A contemporary analysis of racial disparities in recommended and received treatment for head and neck cancer.

BACKGROUND: Racial disparities in squamous cell carcinoma of the head and neck (HNSCC) negatively affect non-Hispanic black (NHB) patients. This study was aimed at understanding how treatment is prescribed and received across all HNSCC subsites. METHODS: With the National Cancer Database, patients from 2004 to 2014 with surgically resectable HNSCCs, including tumors of the oral cavity (OC), oropharynx (OP), hypopharynx (HP), and larynx (LX), were studied. The treatment received was either upfront surgery or nonsurgical treatment. Treatment patterns were compared according to race and subsite, and how these differences changed over time was evaluated. RESULTS: NHB patients were less likely than non-Hispanic white (NHW) patients to receive surgery across all subsites (relative risk [RR] for OC, 0.87; RR for OP, 0.75; RR for HP, 0.73; RR for LX, 0.87; all P values <.05). They were also more likely to refuse a recommended surgery (RR for OC, 1.50; RR for OP, 1.23; RR for HP, 1.23; RR for LX, 1.34), and this difference was significant except for HP. NHB patients were more likely to not be offered surgery across all subsites (RR for OC, 1.38; RR for OP, 1.07; RR for HP, 1.05; RR for LX, 1.03; all P values <.05). Rates of surgery increased and rates of not being offered surgery declined for both NHB and NHW patients from 2004 to 2014, but the absolute disparities persisted in 2014. CONCLUSIONS: Across all HNSCC subsites, NHB patients were less likely than NHW patients to be recommended for and receive surgery and were more likely to refuse surgery. These differences have closed over time but persist. Enhanced shared decision making may improve these disparities.

Failed larynx preservation and survival in patients with advanced larynx cancer.

PURPOSE: To evaluate the survival benefit of total laryngectomy (TL) after induction chemotherapy in locally advanced laryngeal cancer patients. MATERIALS AND METHODS: This is a retrospective study utilizing the National Cancer Database, which captures >80% of newly diagnosed head and neck squamous cell carcinoma cases in the United States. We included patients diagnosed with advanced stage laryngeal squamous cell carcinoma between 2004 and 2013 (n = 5649) who received either TL (n = 4113; 72.8%) or induction chemotherapy followed by either radiation therapy (n = 1431) or TL (n = 105). Kaplan-Meier curves and Cox proportional hazards regression were used to evaluate overall survival. A Cox regression model was computed to examine how the prognostic impact of treatment differed by clinical stage. RESULTS: In multivariable analysis, when compared to patients receiving TL alone, those receiving induction chemotherapy followed by TL experienced no significant difference in survival (HR 0.85, 95% CI 0.63-1.13), while those receiving induction chemotherapy followed by radiation experienced poorer survival (HR 1.15, 95% CI 1.06-1.26). Induction chemotherapy followed by TL was associated with improved survival compared to induction chemotherapy and radiation (P = .042). Among patients with T4a tumors, TL (P < .001) and induction chemotherapy followed by TL (P = .002) were both associated with improved survival compared to induction chemotherapy and radiation. There were no survival differences between TL and induction chemotherapy followed by TL (HR 0.76, 95% CI 0.52-1.10). CONCLUSIONS: Larynx preservation may be attempted without compromising survival in patients with locally advanced larynx cancer who fail induction chemotherapy and undergo TL.

Association of Facility Volume With Positive Margin Rate in the Surgical Treatment of Head and Neck Cancer.

Importance: The achievement of complete tumor resection with tumor-free margins is one of the main principles of oncologic surgery for head and neck squamous cell carcinoma (HNSCC). The negative prognostic influence of a positive margin (PM) across all head and neck subsites has been well established. National guidelines recommend the use of adjuvant chemoradiation therapy (CRT) in the setting of PM. Objective: To determine the incidence of PM in HNSCC across multiple subsites, as well as the factors associated with its occurrence. Design, Setting, and Participants: This retrospective cohort study used the National Cancer Database to identify patients diagnosed with HNSCC between 2010 and 2014 and who underwent surgical resection (n = 28 840). Main Outcomes and Measures: Predictors of PM rate and likelihood to receive adjuvant CRT. Results: Among the 28 840 patients included in this study, 19 727 (68.4 %) were men, and the average age was 62.4 years (range, 40 to ≥90 years). In univariable analysis, a lower PM rate was associated with higher facility volume (26.3% for the lowest volume quartile, 16.5% for the middle 2 quartiles, and 10.8% for the highest volume quartile) and treatment at academic vs nonacademic facilities (14.0% vs 22.7%). In multivariate analysis, those treated at higher-volume facilities remained significantly less likely to have PM (adjusted odds ratio, 0.85; 95% CI, 0.83-0.88). The trend of decreasing PM rate with increasing facility volume was observed in both academic (aOR, 0.88 per 10-case volume increase [95% CI, 0.85-0.91]) and nonacademic (aOR, 0.73 per 10-case volume increase [95% CI, 0.68-0.80]) facilities. There was no association between facility volume and patient likelihood of receiving adjuvant CRT in the setting of PM (compared with CCPs: aOR, 0.98 per 10-case volume increase [95% CI, 0.84-1.14] for CCCPs; and aOR, 1.24 [95% CI, 0.99-1.55] for INCPs). Conclusions and Relevance: These findings suggest that high-volume facilities are associated with lower rates of PM in the surgical treatment of HNSCC in both academic and nonacademic settings. Facility volume for head and neck oncologic surgeries may be considered a benchmark for quality of care.

Racial disparities in the choice of definitive treatment for squamous cell carcinoma of the oral cavity.

BACKGROUND: Definitive surgery is recommended for oral cavity squamous cell carcinoma (SCC). The purpose of this study was to present our assessment of the disparities in treatment selection for oral cavity SCC. METHODS: Non-Hispanic white and non-Hispanic black patients with oral cavity SCC were identified in the National Cancer Database (NCDB). Regression models were used to estimate relative risk (RR) of receiving surgery and absolute difference between non-Hispanic white and non-Hispanic black patients. RESULTS: There were 82.3% of non-Hispanic white patients who received surgery, compared to 64.2% of non-Hispanic black patients (P < .001). The non-Hispanic black patients were less likely to receive surgery than non-Hispanic white patients (RR 0.87) with an absolute difference of 10.9%. The non-Hispanic black patients were significantly more likely to not be offered surgery (RR 1.42) and to refuse recommended surgery (RR 1.38) but not have a contraindication to surgery (RR 1.17). CONCLUSION: The non-Hispanic black patients are less likely to receive or be recommended surgery for oral cavity SCC and are more likely to refuse surgery. Further study is needed to identify strategies to close this disparity.

Association of a Proactive Swallowing Rehabilitation Program With Feeding Tube Placement in Patients Treated for Pharyngeal Cancer.

Importance: A proactive speech and language pathology (SLP) program is an important component of the multidisciplinary care of patients with head and neck squamous cell carcinoma (HNSCC). Swallowing rehabilitation can reduce the rate of feeding tube placement, thereby significantly improving quality of life. Objective: To evaluate the initiation of a proactive SLP rehabilitation program at a single institution and its association with rates of feeding tube placement and dietary intake in patients with HNSCC. Design, Setting, and Participants: Cohort study at a tertiary care and referral center for patients with HNSCC serving the northern Chicago region. Patients were treated for squamous cell carcinomas of the hypopharynx, oropharynx, and nasopharynx from 2004 to 2015 with radiation or chemoradiation therapy in the definitive or adjuvant setting. Patients who received less than 5000 cGy radiation or underwent reirradiation were excluded. Interventions: A proactive SLP program for patients with HNSCC was initiated in 2011. Study cohorts were divided into 2 groups: 2004 through 2010 and 2011 through 2015. Main Outcomes and Measures: Primary outcome variables were SLP referral placement and timing of the referral. Secondary outcomes were feeding tube placement and ability to tolerate any oral intake. Results: A total of 254 patients met inclusion criteria (135 before and 119 after implementation of SLP program; median age, 60 years [range, 14-94 years]; 77% male). With the initiation of a proactive SLP program, pretreatment evaluations increased from 29 (21.5%) to 70 (58.8%; risk ratio [RR], 2.74; 95% CI, 1.92-3.91), and rate of referral overall at any time increased from 60.0% to 79.8% (RR, 1.33; 95% CI, 1.13-1.57). Feeding tube placement rates decreased from 45.9% (n = 62) to 29.4% (n = 35; RR, 0.64; 95% CI, 0.46-0.89). Among patients receiving a swallow evaluation, feeding tube requirements were less frequent for those receiving a pretreatment evaluation (31 of 99 [31%]) than for those referred during (11 of 18 [61%]) or after (38 of 59 [64%]) treatment. The rate of tolerating any oral intake at the end of treatment improved from 71.1% (n = 96) in the preimplementation period to 82.4% (n = 98; RR, 1.16; 95% CI, 1.01-1.33). Conclusions and Relevance: A proactive SLP program can be successfully established as part of the multidisciplinary care of patients with HNSCC and improve patient quality of life.

Surgical quality of wedge resection affects overall survival in patients with early stage non-small cell lung cancer.

OBJECTIVES: Very few studies have examined the quality of wedge resection in patients with non-small cell lung cancer. Using the National Cancer Database, we evaluated whether the quality of wedge resection affects overall survival in patients with early disease and how these outcomes compare with those of patients who receive stereotactic radiation. METHODS: We identified 14,328 patients with cT1 to T2, N0, M0 disease treated with wedge resection (n = 10,032) or stereotactic radiation (n = 4296) from 2005 to 2013 and developed a subsample of propensity-matched wedge and radiation patients. Wedge quality was grouped as high (negative margins, >5 nodes), average (negative margins, ≤5 nodes), and poor (positive margins). Overall survival was compared between patients who received wedge resection of different quality and those who received radiation, adjusting for demographic and clinical variables. RESULTS: Among patients who underwent wedge resection, 94.6% had negative margins, 44.3% had 0 nodes examined, 17.1% had >5 examined, and 3.0% were nodally upstaged; 16.7% received a high-quality wedge, which was associated with a lower risk of death compared with average-quality resection (adjusted hazard ratio [aHR], 0.74; 95% confidence interval [CI], 0.67-0.82). Compared with stereotactic radiation, wedge patients with negative margins had significantly reduced hazard of death (>5 nodes: aHR, 0.50; 95% CI, 0.43-0.58; ≤5 nodes: aHR, 0.65; 95% CI, 0.60-0.70). There was no significant survival difference between margin-positive wedge and radiation. CONCLUSIONS: Lymph nodes examined and margins obtained are important quality metrics in wedge resection. A high-quality wedge appears to confer a significant survival advantage over lower-quality wedge and stereotactic radiation. A margin-positive wedge appears to offer no benefit compared with radiation.

Assessment of adjuvant therapy in resected head and neck cancer with high-risk features.

OBJECTIVES: Subgroup analysis from two randomized trials showed a survival benefit for adjuvant chemoradiation (CRT) over radiation alone (RT) in patients with extracapsular spread (ECS) of involved lymph nodes and/or positive margins (PM) in resected head and neck cancer (HNSCC). However, results were not analyzed separately for patients with ECS or PM and were not stratified by tumor subsite/HPV status. We therefore sought to determine whether adjuvant CRT is associated with a survival benefit, separately among patients with ECS or PM and stratified by subsite/HPV status. METHODS: Using the National Cancer Database (NCDB), we identified 6948 patients diagnosed with HNSCC between 2010 and 13 who underwent surgical resection and had either ECS or PM. The impact of adjuvant therapy on OS from surgery was evaluated using Cox proportional hazards regression adjusting for clinical and demographic factors. RESULTS: Adjuvant CRT was associated with a significant survival benefit over RT alone among patients with ECS (aHR 0.83, 95%CI 0.71-0.97) but not among those with PM (aHR 0.89, 95%CI 0.77-1.04). In patients with HPV-negative tumors, CRT was associated with a benefit over RT alone in the setting of ECS (aHR 0.83, 95%CI 0.70-0.98) but not PM (aHR 0.91, 95%CI 0.78-1.06). However, in patients with HPV-positive oropharynx tumors, CRT was not associated with a benefit over RT in ECS (aHR 0.94, 95%CI 0.47-1.88) but appeared beneficial in PM (aHR 0.54, 95%CI 0.32-0.90). CONCLUSIONS: CRT appears beneficial over RT in ECS among patients with HPV-negative tumors, and beneficial in PM among patients with HPV-positive tumors.

Adjuvant radiation and survival following surgical resection of sinonasal melanoma.

BACKGROUND: Surgery remains the mainstay of treatment for sinonasal melanoma, but it is often difficult to obtain clear, negative margins. Therefore, patients often receive adjuvant radiation therapy (RT), however its impact on overall survival (OS) is not well understood. METHODS: Patients with surgically resected sinonasal melanoma were identified from the National Cancer Data Base (NCDB, n=696). Kaplan-Meier curves and parametric survival regression were used to analyze the impact of adjuvant RT on OS from surgery. Adjusted time ratios (aTRs) were computed, with values >1 corresponding to improved survival. RESULTS: 399 (57.3%) patients received adjuvant RT. Those receiving RT tended to be younger but with more advanced disease and greater likelihood of positive margins, compared to those receiving no adjuvant therapy. Median survival was 25.0months for those treated with surgery alone, compared to 28.3months for those receiving adjuvant RT (log-rank P=0.408). When adjusting for potential confounders, there was a trend towards greater survival with adjuvant RT (aTR 1.16, 95%CI 0.98-1.37). RT appeared beneficial in those with stage IVB disease (aTR 2.58, 95%CI 1.40-4.75) but not stage IVA (aTR 1.19, 95%CI 0.88-1.61) or III (aTR 0.85, 95%CI 0.65-1.13) disease. In contrast, there were no differences in impact of RT according to margin status (aTR 1.16 for both positive and negative margins). CONCLUSIONS: Adjuvant therapy does not appear to provide a significant survival benefit in resected sinonasal melanomas regardless of margin status, except those with stage IVB disease. Practitioners should carefully consider the added benefit of adjuvant therapy in these patients.

The Impact of Facility Volume on Rates of Pathologic Complete Response to Neoadjuvant Chemotherapy Used in Breast Cancer.

BACKGROUND: Patient and tumor factors have been associated with rates for pathologic complete response (pCR) to neoadjuvant chemotherapy (NAC) for breast cancer, but variation in pCR rates across facilities has not been studied. METHODS: This study used the National Cancer Data Base to identify women with clinical stages 1-3a breast cancer undergoing NAC from 2010 to 2013. Generalized estimation equation models were used to examine the relationship between facility characteristics and pCR rates, with adjustment for patient and tumor factors, while accounting for patient clustering at facilities. Analyses were stratified by tumor molecular subtype. RESULTS: Overall, 16,885 women underwent NAC, of whom 3130 (18.5%) were hormone receptor-positive (HR+) and human epidermal growth factor 2-positive (HER2+), 7045 (41.7%) were HR+HER2-, 1847 (10.9%) were HR-HER2+, and 4863 (28.8%) were HR-HER2-. Overall, 4002 of the patients (23.7%) achieved a pCR. The pCR rates were 29.5% for HR+HER2+, 10.8% for HR+HER2-, 45.3% for HR-HER2+, and 30.5% for HR-HER2- tumors. Multivariable analysis showed that pCR rates were significantly higher at high-volume facilities (>75th vs. <25th percentile) for all tumor subtypes except HR+HER2- tumors. Facility location and type were not significant. Adjustment for time from NAC to surgery decreased the likelihood of a pCR in high- versus low-volume facilities, but facility volume remained significantly associated with pCR. CONCLUSION: Facility volume, not location or type, was significantly associated with higher pCR rates in this exploratory analysis. Time to surgery has a modest impact on pCR rates across facilities, but further study to identify other potentially modifiable factors is needed.

Smoking and olfactory dysfunction: A systematic literature review and meta-analysis.

OBJECTIVES/HYPOTHESIS: A systematic review and meta-analysis of the literature was undertaken, examining the association between tobacco smoking and olfactory function in humans, utilizing PubMed and Web of Science (1970-2015) as data sources. STUDY DESIGN: Systematic literature review and meta-analysis. METHODS: This database review of studies of smoking and olfaction, with a focus on identifying high-quality studies (based on modified versions of the Newcastle-Ottawa Scale), used validated olfactory tests among the generally healthy population. RESULTS: We identified 11 studies meeting inclusion criteria. Of 10 cross-sectional studies, two were excluded from meta-analysis because the cohorts they studied were included in another article in the review. In meta-analysis, current smokers had substantially higher odds of olfactory dysfunction compared to never smokers (odds ratio [OR] = 1.59, 95% confidence interval [CI] = 1.37-1.85). In contrast, former smokers were found to have no difference in risk of impaired olfaction compared to never smokers (OR = 1.05, 95% CI = 0.91-1.21). The single longitudinal study reviewed found a trend toward increased risk of olfactory decline over time in ever smokers; this trend was stronger in current as compared to former smokers. CONCLUSIONS: Current smoking, but not former smoking, is associated with significantly increased risk of olfactory dysfunction, suggesting that the effects of smoking on olfaction may be reversible. Future studies that prospectively evaluate the impact of smoking cessation on improvement in olfactory function are warranted. LEVEL OF EVIDENCE: N/A. Laryngoscope, 127:1753-1761, 2017.

Allergy and asthma medication use in home-dwelling U.S. older adults.

BACKGROUND: Little is known about the use of allergy and asthma medications in older adults. This study aimed to assess the prevalence of use of these medications in older adults and evaluate predictors of their use. METHODS: Cross-sectional study using data from the National Social Life, Health, and Aging Project (NSHAP), a nationally representative sample of community-dwelling, U.S. adults 57 to 85 years (n = 2976) collected in 2005-2006. We determined prevalence of medication use and used logistic regression to evaluate sociodemographic and health factors associated with their use. RESULTS: Overall prevalence of allergy medication usage was 8.4% (most commonly antihistamines), and prevalence of asthma medication usage was 8.0% (most commonly bronchodilators). Allergy medication use was significantly associated with history of asthma (odds ratio [OR] 2.37; 95% confidence interval [CI], 1.52 to 3.69), chronic obstructive pulmonary disease (COPD) (OR 2.35; 95% CI, 1.58 to 3.51), or nasal surgery (OR 1.97; 95% CI, 1.00 to 3.86). Older age was associated with decreased allergy medication use (per decade, OR 0.80; 95% CI, 0.66 to 0.98). Although increased education was associated with increased overall allergy medication use, it was associated with decreased use of allergy medications generally contraindicated in the elderly. In contrast, the only significant predictors of asthma medication use were history of asthma (OR 19.66; 95% CI, 3.18 to 121.70) or COPD (OR 4.25; 95% CI, 0.88 to 20.44). CONCLUSION: Allergy and asthma medication use is prevalent among older adults and driven mostly by history of asthma or COPD. Additional sociodemographic factors predict allergy (but not asthma) medication use. Further studies are needed to evaluate efficacy of these drugs in the elderly.

Fine particulate matter exposure and olfactory dysfunction among urban-dwelling older US adults.

OBJECTIVES: The olfactory nerve is anatomically susceptible to injury from pollution in inspired air, but there are no large-scale epidemiologic studies investigating this relationship. METHODS: Cross-sectional study using data from the National Social Life, Health, and Aging Project, a representative sample of home-dwelling US adults age 57-85 years. Olfactory function was tested using a validated 5-item odor identification test (Sniffin' Sticks). Exposure to fine particulate matter (PM2.5) at each respondent's home was estimated as 1-12 month moving averages prior to olfactory assessment using validated spatio-temporal models. RESULTS: Olfactory dysfunction was significantly associated with PM2.5 exposures averaged over 3-12 months in urban-dwelling respondents. The strongest effect was for 6 month average exposure (per 1-IQR increase in PM2.5: OR 1.28, 95% CI 1.05, 1.55) adjusting for age, gender, race/ethnicity, education, cognition, comorbidity, smoking, and the season. Interestingly, the most deleterious effects were observed among the youngest respondents, 57-64 years old, and those living in the northeast and south. CONCLUSIONS: We show for the first time that air pollution exposure is associated with poor olfaction among urban-living, older US adults.

Nitrogen dioxide pollution exposure is associated with olfactory dysfunction in older U.S. adults.

BACKGROUND: Olfactory dysfunction has profound effects on quality of life, physical and social function, and mortality itself. Nitrogen dioxide (NO2 ) is a pervasive air pollutant that is associated with respiratory diseases. Given the olfactory nerve's anatomic exposure to airborne pollutants, we investigated the relationship between NO2 exposure and olfactory dysfunction. METHODS: The ability to identify odors was evaluated using a validated test in respondents from the National Social Life, Health, and Aging Project (NSHAP), a representative probability sample of home-dwelling, older U.S. adults age 57 to 85 years. Exposure to NO2 pollution was assessed using measurements obtained from the U.S. Environmental Protection Agency (EPA) Aerometric Information Retrieval System (AIRS) ambient monitoring site closest to each respondent's home. We tested the association between NO2 exposure and olfactory dysfunction using multivariate logistic regression. RESULTS: Among older adults in the United States, 22.6% had impaired olfactory function, defined as ≤3 correct (out of 5) on the odor identification test. Median NO2 exposure during the 365 days prior to the interview date was 14.7 ppb (interquartile range [IQR], 10.8 to 19.7 ppb). An IQR increase in NO2 exposure was associated with increased odds of olfactory dysfunction (OR, 1.35; 95% CI, 1.07 to 1.72), adjusting for age, gender, race/ethnicity, education, cognition, comorbidity, smoking, and season of the home interview (n = 1823). CONCLUSION: We show for the first time that NO2 exposure is associated with olfactory dysfunction in older U.S. adults. These results suggest an important role for NO2 exposure on olfactory dysfunction, and, potentially, nasal disease more broadly.

Effects of Ambient Air Pollution Exposure on Olfaction: A Review.

BACKGROUND: Olfactory dysfunction affects millions of people worldwide. This sensory impairment is associated with neurodegenerative disease and significantly decreased quality of life. Exposure to airborne pollutants has been implicated in olfactory decline, likely due to the anatomic susceptibility of the olfactory nerve to the environment. Historically, studies have focused on occupational exposures, but more recent studies have considered effects from exposure to ambient air pollutants. OBJECTIVES: To examine all relevant human data evaluating a link between ambient pollution exposure and olfaction and to review supporting animal data in order to examine potential mechanisms for pollution-associated olfactory loss. METHODS: We identified and reviewed relevant articles from 1950 to 2015 using PubMed and Web of Science and focusing on human epidemiologic and pathophysiologic studies. Animal studies were included only to support pertinent data on humans. We reviewed findings from these studies evaluating a relationship between environmental pollutant exposure and olfactory function. RESULTS: We identified and reviewed 17 articles, with 1 additional article added from a bibliography search, for a total of 18 human studies. There is evidence in human epidemiologic and pathologic studies that increased exposure to ambient air pollutants is associated with olfactory dysfunction. However, most studies have used proxies for pollution exposure in small samples of convenience. Human pathologic studies, with supporting animal work, have also shown that air pollution can contact the olfactory epithelium, translocate to the olfactory bulb, and migrate to the olfactory cortex. Pollutants can deposit at each location, causing direct damage and disruption of tissue morphology or inducing local inflammation and cellular stress responses. CONCLUSIONS: Ambient air pollution may impact human olfactory function. Additional studies are needed to examine air pollution-related olfactory impacts on the general population using measured pollution exposures and to link pollution exposure with olfactory dysfunction and related pathology. Citation: Ajmani GS, Suh HH, Pinto JM. 2016. Effects of ambient air pollution exposure on olfaction: a review. Environ Health Perspect 124:1683-1693; http://dx.doi.org/10.1289/EHP136.

Aluminum-humic colloid formation during pre-coagulation for membrane water treatment: mechanisms and impacts.

Precoagulation has been widely used by low pressure membrane filtration (LPMF) plants to reduce membrane fouling and increase natural organic matter (NOM) removal. Formation of aluminum and aluminum-NOM moieties plays a fundamental role in this important water treatment process. This study comprehensively investigated the mechanisms of aluminum-NOM species formation during precoagulation and their impacts on LPMF performance. The results show that, at low alum doses, e.g. 0.5 mg and 1.0 mg Al L(-1), humic substances (HS) and Al species (amorphous Al(OH)3, or Al(OH)3(am)) reacted to form small Al(OH)3(am)-HS colloids. Increases in alum dose resulted in sequential transitions of the Al-HS moieties to larger particles and, eventually, precipitates. Compared to waters containing only naturally occurring organic colloids (OC) or HS, the coexistence of OC and HS facilitated the formation of Al-HS precipitates, thereby increasing the removal of HS by 7-15%, but the removal of OC was decreased by 3-20%. Interestingly, these transitions in Al-HS moieties did not affect membrane fouling. Both short-term and long-term filtration results demonstrate that OC, rather than the Al(OH)3(am)-HS colloids, primarily caused membrane fouling. These findings highlight the dynamics of particulate Al-NOM formation during precoagulation and its relationship with membrane fouling, which can be utilized to optimize the operation of integrated precoagulation-LPMF systems on full-scale installations.

Static and dynamic removal of aquatic natural organic matter by carbon nanotubes.

Carbon nanotubes (CNTs) were investigated for their capability and mechanisms to simultaneously remove colloidal natural organic matter (NOM) and humic substances from natural surface water. Static removal testing was conducted via adsorption experiments while dynamic removal was evaluated by layering CNTs onto substrate membranes and filtering natural water through the CNT-layered membranes. Analyses of treated water samples showed that removal of humic substances occurred via adsorption under both static and dynamic conditions. Removal of colloidal NOM occurred at a moderate level of 36-66% in static conditions, independent of the specific surface area (SSA) of CNTs. Dynamic removal of colloidal NOM increased from approximately 15% with the unmodified membrane to 80-100% with the CNT-modified membranes. Depth filtration played an important role in colloidal NOM removal. A comparison of the static and dynamic removal of humic substances showed that equilibrium static removal was higher than dynamic (p < 0.01), but there was also a significant linear relationship between static and dynamic removal (p < 0.05). Accounting for contact time of CNTs with NOM during filtration, it appeared that CNT mat structure was an important determinant of removal efficiencies for colloidal NOM and humic substances during CNT membrane filtration.

Evaluating nanoparticle breakthrough during drinking water treatment.

BACKGROUND: Use of engineered nanoparticles (NPs) in consumer products is resulting in NPs in drinking water sources. Subsequent NP breakthrough into treated drinking water is a potential exposure route and human health threat. OBJECTIVES: In this study we investigated the breakthrough of common NPs--silver (Ag), titanium dioxide (TiO2), and zinc oxide (ZnO)--into finished drinking water following conventional and advanced treatment. METHODS: NPs were spiked into five experimental waters: groundwater, surface water, synthetic freshwater, synthetic freshwater containing natural organic matter, and tertiary wastewater effluent. Bench-scale coagulation/flocculation/sedimentation simulated conventional treatment, and microfiltration (MF) and ultrafiltration (UF) simulated advanced treatment. We monitored breakthrough of NPs into treated water by turbidity removal and inductively coupled plasma-mass spectrometry (ICP-MS). RESULTS: Conventional treatment resulted in 2-20%, 3-8%, and 48-99% of Ag, TiO2, and ZnO NPs, respectively, or their dissolved ions remaining in finished water. Breakthrough following MF was 1-45% for Ag, 0-44% for TiO2, and 36-83% for ZnO. With UF, NP breakthrough was 0-2%, 0-4%, and 2-96% for Ag, TiO2, and ZnO, respectively. Variability was dependent on NP stability, with less breakthrough of aggregated NPs compared with stable NPs and dissolved NP ions. CONCLUSIONS: Although a majority of aggregated or stable NPs were removed by simulated conventional and advanced treatment, NP metals were detectable in finished water. As environmental NP concentrations increase, we need to consider NPs as emerging drinking water contaminants and determine appropriate drinking water treatment processes to fully remove NPs in order to reduce their potential harmful health outcomes.

Modification of low pressure membranes with carbon nanotube layers for fouling control.

Carbon nanotubes (CNTs) with different physiochemical properties were layered onto low pressure membranes and tested for antifouling properties using a natural surface water with high fouling potential. Membranes modified with the largest diameter pristine multi-walled CNTs (MWCNTs) were most effective in controlling membrane fouling, tripling the time it took for the membrane to become noticeably fouled at a CNT loading of 22 g/m(2). The differences in the structure of CNT layers were an important contributing factor for antifouling properties; scanning electron microscopy imaging showed that large diameter MWCNTs formed homogeneous porous layers across the membrane surface, while less effective, small diameter MWCNTs formed heterogeneous layers. Water quality analysis showed that CNT-membranes constructed with larger diameter CNTs were more effective at removing larger organic macromolecules responsible for fouling from feedwater compared to membranes made with smaller diameter CNTs. This reduced the concentration of foulants reaching the PVDF membrane and thus helped reduce membrane fouling. Beneficial for application, increased loadings of CNTs onto the membrane surface increased resistance to fouling while only slightly reducing the clean water permeability of the modified membranes. Overall, CNT layered membranes were shown to highly resist membrane fouling with potential applications in sustainable water treatment.