Relative contributions of transmission routes for COVID-19 among healthcare personnel providing patient care.

The routes of COVID-19 transmission to healthcare personnel from infected patients is the subject of debate, but is critical to the selection of personal protective equipment. The objective of this paper was to explore the contributions of three transmission routes-contact, droplet, and inhalation-to the risk of occupationally acquired COVID-19 infection among healthcare personnel (HCP). The method was quantitative microbial risk assessment, and an exposure model, where possible model parameters were based on data specific to the SARS-CoV-2 virus when available. The key finding was that droplet and inhalation transmission routes predominate over the contact route, contributing 35%, 57%, and 8.2% of the probability of infection, on average, without use of personal protective equipment. On average, 80% of inhalation exposure occurs when HCP are near patients. The relative contribution of droplet and inhalation depends upon the emission of SARS-CoV-2 in respirable particles (<10 µm) through exhaled breath, and inhalation becomes predominant, on average, when emission exceeds five gene copies per min. The predicted concentration of SARS-CoV-2 in the air of the patient room is low (< 1 gene copy per m3 on average), and likely below the limit of quantification for many air sampling methods. The findings demonstrate the value of respiratory protection for HCP, and that field sampling may not be sensitive enough to verify the contribution of SARS-CoV-2 inhalation to the risk of occupationally acquired COVID-19 infection among healthcare personnel. The emission and infectivity of SARS-CoV-2 in respiratory droplets of different sizes is a critical knowledge gap for understanding and controlling COVID-19 transmission.

Short Communication: Health Interventions in Volcanic Eruptions-Community Wearability Assessment of Respiratory Protection against Volcanic Ash from Mt Sinabung, Indonesia.

Inhalation of ash can be of great concern for affected communities, during and after volcanic eruptions. Governmental and humanitarian agencies recommend and distribute a variety of respiratory protection (RP), commonly surgical masks but, also, industry-certified N95-style masks. However, there is currently no evidence on how wearable they are within affected populations or how protective wearers perceive them being against volcanic ash (which will influence the likelihood of uptake of recommended interventions). Volunteers living near Mt. Sinabung, Sumatra, Indonesia, participated in a field wearability study, which included a high-efficiency mask certified to industry standards (N95-equiv.); a standard, pleated surgical mask (Surgical); a Basic flat-fold mask (Flat-fold), and the surgical mask plus a scarf tied over the top (Surgical Plus) to improve fit. These types of RP had all performed well during earlier laboratory filtration efficiency tests. The N95-equiv. mask had performed significantly better than the other RP in the subsequent total inward leakage volunteer trials, whilst the Flat-fold and Surgical masks performed poorly, letting in a third of PM2.5 particles (data published elsewhere). Thirty volunteers wore each mask for a 15-min walk before being asked to rate the comfort, breathability and perceived protection and fit of each. After wearing all of the masks, volunteers compared and identified their preferred type of protection. The feedback received from the volunteers suggested that the Surgical Plus and N95-equiv. masks were rated as being significantly hotter and more humid than other masks. The Flat-fold was rated to have better breathability than the other masks. The N95-equiv. mask was ranked as providing the best level of effectiveness of the four masks tested. Ultimately, when asked which type of mask they would choose to wear during ashfall, 33% selected the Flat-fold mask due to its comfort and simplicity, with the Surgical Plus being the least likely to be chosen of the four tested. The study findings are of benefit to agencies who need to make informed decisions on the procurement and distribution of RP for use by those affected in future eruptions and the provision of advice to communities on their usage.

Assessment of occupational exposure to asbestos fibers: Contribution of analytical transmission electron microscopy analysis and comparison with phase-contrast microscopy.

From November 2009 to October 2010, the French general directorate for labor organized a large field-study using analytical transmission electron microscopy (ATEM) to characterize occupational exposure to asbestos fibers during work on asbestos containing materials (ACM). The primary objective of this study was to establish a method and to validate the feasibility of using ATEM for the analysis of airborne asbestos of individual filters sampled in various occupational environments. For each sampling event, ATEM data were compared to those obtained by phase-contrast optical microscopy (PCOM), the WHO-recommended reference technique. A total of 265 results were obtained from 29 construction sites where workers were in contact with ACM. Data were sorted depending on the combination of the ACM type and the removal technique. For each "ACM-removal technique" combination, ATEM data were used to compute statistical indicators on short, fine and WHO asbestos fibers. Moreover, exposure was assessed taking into account the use of respiratory protective devices (RPD). As in previous studies, no simple relationship was found between results by PCOM and ATEM counting methods. Some ACM, such as asbestos-containing plasters, generated very high dust levels, and some techniques generated considerable levels of dust whatever the ACM treated. On the basis of these observations, recommendations were made to measure and control the occupational exposure limit. General prevention measures to be taken during work with ACM are also suggested. Finally, it is necessary to continue acquiring knowledge, in particular regarding RPD and the dust levels measured by ATEM for the activities not evaluated during this study.

Modeling risk of occupational zoonotic influenza infection in swine workers.

Zoonotic transmission of influenza A virus (IAV) between swine and workers in swine production facilities may play a role in the emergence of novel influenza strains with pandemic potential. Guidelines to prevent transmission of influenza to swine workers have been developed but there is a need for evidence-based decision-making about protective measures such as respiratory protection. A mathematical model was applied to estimate the risk of occupational IAV exposure to swine workers by contact and airborne transmission, and to evaluate the use of respirators to reduce transmission. The Markov model was used to simulate the transport and exposure of workers to IAV in a swine facility. A dose-response function was used to estimate the risk of infection. This approach is similar to methods previously used to estimate the risk of infection in human health care settings. This study uses concentration of virus in air from field measurements collected during outbreaks of influenza in commercial swine facilities, and analyzed by polymerase chain reaction. It was found that spending 25 min working in a barn during an influenza outbreak in a swine herd could be sufficient to cause zoonotic infection in a worker. However, this risk estimate was sensitive to estimates of viral infectivity to humans. Wearing an excellent fitting N95 respirator reduced this risk, but with high aerosol levels the predicted risk of infection remained high under certain assumptions. The results of this analysis indicate that under the conditions studied, swine workers are at risk of zoonotic influenza infection. The use of an N95 respirator could reduce such risk. These findings have implications for risk assessment and preventive programs targeting swine workers. The exact level of risk remains uncertain, since our model may have overestimated the viability or infectivity of IAV. Additionally, the potential for partial immunity in swine workers associated with repeated low-dose exposures or from previous infection with other influenza strains was not considered. Further studies should explore these uncertainties.

Social marketing campaign promoting the use of respiratory protection devices among farmers.

This article describes the formal use of marketing concepts in a systematic approach to influence farmers to voluntarily increase respiratory protective device (RPD) use. The planning process for the project incorporated six key decision or action points, each informed by formative research or health behavior theory. The planning process included developing behavior change strategies based on a 4P model (product, price, place, and promotion). The resulting campaign elements included print and e-mail messages that leveraged motivators related to family and health in order to increase farmers' knowledge about the risks of exposure to dusty environments, four instructional videos related to the primary barriers identified in using RPDs, and a brightly colored storage bag to address barriers to using RPDs related to mask storage. Campaign implementation included a series of e-mails using a bulk e-mail subscription service, use of social media in the form of posting instructional videos on a YouTube channel, and in-person interactions with members of the target audience at farm shows throughout the Central States Center for Agricultural Safety and Health seven-state region. Evaluation of the e-mail campaigns indicated increased knowledge about RPD use and intent to use RPDs in dusty conditions. YouTube analytic data indicated continuing exposure of the instructional videos beyond the life of the campaign. The project demonstrates the efficacy of a planning process that incorporates formative research and clear decision points throughout. This process could be used to plan health behavior change interventions to address other agriculture-related health and safety issues.

Prevention of laboratory animal allergy in the United States: a national survey.

OBJECTIVE: Respiratory allergy to laboratory animals is a common and preventable occupational health problem. This study documents current laboratory animal allergy (LAA) prevention programs in the United States. METHODS: An online survey was e-mailed to designated institutional officials at laboratory animal facilities identified by the National Institutes of Health Office of Laboratory Animal Welfare. RESULTS: A total of 198 organizations responded and more than 80% required the use of uniforms and gloves to control exposure. Respirators were required by 25% of organizations. Medical surveillance was mandated by 58% of organizations (70% for organizations with at least 100 employees working with animals). Work restriction practices varied. Only 25% of organizations reported knowing the prevalence (range: 0% to 75%) and 29% reported knowing the incidence of LAA (range: 0% to 18%). CONCLUSIONS: There is broad variation in policy and practice to prevent LAA. An evidence-based consensus would ensure greater protection of workers.

An assessment of workplace programmes designed to control inhalation risks using respiratory protective equipment.

OBJECTIVES: Few studies have assessed respiratory protective equipment (RPE) failures at the organizational level despite evidence to suggest that compliance with good practice may be low. The aim of this study was to develop an understanding of what current RPE programmes look like across industry and how this compares with good practice. METHODS: Twenty cross-industry site visits were conducted with companies that had RPE programmes in place. Visits involved management interviews to explore current RPE systems and procedures and the decision making underpinning these. Observations of RPE operatives were included followed by short interviews to discuss the behaviours observed. Post-site assessments jointly undertaken by an RPE scientist and psychologist produced ratings for each site on six critical aspects of RPE programmes (knowledge/awareness, selection, use, training/information, supervision, and storage/cleaning/maintenance). Overall ratings for theoretical competence (i.e. management knowledge of RPE) and practical control (i.e. actual RPE practice on the shop floor) were also given. Qualitative analysis was performed on all interview data. RESULTS: The performance of RPE programmes varied across industry. Fewer than half the companies visited were considered to have an acceptable level of theoretical competence and practical control. Four distinct groups emerged from the 20 sites studied, ranging from Learners (low theoretical competence and practical control--four sites), Developers (acceptable theoretical competence and low practical control--five sites), and Fortuitous (low theoretical competence and acceptable practical control--two sites), to Proficient (acceptable theoretical competence and practical control--nine sites). None of the companies visited were achieving optimal control through the use of RPE. Widespread inadequacies were found with programme implementation, particularly training, supervision, and maintenance. CONCLUSIONS: Our taxonomy based on the four groups (Learners, Developers, Fortuitous, and Proficient) provided a useful expert-informed tool for explaining the variation in performance of RPE programmes across industry. Although further research and development are required, this taxonomy offers a useful starting point for the development of practical tools that may assist managers in making the much-needed improvements to all facets of programme implementation, particularly training, supervision, and maintenance.

Reduction of exposure in the management of occupational asthma.

PURPOSE OF REVIEW: The management of immunologically mediated occupational asthma may be difficult in clinical practice since complete avoidance of exposure to the sensitizing agent is associated with a substantial adverse socio-economic impact. The purpose of this review was to critically analyze the available information on the effectiveness of reducing exposure as an alternative to complete avoidance. RECENT FINDINGS: Short-term exposure studies showed that respiratory protective devices can reduce bronchial responses to sensitizing agents in patients with occupational asthma, but do not provide complete protection. Recent systematic reviews of long-term follow-up studies of workers with occupational asthma indicated that reduction of exposure to the causal agent is associated with a lower likelihood of improvement in asthma symptoms and a higher risk of worsening of symptoms and nonspecific bronchial hyper-responsiveness. There are insufficient data to compare the socio-economic consequences related to both of these management options. SUMMARY: Available data indicate that a reduction of exposure to the agents causing occupational asthma cannot be routinely recommended as an alternative to complete avoidance. However, due to the methodological weaknesses of the published studies, further investigations are required to determine the evidence-based cost-effectiveness of the occupational asthma management strategies.

Dust control technology usage patterns in the drywall finishing industry.

A telephone survey was conducted to quantify drywall finishing industry usage rates of dust control technology, identify barriers to technology adoption, and explore firm owner perception of risk. Industry use of the following technologies was described: wet methods, respiratory protection, pole sanders, ventilated sanders, and low-dust joint compound. A survey instrument composed of both Likert-type scaled items and open-ended items was developed and administered by telephone to the census population of the owners of member firms of trade associations: Finishing Contractors Association and Association of the Wall and Ceiling Industries. Of 857 firms, 264 interviews were completed. Along with descriptive statistics, results were analyzed to examine effects of firm size and union affiliation on responses. Responses to open-ended items were analyzed using content analysis procedures. Firm owners rated the risk of dust to productivity and customer satisfaction as low-moderate. Half rated the dust as having some impact on worker health, with higher impacts indicated by owners of small firms. Among the available control technologies, respiratory protection was used most frequently. Several barriers to implementation of the more effective control technologies were identified. Barriers associated with technology usability, productivity, and cost, as well as misperceptions of risk, should be addressed to improve dust control in the drywall finishing industry.

Inference and sample size calculation in the fit assessment of filtering facepiece respirators.

Filtering facepiece respirators have recently been cleared by the U.S. Food and Drug Administration (FDA) for use by the general public in public health medical emergencies such as pandemic influenza. In the fit assessment of these devices it is important to distinguish between the two sources of variability: population heterogeneity and random fluctuations over repeated donnings. The FDA Special Controls Guidance Document (SCGD) which describes these devices and their evaluation, recommends that the fit performance of a filtering facepiece respirator be evaluated in terms of the proportion of users who will receive a specified level of protection 95% of the time. A point estimator of this proportion is easily obtained under an analysis of variance model, and the SCGD suggests bootstrap as one possible approach to interval estimation. This paper describes a closed-form procedure to obtain confidence intervals and provides sample size formulas. Simulation results suggest that the proposed procedure performs well in realistic settings and compares favorably to two simple bootstrap procedures.

Decision model for optimizing respirator protection.

Respirators are widely used for protection against inhaled toxins. The emphasis of research and implementation effort has evolved through several stages: the respirator device itself, use situation, respirator program factors under employer control, individual worker factors not under employer control, and occupational health systems. For this study, a computer-simulation decision assistance model was developed to assess the impact of various factors on the number of workers receiving adequate protection. Factors include the respirator protection factor, identification of sites needing respirator protection, selection of proper device, availability when needed, frequency of ever use, regularity of use among users, and variability in personal susceptibility or other factors. This analysis demonstrates that for both moderate-risk and high-risk (i.e., IDLH, immediately dangerous to life and health) exposures under current circumstances, the actual protection afforded depends upon the optimization of program factors and detection of atypical outlier persons and worksites. Therefore, programs and research must focus on these areas. Occupational medicine specialists should help optimize these areas and, in addition, use each case of respiratory protection failure as an index case to improve the overall programs.

Respirator leakage in the pharmaceutical industry of northwest England.

Field qualitative fit tests were conducted at 10 separate companies in the Northwest of England to determine the proportion of leaking respirators in a cross-section of pharmaceutical manufacturing industries. The 3 M FT-10 Qualitative Fit Test Apparatus was used to test a total of 211 half-face particulate respirator wearers. Participants wore their own respirators and were asked to don them as they would normally. In all cases, no specific intervention had occurred prior to testing. Results indicated a failure rate of 69% (of the 211 subjects tested, 145 respirators were leaking). Successful results were not associated with the frequency of use (p = 0.71) or years of experience wearing respirators (p = 0.59). Similarly, successful results were not associated with respirator training in the current job (p = 0.38) or training in previous jobs (p = 0.49). Leakage was not consistent across the 10 companies, with two companies exhibiting a 100% failure rate while another company had 26 successful tests in 50 wearers (52% pass rate). Only 35 of the 211 participants performed a negative pressure test. Of these, 80% successfully passed the test, which was significantly greater than the 22% pass rate among those who had not performed the pressure test (p < 0.001).

APIC and CDC survey of Mycobacterium tuberculosis isolation and control practices in hospitals caring for children. Part 2: Environmental and administrative controls. Association for Professionals in Infection control and Epidemiology, Inc.

BACKGROUND: The 1994 Centers for Disease Control and Prevention draft Guidelines for Preventing the Transmission of Mycobacterium tuberculosis in Health-Care Facilities did not exempt pediatric facilities from instituting controls to prevent nosocomial tuberculosis (TB) transmission. Many researchers contend that TB disease in children does not require such rigid controls. We surveyed acute-care pediatric facilities in the United States to determine adherence to environmental and administrative control recommendations. METHODS: The study included 4 mailings of a survey to infection control professionals at 284 US children's hospitals and adult acute-care hospitals with > 30 pediatric beds. RESULTS: Isolation rooms (IRs) generally conformed to recommended guidelines; 92% of respondents reported IRs with > or = 6 air changes per hour, 90% reported 1-pass air and negative pressure, and 89% reported that IRs were private rooms. A sufficient number of inpatient IRs were reported by 88%, but only 42% had IRs in outpatient areas, and 19% had IRs in off-site clinics. Employee tuberculin skin-test programs were in place at 98% of facilities, but policies pertaining to implementation varied. Employees' use of personal respirators increased at respondent hospitals from 1991 to 1994, but as late as 1994, nearly one third still used surgical masks for high-risk procedures. CONCLUSIONS: Environmental and administrative controls used by respondent hospitals largely conformed to published guidelines. Because definitive studies that quantify the risk of nosocomial M tuberculosis transmission in pediatric settings have yet to be performed, pediatric facilities are required to have the same protections in place as do their adult counterparts.