US oil and gas system emissions from nearly one million aerial site measurements.

As airborne methane surveys of oil and gas systems continue to discover large emissions that are missing from official estimates1-4, the true scope of methane emissions from energy production has yet to be quantified. We integrate approximately one million aerial site measurements into regional emissions inventories for six regions in the USA, comprising 52% of onshore oil and 29% of gas production over 15 aerial campaigns. We construct complete emissions distributions for each, employing empirically grounded simulations to estimate small emissions. Total estimated emissions range from 0.75% (95% confidence interval (CI) 0.65%, 0.84%) of covered natural gas production in a high-productivity, gas-rich region to 9.63% (95% CI 9.04%, 10.39%) in a rapidly expanding, oil-focused region. The six-region weighted average is 2.95% (95% CI 2.79%, 3.14%), or roughly three times the national government inventory estimate5. Only 0.05-1.66% of well sites contribute the majority (50-79%) of well site emissions in 11 out of 15 surveys. Ancillary midstream facilities, including pipelines, contribute 18-57% of estimated regional emissions, similarly concentrated in a small number of point sources. Together, the emissions quantified here represent an annual loss of roughly US$1 billion in commercial gas value and a US$9.3 billion annual social cost6. Repeated, comprehensive, regional remote-sensing surveys offer a path to detect these low-frequency, high-consequence emissions for rapid mitigation, incorporation into official emissions inventories and a clear-eyed assessment of the most effective emission-finding technologies for a given region.

California's methane super-emitters.

Methane is a powerful greenhouse gas and is targeted for emissions mitigation by the US state of California and other jurisdictions worldwide1,2. Unique opportunities for mitigation are presented by point-source emitters-surface features or infrastructure components that are typically less than 10 metres in diameter and emit plumes of highly concentrated methane3. However, data on point-source emissions are sparse and typically lack sufficient spatial and temporal resolution to guide their mitigation and to accurately assess their magnitude4. Here we survey more than 272,000 infrastructure elements in California using an airborne imaging spectrometer that can rapidly map methane plumes5-7. We conduct five campaigns over several months from 2016 to 2018, spanning the oil and gas, manure-management and waste-management sectors, resulting in the detection, geolocation and quantification of emissions from 564 strong methane point sources. Our remote sensing approach enables the rapid and repeated assessment of large areas at high spatial resolution for a poorly characterized population of methane emitters that often appear intermittently and stochastically. We estimate net methane point-source emissions in California to be 0.618 teragrams per year (95 per cent confidence interval 0.523-0.725), equivalent to 34-46 per cent of the state's methane inventory8 for 2016. Methane 'super-emitter' activity occurs in every sector surveyed, with 10 per cent of point sources contributing roughly 60 per cent of point-source emissions-consistent with a study of the US Four Corners region that had a different sectoral mix9. The largest methane emitters in California are a subset of landfills, which exhibit persistent anomalous activity. Methane point-source emissions in California are dominated by landfills (41 per cent), followed by dairies (26 per cent) and the oil and gas sector (26 per cent). Our data have enabled the identification of the 0.2 per cent of California's infrastructure that is responsible for these emissions. Sharing these data with collaborating infrastructure operators has led to the mitigation of anomalous methane-emission activity10.

Strong methane point sources contribute a disproportionate fraction of total emissions across multiple basins in the United States.

Understanding, prioritizing, and mitigating methane (CH4) emissions requires quantifying CH4 budgets from facility scales to regional scales with the ability to differentiate between source sectors. We deployed a tiered observing system for multiple basins in the United States (San Joaquin Valley, Uinta, Denver-Julesburg, Permian, Marcellus). We quantify strong point source emissions (>10 kg CH4 h-1) using airborne imaging spectrometers, attribute them to sectors, and assess their intermittency with multiple revisits. We compare these point source emissions to total basin CH4 fluxes derived from inversion of Sentinel-5p satellite CH4 observations. Across basins, point sources make up on average 40% of the regional flux. We sampled some basins several times across multiple months and years and find a distinct bimodal structure to emission timescales: the total point source budget is split nearly in half by short-lasting and long-lasting emission events. With the increasing airborne and satellite observing capabilities planned for the near future, tiered observing systems will more fully quantify and attribute CH4 emissions from facility to regional scales, which is needed to effectively and efficiently reduce methane emissions.

Impact of Maximal Transurethral Resection on Pathological Outcomes at Cystectomy in a Large, Multi-institutional Cohort.

PURPOSE: While the presence of residual disease at the time of radical cystectomy for bladder cancer is an established prognostic indicator, controversy remains regarding the importance of maximal transurethral resection prior to neoadjuvant chemotherapy. We characterized the influence of maximal transurethral resection on pathological and survival outcomes using a large, multi-institutional cohort. MATERIALS AND METHODS: We identified 785 patients from a multi-institutional cohort undergoing radical cystectomy for muscle-invasive bladder cancer after neoadjuvant chemotherapy. We employed bivariate comparisons and stratified multivariable models to quantify the effect of maximal transurethral resection on pathological findings at cystectomy and survival. RESULTS: Of 785 patients, 579 (74%) underwent maximal transurethral resection. Incomplete transurethral resection was more frequent in patients with more advanced clinical tumor (cT) and nodal (cN) stage (P < .001 and P < .01, respectively), with more advanced ypT stage at cystectomy and higher rates of positive surgical margins (P < .01 and P < .05, respectively). In multivariable models, maximal transurethral resection was associated with downstaging at cystectomy (adjusted odds ratio 1.6, 95% CI 1.1-2.5). In Cox proportional hazards analysis, maximal transurethral resection was not associated with overall survival (adjusted HR 0.8, 95% CI 0.6-1.1). CONCLUSIONS: In patients undergoing transurethral resection for muscle-invasive bladder cancer prior to neoadjuvant chemotherapy, maximal resection may improve pathological response at cystectomy. However, the ultimate effects on long-term survival and oncologic outcomes warrant further investigation.

Clinical experience improves academic outcomes in dental Oral surgery education.

INTRODUCTION: This paper aimed to determine if the level of a dental student's clinical experience in oral surgery influences the student's oral surgery academic outcomes. MATERIALS AND METHODS: The oral surgery clinical activity and academic outcomes for all students who completed their dental training in 2017, 2018, 2019 and 2020 from the University of Sydney were analysed for correlation. RESULTS: The clinical activity performed by 313 students was recorded. There was a weak, but statistically significant, Pearson correlation between total dental extractions and academic outcomes (r = .243, p = <.001). The total number of dental extractions performed was the only statistically significant variable on academic outcomes with linear regression analysis (ß = .227, p = .005; model R2  = .077). The increase of a student's clinical experience from less than 45 to more than 65 dental extractions raised their oral surgery academic results by an average of 6.4%. There were no academic benefits to earlier clinical experience. CONCLUSION: An increase in experience with dental extractions resulted in an increase in oral surgery academic outcomes, plateauing at 65 dental extractions. There was no academic advantage to dental student's having earlier clinical experience.

Dental student oral surgery training-Comparing the impact of COVID-19 and cohort sizes.

INTRODUCTION: The response to the COVID-19 pandemic potentially reduced the clinical experience and academic education of dental trainees through reduced supervised clinical sessions. Graduating dental students, future employers and regulators may be concerned over the level of clinical experience of graduates trained within the COVID-19 pandemic. The purpose of this study was to try and document the evidence for, and significance of, this impact. MATERIALS AND METHODS: From dental student data in the 2017, 2018, 2019 and 2020 cohorts attending the University of Sydney, Australia, the number of dental extractions and adjunct oral surgery procedures, as well as final end-of-year examination results, was recorded. Results were compared to determine whether differences in experience and final academic achievement existed between these cohorts. RESULTS: The smallest student cohort, 2017, demonstrated greater clinical experience than the 2018, 2019 and 2020 cohorts. The 2020 COVID-19-affected cohort demonstrated no statistically significant reduction in clinical experience in all measured clinical procedures when compared to the 2018 and 2019 cohorts. The decrease in city teaching hospital clinical experience was compensated by an increase in rural placements. The 2020 cohort achieved the lowest academic results, and this was statistically significant. CONCLUSION: The oral surgery clinical experience of the 2020 dental cohort at the University of Sydney was comparable to prior cohorts. Rural clinics were able to compensate for COVID-19 interruptions to clinical training. The number of students in a cohort, if all other variables remain constant, appeared to affect clinical exposure to a greater extent than COVID-19.

Maintenance of Remission With Tofacitinib Therapy in Patients With Ulcerative Colitis.

BACKGROUND & AIMS: Tofacitinib is an oral, small molecule Janus kinase inhibitor for the treatment of ulcerative colitis (UC). The efficacy and safety of tofacitinib in patients with moderate to severe UC, up to 1 year, have been reported. We investigated maintenance of efficacy in patients in remission after 52 weeks of maintenance treatment in the pivotal phase 3 study (OCTAVE Sustain); these patients received open-label, long-term treatment with tofacitinib 5 mg twice daily. METHODS: Patients with moderate to severe UC who completed a 52-week, phase 3 maintenance study (OCTAVE Sustain) were eligible to enroll into the ongoing, phase 3, multicenter, open-label, long-term extension (OCTAVE Open). We analyzed data from 142 patients who were in remission following tofacitinib treatment in OCTAVE Sustain who received tofacitinib 5 mg twice daily during OCTAVE Open. We assessed efficacy (including remission [based on total Mayo score], endoscopic improvement, clinical response, and partial Mayo score up to month 36 of OCTAVE Open) and safety data. RESULTS: After 12 months of tofacitinib 5 mg twice daily in OCTAVE Open, 68.3% of patients were in remission, 73.9% had endoscopic improvement, and 77.5% had a clinical response. At month 36, 50.4%, of the patients were in remission, 55.3% had endoscopic improvement, and 56.0% had a clinical response. The safety profile of tofacitinib 5 mg twice daily revealed no new safety risks associated with long-term exposure up to 36 months. CONCLUSIONS: Efficacy endpoints were maintained for up to 36 months, regardless of prior tofacitinib dose, including patients who reduced from tofacitinib 10 mg to 5 mg twice daily upon OCTAVE Open entry. No new safety risks were identified. ClinicalTrials.gov: OCTAVE Sustain (NCT01458574); OCTAVE Open (NCT01470612).

Identifying the Optimal Number of Neoadjuvant Chemotherapy Cycles in Patients with Muscle Invasive Bladder Cancer.

PURPOSE: We investigated the pathological response rates and survival associated with 3 vs 4 cycles of cisplatin-based neoadjuvant chemotherapy (NAC) in patients with cT2-4N0M0 muscle invasive bladder cancer. MATERIALS AND METHODS: In this cohort study we analyzed clinical data of 828 patients treated with NAC and radical cystectomy between 2000 and 2020. A total of 384 and 444 patients were treated with 3 and 4 cycles of NAC, respectively. Pathological objective response (pOR; ypT0-Ta-Tis-T1 N0), pathological complete response (pCR; ypT0 N0), cancer-specific survival and overall survival were investigated. RESULTS: pOR and pCR were achieved in 378 (45%; 95% CI 42, 49) and 207 (25%; 95% CI 22, 28) patients, respectively. Patients treated with 4 cycles of NAC had higher pOR (49% vs 42%, p=0.03) and pCR (28% vs 21%, p=0.02) rates compared to those treated with 3 cycles. This effect was confirmed on multivariable logistic regression analysis (pOR OR 1.46 p=0.008, pCR OR 1.57, p=0.007). On multivariable Cox regression analysis, 4 cycles of NAC were significantly associated with overall survival (HR 0.68; 95% CI 0.49, 0.94; p=0.02) but not with cancer-specific survival (HR 0.72; 95% CI 0.50, 1.04; p=0.08). CONCLUSIONS: Four cycles of NAC achieved better pathological response and survival compared to 3 cycles. These findings may aid clinicians in counseling patients and serve as a benchmark for prospective trials. Prospective validation of these findings and assessment of cumulative toxicity derived from an increased number of cycles are needed.

Multicenter evaluation of neoadjuvant and induction gemcitabine-carboplatin versus gemcitabine-cisplatin followed by radical cystectomy for muscle-invasive bladder cancer.

PURPOSE: Cisplatin-based chemotherapy followed by radical cystectomy (RC) is recommended in patients with muscle-invasive bladder cancer (MIBC). However, up to 50% of patients are cisplatin ineligible. The aim of this study was to compare clinical outcomes after ≥ 3 cycles of preoperative gemcitabine-carboplatin (gem-carbo) versus gemcitabine-cisplatin (gem-cis). METHODS: We identified 1865 patients treated at 19 centers between 2000 and 2013. Patients were included if they had received ≥ 3 cycles of neoadjuvant (cT2-4aN0M0) or induction (cTanyN + M0) gem-carbo or gem-cis followed by RC. RESULTS: We included 747 patients treated with gem-carbo (n = 147) or gem-cis (n = 600). Patients treated with gem-carbo had a higher Charlson Comorbidity Index (p = 0.016) and more clinically node-positive disease (32% versus 20%; p = 0.013). The complete pathological response (pCR; ypT0N0) rate did not significantly differ between gem-carbo and gem-cis (20.7% versus 22.1%; p = 0.73). Chemotherapeutic regimen was not significantly associated with pCR (OR 0.99 [95%CI 0.61-1.59]; p = 0.96), overall survival (OS) (HR 1.20 [95%CI 0.85-1.67]; p = 0.31), or cancer-specific survival (CSS) (HR 1.35 [95%CI 0.93-1.96]; p = 0.11). Median OS of patients treated with gem-carbo and gem-cis was 28.6 months (95%CI 18.1-39.1) and 45.1 months (95%CI 32.7-57.6) (p = 0.18), respectively. Median CSS of patients treated with gem-carbo and gem-cis was 28.8 months (95%CI 9.8-47.8) and 71.0 months (95%CI median not reached) (p = 0.02), respectively. Subanalyses of the neoadjuvant and induction setting did not show significant survival differences. CONCLUSION: Our results show that a subset of cisplatin-ineligible patients with MIBC achieve pCR on gem-carbo and that survival outcomes seem comparable to gem-cis provided patients are able to receive ≥ 3 cycles and undergo RC.

Recent Advances Toward Transparent Methane Emissions Monitoring: A Review.

Given that anthropogenic greenhouse gas (GHG) emissions must be immediately reduced to avoid drastic increases in global temperature, methane emissions have been placed center stage in the fight against climate change. Methane has a significantly larger warming potential than carbon dioxide. A large percentage of methane emissions are in the form of industry emissions, some of which can now be readily identified and mitigated. This review considers recent advances in methane detection that allow accurate and transparent monitoring, which are needed for reducing uncertainty in source attribution and evaluating progress in emissions reductions. A particular focus is on complementary methods operating at different scales with applications for the oil and gas industry, allowing rapid detection of large point sources and addressing inconsistencies of emissions inventories. Emerging airborne and satellite imaging spectrometers are advancing our understanding and offer new top-down assessment methods to complement bottom-up methods. Successfully merging estimates across scales is vital for increased certainty regarding greenhouse gas emissions and can inform regulatory decisions. The development of comprehensive, transparent, and spatially resolved top-down and bottom-up inventories will be crucial for holding nations accountable for their climate commitments.

Neoadjuvant chemotherapy plus radical cystectomy versus radical cystectomy alone in clinical T2 bladder cancer without hydronephrosis.

OBJECTIVES: To assess the efficacy of neoadjuvant chemotherapy (NAC) before radical cystectomy (RC) in a retrospective multicentre cohort of patients with cT2N0M0 bladder cancer (BCa) without preoperative hydronephrosis. PATIENTS AND METHODS: This was a propensity-based analysis of 619 patients. Of these, 316 were treated with NAC followed by RC and 303 with upfront RC. After multiple imputations, inverse probability of treatment weighting (IPTW) was used to account for potential selection bias. Multivariable logistic regression analysis was performed to evaluate the impact of NAC on pathological complete response and downstaging at RC, while IPTW-adjusted Kaplan-Meier curves and Cox regression models were built to evaluate the impact of NAC on overall survival (OS). RESULTS: After IPTW-adjusted analysis, standardised differences between groups were <15%. A complete response (pT0N0) at final pathology was achieved in 94 (30%) patients receiving NAC and nine (3%) undergoing upfront RC. Downstaging to non-muscle-invasive disease (

Comparative effectiveness of neoadjuvant chemotherapy in bladder and upper urinary tract urothelial carcinoma.

OBJECTIVE: To assess the differential response to neoadjuvant chemotherapy (NAC) in patients with urothelial carcinoma of the bladder (UCB) compared to upper tract urothelial carcioma (UTUC) treated with radical surgery. PATIENTS AND METHODS: Data from 1299 patients with UCB and 276 with UTUC were obtained from multicentric collaborations. The association of disease location (UCB vs UTUC) with pathological complete response (pCR, defined as a post-treatment pathological stage ypT0N0) and pathological objective response (pOR, defined as ypT0-Ta-Tis-T1N0) after NAC was evaluated using logistic regression analyses. The association with overall (OS) and cancer-specific survival (CSS) was evaluated using Cox regression analyses. RESULTS: A pCR was found in 250 (19.2%) patients with UCB and in 23 (8.3%) with UTUC (P < 0.01). A pOR was found in 523 (40.3%) patients with UCB and in 133 (48.2%) with UTUC (P = 0.02). On multivariable logistic regression analysis, patients with UTUC were less likely to have a pCR (odds ratio [OR] 0.45, 95% confidence interval [CI] 0.27-0.70; P < 0.01) and more likely to have a pOR (OR 1.57, 95% CI 1.89-2.08; P < 0.01). On univariable Cox regression analyses, UTUC was associated with better OS (hazard ratio [HR] 0.80, 95% CI 0.64-0.99, P = 0.04) and CSS (HR 0.63, 95% CI 0.49-0.83; P < 0.01). On multivariable Cox regression analyses, UTUC remained associated with CSS (HR 0.61, 95% CI 0.45-0.82; P < 0.01), but not with OS. CONCLUSIONS: Our present findings suggest that the benefit of NAC in UTUC is similar to that found in UCB. These data can be used as a benchmark to contextualise survival outcomes and plan future trial design with NAC in urothelial cancer.

Association of age with response to preoperative chemotherapy in patients with muscle-invasive bladder cancer.

PURPOSE: To assess the association of patient age with response to preoperative chemotherapy in patients with muscle-invasive bladder cancer (MIBC). MATERIALS AND METHODS: We analyzed data from 1105 patients with MIBC. Patients age was evaluated as continuous variable and stratified in quartiles. Pathologic objective response (pOR; ypT0-Ta-Tis-T1N0) and pathologic complete response (pCR; ypT0N0), as well survival outcomes were assessed. We used data of 395 patients from The Cancer Genome Atlas (TCGA) to investigate the prevalence of TCGA molecular subtypes and DNA damage repair (DDR) gene alterations according to patient age. RESULTS: pOR was achieved in 40% of patients. There was no difference in distribution of pOR or pCR between age quartiles. On univariable logistic regression analysis, patient age was not associated with pOR or pCR when evaluated as continuous variables or stratified in quartiles (all p > 0.3). Median follow-up was 18 months (IQR 6-37). On Cox regression and competing risk regression analyses, age was not associated with survival outcomes (all p > 0.05). In the TCGA cohort, patient with age ≤ 60 years has 7% less DDR gene mutations (p = 0.59). We found higher age distribution in patients with luminal (p < 0.001) and luminal infiltrated (p = 0.002) compared to those with luminal papillary subtype. CONCLUSIONS: While younger patients may have less mutational tumor burden, our analysis failed to show an association of age with response to preoperative chemotherapy or survival outcomes. Therefore, the use of preoperative chemotherapy should be considered regardless of patient age.

Assessment of Regional Methane Emission Inventories through Airborne Quantification in the San Francisco Bay Area.

This study derives methane emission rates from 92 airborne observations collected over 23 facilities including 5 refineries, 10 landfills, 4 wastewater treatment plants (POTWs), 2 composting operations, and 2 dairies in the San Francisco Bay Area. Emission rates are measured using an airborne mass-balance technique from a low-flying aircraft. Annual measurement-based sectorwide methane emissions are 19,000 ± 2300 Mg for refineries, 136,700 ± 25,900 Mg for landfills, 11,900 ± 1,500 Mg for POTWs, and 11,100 ± 3,400 Mg for composting. The average of measured emissions for each refinery ranges from 4 to 23 times larger than the corresponding emissions reported to regulatory agencies, while measurement-derived landfill and POTW estimates are approximately twice the current inventory estimates. Significant methane emissions at composting facilities indicate that a California mandate to divert organics from landfills to composting may not be an effective measure for mitigating methane emissions unless best management practices are instituted at composting facilities. Complementary evidence from airborne remote sensing imagery indicates atmospheric venting from refinery hydrogen plants, landfill working surfaces, composting stockpiles, etc., to be among the specific source types responsible for the observed discrepancies. This work highlights the value of multiple measurement approaches to accurately estimate facility-scale methane emissions and perform source attribution at subfacility scales to guide and verify effective mitigation policy and action.

Airborne methane remote measurements reveal heavy-tail flux distribution in Four Corners region.

Methane (CH4) impacts climate as the second strongest anthropogenic greenhouse gas and air quality by influencing tropospheric ozone levels. Space-based observations have identified the Four Corners region in the Southwest United States as an area of large CH4 enhancements. We conducted an airborne campaign in Four Corners during April 2015 with the next-generation Airborne Visible/Infrared Imaging Spectrometer (near-infrared) and Hyperspectral Thermal Emission Spectrometer (thermal infrared) imaging spectrometers to better understand the source of methane by measuring methane plumes at 1- to 3-m spatial resolution. Our analysis detected more than 250 individual methane plumes from fossil fuel harvesting, processing, and distributing infrastructures, spanning an emission range from the detection limit [Formula: see text] 2 kg/h to 5 kg/h through [Formula: see text] 5,000 kg/h. Observed sources include gas processing facilities, storage tanks, pipeline leaks, and well pads, as well as a coal mine venting shaft. Overall, plume enhancements and inferred fluxes follow a lognormal distribution, with the top 10% emitters contributing 49 to 66% to the inferred total point source flux of 0.23 Tg/y to 0.39 Tg/y. With the observed confirmation of a lognormal emission distribution, this airborne observing strategy and its ability to locate previously unknown point sources in real time provides an efficient and effective method to identify and mitigate major emissions contributors over a wide geographic area. With improved instrumentation, this capability scales to spaceborne applications [Thompson DR, et al. (2016) Geophys Res Lett 43(12):6571-6578]. Further illustration of this potential is demonstrated with two detected, confirmed, and repaired pipeline leaks during the campaign.

Laboratory comparison of new high flow rate respirable size-selective sampler.

A newly developed high flow rate respirable size-selective cyclone sampler (GK4.162-also known as the Respirable Air Sampling Cyclone Aluminum Large (RASCAL)) was calibrated to determine its optimum operating flow rate. The Health and Safety Laboratory in the United Kingdom and two laboratories from the National Institute for Occupational Safety and Health in the United States conducted experiments using two different methods: (1) polydisperse aerosol and time-of-flight direct reading instrument (Aerodynamic Particle Sizer (APS)) and (2) monodisperse aerosol and APS. The measured performance data for the cyclone was assessed against the international respirable convention using the bias map approach. Although the GK4.162 cyclone was tested using different aerosols and detection methods, the results from the three laboratories were generally similar. The recommended flow rate based on the agreement of results from the laboratories was 9.0 L/min.

Performance of High Flow Rate Personal Respirable Samplers When Challenged with Mineral Aerosols of Different Particle Size Distributions.

It is thought that the performance of respirable samplers may vary when exposed to dust aerosols with different particle sizes and wind speeds. This study investigated the performance of the GK 4.16 (RASCAL), GK 2.69, PPI 8, and FSP 10, high flow rate personal samplers when exposed to aerosols of mineral dust in a wind tunnel at two different wind speeds (1 and 2 m s(-1)) and orientations (towards and side-on to the source of emission). The mass median aerodynamic diameter of four aerosolized test dusts ranged from 8 to 25 µm with geometric standard deviations from 1.6 to 2 µm. The performance of each sampler type was compared with that of the SIMPEDS (Higgins-Dewell design) sampler. There was slight evidence to suggest that the performance of the FSP 10 is affected by the direction of the inlet relative to the air flow, although this was not significant when most respirable dust concentrations were compared, possibly due to the variability of paired dust concentration results. The GK 2.69, RASCAL, and PPI 8 samplers had similar performances, although the results when side-on to the emission source were generally slightly lower than the SIMPEDS. Despite slight differences between respirable dust concentrations the respirable crystalline silica values were not significantly different from the SIMPEDS. The GK family of cyclones obtained most precise results and more closely matched the SIMPEDS. A comparison with dust concentration results from previous calm air chamber studies (where wind speeds were < 0.4 m s(-1)) found that the relative performance between samplers was similar to those observed in this work indicating consistent performance relative to the SIMPEDS in both calm and moving air.

A New Miniature Respirable Sampler for In-mask Sampling: Part 1-Particle Size Selection Performance.

The Health and Safety Laboratory has developed a miniature respirable sampler to gain a better understanding of the exposure of workers to hazardous substances when they are wearing respiratory protective equipment (RPE) or helmets with visors in the workplace. The study was in two parts and the first part, described herein, was to develop the sampler and test its collection characteristics. Assessment of the impact of the sampler on RPE safety and its comparability with traditional laboratory-based approaches to measure protection factors was discussed in a second article. The miniature sampler (weight-5.4g, length-13mm) was designed to fit into the space available between the nose and chin of an individual inside a filtering facepiece type mask and has a radially omnidirectional inlet with a porous foam particle selector that allows the collection of the respirable fraction on a downstream filter. The sampling efficiency was compared with the respirable convention. A close match with the respirable convention was obtained at a flow rate of 1 l min-1 and the 50% penetration cut off value (d 50) was 4.08 µm. After 3 hours sampling in high humidity (95%), the penetration curve had shifted towards smaller particle sizes (d 50 = 3.81 µm) with 88% of the calculated bias values within 10%. The miniature sampler measured respirable dust and crystalline silica mass concentrations comparable with performance of the Safety In Mines Personal Dust Sampler (SIMPEDS), commonly used in Great Britain, at a flow rate of 0.8 l min-1 The d 50 for the miniature sampler at 0.8 l min-1 (4.4 µm) is within 5% of the d 50 of the SIMPEDS at its prescribed flow rate of 2.2 l min-1 (4.2 µm). These results indicated that the miniature sampler was a good candidate to proceed with tests with RPE described in the second part of this series of two papers.

Calibration of high flow rate thoracic-size selective samplers.

High flow rate respirable size selective samplers, GK4.126 and FSP10 cyclones, were calibrated for thoracic-size selective sampling in two different laboratories. The National Institute for Occupational Safety and Health (NIOSH) utilized monodisperse ammonium fluorescein particles and scanning electron microscopy to determine the aerodynamic particle size of the monodisperse aerosol. Fluorescein intensity was measured to determine sampling efficiencies of the cyclones. The Health Safety and Laboratory (HSL) utilized a real time particle sizing instrument (Aerodynamic Particle Sizer) and polydisperse glass sphere particles and particle size distributions between the cyclone and reference sampler were compared. Sampling efficiency of the cyclones were compared to the thoracic convention defined by the American Conference of Governmental Industrial Hygienists (ACGIH)/Comité Européen de Normalisation (CEN)/International Standards Organization (ISO). The GK4.126 cyclone showed minimum bias compared to the thoracic convention at flow rates of 3.5 l min(-1) (NIOSH) and 2.7-3.3 l min(-1) (HSL) and the difference may be from the use of different test systems. In order to collect the most dust and reduce the limit of detection, HSL suggested using the upper end in range (3.3 l min(-1)). A flow rate of 3.4 l min(-1) would be a reasonable compromise, pending confirmation in other laboratories. The FSP10 cyclone showed minimum bias at the flow rate of 4.0 l min(-1) in the NIOSH laboratory test. The high flow rate thoracic-size selective samplers might be used for higher sample mass collection in order to meet analytical limits of quantification.