Poison

One problem with advanced productive nanosystems is that it seems plausible that it'll become extremely simple to produce potent poisons in high quantities from extremely abundant and accessible raw materials. This includes even plain air.
Here's the obvious synthesis-path from plain air to cyanide (and ozone):
(H₂O + 2CO₂ + N₂ → (MeSy) → 2HCN + O₃ + O₂).

Why it's likely not as bad as it may sound initially

reducing the likeliness part of the risk

• High levels of mutual symmetric surveillance. A nicer term for that is high levels of "transparency" and trust. (Balancing surveillance with "sousveillance".)

Technical complexity alone will likely be enough deterrent for the large reservoir of "script kiddies".

reducing the severeness part of the risk

• No development in isolation. With the rise of these dangerous capabilities countermeasures will rise too. Poison sensors, various means for detoxification, even airspace compartmentalisation.

Countermeasures that likely won't work and instead may even backfire

• DRM like lock of functionality
• streaming (maybe even with "untappable" quantum communication)

Why won't these work?

• No permanent safety against hacking (by smart humans & AI)
• Direct access to hardware where the untappable must be converted back to something tappable
• Way too easy reimplementability. Not from zero - that's the very hard problem of bootstrapping we have now - but from other advanced systems.

Correlations between: element, rarity and toxicity

There seem to be correlations:

• between specific elements and poisonousness (mostly independent on compound)
• between rarity of element in the biosphere and poisonousness

To get rid of foreign compounds living systems break them down. In case of the breakdown organic molecules (mostly hydrocarbons) containing only benign elements one always ends up with similar simple small compounds where the organism knows how to deal with it. That is the organism knows how to quickly guide it out of the organism without damaging itself (a good example is urea aka carbamide).

When some troublesome element is included in the ingested compound the degradation will still often lead reproducibly to a simple small remnant compound containing this element that is terminally unmetabolizable. But the compound will cause problems roughly like this:

• overall_damage = damage_per_time times time_to_excreteion times concentration

Note: The preceding metabolization steps can be problematic too:

• overall_damage_additional = damage_per_time times time_to_metabolization times concentration

But in case of poisonous elements the last one is of special importance.

Normally putting the same chemical elements in different chemical compounds (being it molecular or crystalline) leads to vastly different properties. This is less so the case for poisonousness/toxicity. So the property of toxicity reaches over a whole class of compounds containing one specific element instead of just specific molecules. The breakdown of a vast spectrum of compounds to a small set of compounds may be the reason for this circumstance.

Except from the rule are compounds that are so incredibly stable that

• the compound does not interact/react with any of the cellular machinery
• the organism cant break it down to something problematic (which would potentially be in there)

Examples are: SF₆, Teflon (CF₂)_N, molecular nitrogen (if not too concentrated - diving illness)

With elements rare in the biosphere (not overall on earth) life was never forced to learn how to cope with compounds containing these. Organisms just process these with their cellular machinery not fit for the problem.

Problematic light elements

The light elements of special concern are (some more some less)

• Li Lithium, Be Beryllium, B Boron, F Fluorine, Al Aluminum

Beryllium (Be) is pretty rare on earth both in the lithosphere and the biosphere. The stories about it's toxicity are rather frightening.

Fluorine (F): Due to its capability to form very strong bonds and thus higly unreactive compounds not all

Aluminium (Al): While extremely abundant in rocks has salts of such low solubility that there are no natural pathways bringing large amounts of these into the biosphere.
The situation with the heavy element lead (Pb) might be somewhat similar. (TODO: check that)
Aluminium salts are far from highly toxic but the exact effect of high concentration of aluminium salts on the human body is poorly understood.

Rather unproblematic light elements

Ingestible in quite high quantities without causing too much trouble (not recommented or suggested!!):

• The benign four alkali and earth alkali metals: Na, K, Mg, Ca

They just need to be packaged in a compound that makes them non caustic.
Carbonates, sulfates, nitrates, phosphates.

Light elements that come both in unproblematic and in highly toxic forms

The three third row nonmetals P, S, Cl are rather unproblematic
as long as they come pachaged in the right compounds. Despite their high abundance phosphorus and chlorine can
form many compounds that are highly toxic.

Unproblematic forms:

• Clorine is consumed in enormous quantities in the form of table salt (not very healthy in over-consumption)
• Phosphoric acid has been mixed in soft drinks in quite high quantity (bad practice, not very healthy long term)

These two elements come with a poisonous twist though ...

Highly toxic forms:

• phosgene (as seen in the burning of PVC plastics)
• (polychlorinated) dioxines
• phosphine
• organophosphor compounds (similar to those used for fighting pests)
• H₂S
• ...

Toxic combustion products

Fortunately

• Many gemstone like compuntds are inherentyl incombustible.
  
• Crystolecules and product made out of them prpoducts have low low hydrogen content, and this hydrogen is what primarily could be replaced by more problematic halogen elements like Chlorine Fluorine Bromine and Iodine.

Iron

Due to it's extreme abundance both overall and in the biosphere it's highly nontoxic albeit being a heavy metal. (It's abundant enough to deserve its own section here.)

Problematic heavy elements

Most of the elements of the higher periods are rare in the biosphere as direct consequence of there overall rarity.
In fact many of them are so rare that their high toxicity is of no practical concern.

Highlights ranking in toxicity are:

• well known: Arsenic (As), Thallium (Tl), Mercury (Hg), Lead (Pb), ...
• well known: Cadmium (Cd), Nickel (Ni), ...
• lesser known since very rare: Osmium (Os), Rhenium (Re), Ruthenium (Ru), ...

Osmium "rust" is a highly toxic transparent liquid (same with Rhenium and Ruthenium "rust") - See: Oddball compounds
Nickel although abundant in space is not so abundant in earth's crust. Nickel is allergenic in skin contact in pure bulk metallic form and can form some highly toxic compounds.
(TODO: is Ni less toxic than Cd? AFAIK the switch from NiCd batteries to NiMH batteries is considered an improvement in environmental impact.)

Noble metals in sufficiently bulk form (even gold flakes count as bulk) are safe.

• well known: Gold (Au), Platinum (Pt), Iridium (Ir)
• lesser known: Indium (In)

In salt form noble metals are (if at all stable) actually especially unstable. A lack of acids capable of dissolving a metal well directly translates into a lack of soluble salts of the metal and a low stability of the salts. Silver (Ag) is a good example for this situation. Silver salts can cause a strange condition of dying your skin blue/purple.

Unproblematic (mostly)

• Copper (Cu), Zinc(Zn), Tin (Sn), ...

Very high toxicity but simple, small and out of abundant elements – some examples

• HCN cyanide
• H₃CNCO Methyl_isocyanate
• COCl₂ phosgene [1]
• AlP aluminum phosphide [2] -- Wikipedia: Acute aluminium phosphide poisoning (AAlPP)
• Ni(CO)₄ Nickel tetracarbonyl [3]
• Fe₃P iron phosphide [4]
• Dioxines [5]. An especially poisonous one being TCDD (already a slightly bigger molecule)

Toxicity of proteins (and foldamers in general)

These are substances natures molecular biology has developed in the course of evolution for defense against predators.

Toxicity here is usually based on shape and not on the included element(s). These toxins are not small molecules but rather big irregular blobs (complexly folded up chains of amino acids). Once toxic proteins are degraded (not merely blocked by a counterpart matching in shape) their toxicity is totally and permanently gone.

Artificially creating a toxic protein (or foldamer) by mere chance (e.g. in the course of de-novo protein design) is very unlikely due to the ginormous space of possibilities of shapes. If it where likely to create toxic proteins by chance we would not cook our food because the heat scrambles up all the proteins in the food a lot. In short heating things would make them highly poisonous.

Actually thermal treatment (sufficient heating) works very effectively for degrading toxic proteins but it's obviously not applicable once the toxin is inside an organism.

• (TODO: Discuss how cells deal with it - blocking - digesting - ...)
• (TODO: Discuss benefits (medical drugs) and problems (weapons) of intentional foldamer toxin development)

Related

• Dangers (including explosives)
• Soil pollutants
• Recycling

External links

• Wikipedia: Risk#Quantitative_analysis

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• Wikipedia: Essential_chemical_elements_for_humans
• Wikipedia: Essential_elements_on_the_periodic_table

The complement of these contains the toxic ones.

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• Wikipedia: Sousveillance