Re: What is the mechanism for the cancer caused by asbestoes.

Cancer caused by asbestos seems to require that the asbestos get inside 
your lungs or digestive tract. The cancers caused by asbestos include lung 
cancer, mesotheloma, which is a cancer of the lining surrounding the lung, 
and cancers of the digestive tract such as stomach and colon cancer. Skin 
cancer does not appear to be caused by asbestos.

The mechanism that asbestos causes cancer seems to be by the bodies immune 
response to the asbestos. Asbestos is an inorganic fiber that the body's 
immune system cannot do anything with. If I breathe in bacteria, my body's 
immune system will kill those right away. If I breathe in asbestos, the 
asbestos will hang around in the lungs forever. 

When the asbestos is in someone's lungs, the body sends its immune system 
cells or white blood cells (WBCs) to attack it. The body's WBCs create 
particles that are toxic to cells, especially free radicals. When the body 
is fighting off bacteria, this is good. The free radicals kill the 
bacteria, the WBCs gobble up the rest of the bacterial debris, and then 
go away. However, when asbestos gets into the lungs, the white blood cells 
keep making free radicals. The free radicals slowly damage the cells that 
are around the asbestos. Some of this damage includes damage to the DNA 
that cause mutations in cancer-causing genes. Apparently, these mutations 
eventially result in cancer in some people who are exposed to asbestos.

However, this is a highly simplified view of how asbestos causes cancer. 
There are many different effects of the free radicals on cells that can 
cause cancer. There are many different ways cancer can occur. And there 
are lot of different changes that occur in cancer cells in cases of cancer 
that appear to have been caused by asbestos. In addition, other factors 
come into play, like the genetic makeup of people who are exposed to 
asbestos (some people are more likely to get cancer from asbestos than 
others), the age that the person was exposed to the asbestos, environment 
factors, like whether the person was exposed to smoking and the type of 
asbestos.

Finally, you asked if asbestos directly affects cellular DNA. I have not 
seen anything that suggests that it does. In addition, the molecules are 
too big to get into a cell. So it seems very unlikely that asbestos 
directly affects DNA. 

Below are links to two articles. Unfortunately, the first one does not 
deal very well with cancer, and the second one is very hard (even for me 
to understand -- you also need a PDF reader to see article, such as Adobe Acrobat). But just 
looking at the second article sort of gives you an idea of how complicated 
the whole thing is. The buttom reference is to a entire issue of 
Scientific American devoted to cancer. It does not really answer your 
questions directly either, but it has good information about cancer.
 http://www.oncolink.upenn.edu/pdq_html/6/engl/600321.html 
http://www.elsevier.nl/gej-ng/10/38/20/29/17/19/article.pdf http://www.sciam.com/explorations/050597natmag/natmag.html<
/a>