Two-year evaluation of Legionella in an aging residential building: Assessment of multiple potable water remediation approaches.

Legionella is an opportunistic waterborne pathogen that is difficult to eradicate in colonized drinking water pipes. Legionella control is further challenged by aging water infrastructure and lack of evidence-based guidance for building treatment. This study assessed multiple premise water remediation approaches designed to reduce Legionella pneumophila within a residential building located in an aging, urban drinking water system over a two-year period. Samples (n = 745) were collected from hot and cold-water lines and quantified via most probable number culture. Building-level treatment approaches included three single heat shocks, three single chemical shocks, and continuous low-level chemical disinfection in the potable water system. The building was highly colonized with L. pneumophila with 71 % L. pneumophila positivity. Single heat shocks had a statistically significant L. pneumophila reduction one day post treatment but no significant L. pneumophila reduction at one week, two weeks, and four weeks post treatment. The first two chemical shocks resulted in statistically significant L. pneumophila reduction at two days and four weeks post treatment, but there was a significant L. pneumophila increase at four weeks following the third chemical shock. Continuous low-level chemical disinfection resulted in statistically significant L. pneumophila reduction at ten weeks post treatment implementation. This demonstrates that in a building highly colonized with L. pneumophila, sustained remediation is best achieved using continuous low-level chemical treatment.

Two-Year Evaluation of Legionella in an Aging Residential Building: Assessment of Multiple Potable Water Remediation Approaches.

Legionella is an opportunistic waterborne pathogen that is difficult to eradicate in colonized drinking water pipes. Legionella control is further challenged by aging water infrastructure and lack of evidence-based guidance for building treatment. This study assessed multiple premise water remediation approaches designed to reduce Legionella pneumophila (Lp) within a residential building located in an aging, urban drinking water system over a two-year period. Samples (n=745) were collected from hot and cold-water lines and quantified via most probable number culture. Building-level treatment approaches included three single heat shocks (HS), three single chemical shocks (CS), and continuous low-level chemical disinfection (CCD) in the potable water system. The building was highly colonized with Lp with 71% Lp positivity. Single HS had a statistically significant Lp reduction one day post treatment but no significant Lp reduction one, two, and four weeks post treatment. The first two CS resulted in statistically significant Lp reduction at two days and four weeks post treatment, but there was a significant Lp increase at four weeks following the third CS. CCD resulted in statistically significant Lp reduction ten weeks post treatment implementation. This demonstrates that in a building highly colonized with Lp, sustained remediation is best achieved using CCD.

Comparative investigation of PFAS adsorption onto activated carbon and anion exchange resins during long-term operation of a pilot treatment plant.

Widespread contamination of groundwater with per- and polyfluoroalkyl substances (PFAS) has required drinking water producers to quickly adopt practical and efficacious treatments to limit human exposure and deleterious health outcomes. This pilot-scale study comparatively investigated PFAS adsorption behaviors in granular activated carbon (GAC) and two strong-base gel anion exchange resin (AER) columns operated in parallel over a 441-day period to treat contaminated groundwater dominated by short-chain perfluorocarboxylic acids (PFCA). Highly-resolved breakthrough profiles of homologous series of 2-8 CF2 PFCA and perfluorosulfonic acids (PFSA), including ultrashort-chain compounds and branched isomers, were measured to elucidate adsorption trends. Sample ports at intermediate bed depths could predict 50% breakthrough of compounds on an accelerated basis, but lower empty bed contact times led to conservative estimates of initial breakthrough. Homologous PFAS series displayed linear (GAC) and log-linear (AER) relationships between chain-length and breakthrough, independent of initial concentration. AERs generally outperformed GAC on a normalized bed volume basis, and this advantage widened with increasing PFAS chain-length. As designed, all treatments would have short full-scale service times (≤142 days for GAC; ≤61 days for AERs) before initial breakthrough of short-chain (2-4 CF2) PFCA. However, AER displayed far longer breakthrough times for PFSA compared to GAC (>3× treatment time), and breakthrough was not observed for PFSA with >4 CF2 in AERs. GAC had a finite molar adsorption capacity for total PFAS, leading to a stoichiometric replacement of short-chain PFCA by PFSA and longer-chain PFCA over time. AERs quickly reached a finite adsorption capacity for PFCA, but they showed substantially greater selectivity for PFSA whose capacity was not reached within the duration of the pilot. Breakthrough characteristics of keto- and unsaturated-PFSA, identified in the groundwater by suspect screening, were also evaluated in absence of reference standards. Modified PFAS structures (branched, keto-, unsaturated-) broke through faster than linear and unmodified perfluorinated structures with equal degrees of fluorination, and the effects were more pronounced in GAC compared to AERs. The results highlight that the design of robust PFAS treatment systems should consider facets beyond current PFAS targets including operational complexities and impacts of unregulated and unmonitored co-contaminants.

Orang Asli Health and Lifeways Project (OA HeLP): a cross-sectional cohort study protocol.

INTRODUCTION: Non-communicable disease (NCD) risk is influenced by environmental factors that are highly variable worldwide, yet prior research has focused mainly on high-income countries where most people are exposed to relatively homogeneous and static environments. Understanding the scope and complexity of environmental influences on NCD risk around the globe requires more data from people living in diverse and changing environments. Our project will investigate the prevalence and environmental causes of NCDs among the indigenous peoples of Peninsular Malaysia, known collectively as the Orang Asli, who are currently undergoing varying degrees of lifestyle and sociocultural changes that are predicted to increase vulnerability to NCDs, particularly metabolic disorders and musculoskeletal degenerative diseases. METHODS AND ANALYSIS: Biospecimen sampling and screening for a suite of NCDs (eg, cardiovascular disease, type II diabetes, osteoarthritis and osteoporosis), combined with detailed ethnographic work to assess key lifestyle and sociocultural variables (eg, diet, physical activity and wealth), will take place in Orang Asli communities spanning a gradient from remote, traditional villages to acculturated, market-integrated urban areas. Analyses will first test for relationships between environmental variables, NCD risk factors and NCD occurrence to investigate how environmental changes are affecting NCD susceptibility among the Orang Asli. Second, we will examine potential molecular and physiological mechanisms (eg, epigenetics and systemic inflammation) that mediate environmental effects on health. Third, we will identify intrinsic (eg, age and sex) and extrinsic (eg, early-life experiences) factors that predispose certain people to NCDs in the face of environmental change to better understand which Orang Asli are at greatest risk of NCDs. ETHICS AND DISSEMINATION: Approval was obtained from multiple ethical review boards including the Malaysian Ministry of Health. This study follows established principles for ethical biomedical research among vulnerable indigenous communities, including fostering collaboration, building cultural competency, enhancing transparency, supporting capacity building and disseminating research findings.

Adaptation of selected models for describing competitive per- and polyfluoroalkyl substances breakthrough curves in groundwater treated by granular activated carbon.

Granular activated carbon (GAC) has proven to be a successful technology for per- and polyfluoroalkyl substances (PFAS) removal from contaminated drinking water supplies. Proper design of GAC treatment relies upon characterization of media service-life, which can change significantly depending on the PFAS contamination, treatment media, and water quality, and is often determined by fitting descriptive models to breakthrough curves. However, while common descriptive breakthrough models are favored for their ease-of-use, they have a significant shortcoming in that they are not able to properly fit PFAS desorption in competitive sorption scenarios. The present work adapts three common descriptive models to fit competitive PFAS breakthrough curves from a GAC pilot study. The adapted and original models were fit to the experimental breakthrough curves for 12 common PFAS and evaluated using adjusted R2 and reduced χ2 values. This study found that the novel adaptation of the common descriptive models successfully accounted for desorption of PFAS compounds from the GAC, accurately describing increased exposure risks due to elevated effluent levels during desorption without significantly increasing the complexity of implementing the models.

Guideline for the diagnosis, treatment and long-term management of cutaneous lupus erythematosus.

Cutaneous lupus erythematosus (CLE) is an inflammatory, autoimmune disease encompassing a broad spectrum of subtypes including acute, subacute, chronic and intermittent CLE. Among these, chronic CLE can be further classified into several subclasses of lupus erythematosus (LE) such as discoid LE, verrucous LE, LE profundus, chilblain LE and Blaschko linear LE. To provide all dermatologists and rheumatologists with a practical guideline for the diagnosis, treatment and long-term management of CLE, this evidence- and consensus-based guideline was developed following the checklist established by the international Reporting Items for Practice Guidelines in Healthcare (RIGHT) Working Group and was registered at the International Practice Guideline Registry Platform. With the joint efforts of the Asian Dermatological Association (ADA), the Asian Academy of Dermatology and Venereology (AADV) and the Lupus Erythematosus Research Center of Chinese Society of Dermatology (CSD), a total of 25 dermatologists, 7 rheumatologists, one research scientist on lupus and 2 methodologists, from 16 countries/regions in Asia, America and Europe, participated in the development of this guideline. All recommendations were agreed on by at least 80% of the 32 voting physicians. As a consensus, diagnosis of CLE is mainly based on the evaluation of clinical and histopathological manifestations, with an exclusion of SLE by assessment of systemic involvement. For localized CLE lesions, topical corticosteroids and topical calcineurin inhibitors are first-line treatment. For widespread or severe CLE lesions and (or) cases resistant to topical treatment, systemic treatment including antimalarials and (or) short-term corticosteroids can be added. Notably, antimalarials are the first-line systemic treatment for all types of CLE, and can also be used in pregnant patients and pediatric patients. Second-line choices include thalidomide, retinoids, dapsone and MTX, whereas MMF is third-line treatment. Finally, pulsed-dye laser or surgery can be added as fourth-line treatment for localized, refractory lesions of CCLE in cosmetically unacceptable areas, whereas belimumab may be used as fourth-line treatment for widespread CLE lesions in patients with active SLE, or recurrence of ACLE during tapering of corticosteroids. As for management of the disease, patient education and a long-term follow-up are necessary. Disease activity, damage of skin and other organs, quality of life, comorbidities and possible adverse events are suggested to be assessed in every follow-up visit, when appropriate.

Detection of ultrashort-chain and other per- and polyfluoroalkyl substances (PFAS) in U.S. bottled water.

Per- and polyfluoroalkyl substances (PFAS) are compounds of emerging concern due to their persistence in the global water cycle and detection in drinking water sources. However, PFAS have been poorly studied in bottled water, especially in the United States. This study investigated the occurrence of PFAS and related factors in 101 uniquely labelled bottled water products for sale in the U.S. Products were screened for 32 target PFAS by solid phase extraction-liquid chromatography-tandem mass spectrometry (SPE-LC-MS/MS). Fifteen of 32 measured analytes were detected, consisting primarily of C3-C10 perfluorocarboxylic acids (PFCA) and C3-C6 and C8 perfluorosulfonic acids (PFSA). PFAS were detected above method detection limits in 39/101 tested products. The Σ32PFAS concentrations detected were 0.17-18.87 ng/L with a median of 0.98 ng/L; 97% of samples were below 5 ng/L. PFCA (83%) and short-chain perfluoroalkyl acids (PFAA) containing 5 or less CF2 groups (67%) were more prevalent on a mass basis than PFSA and longer-chain PFAA, respectively. Ultrashort-chain PFPrA, measured for the first time in bottled water, accounted for the greatest individual fraction of detected PFAS mass (42%) and was found almost exclusively in products labeled as Spring water. Purified water products contained significantly less PFAS than Spring water products, which was attributed to the use of reverse osmosis (RO) treatment in the majority of Purified waters (25/35) compared to Spring waters (1/45). RO-treated products contained significantly lower Σ32PFAS, long-chain, short-chain, and PFPrA concentrations than products without RO. Although no enforceable PFAS regulations exist for bottled water in the U.S., the finding that some products approach levels of concern justify a framework for monitoring PFAS in bottled water production.

Sequential biodegradation of 1,2,4-trichlorobenzene at oxic-anoxic groundwater interfaces in model laboratory columns.

Halogenated organic solvents such as chlorobenzenes (CBs) are frequent groundwater contaminants due to legacy spills. When contaminated anaerobic groundwater discharges into surface water through wetlands and other transition zones, aeration can occur from various physical and biological processes at shallow depths, resulting in oxic-anoxic interfaces (OAIs). This study investigated the potential for 1,2,4-trichlorobenzene (1,2,4-TCB) biodegradation at OAIs. A novel upflow column system was developed to create stable anaerobic and aerobic zones, simulating a natural groundwater OAI. Two columns containing (1) sand and (2) a mixture of wetland sediment and sand were operated continuously for 295 days with varied doses of 0.14-1.4 mM sodium lactate (NaLac) as a model electron donor. Both column matrices supported anaerobic reductive dechlorination and aerobic degradation of 1,2,4-TCB spatially separated between anaerobic and aerobic zones. Reductive dechlorination produced a mixture of di- and monochlorobenzene daughter products, with estimated zero-order dechlorination rates up to 31.3 µM/h. Aerobic CB degradation, limited by available dissolved oxygen, occurred for 1,2,4-TCB and all dechlorinated daughter products. Initial reductive dechlorination did not enhance the overall observed extent or rate of subsequent aerobic CB degradation. Increasing NaLac dose increased the extent of reductive dechlorination, but suppressed aerobic CB degradation at 1.4 mM NaLac due to increased oxygen demand. 16S-rRNA sequencing of biofilm microbial communities revealed strong stratification of functional anaerobic and aerobic organisms between redox zones including the sole putative reductive dechlorinator detected in the columns, Dehalobacter. The sediment mixture column supported enhanced reductive dechlorination compared to the sand column at all tested NaLac doses and growth of Dehalobacter populations up to 4.1 × 108 copies/g (51% relative abundance), highlighting the potential benefit of sediments in reductive dechlorination processes. Results from these model systems suggest both substantial anaerobic and aerobic CB degradation can co-occur along the OAI at contaminated sites where bioavailable electron donors and oxygen are both present.

A clinician's reference guide for the management of atopic dermatitis in Asians.

BACKGROUND: Atopic dermatitis (AD) is a common skin condition among Asians. Recent studies have shown that Asian AD has a unique clinical and immunologic phenotype compared with European/American AD. OBJECTIVE: The Asian Academy of Dermatology and Venereology Expert Panel on Atopic Dermatitis developed this reference guide to provide a holistic and evidence-based approach in managing AD among Asians. METHODS: Electronic searches were performed to retrieve relevant systematic reviews and guidelines on AD. Recommendations were appraised for level of evidence and strength of recommendation based on the U.K. National Institute for Health and Care Excellence and Scottish Intercollegiate Guidelines Network guidelines. These practice points were based on the consensus recommendations discussed during the Asia Pacific Meeting of Experts in Dermatology held in Bali, Indonesia in October 2016 and April 2017. RESULTS: The Expert Panel recommends an approach to treatment based on disease severity. The use of moisturizers is recommended across all levels of AD severity, while topical steroids are recommended only for flares not controlled by conventional skin care and moisturizers. Causes of waning efficacy must be explored before using topical corticosteroids of higher potency. Topical calcineurin inhibitors are recommended for patients who have become recalcitrant to steroid, in chronic uninterrupted use, and when there is steroid atrophy, or when there is a need to treat sensitive areas and pediatric patients. Systemic steroids have a limited role in AD treatment and should be avoided if possible. Educational programs that allow a patient-centered approach in AD management are recommended as an adjunct to conventional therapies. Recommendations on the use of phototherapy, systemic drugs, and emerging treatments are also included. CONCLUSION: The management of AD among Asians requires a holistic approach, integrating evidence-based treatments while considering accessibility and cultural acceptability.

Synergistic co-digestion of wastewater grown algae-bacteria polyculture biomass and cellulose to optimize carbon-to-nitrogen ratio and application of kinetic models to predict anaerobic digestion energy balance.

This study investigated enhancing methane production from algal-bacteria biomass by adjusting the C/N ratio through co-digestion with a nitrogen-poor co-substrate - cellulose. A biomethane potential test was used to determine cumulative biogas and methane production for pure and co-digested substrates. Four kinetic models were evaluated for their accuracy describing experimental data. These models were used to estimate the total energy output and net energy ratio (NER) for a scaled AD system. Increasing the algal C/N ratio from 5.7 to 20-30 (optimal algae:cellulose feedstock ratios of 35%:65% and 20%:80%) improved the ultimate methane yield by >10% and the first ten days production by >100%. The modified Gompertz kinetic model demonstrated highest accuracy, predicting that co-digestion improved methane production by reducing the time-lag by ∼50% and increasing rate by ∼35%. The synergistic effects increase the AD system energy efficiency and NER by 30-45%, suggesting potential for substantial enhancements from co-digestion at scale.

Engineering of a miniaturized, robotic clinical laboratory.

The ability to perform laboratory testing near the patient and with smaller blood volumes would benefit patients and physicians alike. We describe our design of a miniaturized clinical laboratory system with three components: a hardware platform (ie, the miniLab) that performs preanalytical and analytical processing steps using miniaturized sample manipulation and detection modules, an assay-configurable cartridge that provides consumable materials and assay reagents, and a server that communicates bidirectionally with the miniLab to manage assay-specific protocols and analyze, store, and report results (i.e., the virtual analyzer). The miniLab can detect analytes in blood using multiple methods, including molecular diagnostics, immunoassays, clinical chemistry, and hematology. Analytical performance results show that our qualitative Zika virus assay has a limit of detection of 55 genomic copies/ml. For our anti-herpes simplex virus type 2 immunoglobulin G, lipid panel, and lymphocyte subset panel assays, the miniLab has low imprecision, and method comparison results agree well with those from the United States Food and Drug Administration-cleared devices. With its small footprint and versatility, the miniLab has the potential to provide testing of a range of analytes in decentralized locations.

Practical management of acne for clinicians: An international consensus from the Global Alliance to Improve Outcomes in Acne.

Scientific advances are continually improving the knowledge of acne and contributing to the refinement of treatment options; it is important for clinicians to regularly update their practice patterns to reflect current standards. The Global Alliance to Improve Outcomes in Acne is an international group of dermatologists with an interest in acne research and education that has been meeting regularly since 2001. As a group, we have continuously evaluated the literature on acne. This supplement focuses on providing relevant clinical guidance to health care practitioners managing patients with acne, with an emphasis on areas where the evidence base may be sparse or need interpretation for daily practice.

Phytoremediation of agriculture runoff by filamentous algae poly-culture for biomethane production, and nutrient recovery for secondary cultivation of lipid generating microalgae.

An integrated system was implemented for water phytoremediation and biofuel production through sequential cultivation of filamentous algae followed by cultivation of lipid-producing microalgae Chlorella sorokiniana. Natural poly-culture of filamentous algae was grown in agricultural stormwater using the Algal Turf Scrubber®, harvested and subjected for lipid extraction and/or methane production using anaerobic digestion (AD). While filamentous algae lipid content was too low for feasible biodiesel production (<2%), both whole biomass and lipid-extracted algal residues (LEA) yielded ∼0.2LmethanepergVS at loading rates up to 5gVS/L-day. Importantly, essential macro-nutrients and trace elements captured from stormwater were released into the AD effluent as soluble nutrients and were successfully tested as fertilizer replacement for cultivation of lipid-accumulating C. sorokiniana in a subsequent stage. Accordingly, filamentous algae poly-culture was exploited for waste nutrient capturing and biofuel feedstock generation. These nutrients were recovered and reused as a concentrated supplement for potentially high-value microalgae.

Role of bilastine in the management of allergic rhinitis and urticaria: an Asia-Pacific consensus statement.

The prevalence of allergic diseases is increasing globally, most particularly in middle- to low-income countries. This article examines the burden of allergic rhinitis and chronic urticaria in the Asia-Pacific region, unmet clinical needs, and the potential role of bilastine in the management of these conditions. An International Advisory Group meeting was convened in association with the Asian Pacific Society of Respirology Annual Congress in November 2014, followed by a literature review, and consensus-based outcomes from the meeting and literature review are described. Regional estimates of the prevalence of allergic rhinitis range from 10% to 50%, while little is known regarding the burden of urticaria in the Asia-Pacific region. A survey of allergy patients in the region identified fast, complete, and long-lasting symptom relief as the medication attributes most important to patients. International treatment guidelines for allergic rhinitis and urticaria advocate the first-line use of second-generation, no-sedating H1-antihistamines, such as bilastine, over their first-generation counterparts and a range of these agents are available to Asia-Pacific patients. The newer agents possess many of the properties of an "ideal" antihistamine (once daily administration, rapid and complete symptom relief, limited potential for drug-drug interactions, minimal side effects). The burgeoning prevalence of allergic diseases in the Asia-Pacific region and the uncontrolled symptoms that these patients experience demand a new antihistamine that offers the highest number of positive features according to the international guidelines.

Frequency and characteristics of acne-related post-inflammatory hyperpigmentation.

In patients with darker skin types (Fitzpatrick phototypes III-VI), acne is often accompanied by post-inflammatory hyperpigmentation (PIH). Further, acne-related pigmentation can pose a greater concern for the patient than the acne lesions. There has been little formal study of this acne-related PIH. Recently, the Asian Acne Board - an international group of dermatologists with interest in acne research - made a preliminary evaluation of the frequency and characteristics of PIH in seven Asian countries. A total of 324 sequential acne subjects were evaluated for the presence of PIH. The majority (80.2%) of subjects had mild to moderate acne and there were more females than males (63.0% vs 37.0%). In this population of patients consulting a dermatologist for acne, 58.2% (188/324) had PIH. The results also showed that pigmentation problems are often long lasting: at least 1 year for more than half of subjects and 5 years or longer in 22.3%. In accordance with our clinical experience, patients reported that PIH is quite bothersome, often as bothersome or more so than the acne itself and sometimes more problematic. Excoriation was commonly reported by patients, and may represent a modifiable risk factor that could potentially be improved by patient education.

DCE-MRI for Pre-Treatment Prediction and Post-Treatment Assessment of Treatment Response in Sites of Squamous Cell Carcinoma in the Head and Neck.

BACKGROUND AND PURPOSE: It is important to identify patients with head and neck squamous cell carcinoma (SCC) who fail to respond to chemoradiotherapy so that they can undergo post-treatment salvage surgery while the disease is still operable. This study aimed to determine the diagnostic performance of dynamic contrast enhanced (DCE)-MRI using a pharmacokinetic model for pre-treatment predictive imaging, as well as post-treatment diagnosis, of residual SCC at primary and nodal sites in the head and neck. MATERIAL AND METHODS: Forty-nine patients with 83 SCC sites (primary and/or nodal) underwent pre-treatment DCE-MRI, and 43 patients underwent post-treatment DCE-MRI, of which 33 SCC sites had a residual mass amenable to analysis. Pre-treatment, post-treatment and % change in the mean Ktrans, kep, ve and AUGC were obtained from SCC sites. Logistic regression was used to correlate DCE parameters at each SCC site with treatment response at the same site, based on clinical outcome at that site at a minimum of two years. RESULTS: None of the pre-treatment DCE-MRI parameters showed significant correlations with SCC site failure (SF) (29/83 sites) or site control (SC) (54/83 sites). Post-treatment residual masses with SF (14/33) had significantly higher kep (p = 0.05), higher AUGC (p = 0.02), and lower % reduction in AUGC (p = 0.02), than residual masses with SC (19/33), with the % change in AUGC remaining significant on multivariate analysis. CONCLUSION: Pre-treatment DCE-MRI did not predict which SCC sites would fail treatment, but post-treatment DCE-MRI showed potential for identifying residual masses that had failed treatment.

Superficial Head and Neck Anatomy for Dermatologic Surgery: Critical Concepts.

BACKGROUND: Thorough understanding of head and neck anatomy is useful and necessary for dermatologic surgery. OBJECTIVE: To highlight pertinent head and neck anatomic structures that are encountered during dermatologic surgery and correlate these with common surgical problems. METHODS: Important anatomic structures and regional cutaneous anatomy are discussed and illustrated. RESULTS: Several important anatomic structures exist within the head and neck that can influence surgical outcomes. CONCLUSION: Anatomic knowledge is helpful to the dermatologic surgeon to optimize reconstructive outcomes.

Anaerobic digestion of lipid-extracted Auxenochlorella protothecoides biomass for methane generation and nutrient recovery.

This study evaluated methane production and nutrient recovery from industrially produced, lipid extracted algal biomass (LEA) of Auxenochlorella protothecoides using semi-continuous anaerobic digestion (AD) at different organic loading rates (OLRs) and hydraulic retention times (HRTs). It was shown, that AD can improve biofuel production efficiency and sustainability, especially for scaled processes, through up to 30% increase in energy generation (up to 0.25 L of methane per g of LEA volatile solids) and partial nutrient recovery and recycling. The nutrient recycling with the AD effluent may reduce the cost of the supplied fertilizers by up to 45%. However, methane production was limited to nearly 50% of theoretical maxima potentially due to biomass recalcitrance and inhibition effects from the residual solvent in the LEA. Therefore, further AD optimization is required to maximize methane yield and nutrient recovery as well as investigation and elimination of inhibition from solvent residues.