Hydrofluorosilicic acid is harmful to aquatic life at low concentrations.79 It has also been found that fluoride is an endocrine disruptor in the aquatic environment.80
If behaviour-altering pollutants such as fluoride are present in critical concentrations, it is likely that the migrating adult salmonids would respond to them in a short time-frame. 81 A large body of evidence shows that salmonids have an acute sense of smell with a low threshold value for many chemicals.82,83,84
Pollutants may cause avoidance or preference, overwhelm biologically relevant odours or damage chemoreceptive mechanisms. Complete avoidance of pollutants may prevent deleterious exposures.
77 Bahls LL. Diatom community response to primary waste water effluent Journal Water Pollution Control Federation 45 134-144 1973.
78 Carpenter R. Factors controlling the marine geochemistry of fluorine. Geochemical et Cosmochimica Acta 33 1153-1167 1969.
79 Material Safety Data Sheet Hydrofluosilicic Acid
80 USA National Research Council, Fluoride in Drinking Water: A Scientific Review of EPA‘s Standards, Committee on Fluoride in Drinking Water, (2006)
81 Damkaer DM, and Dey DB 1989. Evidence for fluoride effects on salmon passage at John Day Dam, Columbia River, 1982-1986. N. Am. J. Fish. Manage.9:154162 Coastal Zone and Estuarine Studies.
82 Brown, S.B., R.E. Evans, B.E. Thompson, and T.J. Hara.1982. Chemoreception and aquatic pollutants, p. 363-393. In T.J. Hara (ed.) Chemoreception in fishes.
Amsterdam. Elsevier.
83 Cooper, J.C., and P.J. Hirsch.1982. The role of chemoreception in salmonid homing, p. 343-362
84 Kleerekoper, H. 1982. The role of olfaction in the orientation of fishes, p. 201-225. In T.J. Hara (ed.) Chemoreception in fishes. Amsterdam. Elsevier.
It is reported that serious hazards to fish could arise through unperceived or unavoidable low level pollutants, in particular altering predator or food detection, reproduction or migration. Fluorides are known to be toxic to trout and other fish.85
The median toxic limits (concentration required to kill 50% of the test fish) in trout have been reported between 2.3 and 7.5ppm fluoride.86,87 While there is very little information regarding the effect of fluorides on fish behaviour, however, there is evidence to suggest that fluorides are known to be enzyme inhibitors and could, therefore, have the potential to reduce activity at sub- lethal concentrations. Limited studies88 have been undertaken that indicate damage to salmon and fisheries including plant ecosystems from fluoride. A number of studies89,90,91 point out that many factors influence susceptibility of fish to fluoride: temperature; water hardness; pH; chloride concentration; and, the strain, age and physiological and reproductive condition of the fish. Warrington undertook research in British Columbia, where the softness of major salmonid watercourses is the rule, combined the findings of Angelovic, and others to calculate that the chronic threshold for rainbow trout at 12 degrees and water hardness of 10 mg/L (calcium carbonate) is 0.2 mgF/L. In the field study by Damkaer and Dey92 it was demonstrated that high salmon loss was caused by the inhibition of migration by fluoride contamination. Damkaer and Dey confirmed the cause-and-effect relationship by means of a two-choice flume for fluoride gradient salmon behaviour tests. The study determined that the "critical level" was 0.2 mgF/L. Damner further reported that there were also significant alterations in levels of blood-T 4 in smolting juveniles kept in fluoride concentrations of 0, 0.3, 0.5, and 1.0 ppm. With the juvenile rainbow/steelhead trout hybrids, there was an elevation of plasma T4 at 0.3 and 0.5 ppm fluoride but not at 1.0 ppm. T4 has been implicated in migratory behaviour of juvenile salmonids.93
85 Damkaer DM, and Dey DB 1989. Evidence for fluoride effects on salmon passage at John Day Dam, Columbia River, 1982-1986. N. Am. J. Fish. Manage.9:154162 Coastal Zone and Estuarine Studies.
86 Neuhold, J.M., and W.F. Sigler. 1960. Effects of sodium fluoride on carp and rainbow trout. Trans. Amer. Fish. Soc. 89(4):358-370.
87 Angelovic, J.W., W.F. Sigler, and J.M. Neuhold. 1961. Temperature and fluorosis in rainbow trout. J. Water Pollution Control Federation 33:371.
88 Damkaer DM, and Dey DB 1989. Evidence for fluoride effects on salmon passage at John Day Dam, Columbia River, 1982-1986. N. Am. J. Fish. Manage.9:154162 Coastal Zone and Estuarine Studies.
89 Groth III E. An evaluation of the potential for ecological damage by chronic low- level environmental pollution by fluoride. Fluoride 6 (4) 224-240 1975.
90 Warrington PD. Ambient Water Quality Criteria for Fluoride. Technical Appendix. British Columbia Ministry Of Environment. 1990.
91 Angelovic JW, Sigler WF, Neuhold JM. Temperature and fluorosis in Rainbow trout. Journal. Water Pollution Control Federation 33 371-381 1961.
92 Damkaer DM, and Dey DB 1989. Evidence for fluoride effects on salmon passage at John Day Dam, Columbia River, 1982-1986. N. Am. J. Fish. Manage.9:154162.
93 Godin, J.G., P.A. Dill, and D.E. Drury. 1974. Effects of thyroid hormones on behavior of yearling Atlantic salmon (Salmo salar). J. Fish. Res. Board Can. 31:1787-1790.
It is very alarming that with over 240 water fluoridation plants located in every water catchment area within the country and over 478 wastewater treatment plants94 discharging fluoride into freshwater, estuarine and coastal waters that the potential ecological impact of fluoride emissions has never been examined. It is not improbable to suggest that the impact may indeed be enormous. This is the case when it is known that over 78,400,000kgs of fluoride has been discharged into the environment from these facilities since fluoridation of water commenced in Ireland. Of this a significant percentage has been discharged directly into the 148 salmon rivers across the Republic of Ireland. It is perhaps not coincidental that the start of the decline in freshwater salmon fish stocks in Ireland mirrors exactly the commencement of water fluoridation. A similar decline has been observed in the USA where the practice of fluoridation also exists (though not as prevalent as Ireland). This decline constrasts with the generally healthy status of salmon in Canada where fluoridation is not practised.
There are other studies that indicate that fluoride at levels below 1.5 mg/L have lethal and other adverse effects on fish. Delayed hatching of rainbow trout95 occurred at 1.5 mgF/L; brown mussels96 died at 1.4 mgF/L; an alga (Porphyria tenera)97 was killed by a four-hour fumigation with fluoride with a critical concentration of 0.9 mgF/L; and levels below 0.1 mgF/L were shown to be lethal to the water flea, Daphnia magna.98 These latter two studies suggest that salmon species may be affected by fluoride-induced reduction of food supply.
The SCHER review‘s examinsation of the impact of fluoride on the marine environment was very simplistic and limited. The analysis of the aquatic effects was based on a bibliographic search and based much of its analysis on the review of fluoride toxicity to aquatic organisms by Camargo (2003).99 Camargo observed that in aquatic animals, fluoride tends to be accumulated in the exoskeleton of invertebrates and in the bone tissue of fishes. The toxic action of fluoride resides in the fact that fluoride ions act as enzymatic poisons, inhibiting enzyme activity and, ultimately, interrupting metabolic processes such as glycolysis and synthesis of proteins.
Fluoride toxicity to aquatic invertebrates and fishes increases with increasing fluoride concentration, exposure time and water temperature, and decreases with increasing intraspecific body size and water content of calcium and chloride. Freshwater invertebrates and fishes, especially net-
94 Urban Waste Water Discharges in Ireland for Population Equivalents Greater than 500 Persons Environmental Protection Agency
95 EIlis MM, Westfall BA, Ellis MD. Determination of Water Quality Research Report 9. Fish and Wildlife Service, Department of Interior, Washington DC 1938 pp 81-82. 96 Hemens J: Warvick RJ, Oleff WD. Effect of extended exposure to low fluoride concentration on estuarine fish and crustacea. Progress in water Technology 7 579- 97 Ishio S, Makagawa H (1971). Cited in: Rose D. Marier J. Environmental Fluoride 1977. National Research Council of Canada, Ottawa 1977 p 30.
98 Dave G. Effects of fluoride on growth reproduction and survival in Daphnia magna. Comparative Biochemistry and Physiology 78c (2) 425-431 1984.
99 Camargo JA (2003) Fluoride toxicity to aquatic organisms: a review. Chemosphere 50: 251-64
spinning caddis fly larvae and upstream-migrating adult salmons, appear to be more sensitive to fluoride toxicity than estuarine and marine animals. Because, in soft waters with low ionic content, a fluoride concentration as low as 0.5 mg F-/l can adversely affect invertebrates and fishes, safe levels below this fluoride/l concentration are recommended in order to protect freshwater animals from fluoride pollution.
Camargo further observed that aquatic organisms living in soft waters may be more adversely affected by fluoride pollution than those living in hard or seawaters because the bio-availability of fluoride ions is reduced with increasing water hardness. It was further found that fluoride can either inhibit or enhance the population growth of algae, depending upon fluoride concentration, exposure time and algal species.
It is clear therefore that much greater research is needed on the lifecycle impacts of fluoride on the environment; in particular any potential impacts on ecological receptors such as fisheries, given that 243 fluoridation plants are located in Ireland with many in sensitive fisheries catchment areas.
Additional research has demonstrated that fluorides released into marine environments have been shown to accumulate in some aquatic organisms.100 It has been further demonstrated that foods characteristically high in fluoride content are certain types of seafood (1.9-28.5 mg/kg).101 In a study by Hemens and Warwick102 toxic effects due to fluorosis were observed in species of mussel, mullet, crab and shrimp in an estuary where waste from an aluminium plant was released.
Hemens and Warick also noted the apparent lack of information on bio- concentration in aquatic organisms and bio-magnification in food chains which the researchers observed would be helpful in assessing the importance of bioaccumulation of fluorides as a route of human exposure to this contaminant.