Guidelines for Canadian Recreational Water Quality

5. Physical and Chemical Characteristics

Methods for determining physical and chemical characteristics of recreational water can be found in Standard Methods for the Examination of Water and Wastewater (American Public Health Association 1989) and the Analytical Methods Manual (Environment Canada 1981).

5.1 pH

Maximum Limits

Both alkaline and acidic waters may cause eye irritation; consequently, the pH of the waters used for total body contact recreation should be in the pH range of 6.5 to 8.5. If the water has a very low buffering capacity, pH values from 5.0 to 9.0 should be acceptable.

Criteria

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 physico-chemical properties as tears, including a pH of 7.4, although there is some evidence to suggest that ophthalmologic 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 to 200 meq/L (microequivalents per litre) of acid-neutralizing capacity (ANC), and many of these lakes have depressed pHs. Detailed maps depicting sensitive areas in some provinces have been prepared by the United States-Canada Research Consultation Group on the Long-Range Transport of Air Pollutants (1979).

Studies completed by Basu et al. (1984) used water from two inland lakes in Ontario: Clearwater Lake (pH about 4.5) with an ANC of -40 meq/L (Yan 1980), and Red Chalk Lake (pH about 6.5) with an ANC of 70 meq/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).

In all cases, 1 eye was exposed to the low-pH water and the other to the higher-pH water. The human eyes were exposed for 5-minute periods, and no unusual signs or symptoms occurred. 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 leucocyte content of tears, changes 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.

5.2 Temperature

Maximum Limits

The thermal characteristics of waters used for bathing and swimming should not cause an appreciable increase or decrease in the deep body temperature of bathers and swimmers.

Criteria

The temperature of natural waters is an important factor governing the character and extent of recreational activities, primarily in the summer months. The upper recommended limit of temperature is 30°C. Scientific evidence suggests that prolonged immersion in water warmer than 34 to 35°C is hazardous. The degree of hazard varies with the water temperature, immersion time, and the metabolic rate of the swimmer.

Persons engaging in winter water recreation such as ice skating and fishing do so with the knowledge that whole body immersion must be avoided. Accidental immersion in water at or near freezing temperatures is dangerous, because the median lethal immersion time is less than 30 minutes for children and most adults (Molnar 1946; National Academy of Sciences 1973) (Figure 1).

Figure 1. Relationship between water temperature and survival time in cold water

There is considerable variation from one individual to another in the rate of body cooling and the incidence of survival in cold water. The variability is a function of body size, fat content, prior acclimatization, 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).

In cold temperatures, the critical problem is to maintain body temperature. In cold water, body heat is lost primarily by conduction from the inner organs through the trunk. Exposure of the limbs plays a relatively minor role in overall heat loss. In several instances where drowning was reported as the cause of death, exposure to cold was probably the responsible factor (Keatinge 1969).

Contrary to earlier opinion, exercise in the water increases the loss of body heat and correspondingly decreases survival time. This is reflected in frequent reports of drownings of expert swimmers who tried to reach shore after a sinking, whereas those who remained in the water near the lost ship survived until rescued. A careful study of reported drowning cases carried out by Press (1969) seemed to bear out much of the above as regards survival in cold waters. He reported that 299 out of 874 drownings, or 34 per cent, occurred in waters that were listed as very cold (assumed to be below 20°C). In addition, a much higher percentage of those succumbing in cold water were considered to be good swimmers.

The safe upper limit of water temperature for recreational immersion varies from individual to individual and seems to depend on psychological rather than physiological considerations. Unlike cold water, the mass to surface area ratio in warm water favours the child. Physiologically, neither adult nor child 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). The rate at which heat is conducted from the immersed human body is so rapid that thermal balance for a body at rest in water can be attained only if the water temperature is about 34°C (Beckman 1963). The survival of an individual submerged in water at a temperature above 34 to 35°C depends on the tolerance to an elevation of the internal temperature, and there is a real risk of injury with prolonged exposure. Water ranging in temperature from 26 to 30°C is comfortable for most swimmers throughout prolonged periods of moderate physical exertion.

5.3 Aesthetics

Webster's Third New International Dictionary (1986) defines aesthetic as "appreciative of, responsive to the beautiful" in nature. Not only should a recreational area be free from objectionable factors, but various aesthetic components of the aquatic ecosystem and surrounding land should be present; for example, trees, other plants, birds, mammals, fish, and insects all play a role in the natural beauty of a recreational area.

All waters should be free from substances attributable to wastewater or other discharges in amounts that would interfere with the existence of life forms of aesthetic value:

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

The absence of visible debris, oil, scum, and other matter resulting from human activity is a strict requirement of aesthetic acceptability. Similarly, suggested values for light penetration, colour, and turbidity must be measured as being not significantly increased over natural background.

5.3.1 Turbidity

Maximum Limits

A limit of 50 Nephelometric Turbidity Units (NTU) is suggested.

Criteria

Because filtration equipment and modern water treatment processes are not feasible at natural bathing areas, safety hazards associated with turbid or unclear water are dependent upon the intrinsic quality of the water itself. However, 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.

The current method of choice for turbidity measurements is the nephelometric method (American Public Health Association 1989). Nephelometric turbidimeters measure the intensity of light scattered at 90 degrees to the path of incident light, and levels can be approximately related to the standard Jackson candle method.

One special component of organic turbidity is microorganisms, which may accumulate in such large amounts that waters become unsightly and turbid. The summer blooms of blue-green algae in recreational surface waters and algal debris are examples of turbidity due to microorganisms (Mackenthun and Keup 1970).

Raw water levels can vary from 1 to 1000 NTU. Runoff water quality measurements indicated levels of 4.8 to 130 NTU during the first hour of an urban rainfall occurrence (U.S. Environmental Protection Agency 1978b). In the quiescent zone of a bathing beach or reservoir impoundment, turbidity measurements in the vicinity of 50 NTU would be sufficient to satisfy most recreational uses, including boating and swimming.

The natural turbidity of some bathing and swimming waters is often so high that visibility through the water is dangerously limited. If such areas conform with all other requirements, they may be used for bathing and swimming, provided that subsurface hazards are removed and the depth of water is clearly indicated by signs that are easily readable (National Academy of Sciences 1973).

5.3.2 Clarity - Light penetration

Maximum Limits

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

Criteria

It is important that water at bathing and swimming areas be clear enough for users to estimate depth, to see subsurface hazards easily, and to detect the submerged bodies of swimmers or divers who may be in difficulty. Aside from the safety factor, clear water fosters enjoyment of the aquatic environment. The clearer the water, the more desirable the swimming area (National Academy of Sciences 1973).

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).

The Secchi disc is a device used to measure visibility depths in water. The upper surface of a circular metal plate, 20 cm in diameter, is divided into 4 quadrants and painted so that the 2 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 plants and animals, suspended mineral particles, stains that impart a colour, detergent foams, dense mats of floating and suspended debris, or a combination of these factors.

5.3.3 Colour

Maximum Limits

An objective for the colour of recreational water largely depends on the preferences of users, and it is impossible to put an absolute value on it. Colour should not be so intense as to impede visibility in areas used for swimming. A maximum limit of 100 platinum-cobalt (Pt-Co) units was proposed by Environment Canada (1972), but no supporting evidence was given.

Criteria

There are two measures of colour in water - true and apparent. The true colour of natural water is the colour of water from which turbidity has been removed (i.e., filtered water) (American Public Health Association 1989).

Natural minerals give true colour to water; for example, calcium carbonate in limestone regions gives a greenish colour, ferric hydroxide, red. Organic substances, tannin, lignin, and humic acids from decaying vegetation also give true colour to water (Reid and Wood 1976).

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 (living) blue-green algae imparts a dark greenish hue; diatoms 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.

To measure true colour, the water has to be filtered or centrifuged to remove the sources of apparent colour. True colour is measured on the platinum-cobalt scale (Pt-Co units) and ranges from very low numbers in clear lakes to over 300 units in the very dark waters of peat bogs (Reid and Wood 1976). Apparent colour is an aesthetic quality and cannot be quantified.

The colour imparted by organic compounds has been discussed by a number of authors. Colloidal material with a diameter of 3.5 to 10 nm accounted for most of the colour in water studies by Black and Christman (1963), and Schindler and Alberts (1974) confirmed this statement. Humic substances are compounds with high molecular weights (ranging from several hundred to tens of thousands) (Schnitzer and Khan 1972) that are resistant to bacterial decomposition (Felbeck 1965; Christman and Ghassimi 1966). The compounds are the result of polymerization and microbial synthesis, which alter plant components such as lignin (Flaig 1964; Felbeck 1971).

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.

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 toward blue or green caused by differential light absorption and scattering of different wavelengths (Ruttner 1963; Reid and Wood 1976).

The colour of stream water is due to the same factors contributing to the colour of lake water, but there is not as much variety as in lakes. The upper reaches of most streams are characterized by clear water, except in the flood season, because of the lack of true plankton. Streams draining swamps are usually coloured by dissolved plant substances such as tannin.

Many industrial effluents and irrigation cause both true and apparent colour in receiving water.

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 colour of water affects aquatic life, but this subject will not be discussed in this document. The main effects of water colour on recreational activities are aesthetic and safety related. The aesthetic colour of water cannot be quantified, as there are as many preferences as there are people. 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 is not altered by any anthropogenic activities.

5.3.4 Oil and grease

Maximum Limits

Oil 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
• can form deposits on shorelines and bottom sediments that are detectable by sight or odour (International Joint Commission 1977).

Criteria

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. Natural biological populations release lipid compounds, which can form natural slicks.

The man-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.

The analytical method for oil and grease (detection limit 1.0 mg/L) gives only a gross idea of the amount present, and individual compounds cannot be identified (Environment Canada 1981).

It is very difficult to establish criteria for oil and grease, as the mixtures falling under this category are very complex. Very small quantities of oily substances make water aesthetically unattractive. The water may have an odour, or it may foul equipment or the bodies of bathers and shorelines, but the possibility exists that recreationists might still use the water in cases of low contamination. The toxicity of oily substances from ingestion, skin absorption, or inhalation of vapours is relatively low except in the case of aromatics (Gage 1924).

5.4 Chemical Characteristics

Some concern has been expressed about a risk to bathers from the presence of chemicals in recreational waters. Very few studies have been found in the literature that equate a hazard to the health of swimmers and others to skin absorption of contaminants present in river or lake water (Brown et al. 1984).

5.4.1 Inorganic chemicals

National surveys of the water quality of lakes and rivers used for recreational activities indicate that concentrations of inorganic chemicals are low (National Water Quality Data Bank 1988). Analyses (1983-1988) for heavy metals indicated that they are present in concentrations considerably below those recommended as guidelines for drinking water (Department of National Health and Welfare 1989). Aquatic life is considerably more sensitive to most toxic chemicals than are humans. It is very unlikely that there is a hazard to people engaged in recreational activities in and around rivers and lakes as a result of the presence in water of inorganic chemicals.

5.4.2 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 (National Water Quality Data Bank 1988).

National surveys have analyzed 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 (Department of National Health and Welfare 1989) and should not pose any threat to human health.

A review by Brown et al. (1984) of volatile solvents compared the estimated skin absorption dose with the oral dose ingested under a number of exposure situations, including swimming, bathing, and drinking. Their findings indicated that skin absorption contributed between 29 and 91 per cent of the total dose. For example, if a 21.9-kg child swam 1 hour in water (90 per cent submerged) and drank 1 L (his normal daily intake) of water containing 0.5 mg/L of toluene, the dose of toluene absorbed by the dermal route would be 91 per cent of the daily absorbed dose from the two sources.

In summary, there are some chemical contaminants that could be a cause for concern in recreational waters. Given the paucity of information on the type of chemical, the effective concentration, and the effects, it is difficult to set guidelines at the present time.

Summary

1. It is recommended that no measurable limits be established for chemicals in recreational water for human exposure risk because of lack of sufficient scientific information. Decisions for use should be based on aesthetic quality (e.g., presence of odour or visible oil and grease) and other factors considered in the environmental health assessment (e.g., proximity to industrial discharge).