Particle Size on Respiratory Protection Provided by Two Types of N95 Respirators on Agricultural Settings

The objective of this study was to compare size-selective workplace protection factors (WPFs) of an N95 elastomeric respirator (ER) and an N95 filtering facepiece respirator (FFR) in agricultural environments. Twenty-five healthy farm workers ranging in age from 20 to 30 years voluntarily participated in the study. Altogether eight farms were included representing three different types: two horse farms, three pig barns, and three grain handling sites. Subjects wore the ER and FFR while performing their daily activities, such as spreading hay, feeding livestock, and shoveling. Aerosol concentrations in an optical particle size range of 0.7–10 µm were determined simultaneously inside and outside of the respirator during the first and last 15 minutes of a 60-minute experiment. For every subject, size-selective WPFs were calculated in one-minute intervals and averaged over 30 minutes. For the ER, geometric mean WPFs were 172, 321, 1013, 2097 and 2784 for particles of 0.7–1.0, 1.0–2.0, 2.0–3.0, 3.0–5.0, and 5.0–10.0 µm, respectively. Corresponding values for the FFR were 69, 127, 324, 893, and 1994. The 5th percentiles for the ER and FFR were higher than the Assigned Protection Factor of 10 and varied from 28 to 250 and from 16 to 225, respectively. The results show that the N95 ER and FFR tested in the study provided expected level of protection for workers on agricultural farms against particles ranging from 0.7 to 10 µm. The WPFs for the ER were higher than those for the FFR in all size ranges, and the WPFs for both respirators increased with increasing particle size

Comparison of Workplace Protection Factors for Different Biological Contaminants

This study compared workplace protection factors (WPFs) for five different contaminants (endotoxin, fungal spores, (1→3)-β-D-glucan, total particle mass, and total particle number) provided by an N95 elastomeric respirator (ER) and an N95 filtering facepiece respirator (FFR). We previously reported size-selective WPFs for total particle numbers for the ER and FFR, whereas the current article is focused on WPFs for bioaerosols and total particle mass. Farm workers (n = 25) wore the ER and FFR while performing activities at eight locations representing horse farms, pig barns, and grain handling facilities. For the determination of WPFs, particles were collected on filters simultaneously inside and outside the respirator during the first and last 15 min of a 60-min experiment. One field blank per subject was collected without actual sampling. A reporting limit (RL) was established for each contaminant based on geometric means (GMs) of the field blanks as the lowest possible measurable values. Depending on the contaminant type, 38–48% of data points were below the RL. Therefore, a censored regression model was used to estimate WPFs (WPFcensored). The WPFcensored provided by the two types of respirators were not significantly different. In contrast, significant differences were found in the WPFcensored for different types of contaminants. GMs WPFscensored for the two types of respirators combined were 154, 29, 18, 19, and 176 for endotoxin, fungal spore count, (1→3)-β-D-glucan, total particle mass, and total particle number, respectively. The WPFcensored was more strongly associated with concentrations measured outside the respirator for endotoxin, fungal spores, and total particle mass except for total particle number. However, when only data points with outside concentrations higher than 176×RL were included, the WPFs increased, and the association between the outside concentrations and the WPFs became weaker. Results indicate that difference in WPFs observed between different contaminants may be attributed to differences in the sensitivity of analytical methods to detect low inside concentrations, rather than the nature of particles (biological or non-biololgical)

Childhood Asthma and Environmental Exposures at Swimming Pools: State of the Science and Research Recommendations

OBJECTIVES: Recent studies have explored the potential for swimming pool disinfection by-products (DBPs), which are respiratory irritants, to cause asthma in young children. Here we describe the state of the science on methods for understanding children's exposure to DBPs and biologics at swimming pools and associations with new-onset childhood asthma and recommend a research agenda to improve our understanding of this issue. DATA SOURCES: A workshop was held in Leuven, Belgium, 21-23 August 2007, to evaluate the literature and to develop a research agenda to better understand children's exposures in the swimming pool environment and their potential associations with new-onset asthma. Participants, including clinicians, epidemiologists, exposure scientists, pool operations experts, and chemists, reviewed the literature, prepared background summaries, and held extensive discussions on the relevant published studies, knowledge of asthma characterization and exposures at swimming pools, and epidemiologic study designs. SYNTHESIS: Childhood swimming and new-onset childhood asthma have clear implications for public health. If attendance at indoor pools increases risk of childhood asthma, then concerns are warranted and action is necessary. If there is no such relationship, these concerns could unnecessarily deter children from indoor swimming and/or compromise water disinfection. CONCLUSIONS: Current evidence of an association between childhood swimming and new-onset asthma is suggestive but not conclusive. Important data gaps need to be filled, particularly in exposure assessment and characterization of asthma in the very young. Participants recommended that additional evaluations using a multidisciplinary approach are needed to determine whether a clear association exists

Breath-, air- and surface-borne SARS-CoV-2 in hospitals

The COVID-19 pandemic has brought an unprecedented crisis to the global health sector. When discharging COVID-19 patients in accordance with throat or nasal swab protocols using RT-PCR, the potential risk of reintroducing the infection source to humans and the environment must be resolved. Here, 14 patients including 10 COVID-19 subjects were recruited; exhaled breath condensate (EBC), air samples and surface swabs were collected and analyzed for SARS-CoV-2 using reverse transcription-polymerase chain reaction (RT-PCR) in four hospitals with applied natural ventilation and disinfection practices in Wuhan. Here we discovered that 22.2% of COVID-19 patients (n = 9), who were ready for hospital discharge based on current guidelines, had SARS-CoV-2 in their exhaled breath (~10⁵ RNA copies/m³). Although fewer surface swabs (3.1%, n = 318) tested positive, medical equipment such as face shield frequently contacted/used by healthcare workers and the work shift floor were contaminated by SARS-CoV-2 (3–8 viruses/cm²). Three of the air samples (n = 44) including those collected using a robot-assisted sampler were detected positive by a digital PCR with a concentration level of 9–219 viruses/m³. RT-PCR diagnosis using throat swab specimens had a failure rate of more than 22% in safely discharging COVID-19 patients who were otherwise still exhaling the SARS-CoV-2 by a rate of estimated ~1400 RNA copies per minute into the air. Direct surface contact might not represent a major transmission route, and lower positive rate of air sample (6.8%) was likely due to natural ventilation (1.6–3.3 m/s) and regular disinfection practices. While there is a critical need for strengthening hospital discharge standards in preventing re-emergence of COVID-19 spread, use of breath sample as a supplement specimen could further guard the hospital discharge to ensure the safety of the public and minimize the pandemic re-emergence risk

Proximal exposure of public schools and students to major roadways: a nationwide US survey

This study addresses the effect of urban planning and road development on the health risk of students attending schools near major roadways. The proximity of public schools and students was quantified to Interstate, US and state highways in nine large Metropolitan Statistical Areas (MSA) of the USA. In total among the surveyed schools and students, over 30% fell within 400 m of a major roadway and over 10% were within 100 m. For some MSAs almost half of the student population attended schools near (≤400m) major roadways, resulting in a potentially increased risk for asthma and other chronic respiratory problems, especially in schools representing the urban fringe locale. It was concluded that proximity of major roadways should be an important factor in considering sites for new schools and developing policies for reducing the exposure in existing schools. The findings provide an important reference point for coordinating future urban development, transportation and environmental policies.proximal exposure, traffic, major roadways, public schools, air pollutants,

Development and evaluation of a new personal sampler for culturable airborne microorganisms

The objective of this study was to develop a new personal sampler for viable airborne microorganisms and to evaluate its performance under controlled laboratory conditions and in a field. In the sampler, air is bubbled through a porous medium submerged in a liquid layer, as has earlier been demonstrated to be highly efficient for air purification. The prototype had the physical collection efficiency >95% for particles >0.32 μm in aerodynamic diameter during 8 h of continuous operation. The pressure drop across the sampler was below 1700 Pa, much lower than that of most conventional bioaerosol samplers. The collection liquid losses due to evaporation and aerosolization did not exceed 18% in 8 h and the culturability of sampled microorganisms remained high: the recovery rate of stress-sensitive gram-negative P. fluorescens bacteria was 61±20%; for stress-resistant B. subtilis bacteria and A. versicolor fungal spores it was 95±9% and 97±6%, respectively. Six identical personal samplers were tested simultaneously on a simplified human manikin in an office environment. The culturable microbial concentration data obtained during 2, 4 and 8-h sampling were not affected by the sampling time. Inter-sample variation did not exceed 30%. The laboratory and field evaluations have demonstrated that the new sampler is capable of long-term personal sampling of airborne culturable microorganisms. The estimation of the detection limits has indicated that the sampler is capable of monitoring microbial exposure in the environments with the bacterial concentrations above 15 CFU/m3 and fungal concentrations above 5 CFU/m3 when using a sampling time of 8 h

Collection of airborne microorganisms into liquid by bubbling through porous medium

A new method for the removal of airborne particles by air bubbling through fibrous filters immersed into a liquid has recently been developed (Agranovski et al. 1999) and shown to be very efficient for cleaning air environments with ultra-fine aerosol particles. The principal objective of the present study was to evaluate the new bubbling technique for the collection of airborne bacteria into a liquid for subsequent physical and microbiological analysis. It was found that the technique is capable of achieving a physical collection efficiency of 98.5% or higher for particles larger than 0.3 wm in aerodynamic diameter. The physical collection efficiency of the prototype bubbler remained at that high level for 8 h of continuous operation with negligible variation of the pressure drop across the device. Evaporation of the collection fluid did not exceed 20% during 8 h, and the reaerosolization effect on the physical collection efficiency of the bubbler prototype was <8%. The recovery rate of gram-negative Pseudomonas fluorescens bacteria collected for 20 min was shown to be as high as 74% - 10%. Its decrease with time was not statistically significant: the recovery rate reached 63% - 15% and 58% - 16% after 4 and 8 h of continuous operation, respectively. Thus the bubbling technique was demonstrated to be suitable for collecting viable airborne bacteria even if they are sensitive to the stress