Background Information and Frequently Asked Questions

The Australian Pesticides and Veterinary Medicines Authority (APVMA) has received many questions about the safety of swimming and spa pool sanitiser products. The questions on safety relate both to the effectiveness of the sanitisers to protect bathers from dangerous microorganisms and to the safety to human health of the chemical sanitisers themselves. The information that follows is intended help answer some of the questions that the APVMA has received about pool sanitiser products.

Please read the APVMA guide for demonstrating efficacy of pool and spa sanitisers (PDF, 124kb).

Why did the APVMA take action against unregistered silver and copper ion-based pool sanitisers?

Chemical pool sanitisers fall into the category of chemical pesticides and are regulated at the Federal level by the APVMA. Although the name of the APVMA refers to “Agricultural Pesticides”, the APVMA still has jurisdiction over swimming and spa pool sanitisers as well as certain other kinds of chemical sanitiser products. There are a large number of registered pool sanitiser products most of which are based on chlorine or bromine. The majority of these were registered under State and Territory registration systems prior to the establishment of the APVMA. These products are based on levels of free chlorine or bromine that meet current standards and are therefore effective when used according to instructions.

The Australian Pesticides and Veterinary Medicines Authority (APVMA) took action in 2004 against a number of companies that were marketing products advertised as sanitisers for swimming and spa pools. These “sanitiser” products were said to act by releasing silver ions or copper and silver ions together into pool water. The metal ion based systems were promoted in most cases as sanitation systems superior to chlorine. The majority were promoted as alternatives to chlorine, and non-chlorine oxidisers such as potassium monopersulfate were recommended for use with them. A few of the products did recommend use of chlorine but at levels substantially below the recommended minimum level of 1 ppm for swimming pools and 2 ppm for spa pools (See Australian Standards 3633 and 2610).

The metal ion based products against which the APVMA took action were not registered with the APVMA and had not been assessed according to scientific standards for safety or efficacy. The APVMA did not have reliable evidence that these products worked effectively to protect the health of pool users. Importantly, the APVMA had scientific information that called the efficacy of these products into question. This raised serious concern about these products because microorganisms transmitted to bathers through pool water can be very dangerous and even deadly.

The following information provides explanation about why the APVMA moved to require warnings with these products and require scientific evidence that these products are safe and effective. The references discussed below are not intended to be comprehensive and are supplied as examples of the information considered by the APVMA.

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Why are unprotected swimming and spa pools a health risk?

A swimming pool or spa provides an effective medium for the transmission of human pathogenic microorganisms (microorganisms that can cause human disease) unless the pool or spa is effectively protected by a sanitiser that can kill those microorganisms. Some of these dangerous microorganisms are present generally in the environment, are carried into pools by wind, birds and debris and are able to grow in numbers in the pool environment. Other kinds of pathogenic microorganisms can be released in large numbers into pools directly by infected individuals. An effective sanitiser needs to be able to kill these microorganisms quickly to prevent spread from person to person. Inadequately sanitised swimming pools and spas have been shown to cause significant illness and even death from both of these kinds of pathogenic microorganisms.

Deaths believed to be caused by spa-sourced Legionella bacteria infections have been documented in Queensland, Victoria and South Australia in 1994, 1996, 1999, 2000 and 2004. Transmission of hepatitis A virus in a spa was documented in 1997 when six new cases of infectious hepatitis were contracted from an infected individual through the spa water at a children’s spa party in Victoria. The few published reports the APVMA has seen so far are not likely to represent the full range of such adverse incidents.

The APVMA received two adverse experience reports in late 2003/early 2004 involving separate incidents of pool transmitted disease in spas using a silver ion based, cartridge-type spa sanitiser system. In one incident, 15 people contracted folliculitis after visiting a private spa. The spa was found shortly after to be contaminated with extremely high counts of Pseudomonas aeruginosa, the causative agent of the folliculitis. In March 2004, a man died from legionellosis following use of a spa shown shortly afterward to contain very high numbers (1300 CFU/mL) of Legionella pneumophila bacteria. The relevant State health authority, after conducting a thorough investigation, concluded that the spa was the most likely source of the man’s fatal infection.

As just described, some pool transmitted microorganisms cause very serious diseases such as legionellosis caused by Legionella bacteria, infectious hepatitis caused by the hepatitis A virus and primary amoebic meningoencephalitis caused by Naegleria and Acanthamoeba species of protozoa. The much more common and numerous types of virus-caused gastroenteritis and colitis are sometimes dismissed as routine risks that are not of as much importance. It is therefore worthwhile to note a few additional points from a recent review article (“Human enteric viruses in the water environment: a mini review. 1998. Bosch. International Microbiology, vol 1, pp191-196.”).

  • In 1979 it was estimated that between 5 and 18 million people die every year from gastroenteritis, and rotaviruses alone are responsible for over 1 million children dying from diarrhoea.
  • Mortality rates for human enteric viruses in developed countries (poliovirus 1, coxsackievirus A & B, hepatitis A, echovirus and rotavirus) have mortality rates ranging from 1 to 9 per 1,000 people infected.
  • The risk of infection is 10 to 10,000 times greater for viruses and protozoa than for bacteria at a similar level of exposure.
  • As a rule, viruses persist longer than enteric bacteria. It is then completely unsafe to rely on bacteriological standards to assess the virological quality of any kind of water.
  • From an epidemiological point of view, the most relevant viral pathogens found in water are the hepatitis A and E viruses and the gastroenteritis viruses, which include rotaviruses, caliciviruses (with SRSV, notably the Norwalk-like viruses), astroviruses and enteric adenoviruses.

A thorough overview of pathogenic microorganisms commonly associated with swimming and spa pools is contained in the World Health Organisation (WHO) document, Guidelines for Safe Recreational Waters Vol 2 – Swimming pools, spas and similar recreational-water environments, chapter 3 – Microbiological hazards (WHO website).

The tables below summarise the principle pathogenic microorganisms that can be transmitted in pools and the associated illness that these microorganisms can cause.

Bacteria Organism Potential health effect
Escherichia coli Enteric infections, conjunctivitis
Legionella pneumophila Legionellosis, Legionnaire’s disease, Pontiac fever
Leptospira interrogans Haemorrhagic jaundice, Aseptic meningitis
Shigella spp Shigellosis
Staphylococcus spp Enteric infections, conjunctivitis, skin infections
Streptococcus spp Enteric infections, conjunctivitis, skin infections
Salmonella spp Enteric infections
Enteric infections Gonorrhoea, meningoencephalitis
Pseudomonas aeruginosa Eye, ear and skin infections
Mycobacteria spp Mycobacteria pulmonary disease
Viruses Organism Potential health effect
Adenoviruses Pharyngoconjunctival fever, keratoconjunctivitis
Hepatitis A virus Infectious hepatitis
Norwalk virus Gastroenteritis
Echovirus Gastroenteritis
Molluscipoxvirus Molluscum contagiosum
Human papilloma virus Plantar wart
Protozoa Organism Potential health effect
Cryptosporidium parvum Cryptosporidiosis, a type of gastroenteritis
Giardia lamblia Giardiasis, a type of gastroenteritis
Naegleria fowleri Meningoencehepalitis (rare – almost always fatal)
Acanthamoeba spp Meningoencehepalitis (rare – invariably fatal)

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Why do pool sanitisers need to act quickly against microorganisms?

Because different people are immersed together in the same body of water, microorganisms can quickly pass from one person to another through entry of water into the eyes, nose and mouth. A significant amount of water is accidentally swallowed while swimming. In their Guidelines for Safe Recreational-water Environments, Vol 2, WHO cites studies showing that children typically ingest 500 millilitres of water per swimming session and competitive swimmers ingest about half that amount.

Human-sourced pathogenic microorganisms enter the water from the eyes, nasal discharges, saliva and skin surfaces of infected individuals. They are also introduced surprisingly often by the accidental release of faeces or vomitus into the pool. The number of pathogenic microorganisms distributed into the water from such a release can be extremely large. For example, children with diarrhoea from Shigella species or bloody diarrhoea from haemorrhagic colitis (E. coli 0157) can release 108 bacterial pathogens per gram of faeces into the water in a single incident. Hepatitis A virus and Norwalk virus can be shed at a rate of 1010 and 1011 per gram of faeces respectively.

Since human pathogens can be released directly into water that could be swallowed by another person shortly after that release, a pool sanitiser needs to be able to inactivate those microorganisms as quickly as possible to reduce the chance that a person might swallow an infectious pathogen.

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What are some of the APVMA’s specific concerns over copper and silver ion based sanitiser systems?

Authoritative expert bodies worldwide agree that silver and copper ion based systems have not been shown to be adequately effective in controlling human pathogens of concern in a swimming or spa pool environment.

In its document, Guidelines for Safe Recreational Waters Vol 2 – Swimming pools, spas and similar recreational-water environments, chapter 5 – Managing Water and Air Quality (WHO website), the World Health Organization states the following.

“The demand for fast biocidal action – to ensure that an infection of swimmers by transmission of bacteria and viruses via pool water does not occur even when the pool is used in rapid succession by large numbers of bathers – rules out the use of silver or other heavy metals for pool water disinfection, because a long exposure period (several hours) is required for these substances to show a biocidal effect. A quick, sensitive, analytical field procedure for measuring low concentrations of silver is not available.”

The German Federal Environmental Agency stated a very similar conclusion in its press release dated 8 February 2001 (external website). It states (in the final dot point):

“Silver-copper compounds, mentioned by the press as alternatives to chlorination, may not be seriously considered for use in public swimming pools. They take effect too slowly. According to DIN 19643, the disinfectant must reduce the concentration of Pseudomonas aeruginosa by four decimal powers within 30 seconds. Silver-copper compounds take an hour or more for this. What is more, they do not have the necessary disinfectant capacity.”

Published papers in the scientific literature indicate that silver and copper ions require lengthy periods of time (usually in the range of several hours) to exhibit significant anti-bacterial activity. In addition to being slow, the antibacterial activity does not kill all cells but may have only a bacteriostatic effect on a portion of the population.

Virucidal activity also appears to be variable or not present for some viral types. Copper and silver ions in the presence of reduced levels of free chlorine (below 1 ppm) do not ensure the total elimination of viral pathogens from water. Two published studies from the 1990’s cited below describe some crucial findings.

  1. Disinfection of human enteric viruses in water by copper and silver in combination with low levels of chlorine. 1994. Abad, Pinto, Diez & Bosch. Applied and Environmental Microbiology, vol 60, pp 2377-2383.
  • The use of copper and silver ions in water systems may not provide a reliable alternative to high levels of free chlorine for the disinfection of viral pathogens.
  • Virus aggregates (which tend to protect viruses from contact with a disinfectant) were seen in the presence of silver and copper ions but not with free chlorine alone.
  • Addition of 700:70 ppb of copper:silver did not enhance the inactivation rates of 0.5 and 0.2 ppm of free chlorine, although on some occasions, it had a similar efficacy to high levels of free chlorine alone.
  1. Disinfection of human enteric viruses in water by copper:silver and reduced levels of chlorine. 1993. Bosch, Diez & Abad. Water Science Technology, vol 27, pp 351-356.
  • The addition of copper:silver ions to reduce the levels of free chlorine does not ensure the total elimination of viral pathogens from water systems.
  • For free chlorine of 0.5 ppm or less, with or without copper:silver, both hepatitis A and rotavirus showed little inactivation.
  • Overall, addition of 700:70 ppb of copper:silver did not enhance the inactivation rates of 0.5 and 0.2 ppm of free chlorine. (Statistical analysis showed that combined copper:silver and free chlorine were not significantly more effective than free chlorine alone.)
  • Without free chlorine, 1200:120 ppb of copper:silver did not achieve a 3 log10 reduction of poliovirus and HAV after a 10 and 30 day exposure respectively.

For protozoan pathogenic microorganisms, antiprotozoan activity does not appear to be significant for metal ions acting alone. The article “Efficacy of a combined system of copper and silver and free chlorine for inactivation of Naegleria fowleri amoebas in water. 1995. Cassells, Yahya, Gerba and Rose. Water Science Technology, vol. 31, pp 119-122” makes the following points:

  • Copper and silver alone, at a ratio of 400:40 to 800:80 ppm caused no significant inactivation of N. fowleri even after 72 hours of exposure.
  • Addition of copper:silver (800:80 ppb) to 1 ppm chlorine enhanced inactivation compared to chlorine alone. However, 400:40 ppb copper:silver (concentrations typical of commercially marketed systems) added to 1 ppm chlorine showed only an apparent but not statistically significant enhancement of inactivation.

There are some reports in the scientific literature that silver and copper ions in combination with chlorine provide greater biocidal activity than an equivalent concentration of free chlorine acting alone. The amount of this reported effect is not well established, and the APVMA does not have evidence to satisfy itself that metal ions allow reduced levels (below 1 ppm) of chlorine to be used safely. The studies showing some enhanced activity of the chlorine and metal ion combination were conducted under laboratory conditions using purified water. In contrast, many heavily used aquatic facilities experience high levels of nitrogenous contaminants in their water. This places a high demand on any disinfection process and decreases its efficacy. As a result, many disinfectants will perform less efficiently under field conditions than indicated under controlled laboratory conditions.

A number of ioniser systems on the market recommend use of peroxygen oxidisers (such as potassium monopersulfate and sodium dipersulfate) with the copper and silver ions instead of chlorine. The APVMA does not have reliable evidence that silver and copper ions in combination with peroxygen oxidisers provide adequate sanitising activity.

The weight of evidence examined so far indicates that silver ions or silver and copper ions together are not effective sanitisers for pools and spas and do not provide a sufficiently enhanced biocidal activity to chlorine to allow reduced levels of chlorine to be used safely. New supportive evidence may change that conclusion in the future, but at this stage the APVMA has not seen such evidence.

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Is it true, as stated in certain product advertising, that the New South Wales State Department of Health approved a copper and silver based ioniser system for use in NSW public swimming pools?

The NSW Department of Health has no power to approve, accredit or otherwise endorse a swimming pool disinfectant or disinfection system. However, it does have criteria by which it can assess and determine the suitability and efficacy of a disinfection process. From such an assessment, NSW environmental health officers can be informed of whether the correct use of that disinfection system would not be likely to cause a risk to public health. If a sanitising system could satisfy those criteria with scientific tests, then the NSW Department of Health would not offer an objection to its use under certain conditions.

Over two years ago, one copper and silver based ioniser system submitted test results showing that it had satisfied the NSW criteria existing at that time. As a result, NSW Health issued a letter dated 17 September 2002, confirming that it had no objection to the use of this system subject to certain conditions as set out in that letter. However, in a hearing of the Administrative Appeals Tribunal in December 2004, sworn testimony revealed that a critical test among those submitted had been done in such a way as to invalidate its results. During the course of the test, chlorine had been added regularly to the pool to supplement the ioniser system, and therefore the ioniser system was not shown to have been alone responsible for a satisfactory test result. As soon as that information was revealed, the NSW Department of Health took rapid steps to withdraw the “letter of no objection”. Since December 2004, such ioniser systems cannot be used in NSW public pools.

It should be noted that the NSW Department of Health withdrew its previous efficacy criteria when the APVMA established its new efficacy guideline in July 2004. NSW Health now refers to the APVMA guideline.

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What evidence does the APVMA need to be satisfied that a pool sanitiser is effective?

Recent experiences with unregistered silver and copper ion based swimming and spa pool sanitiser (claimed) products led to a re-examination of the standards that the APVMA uses for demonstrating efficacy of pool sanitisers against harmful micro-organisms. Existing laboratory test standards for swimming and spa pool sanitisers seem to have been developed with the expectation that new products required to meet the standards would be based on chlorine or bromine. Chlorine in particular is so well studied and documented that, provided enough free chlorine is present, there is ready acceptance of its ability to adequately sanitise water (with a few exceptions such as Giardia and Cryptosporidium which are not completely controlled by standard levels of chlorine) for the range of human pathogen classes likely to be encountered in a pool or spa environment (bacteria, mycobacteria, viruses, fungi and protozoa).

Current typical laboratory standards call for a four log10 reduction (meaning a reduction of 99.99%)) of one or more defined bacterial indicator species within a specified time period such as 30 seconds. (Chlorine-based sanitisers, for example, easily meet this standard at recommended concentrations.) It has been assumed in the past that if such efficacy can be demonstrated against the test bacteria, then one can also be confident that the test product will perform adequately against viral, fungal and protozoan pathogens.

However, that assumption may not be valid when a new, significantly different sanitiser type is proposed for registration, one that does not have an extensive history of testing and a well-established consensus supporting its broad efficacy. The new type of sanitiser needs to have its efficacy demonstrated against the range of human pathogen types, and its degree of efficacy should compare favourably with proven sanitisers. This requirement is fundamental to protecting the health of users of pools and spas. Moreover, that broad efficacy should first be demonstrated convincingly under controlled laboratory conditions before “field testing” is carried out in a real pool or spa environment.

The APVMA has therefore developed guidelines in collaboration with State health authorities and members of the testing industry to ensure that the guidelines are appropriate and reasonable. The guideline is called APVMA guide for demonstrating efficacy of pool and spa sanitisers (PDF, 124kb). The APVMA guide applies to “new” pool and spa sanitiser active constituents that have not been previously approved or registered with the APVMA or its predecessor.

The performance characteristics for new sanitisers called for in the APVMA Guide are equivalent to those of hypochlorous acid/hypochlorite (chlorine). In other words, the APVMA has chosen the performance level of chlorine as a standard and has set the performance criteria in the APVMA Guide to be the same as those already established for chlorine (see Table 1 below). (For example, this means that existing registered chlorine sanitiser products are already known to meet the performance criteria outlined in the new APVMA Guide.)

Applicants must be able to establish that the proposed new sanitiser is effective against the key pathogens in the major classes of human pathogenic microorganisms commonly found in swimming pool and spa pool environments, namely bacteria, protozoa, viruses and fungi. As a general guide, applicants must be able to establish that the product is equivalent in efficacy to registered sanitisers based on hypochlorous acid/hypochlorite against these classes of microorgansisms.

In addition to efficacy equivalent to hypochlorous acid/hypochlorite as demonstrated in laboratory and field tests, a swimming pool or spa pool sanitiser or disinfectant process must have the following general performance features or properties.

  • An effective residual concentration of sanitiser can be maintained in the body of the pool to provide continuous disinfection within the water at all times.
  • The concentration of the residual sanitiser (or its principal components if there is more than one active constituent) is capable of being measured using a field test kit or other simple method that can be properly managed by an average home pool owner.
  • The sanitiser is capable of supplementary dosing if measured levels are found to be below the recommended effective concentration.
  • A minimum efficacy threshold concentration has been identified for the sanitiser so that a known efficacy safety margin can be established for normal operating concentrations.
  • For sanitisers containing more than one active constituent, the relative contributions of each principal active constituent to the overall efficacy have been identified.

The performance characteristics of an effective sanitiser against the specified test organisms are shown below. These performance characteristics are the same as those of chlorine (hypochlorous acid/hypochlorite).

Test Organism - Fungi Number of log10 reductions to be achieved Time of exposure to test sanitiser at normal* concentration during which reduction is to be achieved
Trichophyton mentagrophytes (conidia) 5 10 seconds
Test Organism - Bacteria Number of log10 reductions to be achieved Time of exposure to test sanitiser at normal* concentration during which reduction is to be achieved
Pseudomonas aeruginosa 4 30 seconds
Legionella pneumophila 4 30 seconds

Test Organism - Viruses Number of log10 reductions to be achieved Time of exposure to test sanitiser at normal* concentration during which reduction is to be achieved
Adenovirus 4 5 minutes
Rotavirus 4 5 minutes
Test Organism - Protozoa Number of log10 reductions to be achieved Time of exposure to test sanitiser at normal* concentration during which reduction is to be achieved
Naegleria fowleri (cysts) 4
30 minutes
Giardia muris (cysts) 3 45 minutes

*the concentration recommended for normal use

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What is the APVMA’s position on health concerns arising from use of chlorine to sanitise water?

The APVMA recognises that some people are concerned by advertising and media reports that chlorine used to disinfect water might be dangerous. Although chlorine is a very effective and long-established water sanitiser, it has been shown to produce small amounts of unwanted disinfection by-products (DBPs) as a result of reacting with organic matter in the water. Some of the DBPs are irritants and some could have a potential for adverse health effects if they were to be present in high enough concentrations.

However, in relation to these possible hazards of chlorine disinfection by-products, the APVMA agrees with the position of the World Health Organization (WHO) final draft report entitled “Guidelines for Safe Recreational-Water Environments, volume 2: swimming pools, spas and similar recreational-water environments, chapter 4 - Chemical Hazards” dated August 2000. WHO stated regarding chemical disinfectants for swimming pools:

“It must be emphasized that although the use of chemical disinfectants in water treatment usually results in the formation of chemical by-products, some of which are potentially hazardous, the risks to health from these by-products at the levels at which they occur in pool water are extremely small in comparison with both the risks associated with inadequate disinfection and the enormous health benefits (including relaxation and exercise) associated with pool use” (at page 4-22).

The overriding importance of disinfection was emphasised in another WHO publication through the International Programme on Chemical Safety (IPCS) – Environmental Health Criteria, Bulletin 216 – Disinfectants and disinfectant by-products (2000). In section 8 under “Conclusions and Recommendations” the WHO stated:

“Disinfection is unquestionably the most important step in the treatment of water for drinking-water supplies. The microbial quality of drinking-water should not be compromised because of concern over the potential long-term effects of disinfectants and disinfection by-products (DBPs). The risk of illness and death resulting from exposure to pathogens in drinking-water is very much greater than the risks from disinfectants and DBPs. Where local circumstances require that a choice be made between microbiological limits or limits for disinfectants and DBPs, the microbiological quality must always take precedence. Efficient disinfection must never be compromised.

The microbiological quality of drinking-water is of paramount importance and must receive priority over any other considerations in relation to drinking-water treatment………The microbiological quality of drinking-water should always receive priority over the minimization of DBPs.”

Under section 8.2, “Toxicology”, the same document states the following.

“None of the chlorination by-products studied to date is a potent carcinogen at concentrations normally found in drinking-water. The toxicology of the DBPs suggests that the likelihood of adverse effects is not significantly different between the described disinfectant options.”

An extract from the WHO Guidelines for Drinking-Water Quality, 3rd edition (2004) makes the following statements:

“The potential health consequences of microbial contamination are such that its control must always be of paramount importance and must never be compromised.” (Vol 1, page 3)

“The use of chemical disinfectants in water treatment usually results in the formation of chemical by-products. However, the risks to health from these by-products are extremely small in comparison with the risks associated with inadequate disinfection, and it is important that disinfection not be compromised in attempting to control such by-products.” (Vol 1, page 5)

This is consistent with the view of the Australian National Health and Medical Research Council (NHMRC). The Australian Drinking Water Guidelines (1996 - updated 2001) as published by the NHMRC, state:

“Action to reduce the concentration of disinfection by-products is encouraged, but disinfection itself must not be compromised: the risk posed by disinfection by-products is considerably smaller than the risk posed by the presence of pathogenic micro-organisms in water which has not been disinfected.” (chapter 3, page 3-4).

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