Guidelines for safe recreational water environments
Volume 1 : Coastal and fresh waters
Chemical and physical agents
Chemical contaminants can enter surface waters or be deposited on beaches from both natural and anthropogenic sources. Exposure is one of the key issues in determining the risk of toxic effects from chemicals in recreational waters. The form of recreational activity will therefore play a significant role. Routes of exposure will be direct surface contact, including skin, eyes and mucous membranes, inhalation and ingestion. In assessing the risk from a particular contaminant, the frequency, extent and likelihood of exposure are crucial parts of the evaluation.
pH has a direct impact on the recreational uses of water only at very low or very high pH values. Under these circumstances, it may contribute to irritation of the skin and eyes.
The potential risks from chemical contamination of coastal and freshwater recreational waters, apart from toxins produced by marine and freshwater cyanobacteria and algae, marine animals or other exceptional circumstances, will be very much smaller than the potential risks from microbial contaminants. It is, therefore, extremely unlikely that water users will come into contact with sufficiently high concentrations of most contaminants to cause ill effects following a single exposure. Even repeated (chronic) exposure is unlikely to result in ill effects at the concentrations of contaminants found in water and with the exposure patterns of recreational users. However, it remains important to ensure that chemical hazards and any potential human health risks associated with them are controlled and that users can be reassured as to their personal safety.
In most cases, the concentration of chemical contaminants will be below drinking-water guidelines. As long as care is taken in their application, the WHO Guidelines for Drinking-water Quality can provide a starting point for deriving values that could be used to make a preliminary risk assessment under specific circumstances. These guideline values relate, in most cases, to lifetime exposure following consumption of 2 litres of drinking-water per day. For recreational water contact, an intake of 200 ml per day — 100 ml per recreational session with two sessions per day — may often be reasonably assumed.
An assessment of the chemical hazards in recreational water may involve inspecting the immediate area to determine if there are any immediate sources of chemical contamination, such as outfalls; considering the pattern and type of recreational use of the water to determine whether there will be extensive contact with the water and/or a significant risk of ingestion; and chemically analysing the water to support a quantitative risk assessment.
It is important that the basis of any guidelines or standards that are considered to be necessary for chemical constituents of recreational waters be made clear. Without this, there is a danger that even occasional, trivial exceedances of guidelines could unnecessarily undermine users’ confidence. It is also important in evaluating chemical hazards that the risks are not overestimated. The risks should be related to risks from other hazards such as drowning or microbial contamination, which will almost invariably be much greater.