Pool Water Research

Making pools a safer place

Dryden Aqua  have been conducting research on swimming pool water treatment for many years.  The objective has been to improve both the water quality and atmospheric conditions just above the surface of the water to make swimming pools a safer environment for the public as well as the pool staff. A secondary objective is to try and reduce the cost of running a public swimming pool by saving water,  energy and by reducing the amount of chemicals used to treat the water.

For the time being it is essential to use chlorine in all public pools to prevent disease transmission between the bathers. Chlorine will  destroy most pathogenic organisms in under 30 seconds, chlorine free products may take many minutes or hours and may not be affective against viri, parasites, certain species of bacteria and fungi.  Pools that do not use chlorine place the public at serious risk of disease.  

Chlorine is a safe relatively non toxic chemical, the problem comes from the by-products formed by chlorine reacting with other chemicals in the water.  There needs to be a rethink about the systems, products and chemicals used to treat swimming pool water. For example you would think that the use of UVc irradiation of the water would be  beneficial, but we know that UV light can generate more toxic  chlorine by-products and that the radiation may mutate a virus into a super-bug  and expose us to a pandemic risk.

Swimming is an excellent form of exercise and should be encourage, but we also know that it is implicated in causing cancer, spinal deformities, asthma, respiratory disease, skin infections, and numerological damage. The mission of Dryden Aqua is to expose the deficiencies in the public swimming pool industry, analyse the problems and provide a solution. We have already found the solution to most of the problems in the pool industry and have quantified the performance of the water treatment systems by means of a Pool Performance Factor.  We are now starting research to quantify exactly what is happening in in the water, the air and the blood of the swimmers in order to determine the best strategy for the industry.

Nitrogen Trichloride

We have known for many years that the chlorine smell from swimming pools is not due to chlorine but a chlorine reaction product called nitrogen trichloride. When you enter a swimming pool building  if you can still smell the nitrogen trichloride after 1 minute,  then it would be best to leave the premises.  You would be healthier jogging around the pool building chain smoking cigarettes.

Nitrogen trichloride costs the swimming pool industry many millions of pounds every year due to Stress Corrosion Cracking of the building structure. The gas will also corrodes stainless steel, ventilation systems and electrical systems. Next time you are in a swimming pool, look up at the roof and the support beams for corrosion.

We know from extensive research et al, (click here for reports) that nitrogen trichloride in the atmosphere will strip-off the mucous lining from your lungs and predispose you to a pathogenic infection,  we also know that it will sensitise lung tissue and may elicit an allergic reaction to pollen, dust mites, or any atmospheric chemical.  This is more applicable to young children because it can develop into respiratory disease such as asthma.   Levels of asthma have increased from 3% of the population to over 25% during the last 30 years.  We are not saying that this has all been due to swimming pools,  but over the same period of time there has been a change in the way pools are operated, and we know for sure that  nitrogen trichloride is implicated. We will never be able quantify the damage to children or to the public, and because of this very little will be done in the UK to rectify the situation.  By way of example, it took around 40 years before any action was taken over the use of asbestos, more recently we know that Transfats in food probably cost the NHS in the region of 30 billion every year and are responsible for the premature deaths of many thousands of people.

Nitrogen trichloride is toxic and dangerous,  but it has the advantage that you can smell the gas and it hurts your eyes.  If your eyes sting when you go swimming then you know for sure that your lungs are also being damaged.

Cloudy Water

There will always be some turbidity  in swimming pools water.  however it is absolutely critical that pool water has a much lower turbidity than drinking water because in most cases the turbidity of pool water will be due to bits of bacteria cell wall, the contents of bacteria and their excretory products.  These chemicals are endotoxic and exotoxic and can initiate and allergic response, gastroenteritis and fevers. Bacteria do not need to be alive to cause a disease,  and dead bacteria as indicated by turbid water are almost as dangerous as living bacteria.  Pool water should always be under 0.05 NTU, most pools are no-where near this standard.  In addition to viable bacteria testing,  the water should also be tested for dead bacteria by ATP analysers.

Lipid soluble volatile gas

When chlorinated water such as swimming pool water is exposed to UV light from the sun, nitrogen trichloride levels and dissolved organics are reduced, but other chemicals such as THM`s (chloroform) and cyanogen chloride are formed. These chemicals do not have the same pungent smell of trichloramine, but they are many times more toxic and are implicated in cancers, neurological damage and spinal deformities.  We also know from research conducted by the NHS in Scotland that exposure to the chemicals at an early age (under 6 months) will result in a much higher risk of scoliosis spinal deformities when the children become teenagers.  We do not know what other damage is being done but lipid soluble chlorinated gases may be implicated  in auto-immune disorders an / or cancers that may cause disease many decades after the initial exposure. 

The concentration of lipid soluble gas is not monitored in public swimming pool industry, yet we suspect that the concentration of gas such as cyanogen chloride (cyanide) exceeds the upper 15 minute exposure limit set by the UK HSE of 0.7 mg/m3 ( Health & Safety Executive).  By way of example, concentrations of 0.14 mg/l of cyanogen chloride will be found in public swimming pool water, (data from Danish Government)  this gas is volatile and will readily diffuse out of the water into the air, but being heavier than air it will then sit on the surface of the water. If the gas from just 150 litres of pool water  (typical pool volume = 500,000 litres)  were to escape the surface and form a layer 50mm  over the entire pool,  this would exceed to the UK Health & Safety Executive upper limit for 15 minute exposure in a work place.  A concentration ten times this level is sufficient to kill a goat in 2 minutes, a much higher concentration 120 mg/m3 is required to cause human mortality.  To put this into perspective,  if a typical 25 m swimming pool were to degas as a consequence of a bus load of children jumping into the pool at the same-time, there is the potential to reach a lethal concentration of cyanide in the atmosphere.

All of the water will degas over a period of 24 hours, and because of the higher UV irradiation levels when exposed to sunlight  it is a issue for out-door pools as well as poorly ventilated indoor pools.   We aim to repeat the work of the Danish Government and more accurately quantify what is happening to the public in a typical pool environment. We know that UV irradiation and exposure of chlorinated water to sunlight to will generate THM`s and cyanogen chloride, so we have developed ACO  as a product that can be added to pool water to act as a sun-block to try and prevent the production of these noxious gases.

We know there is potentially a major public health risk, but  it has not been fully quantified so we do not know the status of the public or private pool industry in the UK, or around Europe. The atmospheric conditions just above the surface of pool water needs further investigation. We believe we have a simple solution to the problems, but the issues need to be quantified and the solution needs to be verified by independent accredited organisation. Dryden Aqua is therefore embarking on a research and development project to quantify exactly what is happening in public swimming pools to the water quality, air quality and blood chemistry of the bathers.   The water treatment systems will then be upgraded and the tests repeated.

Project partners

Dryden Aqua  confirmed

Swimming pool Teachers Association  confirmed

Edinburgh Leisure confirmed

Edinburgh University (in discussions)

Glasgow Caledonian University (in discussions)

National Health Service. Scotland  confirmed

For a presentation on Pool water treatment  click here