MadSci Network: General Biology

Re: Can you explain in detail why and how cockroaches survive radiation?

Date: Wed Feb 24 14:26:05 1999
Posted By: Andrew Karam, Staff, Radiation Safety / Geological Sciences, University of Rochester
Area of science: General Biology
ID: 919222382.Gb

There are a couple of reasons why insects (including our friend the
cockroach) are more resistant to the effects of radiation than we are.
Specifically, insects are less complex organisms, they have less genetic
material, and they don't live very long.  I'll explain these below.

The more complex an organism is, the more sensitive it is to the effects of
radiation.  Part of the reason is that more complicated things have a lot
more that can go wrong.  For example, think of the difference between a
brick and a watch.  It's hard to hurt a brick because all it really does it
sit there.  It is simple and it has a simple function.  It can take a lot
of punishment and still do it's job of holding up a wall.  On the other
hand, a watch is much more complicated and a simple drop can break it
because there are so many fragile and closely-machined parts.  Similarly,
cockroaches are simpler organisms than we are with less to go wrong and
they can take more damage before they "break".

Because of our added complexity, we have more genetic material.  Part of
the damage radiation can do is to cause mutations in our DNA.  Like with
target shooting, you have a better chance of hitting something if there are
more targets.  Cockroaches and other insects have relatively small amount
of DNA, making it harder to hit and damage.

Finally, cockroaches don't live that long, so there's less chance to have
anything go wrong.  In humans, cancer is a multi-stage process that takes
10 years or more to occur after exposure to radiation.  Cockroaches just
don't live long enough to develop cancer.  Actually, humans didn't usually
live long enough to develop cancer until rather recently.  You might be
interested to know that, although the overall number of cancers has
increased, when we adjust that to account for the fact that we live a lot
longer than we used to, the age-adjusted cancer rate is not very different
today than it was 100 years ago.  

I hope this answers your question.  For more information, I'd suggest
reading any of the reports by the United Nations Science Committee on the
Effects of Atomic Radiation (UNSCEAR), reports by the National Academy of
Science on the Biological Effects of Ionizing Radiation (BEIR reports), or
basic textbooks in radiation safety.  One particularly good one is written
by Herman Cember and is called (I think) Introduction to Health Physics.  
Andrew Karam, MS, CHP         
RSO, University of Rochester    

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