but some references to back up your claims would be nice. from what i've seen and heard, reality is considerably different.
point #1 - weapons use of DU barely changes environment levels of DU (which is essentially "natural uranium"):there were 320 tons (290,560 kg) of depleted uranium used in the first gulf war. let’s assume that all of it was aerosolized and deposited into the environment. now let’s analyze the environmental effects compared to how much uranium was already there.
from
http://www.physics.isu.edu/radinf/natural.htm we learn that a typical square mile of land area contains 2,200 kg of uranium in the uppermost 1 foot of soil (where it is most likely to be disturbed by a passing tank, for example, and have the opportunity to interact with a human). considering that iraq covers 168,000 sq. mi., if the depleted uranium used in weapons was even dispersed, there would be an additional 1.73 kg added to the natural burden of uranium (per square mile). of course, the battles were not fought over all the country, if we assume that the depleted uranium was localized to 10% of the country, that means an additional 17.3 kg/sq.mi., or if the fighting was extremely localized to only 1% of the country (and the depleted uranium dust was somehow similarly localized), that means there’d be an additional 173 kg/sq.mi.
converting to ppm data, we see:
natural levels of uranium: 1.764 ppm
w/weapons DU spread over all of iraq: 1.766 ppm
w/weapons DU localized to 10% of iraq: 1.778 ppm
w/weapons DU localized to 1% of iraq: 1.903 ppm
ok, we see that the use of DU weapons incurs a very small, but nevertheless measurable, increase in uranium levels in the environment. but the key question is, is the increase large enough to cause health problems?
from this map:
we see that the environmental levels of naturally-occurring uranium in the united states varies much more than happened upon use of all those depleted uranium weapons. in fact, the use of DU-containing weapons releases so little uranium as to be hard pressed to cause a color gradiation shift in the above map –
note that certain parts of the country have 10 times more environmental uranium (such as in the southwest) than others (such as central florida) but cancer rates show no correlation – clearly the increased long-term environmental load of DU in iraq due to weapons use is minimal.
point #2 - it is possible to calculate approximately how much radiation is produced by a DU particle:addressing the question “how much radiation does an inhaled DU particle produce?”
to answer this question, we consider that the size of depleted uranium aerosolized particles is 2.5 microns:
from
http://www.gavagai.pl/nato/depleted.htmand then calculate the number of uranium atoms present in the particle by using the relationship:
volume = 4/3(pi)r3 ;
one particle has therefore has:
a volume of 8.18 x 10e-18 m3 or 8.18 x 10e-15 L3 or 8.18 x 10e-12 cm3
a mass of (8.18 x 10e-12 cm3) x (17.9 g/cm3) = 1.46 x 10e-10 g
(based on a density of 17.9 g/cm3)
Now, to calculate the number of atoms in one particle:
(1.46 x 10e-10 g) x (1 mole/238 g) x (6.02 x 10e23 molecules/mole) = 3.7 x 10e11 atoms
now let’s calculate how many alpha particles are released each day:
(3.7x 10e11 atoms/particle) / <(4.5 x 10e9 years/decay half-life) x (365 days/year) x (2*)> = 0.0282 decay events per particle per day
* factoring in half-life considerations
for comparison purposes, a similarly sized particle of plutonium would support ~320,00 decay events per day.
it should be noted that each radioactive decay event starting with DU starts a cascade of additional radioactive decay events (eventually leading to lead, which is stable):
http://www.ccnr.org/decay_U238.htmlin all there are 14 subsequent decay events, but only the first two Th-234 to Pa-234 (1/2 life = 24.1 days) and Pa-234 to U-234 (1/2 life = 6.7 hours) would be expected to occur in the lifetime of the host and need to be considered. for simplicity’s sake, let’s assume these decay events happen simultaneously with the original U-238 to Th-234 alpha emission (note: this assumption increases the danger level, so it’s not like i’m trying to minimize risks).
ok, let’s summarize the decay events:
U-238 to Th-234: alpha emission @ 4.270 MeV
Th-234 to Pa-234: beta emission @ .273 MeV
Pa-234 to U-234: beta emission @ 2.197 MeV
total energy released is 6.740 MeV per decay event (energy levels are from
http://www2.bnl.gov/ton/index.html ), and since (on average) 0.0282 decay events per day occur,
that’s 0.190 MeV per day of high energy particles that a cell must deal with over the long term (note that MeV represents mega-electron volts, so 0.190 MeV is 190,000 eV). point #3 - the rate of oxidative damage from a DU particle is much less than from natural metabolism:
now let’s turn to cellular damage. high energy ionizing radiation damages cells indirectly by ‘damaging’ water (the most common molecule in a cell; this process is described in detail at
http://www.photobiology.com/educational/len/part2.htm ). basically what happens is that the high energy particle impacts water molecules, successively damaging them by creating reactive oxygen species such as hydroxyl radicals. each interaction reduces the energy of the high energy particle by about 47 eV. consequently the 190,000 eV per day calculated above translates into the generation of about 4,042 reactive oxygen species per day.
each of these reactive oxygen species has the potential to damage dna. but there are enzymes (superoxide dismutase, for example that actively scavenge reactive oxygen species specifically so that dna damage is avoided. furthermore, you may have been seduced by your trendy friends to take anti-oxidants as a dietary supplement – if so, they’re also going to be hanging around to intercept the potentially damaging reactive oxygen species before they can damage your dna). but let’s discount these factors in order to maximize the danger from the radiation. in this case, let’s assume that all reactive oxygen species will react with what cellular biomolecule they encounter first. considering that most cells are from 1 to 10% DNA by volume (the DNA stays the same, but the rest of the cell varies dramatically) that means at most 10% of the 4,042 reactive oxygen species will be able to damage dna. that’s ~400 sites of damage per day, but considering that a cell normally has to deal with 50,000 to 250,000 sites of damage per day (by repairing them - check out the work of bruce ames at UCBerkeley for verification of these numbers), the additional repair load is only between 0.2 and 1.0% (in reality, many of the damages would not occur because the damaging molecules would have been scavenged by the protective enzymes or anti-oxidants long they could damage anything).
point #4 - you propose some medically impossible events when you suggest that irradiation from DU harms cells. the information i provide above shows that there is no realistic cellular mechanism for the radiation of DU to harm cells. claiming that it does makes one look rather foolish and allows arguments against DU to be easily dismissed by someone who is scientifically literate - which is unfortunate because DU may actually be harmful, but due to it's chemical toxicity which is one-million fold higher than it's radiation
toxicity, (see J Inorg Biochem 2002 Jul 25;91(1):246-52
Depleted uranium-catalyzed oxidative DNA damage: absence of significant alpha particle decay. Miller AC, Stewart M, Brooks K, Shi L, Page N. for more information). it's kinda like claiming mr. george w. bush is evil because he's a child rapist - sure, he may be evil, but making this claim just makes one look like a mis-guided, and easily ignored, crank.
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