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Is osmium toxic?

Crystalline osmium is the safest form of osmium and is considered non-toxic. Sintered osmium (for example as ingots) is also considered non-toxic. The osmium sold in the MetaMetals store is therefore harmless to the human body and poses no health risks when used properly. What is considered highly toxic, however, is unprocessed raw osmium, which, in combination with oxygen in the air (O2), produces the toxic gas "OsO4" (osmium tetroxide).



  • Raw osmium (powder; also known as "osmium sponge")

It is important to note that high-quality production is also crucial for the products listed under "non-toxic" in order to ensure the highest possible purity. Osmium should therefore only be purchased as crystals or bars from trustworthy dealers such as MetaMetals. We work to the highest quality standards to ensure the purity and therefore safety of the osmium ordered.

Is osmium toxic or harmless to health?

On the internet, many people interested in osmium sooner or later come across a certain topic in blog articles and various forums such as Reddit: osmium is said to be toxic / poisonous. As hardly anyone wants to expose themselves to health risks, some prospective buyers understandably have a bad feeling about this. However, concerns about toxicity are completely unfounded as long as you buy properly processed osmium!

But first things first.

Basically, it should be noted that every substance is toxic. Even the famous physician and philosopher Paracelsus said: "All things are poison, and nothing is without poison. Only the dose makes a thing not a poison." Now, of course, we are aware of what is meant by "poisonous" or "harmful". The question "Is osmium toxic?" naturally refers to a potential excessive health risk compared to other substances or metals. Anyone who has concerns here is right but also wrong at the same time. It depends on the form in which the osmium (OS76) is present. Powdered raw osmium (also known as osmium sponge) is what would be described as "toxic" and therefore harmful to health. However, this explicitly does not apply to the osmium sold in our store. This is because the crystallization process causes the osmium to lose its ability to form relevant quantities of OsO4 and is therefore no longer toxic or harmful. The same applies to sintered osmium, which we will discuss later.

Caution: Raw osmium (osmium sponge) or osmium in powder form is toxic!

The greatest caution is required with raw osmium. Raw osmium is a powdery metal that forms a poisonous gas when exposed to air, which must not be inhaled. Raw osmium (also known as "osmium sponge") should also not come into contact with your own skin.

The potential toxicity of osmium fused beads is also a recurring issue. Although these are not the same as powdered raw osmium, some interested parties point out that the toxic osmium tetroxide gas is also produced here. We will take a detailed look at whether this is true and the scientific situation is in this regard below.

A controversial question about the toxicity of osmium fused beads

Discussions about the toxicity of osmium fused beads continue to flare up in precious metal forums. One side is convinced that fused osmium beads also emit toxic oxides in the form of osmium tetroxide (OsO4) gas, while the other side disagrees and considers fused osmium beads to be harmless to health.

The scientific view: Oxide evaporation and high-temperature behavior of osmium fused beads and other metals of the platinum group

The data available tends to speak in favor of the safety of osmium fused beads. For example, there is a paper [1] that deals with this question and comes to the conclusion that compact osmium such as beads, but also crystals, do not react with the oxygen in the air (O2) to form the toxic osmium tetroxide - as long as the temperature does not exceed 600 degrees Celsius. When these data are extrapolated to room temperature, the oxidation rate of osmium beads (OsMWBB) and crystals (OsMWC) is less than 0.001mg per year, which is an extremely low value.

According to the paper, 400 degrees Celsius is a temperature that provides sufficient "safety distance" from the aforementioned 600 degrees Celsius, above which it can become dangerous. From a scientific point of view, we therefore draw the line at 400°C for our products, below which the heating of metallic osmium (where osmium fused beads fall under) and crystalline osmium is considered safe.

However, the formation of toxic OsO4 gas can also occur at temperatures below 400 degrees Celsius. However, this would require deliberate heating. At normal room temperature, but also if the osmium is exposed to sunlight, for example, there is no danger.

In addition to excessive heat, mechanical processing of osmium should of course also be avoided. This applies in particular to sintered (pressed) osmium products. A relevant factor in the risk assessment of osmium is always the size of the so-called "effective surface area" of an osmium product. The more porous and permeable the osmium, the larger the effective surface area. The larger this surface area is, the more toxic OsO4 can escape. However, commonly large osmium crystals, ingots or fused beads are generally well below the relevant surface area thresholds at which it can become dangerous. The reduction in surface area is achieved by the strong pressing of osmium ingots, for example, or by the melting of osmium beads.

With osmium sponge (raw osmium), for example, the effective (porous) surface area is very large, which is why we strongly advise against this form of osmium.

Of course, the above information only applies to high-quality osmium that does not contain any significant impurities.

A small osmium ingot may have a relatively small surface area, but if it is poorly sintered, the internal spaces/porosities will be larger and thus also the effective surface area. OsO4 therefore becomes a problem again, although one would actually believe that the surface area is small.

For the sake of completeness, however, we would like to point out that there are also opposing opinions on fused beads in particular. Ultimately, it is up to each interested party to decide for themselves.

What you should definitely bear in mind with osmium fused beads, however, is that they have limited marketability. This means that even if you were able to purchase high-quality osmium beads at a good price, it may be difficult to resell them.

[1] https://www.sciencedirect.com/science/article/abs/pii/0022508884900729

An important factor for pure and non-toxic osmium: trustworthy dealers

However, what plays an important role in the safety of osmium melting beads (and all other osmium products) is the production process of the precious metals and the associated trustworthiness of the platinum metal traders.

In the world of osmium, there are reputable and dubious sellers who also apply different quality standards to the products they sell. Osmium products such as fused beads, bars or crystals may contain impurities, which means that you are holding less "pure" osmium in your hands, which in turn can affect the value or tradability.

The second, no less important point, is the potential toxicity of osmium discussed in this article, which means that poor quality osmium products can no longer be classified as "safe".

For these reasons, it is essential to not only focus on the lowest possible price in order to end up with a lot of osmium in terms of quantity, but which has not been manufactured according to high quality standards and there is no guarantee of the purity and safety of the products.

Note: MetaMetals ensures that the precious metals you purchase are classified as harmless.

Osmium toxicity: Oxygen causes the oxidation of osmium (OS 76) and forms harmful osmium tetroxide gas (OsO4). However, this does not apply to crystalline osmium!

In order to understand this chemical process, which is harmful to health, let's take a brief excursion into the world of oxides. Oxygen compounds of an element, in this case OS76 (osmium), are called "oxides". The oxidizing agent is oxygen, which is present in our air and reacts with the element in question, causing it to oxidize. In the case of raw osmium (but not crystalline osmium), increased quantities of a toxic gas called osmium tetraoxide (OsO4) are formed in this way, which should not be inhaled under any circumstances.

Crystalline osmium is non-toxic. But what about (sintered) osmium ingots?

So far, we have mainly talked about crystalline osmium as being harmless to health. However, we at MetaMetals also sell osmium bars that are not crystalline, for example. Does this mean that osmium bars are toxic? We can give the all-clear here too, but of course we can only speak for the osmium sold in our precious metal store. High-quality sintering plays a role here. Properly (!) sintered osmium is equivalent to osmium crystals with regard to the release of the OsO4 gas (osmium tetroxide) mentioned above and is therefore non-toxic under normal temperatures.

However, if sintering is not carried out at a high quality level, the surface could be more porous, which leads to an increased risk of oxidation to osmium tetroxide (OsO4) in combination with the oxygen in the air. This is because the more surface area there is, the more space there is for oxidation to take place. A sponge can be used to better illustrate this. A sponge is very porous or permeable. Accordingly, there is a lot of surface area.

From a purely technical point of view, the more compact and dense the osmium is, the smaller the formation of OsO4. Our osmium ingots are brought into a very compact form under high pressure and temperature. For this reason, the formation of toxic OsO4 becomes irrelevant, as the oxygen cannot attack the osmium atoms.

The formation of OsO4 depends not only on the surface but also on the temperature. The higher the temperature, the easier oxidation occurs.

This density and compactness of osmium ingots is achieved through the aforementioned "sintering" process. This is a process in which powdered raw materials such as osmium are pressed together using high heat and pressure. At room temperature or when exposed to sunlight, osmium pressed in this way poses no health risk. Only when deliberately heated, in combination with oxygen, the toxic osmium tetroxide can form in relevant quantities. We therefore strongly advise against strong heating or mechanical processing by non-expert personnel. Of course, this also applies to the crystals.

In contrast to osmium crystals, health safety is not achieved through the crystallization process, but through high-quality sintering (special pressing process).

Osmium toxicity: Detailed view of OsO4 (osmium(VIII)-oxide)

The odor of contaminated osmium is often described as very intense and "chlorine-like". The vapors cause severe eye irritation.

OsO4 (osmium tetroxide) is considered highly toxic and is formed in combination with the oxygen in our air on the surface of raw osmium or contaminated osmium products. Osmium(VIII) oxide forms monoclinic crystals (not to be confused with osmium crystals) and is volatile. "Volatile" is a chemical term that indicates that certain substances evaporate ("volatilize") quickly due to their low boiling point.

However, even though the colorless osmium tetroxide is toxic, the substance still has many uses. For example, it is used in dactyloscopy to detect fingerprints. OsO4 (osmium tetroxide) is also used as a catalyst. A catalyst is a chemical substance that increases the speed of a chemical reaction without itself being consumed in the process. This can be helpful in the manufacture of pharmaceutical products, which are then marketed as medicines or pesticides. Osmium tetroxide is also used as a homogeneous catalyst in optical microscopy.

OsO4 is also suitable for fixing proteins and lipids. 

Tip: There is a relatively simple visual test to determine whether OsO4 is formed on an osmium product. To do this, wrap the osmium sample in plastic. If the plastic turns black, it is OsO4 gas.

Toxicity: Is touching osmium safe or harmful?

Osmium crystals, but also properly sintered osmium in forms such as ingots, can be held and touched. However, it is important to purchase osmium from trustworthy dealers such as MetaMetals to ensure that you are holding osmium products that are safe for your health.

However, raw osmium (osmium sponge), unlike crystalline or sintered osmium, should not be touched and can cause skin irritation, as the OsO4 gas (osmium tetroxide) that forms in the air can enter the body through the skin or by inhalation into the lungs. OsO4 is also harmful to the eyes.

Is osmium jewelry on the skin a health hazard?

Osmium crystals are usually used in osmium jewelry. As already described in detail, crystalline osmium poses no health risk and is considered safe as far as toxic substances are concerned.

Is osmium carcinogenic?

Carcinogenic is the term used to describe cancer-causing substances. Osmium is not carcinogenic. There is even active research into using osmium, along with other metals of the platinum group, in cancer therapies. 

Is osmium radioactive?

Osmium is the rarest and densest precious metal, or metal in general, which is non-radioactive. Osmium has a single isotope (186Os), which is radioactive, but only very weakly. Radioactivity is therefore nothing to worry about with osmium.

Is the consumption of osmium harmless to health?

Osmium is a metal (precious metal) and therefore, like other metals such as platinum, silver or gold, is not suitable for consumption. Opinions differ on non-toxic, crystalline osmium and what would happen to it in the body. However, we take a strict stance here for safety reasons and advise against putting osmium in your mouth in all cases. Last but not least, the sharp edges of the osmium crystals can cause injuries.

Even if breakage is unlikely, there is at least a theoretical risk of breakage with sintered osmium, which could release the powder and form the toxic osmium tetroxide gas. However, as already mentioned, even intact sintered osmium should not be ingested.

What applies to processed osmium in crystal or ingot form applies even more strictly to raw osmium (osmium sponge) in powder form. This would be guaranteed to cause severe damage to health.

Conclusion: Crystalline and sintered osmium is considered non-toxic (harmless to health). However, raw osmium is toxic!

In summary, it can be said that raw osmium as a powder poses a health hazard due to its toxicity, which is caused by the OsO4 gas that forms. High-quality crystalline osmium (osmium crystals), on the other hand, is non-toxic and is considered the best in terms of safety. Properly sintered osmium (for example as ingots) without breakage is considered equally non-toxic and therefore harmless. However, even in the latter case, the osmium should only be obtained from trustworthy sources to ensure that high quality standards are maintained during production, which in turn are largely responsible for its harmlessness to health.