# Are radioactive isotopes of silver dangerous?

I know we all think of things like uranium as being radioactive in the nasty radiation poisoning sort of way. But do elements like silver have similar effects in their radioactive isotopes?

I'm an author doing some research for a book I'm working on. Would there be a particular quantity or exposure time that would be necessary to make it toxic?

Say we did know the amount to make it toxic. I know regular silver can cause Argyria which is mostly a cosmetic illness, but would the side effects of the radioactive silver be similar to that of other radioactive materials?

• @Kaylyn, that depends on the radioactive decay chain. Turns out the majority of radioactive silver isotopes decay via beta minus decay. The biological effect of radioactive silver is therefore similar as for radioactive isotopes of other elements that emit beta minus radiation. This is more dangerous externally to biological systems than alpha particles emitted by radioactive isotopes of uranium say which are more dangerous once they get into the body since they can be blocked by the skin. – user7232 Sep 24 '14 at 22:16
• @TheJsyChemist If you wanted to expand on that, it would make a good answer (the other answer covers some of it, but not all) – jonsca Sep 25 '14 at 2:04
• I incorporated some of the information from the comments into your question so they are more permanent. – jonsca Sep 25 '14 at 2:05
• Please do not mix up toxicity of silver with "radiation poisoning" or other health hazards coming from radiation. Carcinogenic health hazards work different way than regular poisons, and the type of risk caused by a minimum amount of carcinogen is different from regular toxic chemicals. – Greg Sep 26 '14 at 4:20

A glance through the table of the isotopes in the venerable CRC handbook reveals that the longest lived radioactive isotope of Ag is $Ag^{108m}$, made by neutron capture by $Ag^{107}$. this has a listed half life of "> 5y", but the capture cross section is only $35\pm5$ barns, pretty small for thermal neutrons. So, it would be really hard to get a lot of radioactive silver.

Next, all isotopes listed decay by $\beta, \beta^{+}$, EC, or IT (electron capture of internal transitions for the metastable nuclei), with decay energies ranging from 93 keV ($Ag^{107m} \rightarrow Ag^{107}$) to 6MeV ($Ag^{116}$). Those are ionizing radiation, which would increase your probability of getting cancer.

The 'nasty radiation poisoning' things are actually nasty primarily because of being heavy metals, the radiation comes along for the ride, so to speak. The normal Uranium isotopes are very long lived, so emit very little radiation per unit time. Polonium, the scary poison of choice in stories and perhaps by the KGB, in contrast, has a short lifetime (138 days for $Po^{210}$), and spews lots of ~5MeV $\alpha$ particles, heavily damaging tissue (much more so than gammas).

Given the difficulty in making the stuff, assuming you would try $Ag^{108m}$, (small cross sections, can't chemically separate from the stable $Ag^{107}$, etc., your best bet would just be acute heavy metal poisoning from Ag salts (which may or may not be highly toxic). Or, using a silver candlestick to bludgeon the poor victim to death.

• Hahaha! Candlesticks may work a bit better. Maybe a dirty candlestick bomb. Everyone's been really helpful, though. Chemistry was my worst subject at university so I really appreciate the time everyone has put in to my random question. – Kaylyn Sep 24 '14 at 22:32

The most important radioactive silver nuclide is Ag-110m (half-life: 249.9 d), which is generated in nuclear reactors.

The effective dose coefficient of Ag-110m for ingestion by adult members of the public is 2.8E−09 Sv/Bq. However, this committed dose is evaluated over 50 years. In order to estimate the deterministic short-term effects of radiation sickness, only the dose that is actually accumulated during a few days is taken into account. For a period of seven days (time after intake), the effective dose coefficient of Ag-110m for ingestion by adults is 1.8E−09 Sv/Bq.

The first symptoms of acute radiation syndrome may occur at a dose of about 1 Sv. Thus, you would need to eat at least 5.6E+08 Bq (or 560 MBq) of Ag-110m in order to find such symptoms within seven days after acute intake.

The corresponding mass of pure Ag-110m amounts to 3.2 µg. However, any real sample of Ag-110m would be “diluted” with a larger amount of stable silver.

The energy of radioactive emission does depend on nucleus decaying. This, however, does not depend only on number of protons in the nucleus, so the fact that silver is, well, silver, does not make its radioactive isotopes less or more dangerous if they somehow enter biological system.

However, it must be noted, that if a radioactive nucleus belongs to element/compound that can deposit/accumulate in human system, its damage potential increases as it stays there longer. This applies to elements/compounds that can deposite in bones (calcium, stroncium, phosphorous) or accumulate by different means (mercury, some other heavy metals, some hydrocarbons. And yes, silver also can accumulate in animals)

Another particulary nasty habit is capability to produce radioactive gases, usually radon. Unlike most common radioactive elements, radon can be inhaled, effectively bypassing skin, that is some (even if little) defense against radioactivity. This is why uranium and torium mines must have especially effective ventilation systems.