Water Sanitation Health

Guidelines for safe recreational water environments
Volume 1 : Coastal and fresh waters

Executive summary

Sun, heat and cold

The recreational use of water environments sometimes leads to exposure of individuals to extreme solar radiation and to extreme conditions of heat or cold.

Ultraviolet radiation (UVR) from sunlight can be divided into three bands: UVA, UVB and UVC. As the ozone layer becomes depleted, the protective filter provided by the atmosphere is progressively reduced, and human beings are exposed to higher UV levels, in particular higher UVB levels.

Overexposure to UVR may result in acute and chronic damage to the skin, the eyes and the immune system. The most noticeable acute effect of excessive UV exposure is erythema, the familiar inflammation of the skin commonly termed sunburn. Photokeratitis and photoconjunctivitis are other acute effects of UV exposure. Chronic effects include two major public health problems: skin cancers (both non-melanoma skin cancers and malignant melanoma) and cataracts. Chronic exposure to UVR also causes a number of degenerative changes in the skin (e.g., freckles) and accelerates skin aging. There is also increasing evidence for an immunosuppressive effect of both acute high-dose and chronic low-dose UV exposure on the human immune system.

Not all effects of UV radiation are adverse. The best known beneficial effect is the stimulation of the production of vitamin D in the skin. UVR from artificial sources is also used to treat several diseases and dermatological conditions, including rickets, psoriasis, eczema and jaundice.

Simple protective measures are available and should be adopted to avoid adverse health effects on the skin, eyes and immune system. These include minimizing the amount of time spent in the sun, including complete avoidance of midday sun exposure; seeking shade; and wearing loose-fitting and tightly woven clothing, a broad-brimmed hat and wrap-around sunglasses. Furthermore, a broad-spectrum sunscreen with sun protection factor of 15 or more should be applied liberally on all areas of the body not covered by clothing and should be reapplied often. Sun protection programmes to raise awareness and achieve changes in lifestyle are urgently needed to slow down and eventually reverse the trend towards more skin cancers. The global solar UV index is an important vehicle to raise public awareness of UVR and the risks of excessive UV exposure and to alert people to the need to adopt protective measures.

Exposure to cold water may cause considerable problems for users of recreational waters. The immediate effect of sudden immersion in cold water can be a debilitating reflex response called “cold shock,” which includes life-threatening respiratory and cardiovascular effects and may lead to drowning. Sudden immersion in cold water often results in impaired swimming ability, which is believed to be responsible for the majority of sudden cold-water immersion deaths. Safety precautions include wearing suitable protective garments when swimming in cold water and using a lifejacket when boating to keep airways clear of water even when unconscious.

In a hot environment, people can suffer serious physical ailments, such as heat cramps, heat exhaustion and heat stroke. The very young, the elderly, patients using drugs that interfere with temperature regulation, people suffering from pre-existing chronic diseases and frequent consumers of alcohol appear to be particularly susceptible. Avoidance measures include consumption of non-alcoholic, non-caffeinated beverages, replacement of salt lost through sweating and retreat to shaded areas. Disorders due to heat occur most frequently when there are rapid changes in thermal conditions, such as during heat waves.