appendix 



The role of some physico-chemical 

 properties of water as causative 

 agents of eye irritation of swimmers 



by Eric W. Mood, M.P.H. 



An important consideration of the physico- 

 chemical characteristics of water used for recrea- 

 tion purposes involves those properties that may 

 cause eye irritation to bathers and swimmers. 

 Water is a foreign environment to the human eye. 

 Under certain conditions, water may be very irri- 

 tating to the eyes of most swimmers and bathers, 

 but under other conditions it may be non-irritating 

 to all but a few. 



Some knowledge about the characteristics of 

 water that generaUy is irritating to the eyes of 

 swimmers has been developed through research 

 efforts of ophthalmologists and others, many of 

 whom were interested in the preparation of oph- 

 thalmic solutions. These researchers assumed that 

 an ideal non-irritating solution would have similar 

 physico-chemical properties as tears. Therefore, 

 studies were undertaken initially to determine the 

 chemical composition of lacrimal fluid, particularly 

 of the following: (l)hydrogen-ion concentration 

 orpH, (2) buffer capacity, and (3) tonicity. 



Early studies of the hydrogen-ion concentration 

 of tears developed values ranging from 6.3 to 8.6. 

 Diligent efforts by Hind and Goyan (1,2) yielded 

 more precise data. They found that lacrimal fluid 

 has a pH of approximately 7.4. This result is not 

 unexpected as the pH of human blood normally is 

 found to range from 7.4 to 7.5. 



Correlated with the hydrogen-ion concentration 

 is buffer capacity of the fluid. A solution of low 

 buffer capacity can have its pH level changed 

 easily, but a solution with a high buffer capacity 

 may not have the hydrogen-ion concentration 

 easily or appreciably altered. Analyses for the 

 chemical constituents of tears denoted the presence 

 of carbonic acid, weak organic acids and proteins 

 (3). These elements allow lacrimal fluid to neu- 

 tralize both weakly acidic and weakly basic solu- 

 tions to the approximate pH of the lacrimal fluid. 

 It has been demonstrated that tears have the ca- 

 pacity to bring the pH of an unbuffered solution 

 from as low as 3.5 or as high as 10.5, to within 

 tolerable limits in a very short time (3) . 



If the chemical constituents of the solution in 

 contact with the eye are such as to resist the buf- 

 fering action of the lacrimal fluid and the pH of the 

 solution in direct contact with the eye is 0.1 or 



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