> Alain schrieb:
>> Back then, the outer wall of any brick or granite house more than 5 
>> years old where mostly black.
>> Now, those same walls have recovered ther original colours, mostly due 
>> to the rain.
> 
> This is how the spires of the Cologne Cathedral look like today:
> 
>   http://en.wikipedia.org/wiki/File:Koelner-dom-spire.jpg
> 
> And this is a photograph from ca. 1880:
> 
>   http://en.wikipedia.org/wiki/File:Detail,_Cologne_Cathedral_Tower.jpg
> 
> Note that the cathedral is - at least in parts - 750 years old. The dark 
> color seen today is almost exclusively from soot, probably most of it 
> from the nearby central railway station (the cathedral is just some 100 
> meters from the platforms).
> 
> The soot has "eaten" its way so deep into the stone that any attempt to 
> wash it off is futile. Only in the process of restoration of other 
> damage does the cathedral regain its original bright color again in some 
> sections.
> 
> Man, that must have been a beautiful building!
> 
>> And, now, old peoples that lived during that time are complaining 
>> about the polution levels we expeiencing now... And say that in ther 
>> time there was no polution.
> 
> Well, the pollution was entirely different. I'm not sure whether it was 
> any better or worse back then: I'm sure it was more obviously bad, but 
> given that we're consuming far more energy these days, I guess the grand 
> total of today's emissions is just as bad.
> 
> For instance, there appears to be a correlation between particulates 
> (which weren't that much of a problem in historic times, most of the 
> emitted sold matter having been bound in larger, visible particles) and 
> pollen allergies (i.e. people seem to more readily develop hayfever in 
> regions with strong particulate pollution).

Conserning hay feever and other alergies, there is a possible corelation 
with the general hygien levels and the use and over use of cleaning.

When a baby or chold imune system is not sufisiently solicited, it don't 
learn to make the difference between harmfull things, like virus and 
bacteria, and hamless things like odrinary dust, earth, polens and some 
food stuff.

Some studies seems to demonstrate that a baby who grew in a aseptised 
environment could be about 1000+ times more suceptible to devlop 
alergies than one who grew in a more hygien relaxed environment.



Alain

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