor a water containing 5.4 mg-C/L of DOC. NH3 had negligible effect on the efficiency of As(III) oxidation by O3, due to the slow kinetics of the O3-NH3 reaction at circumneutral pH. Time-resolved measurements of As(III) loss during chlorination and ozonation of real waters were accurately modeled using the rate constants determined in this investigation.

Oxidation of antibacterial molecules by aqueous ozone: moiety-specific reaction kinetics and application to ozone-based wastewater treatment

Ozone and hydroxyl radical (*OH) reaction kinetics were measured for 14 antibacterial compounds from nine structural families, to determine whether municipal wastewater ozonation is likely to result in selective oxidation of these compounds' biochemically essential moieties. Each substrate is oxidized by ozone with an apparent second-order rate constant, k''(O3,app) > 1 x 10(3) M(-1) s(-1), at pH 7, with the exception of N(4)-acetylsulfamethoxazole (K''(O3,app) is 2.5 x 102 M(-1) s(-1)). k''(O3,app) values (pH 7) for macrolides, sulfamethoxazole, trimethoprim, tetracycline, vancomycin, and amikacin appear to correspond directly to oxidation of biochemically essential moieties. Initial reactions of ozone with N(4)-acetylsulfamethoxazole, fluoroquinolones, lincomycin, and beta-lactams do not lead to appreciable oxidation of biochemically essential moieties. However, ozone oxidizes these moieties within fluoroquinolones and lincomycin via slower reactions. Measured k''(O3,app) values and second-order *OH rate constants, k''(*OH,app) were utilized to characterize pollutant losses during ozonation of secondary municipal wastewater effluent. These losses were dependent on k''(O3,app), but independent of k''(*OH,app). Ozone doses > or =3 mg/L yielded > or =99% depletion of fast-reacting substrates (K''(O3,app) > 5 x 10(4) M(-1) s(-1)) at pH 7.7. Ten substrates reacted predominantly with ozone; only four were oxidized predominantly by .OH. These results indicate that many antibacterial compounds will be oxidized in wastewater via moiety-specific reactions with ozone.

Interactions of fluoroquinolone antibacterial agents with aqueous chlorine: reaction kinetics, mechanisms, and transformation pathways

Kinetics, products, and mechanistic aspects of reactions between free available chlorine (HOCl/OCl-), ciprofloxacin (CF), and enrofloxacin (EF) were extensively investigated to elucidate the behavior of fluoroquinolone antibacterial agents during water chlorination processes. Although the molecular structures of these two substrates differ only with respect to degree of N(4) amine alkylation, CF and EF exhibit markedly different HOCl reaction kinetics and transformation pathways. HOCI reacts very rapidly at CF's secondary N(4) amine, forming a chloramine intermediate that spontaneously decays in aqueous solution by concerted piperazine fragmentation. In contrast, HOCl reacts relatively slowly at EF's tertiary N(4) amine, apparently forming a highly reactive chlorammonium intermediate (R3N-(4)Cl+) that can catalytically halogenate EF or other substrates present in solution. Flumequine, a fluoroquinolone that lacks the characteristic piperazine ring, exhibits no apparent reactivity toward HOCI but appears to undergo facile halodecarboxylation in the presence of R3N(4)-Cl+ species derived from EF. Measured reaction kinetics were validated in real water matrixes by modeling CF and EF losses in the presence of free chlorine residuals. Combined chlorine (CC) kinetics were determined under selected conditions to evaluate the potential significance of reactions with chloramines. CF's rapid kinetics in direct reactions with HOCl, and relatively high reactivity toward CC, indicate that secondary amine-containing fluoroquinolones should be readily transformed during chlorination of real waters, whether applied chlorine doses are present as free or combined residuals. However, EF's slower HOCl reaction kinetics, recalcitrance toward CC, and participation in the catalytic halogenation cycle described herein suggest that tertiary amine-containing fluoroquinolones will be comparatively stable during most full-scale water chlorination processes.

Cochlear implants: 100 pediatric case conversions from the body worn to the nucleus esprit 22 ear level speech processor

OBJECTIVE

To assess performance of Nucleus 22 mini system pediatric users converted from the Spectra 22 body-worn to the ESPrit 22 ear-level speech processor using aided thresholds and speech discrimination measures before and after the conversion.

STUDY DESIGN

Spectra 22 body-worn speech processor users were chosen using preselection criteria (stable map, ability to report on the quality of the signal, no device problems). The subjects underwent tuning, map conversion, fitting of the ESPrit 22, and aided soundfield threshold and speech discrimination testing.

SUBJECTS

The first 100 consecutive conversions are analyzed in this study. Fifty children (50%) were female, and 50 (50%) were male. The average age at implantation was 4.6 years (median 4.3 years, range 1.7 to 11 years). The average age of fitting the ear level speech processor was 11.1 years (median 11 years, range 6.2 to 18.2 years).

SETTING

Tertiary referral pediatric cochlear implant center in the United Kingdom.

RESULTS

Of the 100 fittings attempted, all Spectra 22 maps could to be converted for use in the ESPrit 22. Of these 100 fittings, 44 were straightforward with no adjustment to map parameters being required, and 56 needed rate reductions and other map adjustments to achieve the conversion. The difference of the mean thresholds before and after the conversion did not exceed 2 dB across the frequencies studied (0.5-4 kHz). In 95% of the cases, the differences were less than 9 dB(A). With regard to speech discrimination testing, the mean threshold before the conversion was 53.4 dB and after the conversion 52.7 dB. Of the 100 conversions, only five children stopped using the ESPrit 22 despite fitting being achieved.

CONCLUSION

Conversion from the Spectra 22 body worn to the ESPrit 22 ear level speech processor was found to be feasible in all the 100 cases studied. Only a minority (5%) of children chose not to use the ear level speech processor suggesting that children and parents were satisfied from the conversion.

Transformation of the antibacterial agent sulfamethoxazole in reactions with chlorine: kinetics, mechanisms, and pathways

Sulfamethoxazole (SMX)--a member of the sulfonamide antibacterial class--has been frequently detected in municipal wastewater and surface water bodies in recent years. Kinetics, mechanisms, and products of SMX in reactions with free chlorine (HOCl/OCl-) were studied in detail to evaluate the effect of chlorination processes on the fate of sulfonamides in municipal wastewaters and affected drinking waters. Direct reactions of free available chlorine (FAC) with SMX were quite rapid. A half-life of 23 s was measured under pseudo-first-order conditions ([FAC]0 = 20 microM (1.4 mg/L) and [SMX]0 = 2 microM) at pH 7 and 25 degrees C in buffered reagent water. In contrast, a half-life of 38 h was determined for reactions with combined chlorine (NH2Cl, NHCl2) under similar conditions. Free chlorine reaction rates were first-order in both substrate and oxidant, with specific second-order rate constants of 1.1 x 10(3) and 2.4 x 10(3) M(-1) s(-1) for SMX neutral and anionic species, respectively. Investigations with substructure model compounds and identification of reaction products verified that chlorine directly attacks the SMX aniline-nitrogen, resulting in (i) halogenation of the SMX aniline moiety to yield a ring-chlorinated product at sub-stoichiometric FAC concentrations (i.e., [FAC]0:[SMX]0 < or = 1) or (ii) rupture of the SMX sulfonamide moiety in the presence of stoichiometric excess of FAC to yield 3-amino-5-methylisoxazole, SO4(2-) (via SO2), and N-chloro-p-benzoquinoneimine. Reaction ii represents an unexpected aromatic amine chlorination mechanism that has not previously been evaluated in great detail. Experiments conducted in wastewater and drinking water matrixes appeared to validate measured reaction kinetics for SMX, indicating that SMX and likely other sulfonamide antibacterials should generally undergo substantial transformation during disinfection of such waters with free chlorine residuals.

Immune suppression by cultured lymphocyte supernates of tumor-bearing hosts

A nonspecific immunosuppressive factor produced by lymphocytes of tumor-bearing hosts has been demonstrated. A modified Jerne plaque was used to quantify IgM antibody production of sheep erythrocyte-immune Swiss mouse lymphocytes (IL). Significant suppression of IgM antibody production was found when IL were treated with cultured lymphocyte supernates of 4198 fibrosarcoma-bearing mice. The suppressive activity was found to be significant six days prior to any visible tumor development, and, through the use of glass and nylon wool columns, appears to be produced by T cells. Similar immunosuppressive activity was found in 22 cancer patients tested as above, compared either to 16 patients who previously had had solid tumors but are now without clinical disease or to 19 normal controls.

Release of soluble "blocking" and "suppressor" factors from normal lymphocytes treated with RNA from spleens of tumour-bearing mice

RNA extracted from the spleens of tumour-bearing (TLRNA) and tumour-immune (ILRNA) mice was shown to transfer to normal lymphocytes (NL) the ability to produce factors that blocked specific tumour-cell cytotoxicity and mediated specific antibody-dependent cell cytotoxicity (ADCC). Aliquots of normal C3H mouse lymphocytes were treated with TLRNA or ILRNA and cultured in vitro in the absence of tumour antigen. Supernatants were collected at 24h intervals and tested in a microcytotoxicity assay for blocking and ADCC activities. Factors that inhibited tumour destruction by specifically sensitized lymphocytes at the level of both the tumour cells and effector cells were demonstrable in culture supernatants of NL pretreated with TLRNA (50 or 100 microgram/4 X 10(6) cells) but not ILRNA. However, treatment of NL with either RNA resulted in the production factors that mediated tumour-specific ADCC. Cytotoxicity testing and absorption studies of the tumour cell and a control cell (LM) indicated that factors mediating ADCC and blocking at the target-cell level were specific for the tumour. Suppressor activity at the effector-cell level was not absorbed by tumour cells and represents a separate and distinct mechanism of immunosuppression. These data indicate that RNA faithfully transfers "suppressive" as well as "positive" types of immune responses that have been reported previously for lymphocytes obtained directly from tumour-bearing and tumour-immune animals.

Immunotherapy of a murine sarcoma using specific antitumor immune RNA

The effect of IRNA therapy in a polyoma-induced fibrosarcoma of C3H mice has been studied. Although a protocol that transferred in vitro cytotoxicity was used, no reduction in incidence of tumors, tumor size, or survival was demonstrated. In one experiment, enhancement of tumor growth occurred. It is concluded that cytotoxicity does not reflect in vivo changes and that therapeutic trials of IRNA are premature.

Anti-tumour cytotoxicity of poly(A)-containing messenger RNA isolated from tumour-specific immunogenic RNA

The transfer of tumour-specific cytotoxicity against a murine fibrosar-coma has been demonstrated in vitro using xenogeneic RNA extracted from tumour-cell-immune animals. Poly(A)-tailed messenger RNA from immunogenic RNA was isolated by passage through an oligo(dT)-cellulose column, and evaluated to determine whether the same tumour-specific cytotoxicity could be transferred. Aliquots of normal C3H mouse lymphocytes were treated with poly(A)-containing immune RNA, whole-cell immune RNA lacking poly(A) and total cellular immune RNA. Treated cells were tested in vitro using an adaptation of the Takasugi and Klein microcytotoxicity assay. Percent cytotoxicity was calculted using cells treated with fractions of normal RNA as control. An increase in tumour cytotoxicity was found with poly(A)-containing immune RNA. The optimum dose of poly(A)-tailed immune RNA was estimated as 6.5 microgram of RNA per 4 x 10(6) lymphocytes. Populations of lymphocytes were separated using glass and nylon wool. T- and B-enriched populations were treated with various RNA components. The adherent cell population showed no significant cytotoxicity, whilst treatment of the nonadherent population with poly(A)-tailed immune RNA produced high levels of cytotoxicity.

The effect of Corynebacterium parvum on the humoral and cellular immune systems in patients with breast cancer

Corynebacterium parvum, a Gram-positive anaerobic bacillus thought to be a strong immunological stimulant, has been shown to decrease tumour growth and prolong survival in patients with metastatic disease. Study of the effect of a single injection of a strain of C. parvum (CN. 6134) in six patients with stage IV metastatic breast cancer is reported. Results of laboratory tests to judge the physical and immunological effects of the drug infusion 24 hr post-treatment and weekly thereafter for 3 weeks are evaluated. Within 24 hr after C. parvum administration, most patients experienced fever and nausea. Blood counts and differential counts exhibited increased values 24 hr after treatment with a strong shift to the left. Lymphocyte and monocyte counts were greatly depressed at 24 hr. T-cell numbers in peripheral blood did not appear to be altered, but the picture with regard to B cells was less clear. Normal count was recovered by day 8. It appears that intravenous administration of C. parvum produces a temporary marked immunological depression which returns to essentially normal values in 8 days. The return to normal may be accompanied by resolution of the endotoxin-like syndrome of side-effects. Further study of patients receiving this therapeutic agent is important to detect enhancement of the anti-tumour immunological response precipitated.

Cellular immunity in neoplasia. Antigen and mitogen responses in patients with bronchiogenic carcinoma

Cellular immune responses of patients with histologically confirmed lung carcinoma were assessed in vivo using cutaneous response and in vitro with a microlymphocyte blastogenic transformation (LBT) assay. In addition, correlation of the cutaneous response with the migration inhibitory factor (MIF) assay and LBT response was examined. The results indicated that cutaneous responses seen in patients with cancer of the lung were consistently lower than similar responses in normal controls (p less than 0.001). Similarily, the percentage of positive cutaneous responses seen with patients included in this study was lower than the frequencies reported by others. Stimulation of cells from lung cancer patients by PHA-M was also depressed when compared to similar lymphocytic responses in normal volunteers (p less than 0.001). The correlation between cutaneous response to tuberculin and the in vitro assays was high. The few instances of disparity demonstrate the need to utilize more than one assay in evaluating cellular immune functions. These data would support the work of others that indicate a depression of cellular immunity in advanced malignancy.

Evaluation of dye exclusion and colony inhibition techniques for detection of polyoma-specific, cell-mediated immunity

Cellular immunity directed against polyoma virus-induced antigen was observed with C3H/HeJ splenic lymphoid cells from mice sensitized by a short-term immunization schedule with syngeneic polyoma 4198 and 4198V tumor cells. Polyoma specificity of the response was shown by demonstration that splenic cells from DBA/2J animals with polyoma virus-induced tumors were cytotoxic for the C3H 4198 and 4198V cells, but not for the L-M cell, another cell line of C3H origin. The polyoma-specific response in the syngeneic system was detectable with the dye exclusion assay but not with the colony inhibition procedure. Colony inhibition with the L-M cell was observed with sensitized lymphoid cells in both allogeneic and syngeneic systems.

Gastrin antibodies: induction, demonstration, and specificity

Antibodies to the antral hormone gastrin have been induced in the rabbit and detected by passive hemagglutination. Specificity of the antibody, as determined by three methods, is directed to gastrins I and II, gastrin pentapeptide, and gastrin tetrapeptide, as well as to the stage-1 gastrin used for immunization.