tions should include a thorough analysis of the 

 sources of contamination and the degree of threat 

 of pathogens from specific sources. 



The Subcommittee notes that fecal discharges 

 from vessels are individually a small contribution 

 to contamination and may not be reflected in bac- 

 terial sampling, but represent a rather direct health 

 hazard and must be controlled in or near primary 

 contact recreational areas. 



In addition to sanitary criteria, the Subcommit- 

 tee recommends criteria on pH for primary con- 

 tact recreation waters. While the Subcommittee 

 recognizes that many waters (marine, naturally 

 alkaline, or acidic fresh waters) cause eye irrita- 

 tion, the relation of pH to eye irritation justifies 

 inclusion of pH criteria to enhance recreation en- 

 joyment where pH can be controlled. 



In the light of its coordinate effect, the buffering 

 capacity should be considered in criteria to prevent 

 eye irritation. 



The lacrimal fluid of the human eye has a 

 normal pH of approximately 7.4 and a very high 

 buffering capacity, due primarily to the presence of 

 buffering agents of the complex organic type. As is 

 true of many organic buffering agents, those of the 

 lacrimal fluid are able to maintain the pH within 

 a very narrow range until their buffering capacity 

 is exhausted. When the lacrimal fluid, through 

 exhaustion of its buffering capacity, is unable to 

 adjust the immediate contact layer of a fluid to a 

 pH of 7.4, eye irritation results. A deviation of no 

 more than 0. 1 unit from the normal pH of the eye 

 may result in discomfort. Appreciable deviation 

 will cause severe pain (see appendix at the end of 

 this section). 



Recommendation : In primary contact recreation waters, 

 the pH should be within the range of 6.5-8.3 except 

 when due to natural causes and in no case shall be less 

 than 5.0 nor more than 9.0. When the pH is less than 

 6.5 or more than 8.3, discharge of substances which 

 would increase the buffering capacity of the water 

 should be limited. 



There are additional criteria the Subcommittee 

 considers to be desirable but not mandatory. 

 Among these are criteria for clarity and tempera- 

 ture. Clarity in recreational waters is highly de- 

 sirable from the standpoint of visual appeal, recre- 

 ational enjoyment, and safety. Variation in natural 

 conditions makes it difficult to set absolute criteria 

 for this factor. However, turbidity attributable to 

 human activity should be controlled in recreation 

 waters where feasible in the light of natural con- 

 ditions. 



Recommendation: For primary contact recreation 

 waters, , clarity should be such that a Secchi disc is 

 visible at a minimum depth of 4 feet. In "leam 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 by safety standards, 

 depending on the height of the diving platform or 

 board. 



The Subcommittee is cognizant that recommen- 

 dations on clarity may have more value for plan- 

 ners of primary recreation areas than for water 

 quality administrators. 



Temperature is another factor which may be 

 important to recreation enjoyment. In some locali- 

 ties and at certain times, elevation of temperature 

 may be desirable (to lengthen a recreation season, 

 for instance), but in most cases total recreation 

 values (including particularly recreational fish- 

 ing) are more likely to be reduced than enlarged 

 by excessive temperature elevation. Except in 

 cases where temperature elevations for primary 

 contact recreation are justified, the Subcommittee 

 suggests a stringent restriction on permissible 

 temperature rises. 



Excessively high temperatures may lessen the 

 pleasure of some water contact sports, as well as 

 be damaging to biota. Moreover, high tempera- 

 tures limit the dissipation of body heat and may, 

 through elevation of the deep body temperature, 

 produce serious physiological disturbances. It has 

 been determined that a person swimming expends 

 energy at the rate of approximately 500 calories 

 per hour. This is about five times the rate when 

 sitting still and about twice the rate when walking. 

 This energy must be dissipated to the environment 

 to avoid a rise in the deep body temperature. When 

 conduction is the principal means of heat transfer 

 from the body and exposure to the environmental 

 conditions is prolonged, 32.2 C (90 F) is the ap- 

 proximate limit for persons expending minimal 

 energy. Since most swimmers utilize energy at a 

 moderate rate, the maximum water temperature 

 that will not induce undesirable physiological ef- 

 fects after prolonged exposure must be less than 

 32.2 C (90 F). Experience with military person- 

 nel exposed to warm water continously for several 

 hours indicates that 30 C (85 F) is a safe maxi- 

 mum limit. 



Limited exposure to water warmer than 30 C 

 (85 F) can be tolerated for short periods of time 

 without causing undesirable physiological effects. 

 In fact, some people get particular enjoyment from 

 bathing in water from hot springs. However, these 

 are special circumstances and persons bathing in 

 such water usually limit their exposure to short 

 periods of time and do not engage in moderate 

 exercise such as swimming for prolonged periods. 



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