Page 13: Guidelines for Canadian Recreational Water Quality – Third Edition

Part II: Guideline Technical Documentation

8.0 Physical, aesthetic and chemical characteristics

This section describes the major physical, aesthetic and chemical characteristics of water that may affect recreational water bodies. Information is provided as to the potential effects each may have on the safe, enjoyable use of recreational waters. Guideline values or aesthetic objectives have been provided where possible. It is intended that the values and associated guidance apply to all recreational waters, regardless of the types of activities practised. Responsible authorities may wish to establish separate guideline values or aesthetic objectives for waters not intended for primary contact use at their discretion.

Methods for determining physical, aesthetic and chemical characteristics of recreational waters can be found in Standard Methods for the Examination of Water and Wastewater (APHA et al., 2005). Sampling for these parameters is at the discretion of the responsible authority, however it is suggested that valuable times may include:

  • when conducting the EHSS;
  • at the start of, and at regular intervals during the swimming season,
  • during area assessments conducted in response to recreational water issues, as appropriate.

8.1 Physical characteristics

8.1.1 pH
Guideline values

Both alkaline and acidic waters may cause eye irritation. To be protective against the risk of eye irritation, the pH of recreational waters should be in the range of 5.0 to 9.0.


Mood (1968) concluded that exposure to water is foreign to the eye and may, under certain circumstances, be very irritating. He assumed that the ideal, non-irritating solution would have the same physicochemical properties as tears, including a pH of 7.4, although there is some evidence to suggest that ophthalmological solutions slightly more alkaline are actually preferred (Raber and Breslin, 1978).

Mood (1968) reported that tears have the capacity to rapidly neutralize an unbuffered solution from a pH as low as 3.5 or as high as 10.5. The neutralizing capacity of the tears would be exceeded by highly buffered waters. However, Mood (1968) concluded that unbuffered waters are not found in nature under normal conditions; hence, he suggested that the pH range for water with low buffering capacity should be between 5.0 and 9.0. Dillon et al. (1978) reported that most lakes in south-central Ontario have 10-200 µeq/L of acid-neutralizing capacity (ANC), and many of these lakes have depressed pH.

Studies completed by Basu et al. (1984) used water from two inland lakes in Ontario: Clearwater Lake (pH approximately 4.5), with an ANC of -40 µeq/L (Ontario Ministry of the Environment, 1980), and Red Chalk Lake (pH approximately 6.5), with an ANC of 70 µeq/L. The eyes of both test rabbits and human volunteers were exposed to these waters, and no significant differences were observed in their reactions (Basu et al., 1984). Basu et al. (1984) exposed one eye to the low-pH water and the other to the higher-pH water. The human eyes were exposed for 5-minute periods, and no ocular effects were noted. The rabbit eyes were exposed for periods of 15 minutes and checked for ocular reactions in terms of conjunctival congestion, corneal epithelial staining with fluorescein, epithelial cell and leukocyte content of tears, change in tear molarity and the penetration of fluorescein into the anterior chamber. Basu et al. (1984) concluded that the exposure of healthy eyes to lake water having a pH as low as 4.5 is not harmful to the external ocular tissues.

8.1.2 Temperature
Guideline value

Precise guideline values for the temperature of waters to be used for swimming cannot be established. Tolerance to water temperatures can vary considerably from individual to individual. Users should not engage in recreational activities at temperature-time combinations sufficient to cause an appreciable increase or decrease in their core body temperature.


Cold water exposures

Water is very efficient at conducting heat away from the body. When in water, unlike air, the surface area available for heat exchange reaches close to 100% (Transport Canada, 2003). Water has 25 times the thermal conductivity of air and cools the body 4-5 times faster than air of the same temperature (Tipton and Golden, 2006).

The definition of cold water must be considered with respect to normal body temperature, duration of exposure and degree of protection by insulation (Canadian Red Cross, 2006). When heat loss exceeds heat production, the temperature of the body will drop below the normal value of 37°C (Tipton and Golden, 2006). Water, even at comfortable levels, can result in the transfer of heat away from the body. Fatalities from cold water immersion have been reported in subtropical waters in which exposure was prolonged. Thermal neutrality in water is reported to occur at 35°C. Below this value, the human body is expected to lose more heat than it is capable of producing. Sudden, unprotected immersion in water of ≤ 15°C is considered to be a potentially life-threatening situation (Canadian Red Cross, 2006).

Figure showing the relationship between water temperatures and the associated expected time of survival

Figure showing the relationship between water temperatures and the associated expected time of survival
Description of the figure showing the relationship between water temperatures and the associated expected time of survival - Text Equivalent
The graph shows increasing water temperature in degrees Celsius on the x-axis and increasing time in hours on the y-axis. The graph has two J-shaped curves: a lower curve starting at the bottom left corner, curving upward and ending at the top right corner, and an upper curve starting at the bottom left corner, curving upwards and ending along the top axis, approximately two-thirds of the way across to the corner. These curves divide the graph area into three sections. These sections represent where the time-temperature combinations are expected to be 'Safe" (the bottom section - half an hour or less at below zero up to 6 hrs at 20 degrees Celsius); "Fatal" (the top section - half an hour or more at below zero up to 6 hrs at 12 degrees Celsius) and "Marginal" (the middle section - half an hour to an hour at 0 degrees Celsius up to 6 hrs at 12 to 20 degrees Celsius). The lower curve also reflects where a person would be conscious while the upper curve reflects where a person would be unconscious.

Experts have identified four sequential stages that can occur following immersion in cold water: 1) gasping and cold shock, 2) swimming failure, 3) hypothermia and 4) post-rescue collapse (Transport Canada, 2003; Canadian Red Cross, 2006). It is believed that most deaths in cold water occur from drowning by submersion of the airways during the first two stages of cold water immersion (Canadian Red Cross, 2006).

The rate of body cooling and the incidence of survival in cold water can vary considerably from individual to individual. This variability can be related to age, sex, body size, ratio of body mass to surface area, percentage body fat and overall physical fitness. The ratio of body mass to surface area is greater in large, heavy individuals, and their temperatures change more slowly than those of small children (Kreider, 1964). Other factors influencing cooling can include the degree of protective clothing and physical behaviour and body posture in the water. The use of drugs or alcohol can also exacerbate the effects of cold water immersion, by impairing alertness and motor skill use and by interfering with the body's temperature regulation mechanisms (Canadian Red Cross, 2006).

Immersion in cold water may occur through intentional or unintentional activities. Persons using recreational waters should remain aware of the risks involved and take appropriate precautions against cold water exposure. The Canadian Red Cross (2008) and Transport Canada (2006) have produced publications that provide information on survival in cold waters. Proper protective garments such as a wetsuit or survival suit should be worn during recreational water activities where cold water exposure is anticipated. Similarly, precautions should be taken against accidental immersions, including use of safety lines and wearing of proper personal flotation devices.

Warm water exposures

By comparison, relatively little information is available regarding the physiological effects of human exposure to warm waters. Early communication on this topic suggested that, physiologically, neither adults nor children would experience thermal stress under modest metabolic heat production, as long as the water temperature was lower than the normal skin temperature of 33°C (Newburgh, 1949). Water ranging in temperature from 20°C to 30°C is considered comfortable for most swimmers (WHO, 2003a, 2006).

In Canada, under most circumstances, ambient temperatures observed during the summer months do not reach levels sufficient to elevate recreational water temperatures above normal human body temperature. Natural hot springs--thermal springs that can reach temperatures in excess of 37°C--are a notable exception. Individuals using these types of facilities should monitor their exposures carefully so as to avoid overheating. For the majority of recreational water areas, the heat effects observed during summertime water activities are largely attributed to sun exposure. Numerous health authorities have provided guidance on avoiding heat exposure during outdoor activities; thus, this information can be viewed as extending to recreational water exposures as well.

Heat stress or heat exhaustion can occur following vigorous exercise in warm environments. Signs of heat exhaustion can include excessive sweating, elevated temperature or pulse rate, headache and dizziness or weakness. The Canadian Red Cross has similarly developed publications on the prevention of heat-related illness or injury (Canadian Red Cross, 2011). Precautionary measures to minimize the effects of heat exposure during recreational water activities are similar to those for reducing sun exposure. These include wearing lightweight clothing and broad-brimmed hats, seeking out cool or shady areas, avoiding activity during midday periods when the sun is most intense, ensuring an adequate supply of drinking water and replenishing any salt losses.

8.2 Aesthetic characteristics

Good aesthetic quality is an important consideration in ensuring the maximum use and enjoyment of recreational waters. A recreational water area should be considered aesthetically acceptable to its users. Waters used for recreation should be free from substances (either attributable to human activities or due to natural processes) that impair its aesthetic appreciation. These can include:

  • substances producing objectionable colour, odour, taste or turbidity;
  • floating debris, oil, scum and other matter;
  • materials that will settle to form objectionable deposits; and
  • substances and conditions or combinations thereof in concentrations that produce undesirable aquatic life.

The term aesthetic has been defined as "concerned with beauty or the appreciation of beauty" (Canadian Oxford Dictionary, 2004). Thus, not only should a recreational water area be free from objectionable factors, but various other aesthetic components of the aquatic ecosystem and surrounding land should be present. Recreational waters should also be considered free from substances in amounts that would interfere with the existence of life forms of aesthetic value.

This section discusses parameters that may affect the aesthetic quality of a recreational water area. For the purposes of this document, it is the effects that these factors may have on aesthetic perception that are of primary significance. However, it should be noted that with these parameters there also exists certain implications for human health and safety. For example, waters in which the visibility has become significantly impaired can present a safety risk for recreational water users.

Aesthetic objectives for turbidity, clarity and colour have been proposed; however, it is recognized that the natural levels of these parameters in Canadian waters can vary considerably. Thus, it is recommended that, when evaluating these parameters as part of an Environmental Health and Safety Survey, the associated values also be interpreted as not being significantly increased over that which would be considered natural background.

8.2.1 Turbidity
Aesthetic objective

An aesthetic objective of 50 nephelometric turbidity units (NTU) is suggested for recreational waters.


Standard Methods for the Examination of Water and Wastewater (APHA et al., 2005) defines turbidity as an "expression of the optical property that causes light to be scattered and absorbed rather than transmitted with no change in direction or flux level through the sample." The current method of choice for turbidity measurements in Canada is the nephelometric method, and the unit of turbidity measured using this method is the nephelometric turbidity unit, or NTU (Health Canada, 2012c).

Turbidity in water is caused by suspended and colloidal matter, such as clay, silt, finely divided organic and inorganic matter, plankton and other microscopic organisms (APHA et al., 2005). This parameter is important for aesthetic, safety and, to a lesser degree, health reasons. High turbidity is aesthetically displeasing and can be a safety concern when it reduces visibility through the water. Because filtration equipment and modern water treatment processes are not feasible at natural swimming areas, safety concerns associated with turbid or unclear water are dependent upon the intrinsic quality of the water itself. Lifeguards and other persons near the water must be able to see and distinguish people in distress. In addition, swimmers should be able to see quite well while under water.

Health considerations associated with turbidity are related primarily to the ability of particles to adsorb microorganisms and chemical contaminants. This can have a number of important effects on water quality:

  • Suspended particles can provide a measure of protection for microorganisms (bacteria, viruses, protozoa) that have been adsorbed to their surface by shielding them from the effects of environmental stresses such as UV radiation and predation by higher microorganisms.
  • The presence of turbidity may interfere with the quantification of faecal indicator organisms. In the enumeration of bacteria, it is assumed that each colony represents one cell; however, a single colony could emanate from a particle containing many bacterial cells adsorbed on its surface. Fewer cells than were actually present would then be recorded. This phenomenon would also lead to an underestimation of bacterial numbers with the MPN technique (Health Canada, 2012c).
  • Particulate matter may also contain chemical contaminants such as heavy metals and biocides (Health Canada, 2012c).

Surface water levels can vary from 1 to more than 1000 NTU (Health Canada, 2012c). Runoff water quality measurements indicated levels of 4.8-130 NTU during the first hour of an urban rainfall occurrence (U.S. EPA, 1978). In the quiescent zone of a swimming beach or other recreational water area, it is suggested that turbidity measurements in the vicinity of 50 NTU would be sufficient to satisfy most recreational uses, including swimming.

8.2.2 Clarity (light penetration)
Aesthetic objective

Water should be sufficiently clear that a Secchi disc is visible at a minimum depth of 1.2 m.


The Canadian Oxford Dictionary (2004) defines "clarity" as "the state or quality of being clear." Clarity is associated with the distance light can penetrate into a body of water and is often interpreted as "how far can one see into the water?" The clarity of a water body can be simply evaluated by using a Secchi disc, which is a device used to approximately measure visibility depths in water. The upper surface of a circular metal plate, 20 cm in diameter, is divided into four quadrants and painted so that the two quadrants directly opposite each other are black and the intervening ones are white. When suspended to various depths of water by means of a graduated line, its point of disappearance indicates the limit of visibility. It is then raised until it reappears, and the average of the two depths is taken as the Secchi disc transparency.

The principal factors affecting the depth of light penetration in natural waters include suspended microscopic and macroscopic organisms, suspended mineral particles, stains that impart a colour, detergent foams, dense mats of floating and suspended debris, or a combination of these factors.

It is important that water at swimming areas be clear enough for users to estimate depth, to see subsurface objects easily and to detect the submerged bodies of swimmers or divers who may be in distress. Aside from the safety factor, clear water fosters enjoyment of the aquatic environment.

For primary contact recreation waters, it has been suggested that clarity be such that a Secchi disc is visible at a minimum depth of 1.2 m (Environment Canada, 1972). In "learn to swim" areas, the clarity should be such that a Secchi disc on the bottom is visible. In diving areas, the clarity shall equal the minimum required safety standards, depending on the height of the diving platform or board (National Technical Advisory Committee, 1968).

8.2.3 Colour
Aesthetic objective

No numerical value can be established for colour in recreational waters. Colour should not be so intense as to impede visibility in areas used for swimming.


The observed colour of water is the result of light backscattered upward from a water body after it has passed through the water to various depths and undergone selective absorption (CCME, 1999). There are two measures of colour in water: true and apparent. The term colour is most often used to mean true colour, the colour of water from which turbidity has been removed. To measure true colour, the water has to be filtered or centrifuged to remove the sources of apparent colour. The standard method for measuring colour is the platinum-cobalt method (APHA et al., 2005). Colour is measured by visual comparison with coloured solutions of known concentrations. Under this method, one Pt-Co unit is equivalent to that produced by 1 mg platinum/L in the form of the chloroplatinate ion. The ratio of cobalt to platinum given matches the true colour of water.

The correct units for true colour are colour units (CU), with one colour unit being equivalent to 1 Pt-Co unit (APHA et al., 2005). True colour can range from less than 5 CU (colour units) in very clear waters to 1200 CU in dark peaty waters (Kullberg, 1992). Natural minerals give true colour to water; for example, calcium carbonate in limestone regions gives a greenish colour, whereas ferric hydroxide gives a red colour. Organic substances, tannin, lignin and humic acids from decaying vegetation also give true colour to water (Department of National Health and Welfare, 1979).

Apparent colour includes not only colour due to substances in solution but also that due to suspended matter (APHA et al., 2005). Measurements for apparent colour are determined on the original sample without filtration or centrifugation (APHA et al., 2005). Apparent colour is usually the result of the presence of coloured particulates, the interplay of light on suspended particles and such factors as bottom or sky reflection. An abundance of cyanobacteria can impart a dark greenish hue to water, whereas diatoms or dinoflagellates may give a yellowish or yellow-brown colour. There are algae that impart a red colour, and, rarely, zooplankton, particularly microcrustaceans, may tint the water red. Polluted waters may have strong apparent colour. Industrial discharges (particularly those from the pulp and paper and textile industries) can be highly coloured and thus may affect water coloration. Factors increasing the turbidity of natural waters may similarly affect apparent colour.

Colour in lakes may not be uniform from surface to bottom; also, the colour may change periodically. Increases in surface runoff contribute great quantities of inorganic and organic substances. Summer or early autumn production of phytoplankton blooms causes lakes to become a "soupy green," which disappears later in the season. Exposure to light causes bleaching of certain colours in natural waters, and this effect will vary according to transparency. Colour may also be dependent on factors that affect the solubility and stability of the dissolved and particulate fractions of water, such as temperature and pH.

Generally, a rich, highly productive lake may appear yellow, grey-blue or brown as a result of quantities of organic matter, and less productive lakes tend towards blue or green caused by differential light absorption and scattering of different wavelengths (Ruttner, 1963; Reid and Wood, 1976).

The causes of colour in marine waters are not thoroughly understood, but dissolved substances are one of the contributory factors. The blue of the sea is a result of the scattering of light by water molecules, as in inland waters. Suspended detritus and living organisms give colours ranging from brown through red and green. Estuarine waters are not as brilliantly coloured as the open sea; the darker colours result from the high turbidity usually found in such situations (Reid and Wood, 1976).

The main effects of water colour on recreational activities are aesthetic and safety related. Very dark water restricts visibility both for swimmers and for people concerned with their safety. In recreational waters, it is desirable that the natural colour of the water not be altered by any human activities. A maximum of 100 CU was proposed by Environment Canada (1972), while a guideline of not more than 30 CU above natural value is used by Alberta Environment (1999). Supporting evidence for these values has not been given. Thus, in the absence of strong supporting evidence, it is recommended that they be considered as guidance values.

8.2.4 Oil and grease
Aesthetic objective

No numerical value can be established for oil and grease in recreational waters. Oil, grease or petrochemicals should not be present in concentrations that:

  • can be detected as a visible film, sheen or discoloration on the surface;
  • can be detected by odour; or
  • can form deposits on shorelines and bottom sediments that are detectable by sight or odour (International Joint Commission, 1987).

Standard Methods for the Examination of Water and Wastewater (APHA et al., 2005) defines "oil and grease" as "any material recovered as a substance soluble in the solvent." The category of oil and grease includes many different substances of mineral, animal, vegetable or synthetic origin--all of which can have vastly different physical, chemical and toxicological properties. Consequently, it is very difficult to establish a numerical criterion for oil and grease.

Contamination of recreational waters with oily substances may have natural origins or may be a result of human activities. Some oils are of natural origin, such as seepage from natural underwater oil deposits or from the decomposition of some materials. For example, natural biological populations release lipid compounds, which can form natural slicks.

Human-made contamination is of greatest concern. It can come from a number of sources, such as the discharge of industrial wastes, road runoff, residual hydrocarbon deposits from motorboat engine exhaust emissions, the discharge of fuel tank contents of ships, either accidentally or deliberately, and shipwrecks. Marinas and boat launches can also be important sources of oil and grease contamination for recreational waters.

Very small quantities of oily substances make water aesthetically unattractive. Oils can form films, and some volatile components may create odours or impart a taste to water (WHO, 2003a). Oil and grease may foul equipment, shorelines or the bodies of swimmers. The possibility exists that recreational users might still use the water in cases of low contamination. The risk of toxicity from exposure to oily substances through ingestion, skin absorption or inhalation of vapours during recreational water activity is regarded to be low. Oils and greases of animal or vegetable origin are generally considered to be non-toxic to humans. Similarly, it is recognized that petroleum compounds become organoleptically objectionable at concentrations far below the levels required for chronic human toxicity. Thus, the consumption of oil-polluted water is unlikely to be a significant source of exposure for humans (Train, 1979).

8.2.5 Litter
Aesthetic objective

No numerical value can be established for litter at recreational water areas. Recreational water areas should be free from floating debris as well as materials that will settle to form objectionable deposits.


There are a variety of types of litter that can be found in recreational waters or deposited on beaches. Some examples include discarded food and food packaging, cardboard and paper products, plastic containers, styrofoam materials, rubber goods, aluminium cans, broken glass, discarded clothing, cigarette butts, medical wastes and dead animals. Large accumulations of seaweed and algae are not technically litter, but they are likely to pose an aesthetic problem (both visually and due to potential odour).

In addition to being aesthetically undesirable, the presence of litter can also present a health and safety risk to recreational water users. Some materials can be injurious to recreational water users who come in direct contact with them. Discarded litter also has the potential to attract wildlife, which can contribute to the faecal contamination of recreational waters. Indeed, litter counts have been considered as a possible indicator of the potential of acquiring gastrointestinal illness though recreational water activities. Similarly, flying and/or biting insects may also be associated with litter. These are considered at the very least a nuisance and could potentially pose a health threat in the form of zoonotic disease (NHMRC, 2008).

8.3 Chemical characteristics

Guideline values

There is insufficient information to support the establishment of guideline values for specific chemical parameters in recreational waters. Risks associated with specific chemical water quality hazards will be dependent on the particular circumstances of the area in question and should be assessed on a case-by-case basis.

In general, potential risks from exposure to chemical parameters will be much smaller than the risks from the microbiological hazards potentially present in recreational waters (WHO, 2003a). With chemical concentrations typically found in water, most recreational water users will not be exposed to sufficient concentrations necessary to elicit either an acute or chronic illness response.


Chemical contaminants can enter recreational waters or be deposited on beaches from both natural and anthropogenic sources (WHO, 2003a). These include point sources, such as industrial outfalls or natural springs, and non-point (diffuse) sources, such as runoff from urban or agricultural areas.

Inorganic chemicals

National surveys of the water quality of lakes and rivers used for recreational activities indicate that concentrations of inorganic chemicals are low (NAQUADAT, 1988; Government of Canada, 1991). Analyses for heavy metals indicated that they are present in concentrations considerably below those recommended as guidelines for drinking water quality (Government of Canada, 1991). Ingestion would be considered the primary pathway of exposure for inorganic chemical contaminants; however, skin absorption is recognized as a route of uptake for certain heavy metal forms. Owing to the low concentrations encountered in most natural waters and the types and degrees of exposure involved during typical recreational water activities, exposure to inorganic chemical contaminants is not considered to represent a significant health risk for recreational water users at recognized swimming areas.

Organic chemicals

There are many sources of contamination by organic chemicals, including industrial manufacture and use and domestic use of such items as paints, fuels, dyes, glues, pesticides and cleaning supplies (NAQUADAT, 1988; Health Canada, 1997).

National surveys have analysed the level of contamination of recreational waters by organic chemicals. The concentrations of organic chemicals that have been detected in waters that could be used for recreational purposes were lower than the recommended drinking water guidelines (Government of Canada, 1991; Marvin et al., 2004) and thus should not pose a significant threat to human health.

It has been suggested that for some organic chemicals, skin absorption can be as important as ingestion in contributing to exposure (Brown et al., 1984; Moody and Chu, 1995). However, it is generally concluded that given the low concentration of organic contaminants encountered in most natural waters and the typical exposure scenarios encountered during recreational water activities, it is not likely that dermal exposure presents a significant risk (Moody and Chu, 1995; Hussain et al., 1998). Nonetheless, precautionary measures such as restricting swimming to public beaches and showering with soap and water following recreational activity will further ensure that any risk is minimized.

Managing health risks

The risk of human exposure to chemical contaminants in Canadian waters through recreational activities is considered low. Nevertheless, scenarios do exist that may contribute to the presence of a chemical water quality hazard at a particular recreational water body. As a result, it is important for beach operators and service providers to have a mechanism in place to ensure that potential chemical hazards and their risks are recognized. An Environmental Health and Safety Survey is an important tool for helping recreational water area operators identify and assess potential sources of chemical contamination that are relevant to their beach area.

Risks associated with specific chemical water quality hazards will be dependent on the particular circumstances of the area under consideration. Thus, in all instances, the risk of human exposure to chemical contaminants in recreational waters must be assessed on a case-by-case basis, taking local factors into account. In general, some key elements that should be included in any approach to assessing chemical water quality hazards in recreational waters are as follows:

  • historical understanding of the area to identify past activities that may result in contaminated water and/or sediments;
  • inspection of the recreational water area to identify any obvious sources of chemical contamination, such as outfalls or discharges;
  • conducting of additional steps as necessary to support a quantitative health risk assessment, including chemical analysis of representative samples (using methods deemed acceptable by the regulating agencies) and review of the available toxicological information on the chemical contaminant(s) in question;
  • consideration of the pattern and type of recreational activity to determine whether significant pathways of human exposure exist (e.g., through ingestion, inhalation or skin absorption); and
  • consideration of the effects of the water body dimensions (area, depth) and other hydrodynamic and meteorological characteristics (tides, currents, prevailing winds) on the impact of the chemical water quality hazard in question.

A multi-barrier approach represents the most effective way of protecting recreational water users from the risk of exposure to chemical contamination at recreational water areas. This approach uses an Environmental Health and Safety Survey to highlight potential chemical water quality hazards as well as to identify barriers that may be implemented to both reduce the risk of chemical contamination and restrict swimmer exposures during periods or in areas perceived to be of increased risk.

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