Degradation of parabens by Pseudomonas beteli and Burkholderia latens

Photocatalytic degradation of parabens: A comprehensive meta-analysis investigating the environmental remediation potential of emerging pollutant

The increasing prevalence of paraben compounds in the environment has given rise to concerns regarding their detrimental impacts on both ecosystems and human health. Over the past few decades, photocatalytic reactions have drawn significant attention as a method to accelerate the otherwise slow degradation of these pollutants. The current study aims to evaluate the current efficacy of the photocatalytic method for degrading parabens in aqueous solutions. An extensive literature review and bibliometric analysis were conducted to identify key research trends and influential areas in the field of photocatalytic paraben degradation. Studies were screened based on the predetermined inclusion and exclusion criteria, which led to 13 studies that were identified as being appropriate for the meta-analysis using the random effects model. Furthermore, experimental parameters such as pH, paraben initial concentration, catalyst dosage, light intensity, and contact time have been reported to have key impacts on the performance of the photocatalytic degradation process. A comprehensive quantitative assessment of these parameters was carried out in this work. Overall, photocatalytic techniques could eliminate parabens with an average degradation efficiency of >80 %. The findings of the Egger's test and the Begg's test were statistically not significant suggesting potential publication bias was not observed. This review provides a holistic understanding of the photocatalytic degradation of parabens and is anticipated to encourage more widespread adoption of photocatalytic procedures as a suitable method for the elimination of parabens from aqueous solutions, opening new avenues for future research in this direction.

Methylparaben toxicity and its removal by microalgae Chlorella vulgaris and Phaeodactylum tricornutum

The widespread occurrence of methylparaben (MPB) has aroused great concern due to its weak estrogenic endocrine-disrupting property and potential toxic effects. However, the degradation potential and pathway of MPB by microalgae have rarely been reported. Here, microalgae Chlorella vulgaris and Phaeodactylum tricornutum were used to investigate their responses, degradation potential and mechanisms towards MPB. MPB showed low-dose stimulation (by 86.02 ± 0.07% at 1 mg/L) and high-dose inhibition (by 60.17 ± 0.05% at 80 mg/L) towards the growth of C. vulgaris, while showed inhibition for P. tricornutum (by 6.99 ± 0.05%-20.14 ± 0.19%). The degradation efficiencies and rates of MPB were higher in C. vulgaris (100%, 1.66 ± 0.54-5.60 ± 0.86 day^-1) than in P. tricornutum (4.3-34.2%, 0.04 ± 0.01-0.08 ± 0.00 day^-1), which could be explained by the significantly higher extracellular enzyme activity and more fluctuation of the protein ratio for C. vulgaris, indicating a higher ability of C. vulgaris to adapt to pollutant stress. Biodegradation was the main removal mechanism of MPB for both the two microalgae. Furthermore, two different degradation pathways of MPB by the two microalgae were proposed. MPB could be mineralized and completely detoxified by C. vulgaris. Overall, this study provides novel insights into MPB degradation by microalgae and strategies for simultaneous biodegradation and detoxification of MPB in the environment.

Parabens Increase Sulfamethoxazole-, Tetracycline- and Paraben-Resistant Bacteria and Reshape the Nitrogen/Sulfur Cycle-Associated Microbial Communities in Freshwater River Sediments

Backgrounds Parabens are pollutants of emerging concern in aquatic environments. Extensive studies regarding the occurrences, fates and behavior of parabens in aquatic environments have been reported. However, little is known about the effects of parabens on microbial communities in freshwater river sediments. This study reveals the effects of methylparaben (MP), ethylparaben (EP), propylparaben (PP) and butylparaben (BP) on antimicrobial-resistant microbiomes, nitrogen/sulfur cycle-associated microbial communities and xenobiotic degrading microbial communities in freshwater river sediments. Methods The river water and sediments collected from the Wai-shuangh-si Stream in Taipei City, Taiwan were used to construct a model system in fish tanks to test the effects of parabens in laboratory. Results Tetracycline-, sulfamethoxazole- and paraben-resistant bacteria increased in all paraben treated river sediments. The order of the overall ability to produce an increment in sulfamethoxazole-, tetracycline- and paraben-resistant bacteria was MP > EP > PP > BP. The proportions of microbial communities associated with xenobiotic degradation also increased in all paraben-treated sediments. In contrast, penicillin-resistant bacteria in both the aerobic and anaerobic culture of paraben-treated sediments decreased drastically at the early stage of the experiments. The proportions of four microbial communities associated with the nitrogen cycle (anammox, nitrogen fixation, denitrification and dissimilatory nitrate reduction) and sulfur cycle (thiosulfate oxidation) largely increased after the 11th week in all paraben-treated sediments. Moreover, methanogens and methanotrophic bacteria increased in all paraben-treated sediments. In contrast, the nitrification, assimilatory sulfate reduction and sulfate-sulfur assimilation associated to microbial communities in the sediments were decreased by the parabens. The results of this study uncover the potential effects and consequences of parabens on microbial communities in a freshwater river environment.

Road runoff as a significant nonpoint source of parabens and their metabolites in urban rivers

Parabens are widely added to food, cosmetics, and medicines as preservatives and are typical contaminants of pharmaceuticals and personal care products (PPCPs). However, their fate and transport in urban watersheds remain largely unexplored. This study investigated the role of road runoff as a critical nonpoint source of parabens and their metabolites in urban rivers based on 73 multimedia (road runoff and dust in different urban land uses, wastewater, stormwater discharge and river water) samples collected from a highly urbanized drainage area. Seven parabens and five metabolites were detected in the road runoff, with mean concentrations of ∑parabens and ∑metabolites equal to 47.5 ng/L and 4710 ng/L, respectively. The concentrations in road runoff were comparable to those in treated wastewater and river water and showed a land use pattern of residential > industrial > commercial. A first flush effect of the contaminants was observed in a heavy rainfall event with an antecedent dry period. In general, the population-based and area-based emission intensities of ∑parabens and ∑metabolites in road runoff were one order of magnitude higher than those in wastewater effluent during the rainfall events. This study provides quantitative evidence that road runoff can be a major pollution source of parabens and their metabolites in rapidly growing cities during the wet season and calls for the integrated management of nonpoint sources to prevent urban river contamination by typical PPCPs.

The curious case of methylparaben: Anthropogenic contaminant or natural origin?

The widespread use of methylparaben as a preservative has caused increased exposure to natural aquatic systems in recent decades. However, current studies have suggested that exposure to this compound can result in endocrine disrupting effects, raising much concern regarding its environmental impact. In contast, methylparaben has also been found to be part of the metabolome of some organisms, prompting the question as to whether this compound may be more natural than previously assumed. Through a combination of field studies investigating the natural presence of methylparaben across different taxa, and a 54-day microcosm experiment examining the bioaccumulation and movement of methylparaben across different life stages of aquatic insects (order Trichoptera), our results offer evidence suggesting the natural origin of methylparaben in aquatic and terrestrial biota. This study improves our understanding of the role and impact this compound has on biota and challenges the current paradigm that methylparaben is exclusively a harmful anthropogenic contaminant. Our findings highlight the need for further research on this topic to fully understand the origin and role of parabens in the environment which will allow for a comprehensive understanding of the extent of environmental contamination and result in a representative assessment of the environmental risk that may pose.

Enhanced photocatalytic degradation of paraben preservative over designed g-C3N4/BiVO4 S-scheme system and toxicity assessment

Paraben preservatives have been listed as emerging pollutants due to their ubiquity in various environmental matrices, especially the water bodies. How to efficiently and practically eliminate these paraben pollutants is therefore of great importance. Herein, a designed S-scheme heterojunction photocatalyst, consisting of graphitic carbon nitride (g-C₃N₄) and monoclinic bismuth vanadate (BiVO₄), was fabricated by a facile hydrothermal synthesis and employed to treat benzyl-paraben (BzP). TEM and XPS analysis testified the intimate interaction between g-C₃N₄ and BiVO₄, and the consequently smoothed interfacial charge transfer rendered the feasible recombination of the photoexcited electrons (from BiVO₄) and holes (from g-C₃N₄). The as-established S-scheme system enabled the left g-C₃N₄ electrons and BiVO₄ holes to maintain the high redox abilities and accelerated the charge separation concurrently. In particular, the g-C₃N₄/BiVO₄ composite generated much higher photocurrent response as compared with pure g-C₃N₄ and BiVO₄, highlighting the improved separation of photoinduced charges. Therefore, under visible light and natural solar light irradiation, the g-C₃N₄/BiVO₄ composite showed the significantly enhanced photocatalytic degradation of BzP, which was further optimized with 5 wt% g-C₃N₄ in the composite. According to the Mott-Schottky plots and identified active species, the mechanism of the g-C₃N₄/BiVO₄ S-scheme heterojunction system was illustrated. In addition, during the photocatalytic degradation process, the acute toxicity of the reaction solutions on zebrafish embryos was notably reduced. In conclusion, the demonstrated strategy to enhance the photocatalytic performance by designing S-scheme heterostructure may provide more insights into the development of high-efficiency photocatalyst towards the solar energy utilization and environmental treatment. Furthermore, photocatalytic degradation had been proved to be an efficient method for eliminating the ecological risk of paraben pollutants, warranting more attention in future work.

Synthesis, characterization and cytotoxic activity studies on cancer cell lines of new paraben-decorated monospiro-cyclotriphosphazenes

Cancer is one of the leading causes of death worldwide. In this study, monospiro-cyclotriphosphazene compounds decorated with different parabens that likely show biological activity were designed and successfully synthesized for the first time.

Toxicity and removal of parabens from water: A critical review

Parabens are biocides used as preservatives in food, cosmetics and pharmaceuticals. They possess antibacterial and antifungal activity due to their ability to disrupt cell membrane and intracellular proteins, and cause changes in enzymatic activity of microbial cells. Water, one of our most valuable natural resource, has become a huge reservoir for parabens. Halogenated parabens from chlorination/ozonation of water contaminated with parabens have shown to be even more persistent in water than other types of parabens. Unfortunately, there is dearth of data on their (halogenated parabens) presence and fate in groundwater which serves as a major source of drinking water for a huge population in developing countries. An attempt to neglect the presence of parabens in water will expose man to it through ingestion of contaminated food and water. Although there are reviews on the occurrence, fate and behaviour of parabens in the environment, they largely omit toxicity and removal aspects. This review therefore, presents recent reports on the acute and chronic toxicity of parabens, their estrogenic agonistic and antagonistic activity and also their relationship with antimicrobial resistance. This article further X-rays several techniques that have been employed for the removal of parabens in water and their drawbacks including adsorption, biodegradation, membrane technology and advanced oxidation processes (AOPs). The heterogeneous photocatalytic process (one of the AOPs) appears to be more favoured for removal of parabens due to its ability to mineralize parabens in water. However, more work is needed to improve this ability of heterogeneous photocatalysts. Perspectives that will be relevant for future scientific studies and which will drive policy shift towards the presence of parabens in our drinking waters are also offered. It is hoped that this review will elicit some spontaneous actions from water professionals, scientists and policy makers alike that will provide more data, effective technologies, and adaptive policies that will address the growing threat of the presence of parabens in our environment with respect to human health.

The degradation of paraben preservatives: Recent progress and sustainable approaches toward photocatalysis

Parabens are a class of compounds primarily used as antimicrobial preservatives in pharmaceutical products, cosmetics, and foodstuff. Their widely used field leads to increasing concentrations detected in various environmental matrices like water, soil, and sludges, even detected in human tissue, blood, and milk. Treatment techniques, including chemical advanced oxidation, biological degradation, and physical adsorption processes, have been widely used to complete mineralization or to degrade parabens into less complicated byproducts. All kinds of processes were reviewed to give a completed picture of parabens removal. In light of these treatment techniques, advanced photocatalysis, which is emerging rapidly and widely as an economical, efficient, and environmentally-friendly technique, has received considerable attention. TiO₂-based and non-TiO₂-based photocatalysts play an essential role in parabens degradation. The effect of experimental parameters, such as the concentration of targeted parabens, concentration of photocatalyst, reaction time, and initial solution pH, even the presence of radical scavengers, are surveyed and compared from the literature. Some representative parabens such as methylparaben, propylparaben, and benzylparaben have been successfully studied the reaction pathways and their intermediates in their degradation process. As reported in the literature, the degradation of parabens involves the production of highly reactive species, mainly hydroxyl radicals. These reactive radicals would attack the paraben preservatives, break, and finally mineralize them into simpler inorganic and nontoxic molecules. Concluding perspectives on the challenges and opportunities for photocatalysis toward parabens remediation are also intensively highlighted.

Hydroxyl radical-mediated degradation of salicylic acid and methyl paraben: an experimental and computational approach to assess the reaction mechanisms

Advanced oxidation processes (AOPs) using various energy sources and oxidants to produce reactive oxygen species are widely used for the destruction of recalcitrant water contaminants. The current study is about the degradation of two emerging pollutants-salicylic acid (SA) and methyl paraben (MP)-by high-frequency ultrasonication followed by identification of the oxidation byproducts and modeling of the reaction mechanisms using the density functional theory (DFT). The study also encompasses prediction of the aquatic toxicity and potential risk of the identified byproducts to some aquatic organisms bussing the ECOSAR (Ecological Structure Activity Relationships) protocol. It was found that the degradation of both compounds was governed by •OH attack and the pathways consisted of a cascade of reactions. The rate determining steps were decarboxylation (~ 60 kcal mol^-1) and bond breakage reactions (~ 80 kcal mol^-1), which were triggered by the stability of the reaction byproducts and overcome by the applied reaction conditions. Estimated values of the acute toxicities showed that only few of the byproducts were harmful to aquatic organisms, implying the environmental friendliness of the experimental method.

Biodegradation of methyl and butylparaben by bacterial strains isolated from amended and non-amended agricultural soil. Identification, behavior and enzyme activities of microorganisms

The aim of the present study was to investigate the kinetics of methylparaben (MPB) and butylparaben (BPB) removal, two emerging pollutants with possible endocrine disrupting effects, from agricultural soil with and without amendment with compost from sewage sludge used as biostimulant. Compound removal is explained by a first-order kinetic model with half-life times of 6.5/6.7 days and 11.4/8.2 days, in presence/absence of compost, for MPB and BPB respectively. % R² for the fitted model were higher than 96% in all cases. Additionally, isolation of bacteria capable to grow using MPB or BPB as carbon source was also carry out. Laboratory tests demonstrated the ability of these bacteria to biodegrade MPB and BPB from culture media in more than 95% in some cases. These strains showed high ability to biodegrade the compounds. Ten isolates, most of them related to Gram positive bacteria of the genus Bacillus, were identified by 16S rRNA gene sequencing. The study of the enzymatic activities of the isolates revealed both esterase (C4) and esterase-lipase activities.

Genomic Analysis of Microbulbifer sp. Strain A4B-17 and the Characterization of Its Metabolic Pathways for 4-Hydroxybenzoic Acid Synthesis

The marine bacterium Microbulbifer sp. A4B-17 produces secondary metabolites such as 4-hydroxybenzoic acid (4HBA) and esters of 4HBA (parabens). 4HBA is a useful material in the synthesis of the liquid crystal. Parabens are man-made compounds that have been extensively used since the 1920s in the cosmetic, pharmaceutical, and food industries for their effective antimicrobial activity. In this study, we completed the sequencing and annotation of the A4B-17 strain genome and found all genes for glucose utilization and 4HBA biosynthesis. Strain A4B-17 uses the Embden-Meyerhof-Parnas (EMP), hexose monophosphate (HMP), and Entner-Doudoroff (ED) pathways to utilize glucose. Other sugars such as fructose, sucrose, xylose, arabinose, galactose, mannitol, and glycerol supported cell growth and 4HBA synthesis. Reverse transcriptional analysis confirmed that the key genes involved in the glucose metabolism were functional. Paraben concentrations were proportionally increased by adding alcohols to the culture medium, indicating that strain A4B-17 synthesizes the 4HBA and the alcohols separately and an esterification reaction between them is responsible for the paraben synthesis. A gene that codes for a carboxylesterase was proposed to catalyze this reaction. The temperature and NaCl concentration for optimal growth were determined to be 35°C and 22.8 g/L.

Biodegradation of four selected parabens with aerobic activated sludge and their transesterification product

Parabens are preservatives widely used in foodstuffs, cosmetics and pharmaceuticals, which have led to elevated paraben concentrations in wastewater and receiving waters. Laboratory-scale batch experiments were conducted to investigate the adsorption and degradation of parabens in an aerobic activated sludge system. Results show that biodegradation plays a key role in removing parabens from the aerobic system of wastewater treatment plants, while adsorption on the sludge is not significant. The effects of parent paraben concentration, concentration of mixed liquor suspended solids (MLSS), initial pH and temperature on degradation were investigated using kinetic models. The data shows that the degradation of parabens could be described by the first-order kinetic model with the rate constant ranging from 0.10 to 0.88 h^-1 at 25 °C and pH 7.0. Paraben degradation can be enhanced by increasing the MLSS concentration and temperature, or by decreasing the parent paraben concentration. Furthermore, the pH of the incubation system should be lower than 8.0. The half-lives of the parabens were estimated to range between 0.79 and 6.9 h, with methylparaben exhibiting the slowest degradation rate. During degradation in the present system, transesterification occurred, with methylparaben being the major transformation product in the incubation systems of ethylparaben, propylparaben and butylparaben. These results were confirmed by mass spectrometry and aliphatic alcohol additive experiments. This is the first discovery of paraben transesterification in an activated sludge system, and it is associated with trace methanol in the system.

Transesterification of para-hydroxybenzoic acid esters (parabens) in the activated sludge

Hydrolysis is generally considered as the main pathway for the degradation of ester-type pollutants in aquatic environments. In this study, we found that when methanol or ethanol presented as the external carbon in the activated sludge, transesterification is very important for the degradation of para-hydroxybenzoic acid esters (parabens). In the activated sludge solutions with 1% methanol added, contribution of transesterification to the degradation of the propyl substituted paraben (PrP) and ethyl substituted paraben (EtP) accounted for 46% and 83%, respectively, in the early stage of the reaction. This indicates that in aquatic environments with alcohols presence, parabens prefer to form small molecule homologues than hydrolysis to acid. The predominant transesterification in the activated sludge is related to enzyme preference. Amano lipase from Pseudomonas fluorescens was verified to catalyze hydrolysis and transesterification of parabens, while the latter was dominant in water solution with 1% methanol or ethanol. Considering the common application of small molecular alcohols as the external carbon sources in wastewater treatment plants, transesterification might be an important pathway for the degradation of parabens pollutants in these engineering aquatic environments.

Cosmetics Preservation: A Review on Present Strategies

Cosmetics, like any product containing water and organic/inorganic compounds, require preservation against microbial contamination to guarantee consumer’s safety and to increase their shelf-life. The microbiological safety has as main goal of consumer protection against potentially pathogenic microorganisms, together with the product’s preservation resulting from biological and physicochemical deterioration. This is ensured by chemical, physical, or physicochemical strategies. The most common strategy is based on the application of antimicrobial agents, either by using synthetic or natural compounds, or even multifunctional ingredients. Current validation of a preservation system follow the application of good manufacturing practices (GMPs), the control of the raw material, and the verification of the preservative effect by suitable methodologies, including the challenge test. Among the preservatives described in the positive lists of regulations, there are parabens, isothiasolinone, organic acids, formaldehyde releasers, triclosan, and chlorhexidine. These chemical agents have different mechanisms of antimicrobial action, depending on their chemical structure and functional group’s reactivity. Preservatives act on several cell targets; however, they might present toxic effects to the consumer. Indeed, their use at high concentrations is more effective from the preservation viewpoint being, however, toxic for the consumer, whereas at low concentrations microbial resistance can develop.

Identification and characterization of Burkholderia multivorans CCA53

Objective

A lignin-degrading bacterium, Burkholderia sp. CCA53, was previously isolated from leaf soil. The purpose of this study was to determine phenotypic and biochemical features of Burkholderia sp. CCA53.

Results

Multilocus sequence typing (MLST) analysis based on fragments of the atpD, gltD, gyrB, lepA, recA and trpB gene sequences was performed to identify Burkholderia sp. CCA53. The MLST analysis revealed that Burkholderia sp. CCA53 was tightly clustered with B. multivorans ATCC BAA-247^T. The quinone and cellular fatty acid profiles, carbon source utilization, growth temperature and pH were consistent with the characteristics of B. multivorans species. Burkholderia sp. CCA53 was therefore identified as B. multivorans CCA53.

Co-metabolic enhancement of organic removal from waste water in the presence of high levels of alkyl paraben constituents of cosmetic and personal care products

The enhanced removal of organic material from municipal waste water containing 50 mg/L of chemical oxygen demand and a given amount of alkyl paraben using a biofilm system was investigated. The parabens used were methyl, ethyl, and propyl paraben. The experiments were conducted at influent paraben concentrations of 10 and 50 mg/L. The influent pH was measured around 4.6 because of paraben hydrolysis. The effluent pH increased due to hydrogen consumption and small molecular acid generation. The higher removal rates were observed for the paraben with longer alkyl chains, which were more hydrophobic and capable of penetrating into microbial cells. The co-existing organic constituents in municipal waste water were found to be competitive with paraben molecules for microbial degradation at low paraben loading (i.e., 10 mg/L). Instead, the co-metabolic effect was observed at a higher paraben loading (i.e., 50 mg/L) due to more active enzymatic catalysis, implying the possible enhancement or organic removal in the presence of high levels of parabens. The difference in BOD and TOC removing ratios for parabens decreased with increasing HRT, implying their better mineralization than that of municipal organic constituents. This was because the microbial organism became more adapted to the reacting system with longer HRT, and more oxygenase was produced to facilitate the catechol formation and ring-opening reactions, causing apparent enhancement in mineralization.

Comparative studies of aerobic and anaerobic biodegradation of methylparaben and propylparaben in activated sludge

The biodegradability of two typical parabens (methylparaben and propylparaben) in activated sludge, at initial concentrations of 1mgL^-1 or 10mgL^-1, was investigated under aerobic and anaerobic conditions. The results showed that microorganisms played a key role in degradation of parabens in WWTPs, especially in aerobic systems. The half-lives of methylparaben and propylparaben under aerobic conditions have been estimated to range between 15.8 and 19.8min, and benzoic acid was found to be one of the major biodegradation products. The calculated biodegradation efficiency of methylparaben and propylparaben in activated sludge under aerobic conditions was significantly higher than that observed under anaerobic (nitrate, sulfate, and Fe (III) reducing) conditions, as methylparaben and propylparaben exhibited comparatively higher persistence in anaerobic systems, with half-lives ≥43.3h and ≥8.6h, respectively. Overall, the results of this study imply that the majority of these parabens can be eliminated by aerobic biodegradation during conventional wastewater treatment processes, whereas minor removal is possible in anaerobic systems if an insufficient hydraulic retention time was maintained.

Intrinsic, adaptive and acquired antimicrobial resistance in Gram-negative bacteria

Gram-negative bacteria are responsible for a large proportion of antimicrobial-resistant infections in humans and animals. Among this class of bacteria are also some of the most successful environmental organisms. Part of this success is their adaptability to a variety of different niches, their intrinsic resistance to antimicrobial drugs and their ability to rapidly acquire resistance mechanisms. These mechanisms of resistance are not exclusive and the interplay of several mechanisms causes high levels of resistance. In this review, we explore the molecular mechanisms underlying resistance in Gram-negative organisms and how these different mechanisms enable them to survive many different stress conditions.

Isolation and characterization of Burkholderia sp. strain CCA53 exhibiting ligninolytic potential

Microbial degradation of lignin releases fermentable sugars, effective utilization of which could support biofuel production from lignocellulosic biomass. In the present study, a lignin-degrading bacterium was isolated from leaf soil and identified as Burkholderia sp. based on 16S rRNA gene sequencing. This strain was named CCA53, and its lignin-degrading capability was assessed by observing its growth on medium containing alkali lignin or lignin-associated aromatic monomers as the sole carbon source. Alkali lignin and at least eight lignin-associated aromatic monomers supported growth of this strain, and the most effective utilization was observed for p-hydroxybenzene monomers. These findings indicate that Burkholderia sp. strain CCA53 has fragmentary activity for lignin degradation.

One-pot synthesis of micro/nano structured β-Bi2O3 with tunable morphology for highly efficient photocatalytic degradation of methylparaben under visible-light irradiation

Micro/nanostructures β-Bi₂O₃ with tunable morphologies were synthesized via an one-pot solvothermal–calcining route for efficient visible-light photocatalytic removal of methylparaben from water.

Occurrence, fate and behavior of parabens in aquatic environments: a review

Parabens are esters of para-hydroxybenzoic acid, with an alkyl (methyl, ethyl, propyl, butyl or heptyl) or benzyl group. They are mainly used as preservatives in foodstuffs, cosmetics and pharmaceutical drugs. Parabens may act as weak endocrine disrupter chemicals, but controversy still surrounds the health effects of these compounds. Despite being used since the mid-1920s, it was only in 1996 that the first analytical results of their occurrence in water were published. Considered as emerging contaminants, it is useful to review the knowledge acquired over the last decade regarding their occurrence, fate and behavior in aquatic environments. Despite treatments that eliminate them relatively well from wastewater, parabens are always present at low concentration levels in effluents of wastewater treatment plants. Although they are biodegradable, they are ubiquitous in surface water and sediments, due to consumption of paraben-based products and continuous introduction into the environment. Methylparaben and propylparaben predominate, reflecting the composition of paraben mixtures in common consumer products. Being compounds containing phenolic hydroxyl groups, parabens can react readily with free chlorine, yielding halogenated by-products. Chlorinated parabens have been detected in wastewater, swimming pools and rivers, but not yet in drinking water. These chlorinated by-products are more stable and persistent than the parent species and further studies are needed to improve knowledge regarding their toxicity.

Investigation of current infection-control practices for ultrasound coupling gel: a survey, microbiological analysis, and examination of practice patterns

BACKGROUND AND OBJECTIVES

Ultrasound coupling gel may serve as a vector for the spread of bacteria and has been the causative agent for significant health care-associated infections. The purpose of this study was to document existing infection-control procedures and level of contamination present within nonsterile ultrasound gel from several clinical departments at a single institution. A second purpose was to examine the effectiveness of clinician education and manufacturer-based ultrasound additives on ultrasound gel contamination and in vitro bacterial proliferation, respectively.

METHODS

Compliance with Health Canada recommended infection-control policies were determined by survey. Contamination of in-use ultrasound gel bottles was determined by inspecting cultures after 72 hours of incubation. After infection-control education, a 28-day interval assessment was used to examine contamination rates in newly provided ultrasound gel. The ability of ultrasound gel containing parabens to prevent bacterial growth was examined in cultures grown with and without ultrasound gel.

RESULTS

Practitioners were not compliant with Health Canada recommendations, but the baseline ultrasound gel contamination rate within these departments was only 2.5%. Education in infection control did not improve the contamination rate over 28 days. Contamination was discovered in ultrasound gel supplied directly from the manufacturer. Ultrasound gel suppressed but did not prevent bacterial growth in a species- and time-specific manner.

CONCLUSIONS

The source of contamination for in-use ultrasound gel may be of manufacturer or human origin. Because additives to the ultrasound gel are not bactericidal, sterile ultrasound gel should be used for invasive and high-risk cases, and improving infection-control policies is warranted.