scary scientific research about allergens

[baratron]

In the process of my (degree) research, I found some terrifying figures about asthma and allergies. So I thought I'd share them with you :) I hope this is comprehensible to people without a science background: I've used the same standard units throughout, so don't worry about what the units are, just compare the figures.

Apparently, each person can shed as much as 1g of skin per day. This dead skin is colonised by saprophytic fungi (whatever they are), and then by dust mites (Dermatophagoides, which means skin-eater. Yum). Dust mites are arthropods measuring 300 micrometers (or 0.3mm), and grow from egg to adult in 25 days. Here is the really disgusting bit: floor or mattress dust samples typically contain 100 to 1000 mites (dead or alive) per gram. Do the maths *shudder*.

Mite faeces are sticky pellets about 20 micrometers (0.02mm) in diameter, and constitute a large proportion of the allergen in house dust. The gastric enzymes produced by the mites become airborne and are eventually inhaled. The concentration of the two specific allergenic proteins necessary to produce an asthma attack in susceptible individuals is as little as 5ng per m^3 of air (ng are nanograms, or 1 x 10^-9g)! Meep!

Significantly more relevant to my research, typical concentrations of the pollutant called "particulate matter" (basically, all solid and liquid material suspended in air) in urban environments are 10 to 50 micrograms per m^3 of air. A "pollution episode" (a time of extremely high pollution, when people with respiratory disease are warned to take extra precautions) would be defined as a concentration of around 100 micrograms PM per m^3 of air. I myself know from looking at air quality information that I notice changes in PM concentration in the order of 10 micrograms per m^3 air: it's enough to make the difference between my preventer inhaler working or not.

As you're probably aware, in the middle of the 20th Century, London suffered a number of extreme smog events. Apparently, on 3 successive days in 1962, the peak particle loading in London was measured as 7000 micrograms per m^3. (No, I didn't put an extra 0 in by mistake). Amazingly, only 700 people died as a result of this: there is absolutely no question that if I had been around then, I would have ceased to be around. I find it absolutely unbelievable that the air could have been that polluted. And we think we've got it bad now...

Comments

[adjectivegail]

This dead skin is colonised by saprophytic fungi (whatever they are)
saprophytic fungi are fungi that eat dead matter. parasitic ones eat live matter :-)

as for the pollution thing...
my dad told me once that the officials in HK devised a pollution index a couple of decades ago, and included it as a standard thing in weather forecasts. you know, "teperatures will have a high of blah, windspeed is blahblah, and humidity is blahblahblah. finally, the pollution index is blah."
apparently when they devised it, they said that when the index hit ten on a regular basis, it would be detrimental to people's health to be there. and apparently the index is now twelve on a good day, and my dad says sometimes it even goes up to fifteen or sixteen.
and no, it's not anything that HK can do anything about; the vast majority of the pollution is actually from south China, and the winds blow it down.
i love HK, but the pollution is a big factor of why i'd never go back to live there again.

[johnckirk.livejournal.com]

> Apparently, each person can shed as much as 1g of skin per day

That doesn't sound too much - did you mean "kg"?

[baratron.livejournal.com]

It said g in the book. It's not very much, until you consider how many dead skin cells it would take to make up 1g. Cells don't weigh very much! And that each 1g of dead skin lying around in a mattress has at least 100 dust mites living in it...