This is what a program on TV said (in UK). A dirty bomb is high explosive that releases a cloud of radioactive dust. The dose from the isotope is spread over a large area. The damage is real as it makes the area dangerous to enter (Like Chernobyl). However there are plenty of photographic records taken in Chernobyl after the accident with no sign of radiation damage. If a photographic plate is left for a few hours in the radiation then there are dots of silver formed. The number will depend on the dose. I wore a small photographic plate when I was a radiation worker. The dose was worked out from the degree of darkening after developing. If the plate is dark then the dose is so high that the worker is taken off radiation work. The badge containing a photographic film was worn for a week at a time then sent for assessment. I believe the dose is measured in "Roentgen" forgive me if I have the spelling wrong or I am using an old unit. It might be millisilverts. Again forgive me for inaccuracies in spelling of unit name. If a Geiger counter is left on in a normal room it clicks in bursts and counts about ten to about one hundred clicks a minute (from memory) in a radiation contaminated area it clicks thousands of times a minute. A radioisotope held close will cause a high count rate. These counts have no noticeable effect of a film. if a person is exposed to a radio-isotope for a while (like a child playing with school radio isotopes) may give him "Red lumps" (cancer in the hands and arm) a few years after exposure. There is no immediate effect. The relationship between getting ill with a small radiation dose is a linear one, with the probability of getting cancer being in direct proportion to the dose. To get ill a ionising particle has to get within the cross section of capture of an active site of the DNA within a cell. Only one cell needs to be converted to cause cancer. Other genetic changes of the germ line can give rise to sick or deformed children. We are exposed all the time to radiation and there is no minimum dose. If we are exposed to radiation increase by the detonation of a dirty bomb then the dose may only be enough to give an increased risk of these things. I would be inclined to leave an effected area a quickly as possible but if it was my home, the cost of re-housing is something to be considered. I am 60 now and if the chance of illness was likely to be in 20 years time then I might just stay put. We run risk all the time, illness is not a certainty at low doses because we all have short limited lives. (Evolution has adapted us to this, may be because of the background radiation). Rain will wash away a radio-isotope and it will end up in the sea. Wind will disperse and dilute it. The dose in industrial areas is about 100 times the dose in rural areas even here in the uk. Dirty bombs are a terror weapon that will have most of its effect by fear. The contaminated area will need to be evacuated for (possibly) hundreds of years, but casualties are likely to be low and difficult to estimate. It will have an economic effect (as desired) because of the disruption. I hope I've not said anything misleading or trod on anyone's toes. I am not a specialist in radiation science. Chris http://www.chrissdomain.com -----Original Message----- From: owner-photoforum@listserver.isc.rit.edu [mailto:owner-photoforum@listserver.isc.rit.edu]On Behalf Of PhotoRoy6@aol.com Sent: 14 February 2003 17:42 To: List for Photo/Imaging Educators - Professionals - Students Subject: Re: why does digital looks better? In a message dated 2/14/03 3:46:58 AM Eastern Standard Time, nimbo@ukonline.co.uk writes: << I don't think the level of radiation produced by a dirty bomb is likely to have a significant effect on any photography. >> I find that hard to believe. Isn't most of the data stored as charged particles on hard drives and on removeable media except for CD? Radiation in a large enough dose to effect humans should also effect hard drives and portable media. I could also read your response another way that the ability of the terrorist to mount an effect dirty bomb is small and any bomb denoted may be more psychological than physical.
