How Effective Is the Filtration of 'KN95' Filtering Facepiece Respirators During the COVID-19 Pandemic?

Objectives

The high demand of filtering facepiece respirators (FFRs) worldwide during the period of the COVID-19 pandemic has led to a critical situation for decision-makers regarding their supply. After authorizing the use of FFRs certified by other regions of the world, decision-makers in many countries have published alerts, particularly concerning the ‘KN95’ type.

Methods

This paper investigated the filtration performance of different FFRs using an experimental setup already employed during several studies on FFRs filtration performance. Its high-resolution measuring devices permit to determine filtration performance according to the normative criteria: the pressure drop and the filtration efficiency. Eight different FFRs have been used: four NIOSH-approved FFRs and four not NIOSH-approved with a ‘KN95’ shape available during the beginning of the COVID-19 pandemic.

Results

The data show a high disparity between different FFRs purchased by healthcare establishments, and between those that are NIOSH-approved and those that are not NIOSH-approved. The results confirm that the NIOSH certification offers good protection according to the normative criteria. The ‘KN95’ types present pressure drops which correspond to the normative value, however their efficiencies are lower than the efficiencies of FFRs certified by NIOSH and lower than 95% at the most penetrate particle size.

Conclusions

FFRs marking is not sufficient to conclude on the FFRs’ efficiency. Visual inspection can not determine which samples are counterfeit or have manufacturing defects.

Modeling occupational exposure to solvent vapors using the Two-Zone (near-field/far-field) model: a literature review

The Two-Zone model is used in occupational hygiene to predict both near-field and far-field airborne contaminant concentrations. A literature review was carried out on 21 scientific publications in which the Two-Zone model was used to assess occupational exposure to solvent vapors. Data on exposure scenarios, solvents, generation/emission rates, near- and far-field parameters, and model performance were collected and analyzed. Over the 24 exposure scenarios identified, 18 were evaluated under controlled conditions, 5 under normal workplace activities, and 1 was reported based on literature data. The scenarios involved a variety of tasks which consisted, mostly, of cleaning metal parts, spraying solvents onto surfaces, spilling liquids, and filling containers with volatile substances. Twenty-eight different solvents were modeled and the most commonly tested were benzene, toluene, and acetone. Emission rates were considered constant in 16 scenarios, exponentially decreasing in 6 scenarios, and intermittent in 2 scenarios. Four-hundred-and-forty-six (446) predicted-to-measured concentration ratios were calculated across the 21 studies; 441 were obtained in controlled conditions, 4 under normal workplace activities, and 1 was calculated based on the literature data. For controlled studies, the Two-Zone model predictive performance was within a factor of 0.3-3.7 times the measured concentrations with 93% of the values between 0.5 and 2. The model overestimated the measured concentrations in 63% of the evaluations. The median predicted concentration for the near-field was 1.38 vs. 1.02 for the far-field. Results suggest that the model might be a useful tool for predicting occupational exposure to vapors of solvents by providing a conservative approach. Harmonization in model testing strategies and data presentation is needed in future studies to improve the assessment of the predictability of the Two-Zone model. Moreover, this review has provided a database of exposure scenarios, input parameter values, and model predictive performances which can be useful to occupational hygienists in their future modeling activities.

Filtering performances of 20 protective fabrics against solid aerosols

Workers can be exposed to solid airborne particles in some occupational environments, and they might be required to wear chemical protective clothing to prevent skin exposure. Dedicated standards exist to certify the protective value of such clothing, but they are not informative enough to identify the main pathways of entry for solid particles nor to compare performances between different chemical protective clothing. In this work, 20 non-woven fabrics used to make chemical protective clothing for solid particle protection were selected to be examined for both filtration and comfort performances. Nine were microporous fabrics (MP), 10 were multilayered nonwoven fibrous media (SMS) and one was a flash spun material (FS). To assess their filtration performances, fabrics were challenged in a benchtop wind tunnel with a 20-3,000 nm diameter sodium chloride aerosol at three low fabric face velocities (0.05, 0.15, 0.3 cm/sec). Airflow resistance and water vapor transmission rate were also measured to provide indications of comfort for the wearer. The penetration results led to the classification of the 20 fabrics into distinct groups of filtration efficiency. The data were analysed based on the porous media characteristics (thickness, fiber diameter, porosity, etc.). MPs were the most efficient fabrics, and SMSs showed a wide range of performances, mostly due to variations in the thickness of the filtering layer as well as to the fabric treatment. Measurements of airflow resistance and water vapor transmission rates revealed major differences between MPs and FSs and SMSs. This highlights the potential of some SMS fabrics to meet a compromise between protection and comfort.

A comparison of low versus high radioiodine administered activity in patients with low-risk differentiated thyroid cancer

Post-surgical therapeutic management of differentiated thyroid cancer (DTC) is still a controversial subject. Indeed, there is no consensus on the dose of ¹³¹I to be administered, although the current trend towards therapy easing through mini-cures for patients with good prognosis. To confirm the non-inferiority in terms of effectiveness of an ablative mini-cure from 1.11 to 1.85 GBq, over a cure of 3.7 GBq, in patients with DTC operated for low and very low risk. We retrospectively studied 157 patients with very low and low risk DTC, followed in the Nuclear Medicine Department of the Salah Azaiez Institute between 2002 and 2012. These patients had a complementary radioiodine therapy with either low dose (group A) or high dose (group B) with an evaluation at 6 months post treatment and in long-term. The study took place at a referral center. The average age was 42.8 ± 13.7 years with a female predominance (86.7 %). The DTC papillary represented the most common etiology (95 %) with a predominance of pure papillary (68 %) on the follicular variant (27 %). The first cure evaluation did not show statistically significant difference between the two approaches in terms of therapeutic ablative efficiency (p = 0.13). The overall success rate was 77 % (121/157), with 83 % (54/65) in group A and 72.8 % (67/92) in group B. The likelihood of having a remission from the first cure was 1.83 times greater for patients treated with low doses (OR = 1.83, 95 % CI 0.23-1.29). At the end of follow, we have noted one case of refractory disease. The male gender (adjusted OR = 2.71, 95 % CI 0.51-4.23, p = 0.03), and the baseline Tg ≥ 10 (ng/ml) (adjusted OR = 3.48, 95 % CI 1.25-9.67, p = 0.01) were significantly independent predictors of successful first cure ablation. The results provide that mini-dose protocol is not less effective for ablation of the thyroid remnant than 3.7 GBq activity.

Risk analysis for confined space entries: Critical analysis of four tools applied to three risk scenarios

Investigation reports of fatal confined space accidents nearly always point to a problem of identifying or underestimating risks. This paper compares 4 different risk analysis tools developed for confined spaces by applying them to 3 hazardous scenarios. The tools were namely 1. a checklist without risk estimation (Tool A), 2. a checklist with a risk scale (Tool B), 3. a risk calculation without a formal hazard identification stage (Tool C), and 4. a questionnaire followed by a risk matrix (Tool D). Each tool's structure and practical application were studied. Tools A and B gave crude results comparable to those of more analytic tools in less time. Their main limitations were lack of contextual information for the identified hazards and greater dependency on the user's expertise and ability to tackle hazards of different nature. Tools C and D utilized more systematic approaches than tools A and B by supporting risk reduction based on the description of the risk factors. Tool D is distinctive because of 1. its comprehensive structure with respect to the steps suggested in risk management, 2. its dynamic approach to hazard identification, and 3. its use of data resulting from the risk analysis.

Particle loading time and humidity effects on the efficiency of an N95 filtering facepiece respirator model under constant and inhalation cyclic flows

It is necessary to investigate the efficiencies of filtering facepiece respirators (FFRs) exposed to ultrafine particles (UFPs) for long periods of time, since the particle loading time may potentially affect the efficiency of FFRs. This article aims to investigate the filtration efficiency for a model of electrostatic N95 FFRs with constant and 'inhalation-only' cyclic flows, in terms of particle loading time effect, using different humidity conditions. Filters were exposed to generated polydisperse NaCl particles. Experiments were performed mimicking an 'inhalation-only' scenario with a cyclic flow of 85 l min(-1) as the minute volume [or 170 l min(-1) as mean inhalation flow (MIF)] and for two constant flows of 85 and 170 l min(-1), under three relative humidity (RH) levels of 10, 50, and 80%. Each test was performed for loading time periods of 6h and the particle penetration (10-205.4nm in electrical mobility diameter) was measured once every 2h. For a 10% RH, the penetration of smaller size particles (<80nm), including the most penetrating particle size (MPPS), decreased over time for both constant and cyclic flows. For 50 and 80% RH levels, the changes in penetration were typically observed in an opposite direction with less magnitude. The penetrations at MPPS increased with respect to loading time under constant flow conditions (85 and 170 l min(-1)): it did not substantially increase under cyclic flows. The comparison of the cyclic flow (85 l min(-1) as minute volume) and constant flow equal to the cyclic flow minute volume indicated that, for all conditions the penetration was significantly less for the constant flow than that of cyclic flow. The comparison between the cyclic (170 l min(-1) as MIF) and constant flow equal to cyclic flow MIF indicated that, for the initial stage of loading, the penetrations were almost equal, but they were different for the final stages of the loading time. For a 10% RH, the penetration of a wide range of sizes was observed to be higher with the cyclic flow (170 as MIF) than with the equivalent constant flow (170 l min(-1)). For 50 and 80% RH levels, the penetrations were usually greater with a constant flow (170 l min(-1)) than with a cyclic flow (170 l min(-1) as MIF). It is concluded that, for the tested electrostatic N95 filters, the change in penetration as a function of the loading time does not necessarily take place with the same rate under constant (MIF) and cyclic flow. Moreover, for all tested flow rates, the penetration is not only affected by the loading time but also by the RH level. Lower RH levels (10%) have decreasing penetration rates in terms of loading time, while higher RH levels (50 and 80%) have increasing penetration rates. Also, the loading of the filter is normally accompanied with a shift of MPPS towards larger sizes.

Does kidney transplantation with multiple arteries affect graft survival?

INTRODUCTION

We compared short- and long-term outcomes of renal transplants with single versus multiple arteries.

PATIENTS AND METHODS

We retrospectively analyzed data from kidney transplants from 208 living donors performed between 1994 and 2010. Renal grafts were divided into two groups: single renal artery (n = 164) versus multiple renal arteries (n = 44). The groups were compared regarding early and late vascular and urological complications. Patient and graft survivals were compared using Kaplan-Meier survivorship curves with comparisons using the log-rank test.

RESULTS

Both groups were comparable regarding acute rejection episodes, posttransplant hypertension, postsurgery renal artery stenosis, and urologic complications. Only hemorrhagic complications and renal artery thrombosis were significantly higher in the multiple renal arteries group (P = .027 and .03, respectively). Warm ischemia time was significantly longer in the multiple renal arteries group without any influence on the incidence of acute tubular necrosis (P = .2). Mean creatinine clearance at 1 year was 65 versus 50 mL/min/1.73 m(2) (P = .5) and at 5 years, 60 versus 55 mL/min/1.73 m(2) (P = .1) for the single versus multiple renal arteries groups, respectively. Return to hemodialysis was necessary for 18.8% of the single and 16.1% of the multiple renal arteries group.

CONCLUSION

The use of an allograft with multiple renal arteries is a safe, successful surgical procedure, that does not influence patient or graft survivals or increase surgical complication rates provided the surgical team is evolved with technical skill.

Relation between male obesity and male infertility in a Tunisian population

Obesity is associated with significant disturbance in the hormonal milieu that can affect the reproductive system. Male infertility affects approximately 6% of reproductive-aged men. It has been suggested that overweight men or men with obese body mass index (BMI) experience prolonged time to pregnancy, although the influence of male BMI on fertility remains understudied. We hypothesised that BMI is inversely correlated with fertility, manifested by reduced sperm concentration and varicocele. Males of mean age 32.74 ± 6.96 years with semen analyses and self-reported BMI were included (n = 98). Patient parameters analysed included age, BMI, pubertal timing, the development of varicocele, and leutinizing hormone, follicle-stimulating hormone and testosterone (n = 18). The mean age of the study population was 32.74 ± 6.96 years. The incidence of azospermia, oligozoospermia, normospermia and the development of varicocele did not vary across BMI categories. Male obesity is not associated with the incidence of sperm concentration and the development of varicocele.

The need for a comprehensive approach to managing confined space entry: summary of the literature and recommendations for next steps

Despite all the regulatory and standard-setting efforts that have been made in North America, judging from the most recent statistics many fatal incidents related to work in confined spaces still occur. In Canada, fatal incidents in the province of Quebec reveal failures in and absence of the identification and preparation of work situations in confined spaces and in risk management. In this study, we performed a literature review consisting of 77 documents on existing hazards and risk assessment for confined spaces. Moreover, we formulated proposals regarding the design of specific and improved tools for assessing such risks. We found that atmospheric hazards monopolized attention in the literature on confined spaces, while risk estimation specific to confined space interventions received little practical coverage overall, apart from atmospheric hazards. The parameters used to establish classes or groupings of confined spaces in existing tools were imprecise. The development of a risk analysis process that is (i) more systematic and based on the concepts recognized in risk management standards, (ii) multidisciplinary, and (iii) adapted to the specific characteristics of confined spaces is therefore needed. Such a process will better support managers and occupational health and safety (OH&S) personnel in their efforts to prioritize and reduce risks. Suggestions on such a risk analysis tool and categorization of interventions in confined spaces are proposed in this article. Lastly, risk analysis tools adapted to confined space interventions are needed to ensure the inherently safe design of these spaces.

Contribution of breathing frequency and inhalation flow rate on performance of N95 filtering facepiece respirators

The investigation of particle penetration through filtering facepiece respirators under cyclic flows is very necessary because cyclic flows represent actual breathing flow patterns. This article reports the development of a procedure to investigate the individual impact of breathing frequency and flow rate on the performance of N95 filtering facepiece respirators. Experiments were performed for two peak inhalation flows (PIFs; 135 and 360 l min(-1)) and two breathing frequencies [24 and 42 breaths per minute (BPM)] for a total of four cyclic flows (Flow A: 135 l min(-1) and 24 BPM; Flow B: 135 l min(-1) and 42 BPM; Flow C: 360 l min(-1) and 24 BPM; and Flow D: 360 l min(-1) and 42 BPM). Each experiment was performed using two different set-ups: the first set-up included both inhalations and exhalations through the filter media and test chamber, while with the second set-up, only inhalation flows were considered. The results showed that, for the most penetrating particle size range, an increase in both PIF and breathing frequency could potentially enhance the penetration with both set-ups; however, the effect of PIF was observed to be much more pronounced than that of frequency. The results indicated that with both set-ups, when the PIF was increased from 135 to 360 l min(-1) (for the given frequency: 24 or 42 BPM), an increase of up to 139-152% in penetration was observed. On the other hand, only a 10-16% increase in penetration occurred when the frequency was changed from 24 to 42 BPM (for a given PIF: 135 or 360 l min(-1)). This suggests that, from low to high respiratory efforts, a huge portion of penetration enhancement is due to PIF variations and only a small portion is contributed by frequency variations.

Primary renal angiosarcoma: Case report and literature review

Angiosarcoma is a rare malignant tumour occurring in less than 2% of soft tissue sarcomas. Angiosarcoma involving the kidney usually represents metastasis from skin or visceral primary lesions, while angiosarcoma primarily occurring in the kidney is a very rare neoplasm. We report a case of angiosarcoma of the right kidney in a 59-year-old male. The computed tomography scan showed a solid tumour with a low increased density after administration of contrast medium. Histological examination of the piece of nephrectomy confirmed the diagnosis.