Toxic Cocktail – lead and silver nitrate.


This photo shows crusts of toxic lead oxide on the piezo disc of a Deprox machine. There are 12 of these discs in each Deprox and they are approximately 70% lead by weight. (See “Lead zirconate titanate”.) These piezoelectric transducers are in direct contact with the “Deproxin” H2O2/AgNO3 fogging disinfectant and are attacked by the combination of strong chemicals and cavitation. As the lead compounds crumble and erode away, they mix with the Deproxin and are emitted with the fog as a fine powder – thus ultimately ending up in the lungs and internal organs of anyone else who enters a recently treated area before the ventilation system has dispersed the dust. Frequently “Deproxed” hospital facilities will become contaminated with a fine black deposit, being a toxic cocktail of silver nitrate with lead oxides.

Lead is a cumulative poison, damaging the brain and peripheral nerves. In children, lead exposure may cause reduced IQ, learning disabilities, decreased growth, hyperactive and antisocial behavior, and impaired hearing. Lead-poisoning in adults may cause muscle and joint pain, digestion problems, memory and concentration problems, high blood pressure, headaches, and dizziness.

The frequent service interval of the Deprox machines is primarily in order to install replacement sets of these piezo discs, as they otherwise become too eroded to atomise the Deproxin efficiently.

Samples of corroded discs from serviced Deprox machines have been sent to the NHS and the HSE for analysis.

Operatives Exposed to Toxic Chemical at 2000 x the Legal Limit

Deproxin, the chemical solution fogged in to the air during the Deprox process, contains 4g of toxic silver nitrate per bottle. (That is enough to kill a child if ingested). As the fog droplets of solution evaporate to release the H2O2 vapour, the silver nitrate crystallises out as a black dust, which can clearly be seen where it has settled on the top of the machine and other white exposed surfaces after the process is complete.

Because it is particularly damaging to the lungs, the legal limit for exposure to airborne silver nitrate dust is very low – 0.01mg/m³ – that’s 1/100,000th of a gram per cubic metre of air.

A typical hospital side ward is 60m³, and uses about 1/3 of a bottle of Deproxin. The process therefore puts a total of about 1.33g of silver nitrate in to the room, which comes to 22mg/m³. This is 2200 times in excess of the legal limit. The hydrogen peroxide in  the air breaks down naturally or is (in theory) removed by the catalyst. However, the silver nitrate does not break down, is NOT removed by the catalyst, and the airflow of the “deactivation unit” will keep the dust suspended in the air, rather than allowing it to settle. The first person to re-enter the room at the end of the process is the Deprox Operative, who not only breathes in the highest concentrations of dust before the room is ventilated, but is exposed to this multiple times every working day.

Hygiene Solutions directors try to hide this serious health hazard from their employees by mislabelling both the Deproxin bottles, and falsifying the official  Deproxin MSDS (Health and safety data sheet) Both state the active ingredient as “Silver 0.2%” The MSDS however has to give the correct reference number for the chemical, which is CAS: 7761-88-8. This is the number for silver nitrate – NOT silver. Silver (inert metal) has no more in common with silver nitrate (toxic oxidising compound) than sodium chloride (table salt) has in common with chlorine (poisonous green gas). To call silver nitrate “silver” is not a little white lie, it is a big dirty dangerous lie.

Operatives should NOT be reentering the room without full face respirators. All exposed surfaces should be wiped down with wet disposable wipes to remove accumulated dust, and an appropriate meter for silver nitrate should be used to check the air quality before nursing staff or patients are readmitted.

If you have any questions, Mr Jit Patel, Hygiene Solutions Health and Safety Officer, will be able to look up CAS: 7761-88-8 and provide appropriate equipment.

Symptoms of silver nitrate inhalation are:

Sore throat. Cough. Burning sensation. Shortness of breath. Laboured breathing. Blue lips or finger nails. Blue skin. Dizziness. Headache. Nausea. Confusion. Convulsions. Unconsciousness. Symptoms may be delayed.

Silver compounds are not excreted, they accummulate permanently in the organs of the body, including the brain, skin and eyes. This can cause a condition called Argyria, where the whites of the eyes and the skin become permanently stained a blue-grey colour.

What are the clinical features of argyria?

Whether or not a person exposed to prolonged or high levels of silver develops argyria depends on many factors including the dose and the duration of exposure. The disease usually begins with a grey-brown staining of the gums which later progresses to involve large areas of the skin.

  • Over a period of months or years depending on the degree of exposure the skin turns a bluish-grey, metallic, to slate-grey colour.
  • The hyperpigmentation is most pronounced in sun-exposed areas such as the face (particularly forehead and nose), neck, arms, and hands. Hence, the discolouration is thought to result from the presence of silver and silver-induced increase in melanin concentration.
  • The fingernails, conjunctival membranes and mucous membranes may become hyperpigmented.
  • In some cases, the entire skin turns a slate blue-grey colour.

There is currently no effective treatment or cure for argyria.

Silver Nitrate deposits at the Royal Liverpool Hospital


Isolation rooms at the Royal Liverpool University Hospital have become so heavily contaminated with silver nitrate that patients have complained, mistaking the black deposits on the windows for dirt. Director of nursing Lisa Grant admitted that the Hydrogen Peroxide Vapour (HPV) bio-decontamination system leaves a “sterile residue” but was apparently unaware that it is silver nitrate. The photo above was submitted to The Liverpool Echo by a patient who attempted to remove the chemical with a tissue. There is enough silver nitrate on the tissue to cause unpleasant chemical burns to the skin. Even more seriously, the AgNO3 dust levels in the room must have been far in excess of the legal maximum, which is an invisibly small 0.01mg/m³ – that’s 1/100,000th of a gram per cubic metre of air.


Further evidence of negligence comes from the blue plastic glove on the ceiling smoke detector, also photographed by the same patient in the same room. (inset in picture above) This is typical of “cowboy” decontamination companies – the ultra-fine silver nitrate particles are very similar to smoke and soot, and will trigger the alarm. To have left the glove in place is extremely careless.

Rogue equipment manufacturers exacerbate the problem by deliberately mislabeling bottles and MSDS for their disinfectants as containing “silver” rather than silver nitrate. No fogging disinfectants actually contain silver as such, so any reference to “silver” or “Ag+” refers to silver nitrate. Below is an extract from the Deproxin MSDS, giving the CAS number for silver nitrate and the description as “silver”.


However the Deproxin bottle label (below) just gives the description “silver” and omits the appropriate “Oxidiser” and “Poison” warning symbols.


Silver nitrate is a cumulative poison, and presents a particular risk to decontamination machine operators who are exposed to the highest levels of the chemical on a daily basis. A former operator who had done over 1000 fogging operations told me that he was very worried as to the long term health effects;

“We were never told about the silver nitrate, and never given any protective equipment at all. When I re-entered the rooms, there was still a visible mist in the air, and I would open a window if possible and tell the nurses to wait a few minutes before going in, because it would start them coughing.”

Hydrogen peroxide HPV fluids should be checked before allowing any processes to take place. If in doubt, there us a simple test for silver nitrate that anyone can do – the video below shows the effect of a droplet of Deproxin on a copper penny.


The Great Silver Lie

Hygiene Solutions Ltd are in denial about the illegal silver nitrate content of their products. The HSE is currently investigating their systems, but they are still trying to mislead both the government and their customers by claiming that their Deproxin contains colloidal metallic silver, rather than poisonous silver nitrate.


This is quite simply a lie. Metallic silver is one of the most powerful catalysts for the decomposition of hydrogen peroxide, in to oxygen and water. It is so effective that it is used in rocket engines and “jet belts” where the explosive and exothermic decomposition of H2O2 as it passes through a silver mesh catalyst creates thrust. The British “Black Arrow” satellite launch system of the 1960s and the Bell “Rocket Belt”, both shown above, use this system. Hydrogen peroxide solution will also decompose, bubbling steam and oxygen, if it is poured in to a silver spoon – see below.


The rate of reaction is proportional to the surface area of the catalyst and the concentration of the solution. The video below shows a 3% H2O2 solution being decomposed by a solid silver bar. The 6% solution used in HPV would be decomposed very rapidly indeed by finely divided “colloidal” silver.


Silver nitrate, however, which is the real form of “silver” in Deproxin is a powerful stabiliser – it slows the natural decomposition of the H2O2, giving the product a much longer shelf life and eliminating the problem of container pressurisation and consequent leakage from the escaping oxygen gas. Elimination of this unique stabiliser would cause huge logistical problems for Hygiene Solutions, hence their desperate attempt to hoodwink the authorities.

I sincerely hope that the HSE obtain authentic samples of these solutions from systems working in the field, and test for silver nitrate, rather than depending on the honesty of the manufacturer.