Archive for December, 2012

Literature round-up, December 2012

Well, I had grand visions of posting links to new literature that I find interesting on a more regular basis than I have been doing. I was shooting for monthly posts, but the last time I posted was back in September! Better late than never I suppose.

Here are a few studies that I’ve come across over the last few months that will hopefully spark some interest:

  • Study on economic impacts of energy service companies – Interesting study on the economic impacts of energy service companies (ESCOs). ESCOs are generally private companies that operate on a model of selling energy performance upgrades to building owners whereby the building owners are motivated to do so because of they are promised long-term energy savings. This study shows that the ESCO industry continued strong growth even through the recession. Additionally, energy payback times are getting longer, suggesting that low-hanging fruit is being plucked in these areas and that more complex (and more expensive) systems with longer rates of returns are being utilized more (Energy Policy).
  • Factors influencing variability in infiltration of PM2.5 – Wonderful paper dissecting a bunch of indoor-outdoor airborne particle measurements that were made in and around about 40 homes in Canada a few years ago. This same team reported their initial findings in several recent papers, but this one tries to explain why some homes had far higher or lower indoor levels of outdoor PM2.5 and ultrafine particles (UFPs). These folks do great work and they show that (quite intuitively) window-opening behaviors, presence and operation of HVAC systems and filters, and the age of homes predicted a good portion of the variation across homes (Atmospheric Environment).
  • Household light makes global heat – This study presents some new lab and field measurements of kerosene wick lamps, which are a significant source of particulate matter emissions, including black carbon (BC), particularly in developing regions of the world. They show tremendously high emission rates of BC, which makes kerosene lamps important in terms of climate forcing and an important contributor to global warming. We’ve already  known a lot about the health and climate impacts of cookstoves in developing regions, but this makes one more important combustion source that needs to be reckoned with. (Environmental Science and Technology).
  • Size and concentration of droplets generated by coughing in human subjects – I’ve been working on a project for the National Air Filtration Association over the last few weeks attempting to quantify what types of effects HVAC filtration may have on the transmission of infectious airborne diseases. In doing so, I’ve come across a few really interesting articles (I’ve already blogged about one of those). In my review, I’ve learned about the aerosols that are expelled from our bodies when we breath, speak, cough, or sneeze. There’s actually a surprising lack of information on the concentrations and sizes of these emitted particles, but this study did a fine job of measuring the particle size distributions of expelled droplets from about 50 human subjects. Very interesting stuff and extremely important for understanding how disease (including influenza and the common cold virus) is transmitted. These researchers showed that a large majority of the droplet nuclei (a fancy word for droplets that have been expelled and then had surrounding liquid evaporated) exist within the 0.7 to 2.1 µm size range (Journal of Aerosol Medicine).

Absurd experiment of the day: airborne transmission of colds

I have been spending much of my time recently working on a project for the National Air Filtration Association (NAFA). The goal is to review literature on the transmission of infectious diseases and explore what kinds of impacts that HVAC particle filters may have on the transmission of infectious aerosols. It’s a wonderfully interesting project that I’m happy to be working on. But it has also sent me digging into a world of literature that I previously didn’t know existed.

For example, I’ve known that there has been a long running debate about whether infectious diseases are transmitted primarily via (i) inhalation of airborne aerosols, (ii) contact with contaminated surfaces, or (iii) some imprecise mixture of the two. In digging in this field, I came across a paper today that details an amazingly absurd, yet extremely helpful, set of experiments.

Check out the following statement from Dick et al. (1987). Aerosol Transmission of Rhinovirus Colds. The Journal of Infectious Diseases. 156(3):442-448:

Twenty-seven to 34 men >18 years of age were inoculated intranasally with 560-2400 TCID50 of safety-tested RV16 [i.e., rhinovirus, or a virus that leads to the common cold] by pipette and spray on two successive days. On the third day, eight men with the most severe colds (donors) played stud and draw poker with 12 antibody-free … men (recipients) between the hours of 8 a.m. and 11 p.m.

Going on…

In experiments A-C the donors and six of the 12 recipients played cards naturally and used cloth handkerchiefs for secretion, cough, and sneeze control, whereas the remaining six recipients in each experiment wore devices that blocked completely all hand-to-head movements.

Did you catch that? A group of men were taken into a lab and injected with cold virus. Then the following day, those men were put together in a room with 12 healthy uninfected men where they played stud and draw poker all day long! The catch was that half of those healthy men were able to touch their faces and behave quite normally; the other half were restrained by these braces such that they couldn’t touch their faces!

This is such an absurd but beautifully constructed experiment to me. I don’t even know if you could get IRB approval for something like this any more. I can just imagine the conversation that led to this experiment. “What if we take a bunch of people, infect them, then make them play poker for 12 hours. Half the people they play poker with can blow their nose, touch their faces, etc., and the other half will be physically restrained — but only to the point where they can’t touch their face… they can still play cards!

In the end, their results are extremely important to the debate on airborne vs. surface transmission of disease. They reported no significant difference between the two groups, suggesting that aerosol transmission must have been the dominant route. Amazing!

Humorous energy efficiency videos

I typically have pretty dim hopes for science, engineering, and technology videos that try to be funny, but I came across a few on home energy efficiency that are actually pretty good!

Here is another one from NYSERDA (the New York State Energy Research and Development Authority).

Added two new project descriptions to the site

I’ve added descriptions of two new projects that we’ve begun this fall! They are described on the Projects page. These two projects include:

Stay tuned as we conduct the research for these projects and post our results!