Experimental assessment of exposure to gaseous pollutants from mattresses and pillows while asleep

Every human spends 30% of his or her lifetime and about 70% of the time he or she is at home in their bed. Mattresses, pillows and bedlinnen are heavily treated with flame-retardants, detergents etc, substances that are known to have, next to a useful effect, an impact on human health. While asleep, the nose and mouth are in the direct proximity of these sources for a long period of time. Although these circumstances seem worrying at the least, virtually no research has been published on the exposure to and intake emissions from bedding. This paper presents the results form climate chamber tests with a breathing thermal mannequin that assess the intake fraction for nose breathing for gaseous emissions from mattresses and pillows under steady state conditions, using a continuous SF6 source. The intake fractions for supine, lateral and prone sleep positions as well as different bedding arrangements are reported. The results demonstrate that the human metabolism is a dominant factor in the dilution of emissions in close proximity of the nose, reducing exposure by 40% compared to a case without metabolic heat output. This effect is more important than the sleep position. Additionally, covering the head with the bedding is shown to increase exposure with magnifying factor of 25 and is therefore to be avoided

Fate of particles released by a puff–dispersion with different air distributions

Well-mixed assumption normally has flaws in the space with continuous-releasing particle sources. For transient point or puff sources, however, particle concentration might vary differently among locations during emission periods and afterwards. This study measures whether and how rapidly ventilation systems can distribute particles emitted from puff-like sources in an indoor space. The impact of ventilation pattern (over-head mixing ventilation and displacement ventilation), particle size (0.77, 2.5 and 7 μm) and source location are also examined. The results show that particles with sizes of 0.77 μm and 2.5 μm can be distributed uniformly by both mixing ventilation and displace ventilation shortly (within a few minutes) after particle injection is terminated, regardless of particle source locations with the absence of obstructed airflow. This paper validates the well-mixed assumption when assessing long-term human exposure to puff-generated particles in the indoor environment. With regard to puff sources, the spatial concentration enhancement in human microenvironment/breathing zone might not be as significant as continuous-releasing particle sources

Walls talk: Microbial biogeography of homes spanning urbanization.

Westernization has propelled changes in urbanization and architecture, altering our exposure to the outdoor environment from that experienced during most of human evolution. These changes might affect the developmental exposure of infants to bacteria, immune development, and human microbiome diversity. Contemporary urban humans spend most of their time indoors, and little is known about the microbes associated with different designs of the built environment and their interaction with the human immune system. This study addresses the associations between architectural design and the microbial biogeography of households across a gradient of urbanization in South America. Urbanization was associated with households' increased isolation from outdoor environments, with additional indoor space isolation by walls. Microbes from house walls and floors segregate by location, and urban indoor walls contain human bacterial markers of space use. Urbanized spaces uniquely increase the content of human-associated microbes-which could increase transmission of potential pathogens-and decrease exposure to the environmental microbes with which humans have coevolved

Surface reservoirs dominate dynamic gas-surface partitioning of many indoor air constituents

Human health is affected by indoor air quality. One distinctive aspect of the indoor environment is its very large surface area that acts as a poorly characterized sink and source of gas-phase chemicals. In this work, air-surface interactions of 19 common indoor air contaminants with diverse properties and sources were monitored in a house using fast-response, on-line mass spectrometric and spectroscopic methods. Enhanced-ventilation experiments demonstrate that most of the contaminants reside in the surface reservoirs and not, as expected, in the gas phase. They participate in rapid air-surface partitioning that is much faster than air exchange. Phase distribution calculations are consistent with the observations when assuming simultaneous equilibria between air and large weakly polar and polar absorptive surface reservoirs, with acid-base dissociation in the polar reservoir. Chemical exposure assessments must account for the finding that contaminants that are fully volatile under outdoor air conditions instead behave as semivolatile compounds indoors

Emission of Volatile Byproducts from Ozone Removal Filters

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Transport of Airborne Particles from an Unobstructed Cough Jet

<div><p>This article presents analytical and experimental results for the velocity distribution and transport of expiratory particles from an artificial cough. The stream-wise penetration distance and velocity field of the cough jet were determined through a combination of dimensionless analysis and experimental techniques. The experiments were conducted in a well-controlled environmental chamber with simplified thermal manikins to simulate human coughs and buoyant thermal plumes, and involved flow visualization, velocity measurements employing high and low velocity hot-wire anemometers, and particle size and concentration measurement. The study analyzed three particle sizes—0.77, 2.5, and 7 μm—to examine the impact of particle size on particle transport in the cough jet region and in the vicinity of a receiver occupant positioned in close proximity to the coughing source. The results indicate that the cough jet has a lower axial velocity but higher span-wise expansion rate than a steady jet with an identical discharge velocity. The particles of three sizes have a similar trajectory when considering the transport in the cough jet region. However, particle concentration distributions of the three size particles show that size is an important factor for particle transport in the vicinity of the receiver occupant where airflow velocity decays to the room background air velocity. Furthermore, the results suggest that a cough jet is able to overcome the buoyant human thermal plume and travel further ahead in the region behind the receiver occupant.</p><p>Copyright 2014 American Association for Aerosol Research</p></div

The Influence of Chemical Interactions At the Human Surface on Breathing Zone Levels of Reactants and Products

Using computational fluid dynamics simulations of an occupant in a ventilated room, we find that breathing zone ozone levels can be substantially lower and ozone reaction products associated with human surfaces (ORPHS) levels considerably higher than room levels. For air exchange rates \u3c3/h, the ratio of the breathing zone to the ozone concentration 1 m from the body (bulk air), rozone, ranges from 0.59 to 0.75 for floor or ceiling air supply. ORPHS are enriched in the breathing zone, with concentrations for these conditions ranging from 1.2 to 2.5 greater than bulk air concentrations. at high air exchange rates (\u3e8/h), the breathing zone concentrations approach bulk air concentrations (rozone \u3e 0.9) with a floor supply, whereas large concentration gradients occur between breathing zone and bulk air with a ceiling supply. at these high air exchange rates, ORPHS levels are 1.6-2.0 and 2.9-6.0 times the bulk air concentrations for floor and ceiling supply, respectively. the extent of depletion of ozone or enrichment of ORPHS is large enough that reliance on micro-environmental measurements alone, to assess the intake of ozone or ORPHS, is undesirable

Experimental assessment of the inhalation zone of standing, sitting and sleeping persons

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Experimental assessment of exposure to gaseous pollutants from mattresses and pillows in common sleep positions

Common sleeping positions (partially) shield the nose and therefore induce rebreathing. Additionally, the close proximity of the nose and materials such as mattresses and bedding will increase exposure to gaseous pollutants emitted from these materials. since Pco2 is known to be a parameter affecting the control of breathing during sleep, this will influence breathing during sleep. Objectives: Quantify the impact of common sleep positions on rebreathing and exposure to gaseous pollutants emitted from 'near filed' sources. Methods: Experiments in which a breathing thermal manikin was exposed to different pollutant sources in a number of common sleep positions and bedding arrays were done in an environmental chamb er. SF6 was used as a tracer for gaseous pollutants as well as to measure the fraction of exhaled air that was rebreathed. To study the adaptation mechanisms that are triggered by these phenomena, the effects of this were tested on real subjects using capnography. Results: The results show that human metabolism and corresponding heat release by the human body are dominant factors in the dilution of pollutants emitted in close proximity of the nose. This effect is more important than the sleep position. An additional important finding is that sleeping with the head under the covers increases intake by a factor 24 and results in a rebreathing rate of over 60%. Adaptation mechanisms include changing breathing frequency and tidal volume. Conclusions: we can conclude that rebreathing in most common sleep positions is mild, but that for specific situations, like sleeping with the head under the covers, it perturbates normal breathing/gas exchange