The lymph node ratio does not provide additional prognostic information compared with the N1/N2 classification in Stage III colon cancer.

AIM: The ratio of positive nodes to total nodes, the lymph node ratio (LNR), is a proposed alternative to the current N1/N2 classification of nodal disease. The true clinical benefit of adopting the LNR, however, has not been definitively demonstrated. This study compared the LNR with the current N1/N2 classification of Stage III colon cancer. METHOD: Patients with Stage III colon cancer were identified from a prospectively maintained database (1996-2012). The specificity and sensitivity of the N1/N2 classification in the prediction of overall survival were determined using R. A cut-off point for the LNR was determined by setting the specificity the same as for the N1/N2 classification. The sensitivity of the two methods was then compared, and bootstrapping 1000-fold was performed. This was then repeated for disease-specific survival. RESULTS: The specificity and sensitivity of the N1/N2 classification in predicting 3-year overall survival in this cohort (n = 402) was 62.2% and 52.1%, respectively. The cut-off point for the LNR was determined to be 0.27 for these data. On comparing LNR with the N1/N2 classification showed that for a given specificity, the LNR did not provide a statistically significant improvement in sensitivity (52.8% vs 52.1%, P = 0.31). For disease-specific death at 3 years, the specificity and sensitivity were 60.8% and 54.6%, respectively. The LNR did not provide a statistically significant improvement (55.4% vs 54.6%, P = 0.44). CONCLUSION: Both the N1/N2 system and the LNR predict survival in colon cancer, but both have low specificity and sensitivity. The LNR does not provide additional prognostic value to current staging for overall or disease-specific survival for a given cut-off point.

Spatial variation of the colonic microbiota in patients with ulcerative colitis and control volunteers.

OBJECTIVES: The relevance of spatial composition in the microbial changes associated with UC is unclear. We coupled luminal brush samples, mucosal biopsies and laser capture microdissection with deep sequencing of the gut microbiota to develop an integrated spatial assessment of the microbial community in controls and UC. DESIGN: A total of 98 samples were sequenced to a mean depth of 31,642 reads from nine individuals, four control volunteers undergoing routine colonoscopy and five patients undergoing surgical colectomy for medically-refractory UC. Samples were retrieved at four colorectal locations, incorporating the luminal microbiota, mucus gel layer and whole mucosal biopsies. RESULTS: Interpersonal variability accounted for approximately half of the total variance. Surprisingly, within individuals, asymmetric Eigenvector map analysis demonstrated differentiation between the luminal and mucus gel microbiota, in both controls and UC, with no differentiation between colorectal regions. At a taxonomic level, differentiation was evident between both cohorts, as well as between the luminal and mucosal compartments, with a small group of taxa uniquely discriminating the luminal and mucosal microbiota in colitis. There was no correlation between regional inflammation and a breakdown in this spatial differentiation or bacterial diversity. CONCLUSIONS: Our study demonstrates a conserved spatial structure to the colonic microbiota, differentiating the luminal and mucosal communities, within the context of marked interpersonal variability. While elements of this structure overlap between UC and control volunteers, there are differences between the two groups, both in terms of the overall taxonomic composition and how spatial structure is ascribable to distinct taxa.

Primary colorectal lymphoma - A single centre experience.

PURPOSE: The incidence of primary colorectal lymphoma (PCL) is rare (0.2-0.6% of large bowel malignancy). Up to one third of Non-Hodgkin's lymphoma will present with extra-nodal manifestations only. Extra-nodal lymphomas arise from tissues other than the lymph nodes and even from sites, which contain no lymphoid tissue. The incidence of Non-Hodgkin's lymphoma has increased over the past fifty years. The objective of this study was to examine our experience of PCL. METHODS: A prospectively-compiled database (1988-2012) of patients with colorectal cancer was retrospectively examined for cases of colorectal lymphoma. A retrospective chart review identified cases of PCL based on Dawson's criteria. Clinical information was obtained from case notes. RESULTS: Eleven patients (0.3% of 4219 patients) were identified (6 male, 5 female). The median age at diagnosis was 63 years. Mode of presentation varied; abdominal pain, a palpable mass and per rectal bleeding being the most frequent. The caecum was the most frequently involved site (5/11). Nine patients underwent surgical management, one had chemotherapy alone and one had radiotherapy alone. All cases were non-Hodgkin's lymphoma, with diffuse large B-cell lymphoma in majority. The median event-free survival of those treated with surgery and post-operative chemotherapy was 10 months (range 5-120 months). CONCLUSION: Primary colorectal lymphoma is rare. Management is multidisciplinary and dependent on the subtype of lymphoma. Due to the rarity of diagnosis, there is a paucity of randomised control trials. Most information published is based on individual case reports and there is, thus, no clear treatment algorithm for these cases.

Tumour microenvironment of both early- and late-stage colorectal cancer is equally immunosuppressive.

BACKGROUND: Tumour microenvironment (TME) of advanced colorectal cancer (CRC) suppresses dendritic cell (DC) maturation. Here, our aim was to determine how the microenvironment of early-stage tumours influences DCs. METHODS: Tumour-conditioned media (TCM) was generated by culturing explant tumour tissue in vitro (n=50). Monocyte-derived DCs (MDDCs) of healthy donors or cancer patients were pretreated with TCM and stimulated with lipopolysaccharide (LPS). DC maturation was assessed by flow cytometry and cytokine production measured by ELISA. RESULTS: TCM from both early- and late-staged tumours abrogated LPS-induction of IL-12p70 secretion, while increasing IL-10. The profile of inflammatory mediators in TCM was similar across stages, and all increased pSTAT3 expression by DCs.CRC patient DCs (n=31) secreted low levels of IL-12p70 and failed to upregulate expression of maturation markers in response to LPS. Furthermore, in vitro culture of autologous DCs with TCM did not change the hypo-responsiveness of patient DCs. CONCLUSION: Our data demonstrates that the TME of all stages of CRC contains inflammatory mediators capable of suppressing local DCs. MDDCs obtained from CRC patients are hyporesponsive to stimuli such as LPS. Measures to reverse the negative influence of the TME on DCs will optimise cancer vaccines in both early- and late-stage CRC.

Anal intraepithelial neoplasia: a single centre 19 year review.

AIM: There is debate about whether the traditional three-tiered grading of anal intraepithelial neoplasia (AIN) should be replaced by a more reproducible two-tiered system. In this study, we review our experience with AIN to determine the most suitable classification system. METHOD: We performed a retrospective review of all histological reports over a 19 year period. All specimens were graded on haemataloxin and eosin appearance and those with dysplasia had immunohistochemistry for p16 and Ki67 performed. RESULTS: Cases included 25 condyloma acuminata, 11 dysplastic cases and 24 invasive squamous cell carcinomas. On review, 18 were classified as condyloma acuminata without dysplasia. Seven had AIN I, five had AIN II and six had AIN III when using a three-tiered system. All cases classified as dysplastic (n = 18) showed an increased proliferation index as measured by Ki67. p16 positivity was seen in all AIN III, two AIN II and none of the AIN I cases. Recurrence was not observed in any of the AIN I cases. Five of eleven AIN II and AIN III cases recurred or persisted at a similar, higher or lower grade. Both of the AIN II cases which recurred or persisted were p16 positive. None of the AIN II cases that were p16 negative recurred. Three of the p16-positive AIN III cases did not recur. None of the 18 AIN cases progressed to carcinoma. CONCLUSION: The findings support the slow progression of AIN as described in the literature. In our small series, a two-tiered system with further subclassification of the traditional AIN II group using p16 appears to be clinically useful.

Carbon mitigation, patient choice and cost reduction--triple bottom line optimisation for health care planning.

OBJECTIVES: Health services must provide safe, affordable clinical care whilst meeting efficiency, environmental and social targets. These targets include achieving reduced greenhouse gas emissions. A care pathway approach based on a decision-support tool can simultaneously reconfigure health services, improve productivity and reduce carbon emissions. STUDY DESIGN: Probabilistic modelling using secondary data analysis. METHODS: Estimates of carbon emitted by a health service drew on a previous carbon accounting study which integrated bottom-up assessment of carbon emissions with top-down analysis of indirect emissions by Duane et al. (2012).(1) Using human resource information, estimates were applied in a decision-support model to measure the carbon footprint and service provision of theoretical scenarios. Using this model, sites with less than 60% utilisation were theoretically reconfigured to reduce carbon emissions and improve service provision. RESULTS: Clinic utilisation rates improved from 50% to 78%. Human resource savings were identified which could be re-directed towards improving patient care. Patient travel for health care was halved resulting in significant savings in carbon emissions. CONCLUSIONS: The proposed model is an effective health care service analysis tool, ensuring optimal utilisation of health care sites and human resources with the lowest carbon footprint.

Clostridium difficile enteritis: a new role for an old foe.

BACKGROUND: Small bowel involvement of Clostridium difficile is increasingly encountered. Data on many management aspects are lacking. AIM: To synthesis existing reports and assess the frequency, pathophysiology, outcomes, risk factors, diagnosis and management of C. difficle enteritis. METHODS: A systematic review of the literature was conducted to evaluate evidence regarding frequency, pathophysiology, risk factors, optimal diagnosis, management and outcomes for C. difficle enteritis. Three major databases (PubMed, MEDLINE and the Cochrane Library) were searched. The review included original articles reporting C. difficle enteritis from January 1950 to December 2012. RESULTS: C. difficle enteritis is rare but increasingly encountered. Presentation is variable and distinct predisposing factors include emergency surgery, white race and increased age. Diagnosis generally involves a sensitive but often non specific screening test for C. difficile antigens. Oral metronidazole represents first line therapy and surgery may be required for complications. Outcomes are inconsistent but may be improving. CONCLUSIONS: A high index of clinical suspicion, early diagnosis and treatment are vital. Further prospective studies are needed to determine the significance of asymptomatic small bowel C. difficile infections.

Management of colorectal cancer in patients with inflammatory bowel disease.

BACKGROUND: This study evaluated the clinicopathological features and survival rates of patients with inflammatory bowel disease who developed colorectal cancer (CRC). METHODS: A retrospective review was performed on a prospectively maintained institutional database (1981-2011) to identify patients with inflammatory bowel disease who developed CRC. Clinicopathological parameters, management and outcomes were analysed. RESULTS: A total of 2,843 patients with inflammatory bowel disease were identified. One thousand six hundred and forty-two had ulcerative colitis (UC) and 1,201 had Crohn's disease (CD). Following exclusion criteria, there were 29 patients with biopsy-proven colorectal carcinoma, 22 of whom had UC and 7 had CD. Twenty-six patients had a preoperative diagnosis of malignancy/dysplasia; 16 of these were diagnosed at surveillance endoscopy. Nodal/distant metastasis was identified at presentation in 47 and 71 % of the UC and CD group, respectively. Operative morbidity for UC and CD was 33 and 17 %, respectively. Despite the less favourable operative outcomes following surgery management of UC-related CRC, overall 5-year survival was significantly better in the UC group compared to the CD group (41 vs. 29 %; p = 0.04) reflecting the difference in stage at presentation between the two groups. CONCLUSIONS: Patients who undergo surgery for UC-related CRC have less favourable short-term outcomes but present at a less advanced stage and have a more favourable long-term prognosis than similar patients with CRC and CD.

Distribution and sources of PCBs (Aroclor 1268) in the Sapelo Island National estuarine research reserve.

Aroclor 1268 is a highly chlorinated PCB mixture that was released into the aquatic environment near Brunswick, GA (BR), as a result of decades of local industrial activity. This extensive contamination has led to US EPA Superfund designation in estuarine areas in and around Purvis Creek, GA. Roughly 50 km to the northeast is the Sapelo Island National Estuarine Research Reserve (SI) where previous studies have documented unexpectedly high Aroclor 1268-like PCB levels in blubber and plasma samples of resident bottlenose dolphins. This result led to a collaborative effort to assess the PCB patterns and concentrations in SI sediment and fish (as potential vectors for PCB transfer to SI resident dolphins). Thirty SI randomly assigned stations were sampled for sediment PCB levels. Additionally, fish were collected and analyzed from SI (n = 31) and BR (n = 33). Results were pooled with regional assessments of PCB concentrations from South Carolina and North Carolina in an effort to determine the association of Aroclor 1268 levels in SI samples. Results indicated that PCB levels in sediment and fish are much lower in the SI estuary compared to BR sediment and fish concentrations. However, PCB congener profiles for both sediments and fish were similar between the two locations and consistent with the Aroclor 1268 signature, indicating possible transport from the Brunswick area. A likely source of Aroclor 1268 in dolphins from SI is contaminated fish prey.

Cluster of Legionnaires disease cases caused by Legionella longbeachae serogroup 1, Scotland, August to September 2013.

We report six confirmed cases of Legionnaires' disease in Scotland caused by Legionella longbeachae serogroup 1, identified over a four-week period in August­September 2013. All cases required admission to hospital intensive care facilities. All cases were amateur gardeners with frequent exposure to horticultural growing media throughout their incubation period. L. longbeachae was identified in five samples of growing media linked to five cases. Product tracing did not identify a common product or manufacturer.

A homozygous stop codon in the lysyl hydroxylase gene in two siblings with Ehlers-Danlos syndrome type VI.

Ehlers-Danlos syndrome (EDS) is characterized by joint hypermobility, alterations in the skin and additional signs of connective tissue involvement. EDS type VI was the first connective tissue disorder for which a specific defect in collagen metabolism was identified, namely a deficiency of lysyl hydroxylase activity. We now report a homozygous single basepair substitution converting the CGA codon (Arg319) to a TGA termination codon in two siblings with EDS type VI. The healthy parents, who are first cousins, and two of the three healthy siblings of the patients are heterozygous. The mutation leads to an almost complete absence of lysyl hydroxylase activity in extracts derived from fibroblasts of the patients.

The surgical significance of residual mucosal abnormalities in rectal cancer following neoadjuvant chemoradiotherapy.

BACKGROUND: Local excision of rectal cancer after neoadjuvant chemoradiotherapy (CRT) has been proposed as an alternative to radical surgery in selected patients. However, little is known about the significance of the morphological and histological features of residual tumour. METHODS: Patients who had undergone CRT at the authors' institution between 1997 and 2010 were identified. Multiple features were assessed as putative markers of pathological response. These included: gross residual disease, diameter of residual mucosal abnormalities, tumour differentiation, presence of lymphovascular/perineural invasion and lymph node ratio. RESULTS: Data from 220 of 276 patients were suitable for analysis. Diameter of residual mucosal abnormalities correlated strongly with pathological tumour category after CRT (ypT) (P < 0·001). Forty of 42 tumours downstaged to ypT0/1 had residual mucosal abnormalities of 2·99 cm or less after CRT. Importantly, 19 of 31 patients with a complete pathological response had evidence of a residual mucosal abnormality consistent with an incomplete clinical response. The ypT category was associated with both pathological node status after CRT (P < 0·001) and lymph node ratio (P < 0·001). Positive nodes were found in only one of 42 patients downstaged to ypT0/1. The risk of nodal metastases was associated with poor differentiation (P = 0·027) and lymphovascular invasion (P < 0·001). CONCLUSION: In this series, the majority of patients with a complete pathological response did not have a complete clinical response. In tumours downstaged to ypT0/1 after CRT, residual mucosal abnormalities were predominantly small and had a 2 per cent risk of positive nodes, thus potentially facilitating transanal excision. The presence of adverse histological characteristics risk stratified tumours for nodal metastases.

Management of synchronous rectal and prostate cancer.

PURPOSE: Although well described, there is limited published data related to management on the coexistence of prostate and rectal cancer. The aim of this study was to describe a single institution's experience with this and propose a treatment algorithm based on the best available evidence. METHODS: From 2000 to 2011, a retrospective review of institutional databases was performed to identify patients with synchronous prostate and rectal cancers where the rectal cancer lay in the lower two thirds of the rectum. Operative and non-operative outcomes were analysed and a management algorithm is proposed. RESULTS: Twelve patients with prostate and rectal cancer were identified. Three were metachronous diagnoses (>3-month time interval) and nine were synchronous diagnoses. In the synchronous group, four had metastatic disease at presentation and were treated symptomatically, while five were treated with curative intent. Treatment included pelvic radiotherapy (74 Gy) followed by pelvic exenteration (three) and watchful waiting for rectal cancer (one). The remaining patient had a prostatectomy, long-course chemoradiotherapy and anterior resection. There were no operative mortalities and acceptable morbidity. Three remain alive with two patients disease-free. CONCLUSIONS: Synchronous detection of prostate cancer and cancer of the lower two thirds of the rectum is uncommon, but likely to increase with rigorous preoperative staging of rectal cancer and increased awareness of the potential for synchronous disease. Treatment must be individualized based on the stage of the individual cancers taking into account the options for both cancers including EBRT (both), surgery (both), hormonal therapy (prostate), surgery (both) and watchful waiting (both).

Taking a bite out of Scotland's dental carbon emissions in the transition to a low carbon future.

BACKGROUND: Climate change is a significant global health threat requiring concerted action to reduce greenhouse gas emissions. This study provides the first systematic attempt to quantify the carbon emissions of a national dental service. METHODS: Carbon accounting combined a top-down approach using input-output analysis for indirect emissions (procurement) and a process analysis (bottom-up) approach for direct emissions (building energy, travel, waste and water). Energy and water consumption were based on meter readings, waste-related emissions from collection contracts and travel from staff and patient questionnaires. Dental companies were approached for carbon footprint data on their products. RESULTS: The carbon footprint for the service was 1798.9 tonnes CO(2)eq per annum. Travel was the greatest source (45.1%) followed by procurement (35.9%) and building energy (18.3%). Perhaps counter-intuitively older clinics had lower footprints than newer clinics as they are less energy intensive. Extrapolating the data suggests that Scotland's NHS dental service annually generates 0.16 mega tonne (Mt)CO(2)eq (4%) of the total Scottish NHS carbon footprint. CONCLUSIONS: The lack of comprehensive data reduces the ability to effectively manage emissions. Consideration needs to be given to the impact of patient travel, staff travel and new clinic construction on the carbon footprint. Medical suppliers are encouraged to provide life cycle analysis (LCA) for dental products.

Cronkhite Canada syndrome with early colorectal carcinoma in a patient.

We relate the first case in the Republic of Ireland of Cronkhite Canada Syndrome (CCS). The patient presented with weight loss, alopecia, nail dystrophy, taste disturbance and classic radiologic and endoscopic features of CCS. She continued to dramatically lose weight and early repeat colonoscopy showed the interim development of an invasive sigmoid adenocarcinoma.J

How I do it: the stapled ileal J pouch at restorative proctocolectomy.

BACKGROUND: Ileal pouch-anal anastomosis (IPAA) following proctocolectomy is the preferred option for patients with medically refractory ulcerative colitis, indeterminate colitis, and familial adenomatous polyposis. However, it remains a procedure associated with morbidity and mortality. Pelvic sepsis, pouch fistulae, and anastomotic dehiscence predispose to pouch failure. We report our experience with an adaptation for the formation of the stapled ileal J pouch using the GIA™ 100 stapling device (Covidien, Mansfield, Massachusetts, USA). When creating the J pouch, we remove the bevelled plastic protector from the thin fork of the stapling device, allowing the staple line to be completed to the tip of the stapled efferent limb of the pouch, thereby minimizing potential blind ending in the efferent limb and injury to the transverse staple line. METHODS: Patients undergoing elective IPAA at our institution over a 5-year period using this adapted stapling technique for creation of the ileal J pouch were reviewed. Data were collected from a prospectively maintained inflammatory bowel disease database, theater records, and patient chart review. RESULTS: Forty-one patients underwent IPAA using this technique at our institution during the study period. Postoperative morbidity was encountered in 11 of 41 patients including pelvic sepsis, pouch fistulae, anastomotic stricture, or leak. There was no morbidity observed related to a blind efferent limb or transverse staple line disruption. No mortality was observed in this series. CONCLUSION: Maximizing the length of the efferent fork of the GIA stapling device can reduce the length of redundant efferent J limb of the ileal J pouch. This may reduce the incidence of torsion, volvulus, distension, fistulae/sinuses, and pelvic sepsis/anastomotic leak following IPAA.

Use of an electrothermal bipolar sealing device in ligation of major mesenteric vessels during laparoscopic colorectal resection.

BACKGROUND: A variety of approaches are available for division of major vascular structures during laparoscopic colorectal resection. Ultrasonic coagulating shears (UCS), vascular staplers, plastic or titanium clips and electrothermal bipolar vessel sealing (EBVS) are currently available. We report our experience with an EBVS device, LigaSure™ (Covidien AG), used in division of the ileocolic, middle colic and inferior mesenteric arteries during laparoscopic colorectal resection. METHODS: We report the immediate outcome of 802 consecutive unselected patients who underwent elective laparoscopic colorectal cancer resection performed with use of the LigaSure™ (5 and 10 mm) at our institution over a 5-year period. Operative procedures included right hemicolectomy (n = 180), left hemicolectomy (n = 96), sigmoid colectomy (n = 347) and anterior resection (n = 179). Data were collected from a prospectively maintained cancer database and operative records. The procedures were performed primarily by three consultant surgeons with an interest in laparoscopic colorectal resection. RESULTS: Of 802 cases in which the LigaSure™ device was employed to divide major vascular structures, immediate effective vessel sealing was achieved in 99.8% (n = 800). Two patients experienced related adverse events both following division of the inferior mesenteric artery with a 5 mm LigaSure™. Both patients had immediate uncontrolled haemorrhage that required laparotomy. CONCLUSIONS: Use of the LigaSure™ device to seal and divide the major mesenteric vessels during laparoscopic colorectal resection is very effective, with a high success rate of 99.8%. Caution should be exercised in elderly atherosclerotic patients, particularly when using the 5-mm LigaSure™ device.

Review: Trends for meat, milk and egg consumption for the next decades and the role played by livestock systems in the global production of proteins.

Meeting the food demands of a growing global population within planetary boundaries is a challenge. Sustainably producing animal-sourced foods while supplying sufficient protein to meet the requirements of a healthy diet is a particular challenge. This paper informs the development of pathways to sustainable animal production by examining trends in animal-sourced foods since 2000, including the significance of animal- relative to plant-protein sources. Drawing on three distinct scenarios defined by the Food and Agriculture Organization (FAO), (i.e. Business As Usual (BAU), a continuation of historical trends of food preferences including initiatives to address Sustainable Development Goal targets; Stratified Societies (SSs), leaving challenges unattended; and Towards Sustainability (TS); a more equitable global society and more sustainable food system due to effective polices), future demand for animal-sourced foods is projected. Analysis is based on FAO Food Balance Sheet data (2000-2017) and projected national protein demand per capita (2012-2050). Analysis is disaggregated to five global regions defined by the World Health Organization. It finds that patterns of past demand for animal-sourced foods vary by food (e.g. red vs white meat) and region. However, the European region consistently has the highest levels of consumption of animal-sourced foods, while the South-East Asian and African regions have the lowest. The ratio of animal to plant-sourced protein varies across regions, ranging from 0.29 in Africa to 1.08 in Europe in 2017. Over time, the ratio is relatively stable or moderately increasing, driven by rising incomes in low- or middle-income countries. Under the future scenarios, all World Health Organization regions show a marked increase in demand for animal-sourced protein across BAU and SS. The TS scenario, however, projects notable declines in consumption across Europe and the Americas when compared to the 2012 BAU baseline, with a decline in milk also in the Western Pacific. In contrast, meat and milk consumption in Africa and South-East Asia is projected to increase, reflecting their far lower starting consumption levels. The analysis and subsequent discussion highlight the importance of having regional-specific strategies to deal with the challenge of sustainable livestock production and consumption, with a requirement to consider the impact of actions in one region on others. Clearly, the challenge is not merely one for science and technology but one based on wider aspects of the food system and its diverse stakeholders.

Effects of chemically spiked sediments on estuarine benthic communities: a controlled mesocosm study.

Ambient sediments were collected from a reference site in the North Edisto River, SC and transferred to a laboratory facility to investigate effects of chemical contaminants on estuarine infaunal communities under controlled mesocosm conditions. Sediment contaminant slurries were prepared using dried sediments collected from the reference site and spiked with a metal (copper), a polycyclic aromatic hydrocarbon (pyrene), and a pesticide (4,4(')-dichlorodiphenyltrichloroethane) to yield nominal mean effects range-median (ERM) quotients of <0.01 (no addition), 0.1, and 1.0 and applied to control, low dose (TRT A), and high dose (TRT B) treatment groups, respectively. Sediment samples for contaminant and benthic analyses were collected at the start of the experiment, 1 month after dosing, and 3 months after dosing. Near-nominal mean ERM quotients of 0.001, 0.075, and 0.818 were measured initially after dosing and remained fairly constant throughout the experiment. Measures of benthic condition, diversity, and richness were significantly reduced in both treatment groups relative to the control 1 month after dosing and persisted in TRT B at 3 months. The results demonstrate that benthic community effects can be observed at mean ERM quotients that are about an order of magnitude lower than levels that have been shown to be associated with significant toxicity in acute laboratory bioassays with single species (e.g., amphipods) in other studies.