The incidence of selected congenital m alform ations in areas with fluoride supplem entation of public water supplies was compared with the incidence in areas where the water supply is deficient in fluoride. Comparison of the incidences of several common birth defects (including Down’s syndrome) in fluoridated and nonfluoridated areas revealed no substantia! or significant differences in which there was a consistent pattern fo r both sets of data.
Water fluoridation and congenital malformations: no association DDS, MPH, PhD MD, MSPM J. William Flynt, Jr., MD, Atlanta Sylvia Hay, AB, San Francisco J. David Erickson,
Godfrey P. Oakley, Jr.,
T o our know ledge, there is no published work on the relationship betw een water fluoridation and congenital malformations in general. There fore, w e have review ed data available to us re garding the incidence o f birth defects and mater nal exposure to w ater supplem ented with fluor ide. Although Rapâport1 in 1956 suggested that fluoride in drinking water might be related to the occurrence o f D o w n ’s syndrom e, his finding has not been replicated by other investigators.2,3
Methods T he data used in this study were taken from two sources: the M etropolitan Atlanta Congenital M alform ations Surveillance Program4 and the N ational C left Lip and Palate Intelligence Ser vice (N I S ).5 T he total number o f births on which our study is based is 1,387,027. T he M etropolitan A tlanta Congenital M alfor m ations Surveillance Program began in O ctober
1967. Malformed infants are ascertained by reg ular staff visits to all hospitals that have obstetric or pediatric services, in C layton, C obb, D eK alb , Fulton, and G w innett counties in G eorgia. The ascertainm ent procedure em phasizes the new born period; children w hose m alform ations are noted after 1 year o f age are not included in the registry. T he data for D o w n ’s syndrom e w ere supplem ented in 1967 and 1968 by a retrospec tive ascertainm ent (using multiple sources) of children born during the period, January 1960 to Septem ber 1967. D ate o f birth and county o f usual maternal residence at the delivery date w ere used in deter mining exposure or nonexposure to a fluoridated water supply (box). M others w ho w ere residents o f C layton and Fulton counties and w ho gave birth during the nine months im m ediately after the im plem entation o f fluoridation w ere con sid ered to have not been exp osed to fluoride. T he total number of births used for com puting rates o f m alform ations was supplied by the G eorgia JADA, Vol. 93, N ovem ber 1976 • 981
Fluoridation history from metropolitan Atlanta and NIS surveillance areas.
Date fluoridation began August 1965 June 1954 April 1951 February, July 1969 No fluoridation
Metropolitan Atlanta Clayton County Cobb County DeKalb County Fulton County (Atlanta) Gwinnett County NIS surveillance areas Baltimore Philadelphia County San Francisco County New York City (5 boroughs) Los Angeles County
November 1952 September 1954 August 1952 After surveillance No fluoridation* *Los Angeles County contains six cities (about 2% of the county population) with natural fluoridated water supplies.
D epartm ent o f Human R esources for 1960 through 1972; the total number o f births in the metropolitan area for 1973 w as estim ated from hospital data collected as a regular part o f the surveillance program. T h e remaining data used here w ere th o se ga thered by the N ational C left Lip and Palate In telligence Service (N IS ). T his program ascer tained malformed children from certificates o f live births in 29 states and tw o cities for various periods o f tim e betw een 1961 and 1966. O nly a subset o f these data has been analyzed in this report; specifically, w e have used areas in which m others’ usual place of residence at birth o f the infant permitted us to determ ine exposure or nonexposure to fluoridated w ater (box). D en o m inators for com puting incidence rates for mal form ations w ere derived from a 1% system atic sam ple o f all births to residents o f the locations in v o lv ed .5 Since w hites and nonw hites have very differ
ent incidence rates for many congenital malfor m ations, because the proportions o f births to whites and nonw hites have been shifting over tim e, and because the institution o f water fluor idation is a tim e-related phenom enon, w e have further limited the data for analysis to births o f w hite children.
Results Crude incidence rates for several com m on birth defects are given in Table 1 for fluoridated and nonfluoridated areas. There are no substantial differences in these rates that form a consistent pattern for the M etropolitan A tlanta and the N IS data; o f the five statistically significant differ en ces found, tw o reflect higher malformation rates in the fluoridated areas whereas three are associated with higher rates in the nonfluoridat ed areas. Furtherm ore, no large differences w ere
Table 1 ■ Incidence of selected common congenital malformations in areas with and without fluoridated water. NIS surveillance areas, 1961-1966
Metropolitan Atlanta, 1967-1973 Fluoride (95,254 total births) No. cases
formation ncephaly diac and other irculatory Astern defects t lip with/without eft palate i palate )foot m's syndrome rocephalus ospadias !uction sformities la bifida [nalformation jses
Nonfluoride (25,373 total births)
Rate/10,000 white births
No. cases
Rate/10,000 white births
X2*
Fluoride (234,300 total birthst) Nonfluoride (1,032,100 total birthst) Rate/10,000 Rate/10,000 No. No. white births cases white births cases
101
10.6
33
13.0
0.83
70
3.0
275
2.7
379
39.8
78
30.7
4.11
120
5.1
456
4.4
107 50 414 166 77 237
11.2 5.2 43.5 9.9 8.1 24.9
35 20 96 86 34 47
13.8 7.9 37.8 8.5 13.4 18.5
0.91 1.96 1.38 1.41 5.59 3.18
185 94 303 115 70 198
7.9 4.0 12.9 4.9 3.0 8.5
784 331 1,642 524 299 736
7.6 3.2 15.9 5.1 2.9 7.1
82 149
8.6 15.6
14 37
5.5 14.6
2.03 0.09
79 146
3.4 6.2
358 535
3.5 5.2
2,787
292.6
685
270.0
3.58
2,264
96.6
10,526
102.0
egree of freedom corrected for continuity; P 0.05=3.84. ¡¡mated from 1% sample for NIS data. 9 8 2 ■ JADA, Vol. 93, November 1976
noted in a comparison o f data (not shown) before and after fluoridation in Fulton County. The dif ferential in rates found in a comparison o f the Metropolitan Atlanta data with the N IS data (for both fluoridated and nonfluoridated areas) merely reflects the more intensive, multiple source type o f ascertainment procedure used by the Atlanta program. Because the occurrence o f D ow n ’s syndrome is so strongly related to maternal age,6 maternal age-specific rates for this malformation are shown separately (Table 2). The rates from both data sets suggest that there may be an increased incidence at young maternal ages and a decreased incidence at older ages in the fluoridated areas. Although the N IS data are fairly consistent in this regard, there is inconsistency in the Atlanta data. The largest (and only statistically signifi cant) differential is found in the 35- to 39-year age group in which the rate is much higher for the nonfluoridated areas, but the difference is again reversed for ages over 40. H owever, the rates for D ow n’s syndrome for mothers 35 years o f age and over (age groups 35 to 39 and over 40 combined) are 46.8 per 10,000 births for the fluor idated areas and 54.4 per 10,000 for the nonfluor idated areas.
based on the study of a large number o f births: 120,627 for the Atlanta data and 1,266,400 for the N IS data. This should provide quite reliable es timates of incidence rates o f birth defects. An other strength o f this study is its design, which permitted simultaneous comparisons to be made in two different samples— samples that were gathered in two different ways. A possibility o f occasional misclassification of maternal exposure to fluoride could arise through maternal migration or lack of exact conformity o f a county’s boundaries and the distribution of public water supplies, the administration o f which is usually under municipal governments. We spoke with dental health officers and water sys tem personnel in the various localities and found only a trivial difference between county borders and water distribution patterns. Indeed, several counties and their respective municipalities were coterminous. There are no data on the dur ation of exposure o f mothers to fluoride within fluoridated areas, or on patterns o f migration. Although it is possible that such variables might influence the classification o f maternal expo sure, w e believe that their overall effect on the conclusions o f this report are negligible, primar ily because o f the large populations studied (a total of 1,387,027 births) and because the results from the two bodies o f data are similar. The reported incidence of malformations var ies with the method o f ascertainment. For exam ple, the rates for birth defects for metropolitan Atlanta, based on a search o f hospital records, are somewhat lower than those that have been reported from studies in which each child was specifically examined for congenital malforma tions (from birth through age 7) under a standard protocol.7 The incidence o f birth defects record ed on birth certificates is lower than that based on a search o f hospital records. It is not surpris ing, therefore, that the N IS rates for both fluor
Discussion These data show no association between water fluoridation and the incidence o f congenital mal formations. Furthermore, this population-based study, with data relating to 1,387,027 births, is the third that has specifically found no correla tion between D ow n ’s syndrome and fluorida tion. Thus, the suggestion o f such a relationship rests wholly on the nonpopulation-based work of Rapâport.1 Our report has considerable strength in being
Table 2
■Maternal age specific incidence of Down’s syndrome in areas with and without fluoridated water.
__________ _______Metropolitan Atlanta, 1960-1973_________________________________________ NIS surveillance areas, 1961-1966__________________ Fluoride (95,254 total births) Maternal age (yr) 40 Total
Nonfluoride (25,373 total births)
No. cases
Rate/10,000 white births
No. cases
19 41 34 25 15 32 166
7.7 6.9 6.8 11.3 18.5 165.3 9.9
7 15 11 13 25 13 86t
Rate/10,000 white births 3.8 4.0 4.1 11.0 45.8 85.1 8.5
X2*
1.98 2.93 1.78 0.01 7.42 3.67 1,41
Fluoride (234,300 total births) No. cases 8 19 22 18 20 28 115
Rate/10,000 white births 3.2 2.2 3.6 5.1 10.0 48.3 4.9
Nonfluoride (1,032,100 total births) No. cases 30 75 76 76 126 141 524
Rate/10,000 white births 2.3 2.0 2.8 4.8 16.4 57.3 5.1
*1 degree of freedom corrected for continuity; P 0.05=3.84. flncludes two cases of unknown maternal age. Erickson— others: FLUORIDATION AND CONGENITAL MALFORMATIONS: NO ASSOCIATION ■ 983
X2*
0.0< o.os 0.7/ 0.0( 1.9: 0.3( 0.0Î
idated and nonfluoridated areas are lower than those found in Atlanta. The comparability of the rates for fluoridated and nonfluoridated areas, rather than the abso lute level of the rates, is the important element. Thus, our comparisons are made only within the data for the metropolitan Atlanta area and with in the data for the N IS areas. In any event, under ascertainment could lead to false conclusions only if the reporting o f defects were biased with respect to the fluoride content o f water supplies. But the apparent randomness o f the rank order o f total malformation rates (a measure o f the completeness o f ascertainment) suggests no bias in the reporting o f defects with respect to the fluoridation or nonfluoridation of water sup plies. For the N IS areas, the rank order is Los Angeles (nonfluoridated) > Baltimore (fluori dated) > Philadelphia (fluoridated) > N ew York (nonfluoridated) > San Francisco (fluoridated). The order for the Atlanta area counties is DeKalb (fluoridated) > Fulton (nonfluoridated) > Fulton (fluoridated) > Clayton (fluoridated) > Gwinnett (nonfluoridated) > Cobb (fluoridated). The generally quoted crude incidence rate for D ow n’s syndrome is 1.5 per 1,000 births,8 where as the rate in Atlanta was found to be about 1.0 per 1,000 births. This seemingly low rate may be attributed to the retrospective ascertainment o f children with this syndrome, bom during the years 1960 through September 1967, and the low average maternal age in Atlanta. Since the risk of having a child with D ow n’s syndrome rises with maternal age, a population such as that for me tropolitan Atlanta, with a high proportion of
984
■ JADA, Vol. 93, November 1976
young mothers, would be expected to have a lower than “ usual” crude rate. The approxi mate equality o f the incidence of D ow n’s syn drome by five-year age groups in Atlanta and in areas having high crude rates6 would seem to confirm this notion.
We thank the many people who, over several years, have con tributed to collecting data used in this report. We particularly thank Allen J. Ebbin, MD, and Suzanne Shimpler, RN, who col lected the data on the incidence of Down’s syndrome in Atlanta for the years 1960 to 1967. Dr. Erickson, Dr. Oakley, and Dr. Flynt are with the Birth Defects Branch, Bureau of Epidemiology, Center for Disease Control, Atlanta, 30333. Miss Hay was formerly with the Congenital An omalies Section, Epidemiology Branch, Dental Health Center, San Francisco. Address requests for reprints to Dr. Erickson. 1. Rapâport, I. Contribution à l’e'tude de mongolisme: role pathoge'nique du fluor. Bull de I’Acad Nat de Med, Nov 6, 1956, p 529. 2. Berry, W.T.C. A study of the incidence of mongolism in rela tion to the fluoride content of water. Am J Ment Defic 62:634 Jan 1958. 3. Needleman, H.L.; Pueschel, S.M.; and Rothman, K.J. Fluor idation and the occurrence of Down's syndrome. N Engl J Med 291:821 Oct 17, 1974. 4. Flynt, J.W., Jr., and others. In Hook, E.B.; Janerich, D.T.; and Porter, I.H., eds. Monitoring birth defects and environment; the problem of surveillance. New York Academic Press, 1971, p 155. 5. Greene, J.C.; Vermillion, J.R.; and Hay, S. Utilization of birth certificates in epidemiologic studies of cleft lip and palate. Cleft Palate J 2:141 April 1965. 6. Lilienfeld, A.M. Epidemiology of mongolism. Baltimore, Johns Hopkins Press, 1969, p 27. 7. Chung, C.S., and Myrianthopoulos, N.C. Racial and prenatal factors in major congenital malformations. Am J Hum Genet 20:44 Jan 1968. 8. Smith, D.W. Recognizable patterns of human malformation: genetic, embryologie, and clinical aspects. Philadelphia, W. B. Saunders Co., 1970, p 33.
Water fluoridation and congenital malformations: no association DDS, MPH, PhD MD, MSPM J. William Flynt, Jr., MD, Atlanta Sylvia Hay, AB, San Francisco J. David Erickson,
Godfrey P. Oakley, Jr.,
T o our know ledge, there is no published work on the relationship betw een water fluoridation and congenital malformations in general. There fore, w e have review ed data available to us re garding the incidence o f birth defects and mater nal exposure to w ater supplem ented with fluor ide. Although Rapâport1 in 1956 suggested that fluoride in drinking water might be related to the occurrence o f D o w n ’s syndrom e, his finding has not been replicated by other investigators.2,3
Methods T he data used in this study were taken from two sources: the M etropolitan Atlanta Congenital M alform ations Surveillance Program4 and the N ational C left Lip and Palate Intelligence Ser vice (N I S ).5 T he total number o f births on which our study is based is 1,387,027. T he M etropolitan A tlanta Congenital M alfor m ations Surveillance Program began in O ctober
1967. Malformed infants are ascertained by reg ular staff visits to all hospitals that have obstetric or pediatric services, in C layton, C obb, D eK alb , Fulton, and G w innett counties in G eorgia. The ascertainm ent procedure em phasizes the new born period; children w hose m alform ations are noted after 1 year o f age are not included in the registry. T he data for D o w n ’s syndrom e w ere supplem ented in 1967 and 1968 by a retrospec tive ascertainm ent (using multiple sources) of children born during the period, January 1960 to Septem ber 1967. D ate o f birth and county o f usual maternal residence at the delivery date w ere used in deter mining exposure or nonexposure to a fluoridated water supply (box). M others w ho w ere residents o f C layton and Fulton counties and w ho gave birth during the nine months im m ediately after the im plem entation o f fluoridation w ere con sid ered to have not been exp osed to fluoride. T he total number of births used for com puting rates o f m alform ations was supplied by the G eorgia JADA, Vol. 93, N ovem ber 1976 • 981
Fluoridation history from metropolitan Atlanta and NIS surveillance areas.
Date fluoridation began August 1965 June 1954 April 1951 February, July 1969 No fluoridation
Metropolitan Atlanta Clayton County Cobb County DeKalb County Fulton County (Atlanta) Gwinnett County NIS surveillance areas Baltimore Philadelphia County San Francisco County New York City (5 boroughs) Los Angeles County
November 1952 September 1954 August 1952 After surveillance No fluoridation* *Los Angeles County contains six cities (about 2% of the county population) with natural fluoridated water supplies.
D epartm ent o f Human R esources for 1960 through 1972; the total number o f births in the metropolitan area for 1973 w as estim ated from hospital data collected as a regular part o f the surveillance program. T h e remaining data used here w ere th o se ga thered by the N ational C left Lip and Palate In telligence Service (N IS ). T his program ascer tained malformed children from certificates o f live births in 29 states and tw o cities for various periods o f tim e betw een 1961 and 1966. O nly a subset o f these data has been analyzed in this report; specifically, w e have used areas in which m others’ usual place of residence at birth o f the infant permitted us to determ ine exposure or nonexposure to fluoridated w ater (box). D en o m inators for com puting incidence rates for mal form ations w ere derived from a 1% system atic sam ple o f all births to residents o f the locations in v o lv ed .5 Since w hites and nonw hites have very differ
ent incidence rates for many congenital malfor m ations, because the proportions o f births to whites and nonw hites have been shifting over tim e, and because the institution o f water fluor idation is a tim e-related phenom enon, w e have further limited the data for analysis to births o f w hite children.
Results Crude incidence rates for several com m on birth defects are given in Table 1 for fluoridated and nonfluoridated areas. There are no substantial differences in these rates that form a consistent pattern for the M etropolitan A tlanta and the N IS data; o f the five statistically significant differ en ces found, tw o reflect higher malformation rates in the fluoridated areas whereas three are associated with higher rates in the nonfluoridat ed areas. Furtherm ore, no large differences w ere
Table 1 ■ Incidence of selected common congenital malformations in areas with and without fluoridated water. NIS surveillance areas, 1961-1966
Metropolitan Atlanta, 1967-1973 Fluoride (95,254 total births) No. cases
formation ncephaly diac and other irculatory Astern defects t lip with/without eft palate i palate )foot m's syndrome rocephalus ospadias !uction sformities la bifida [nalformation jses
Nonfluoride (25,373 total births)
Rate/10,000 white births
No. cases
Rate/10,000 white births
X2*
Fluoride (234,300 total birthst) Nonfluoride (1,032,100 total birthst) Rate/10,000 Rate/10,000 No. No. white births cases white births cases
101
10.6
33
13.0
0.83
70
3.0
275
2.7
379
39.8
78
30.7
4.11
120
5.1
456
4.4
107 50 414 166 77 237
11.2 5.2 43.5 9.9 8.1 24.9
35 20 96 86 34 47
13.8 7.9 37.8 8.5 13.4 18.5
0.91 1.96 1.38 1.41 5.59 3.18
185 94 303 115 70 198
7.9 4.0 12.9 4.9 3.0 8.5
784 331 1,642 524 299 736
7.6 3.2 15.9 5.1 2.9 7.1
82 149
8.6 15.6
14 37
5.5 14.6
2.03 0.09
79 146
3.4 6.2
358 535
3.5 5.2
2,787
292.6
685
270.0
3.58
2,264
96.6
10,526
102.0
egree of freedom corrected for continuity; P 0.05=3.84. ¡¡mated from 1% sample for NIS data. 9 8 2 ■ JADA, Vol. 93, November 1976
noted in a comparison o f data (not shown) before and after fluoridation in Fulton County. The dif ferential in rates found in a comparison o f the Metropolitan Atlanta data with the N IS data (for both fluoridated and nonfluoridated areas) merely reflects the more intensive, multiple source type o f ascertainment procedure used by the Atlanta program. Because the occurrence o f D ow n ’s syndrome is so strongly related to maternal age,6 maternal age-specific rates for this malformation are shown separately (Table 2). The rates from both data sets suggest that there may be an increased incidence at young maternal ages and a decreased incidence at older ages in the fluoridated areas. Although the N IS data are fairly consistent in this regard, there is inconsistency in the Atlanta data. The largest (and only statistically signifi cant) differential is found in the 35- to 39-year age group in which the rate is much higher for the nonfluoridated areas, but the difference is again reversed for ages over 40. H owever, the rates for D ow n’s syndrome for mothers 35 years o f age and over (age groups 35 to 39 and over 40 combined) are 46.8 per 10,000 births for the fluor idated areas and 54.4 per 10,000 for the nonfluor idated areas.
based on the study of a large number o f births: 120,627 for the Atlanta data and 1,266,400 for the N IS data. This should provide quite reliable es timates of incidence rates o f birth defects. An other strength o f this study is its design, which permitted simultaneous comparisons to be made in two different samples— samples that were gathered in two different ways. A possibility o f occasional misclassification of maternal exposure to fluoride could arise through maternal migration or lack of exact conformity o f a county’s boundaries and the distribution of public water supplies, the administration o f which is usually under municipal governments. We spoke with dental health officers and water sys tem personnel in the various localities and found only a trivial difference between county borders and water distribution patterns. Indeed, several counties and their respective municipalities were coterminous. There are no data on the dur ation of exposure o f mothers to fluoride within fluoridated areas, or on patterns o f migration. Although it is possible that such variables might influence the classification o f maternal expo sure, w e believe that their overall effect on the conclusions o f this report are negligible, primar ily because o f the large populations studied (a total of 1,387,027 births) and because the results from the two bodies o f data are similar. The reported incidence of malformations var ies with the method o f ascertainment. For exam ple, the rates for birth defects for metropolitan Atlanta, based on a search o f hospital records, are somewhat lower than those that have been reported from studies in which each child was specifically examined for congenital malforma tions (from birth through age 7) under a standard protocol.7 The incidence o f birth defects record ed on birth certificates is lower than that based on a search o f hospital records. It is not surpris ing, therefore, that the N IS rates for both fluor
Discussion These data show no association between water fluoridation and the incidence o f congenital mal formations. Furthermore, this population-based study, with data relating to 1,387,027 births, is the third that has specifically found no correla tion between D ow n ’s syndrome and fluorida tion. Thus, the suggestion o f such a relationship rests wholly on the nonpopulation-based work of Rapâport.1 Our report has considerable strength in being
Table 2
■Maternal age specific incidence of Down’s syndrome in areas with and without fluoridated water.
__________ _______Metropolitan Atlanta, 1960-1973_________________________________________ NIS surveillance areas, 1961-1966__________________ Fluoride (95,254 total births) Maternal age (yr) 40 Total
Nonfluoride (25,373 total births)
No. cases
Rate/10,000 white births
No. cases
19 41 34 25 15 32 166
7.7 6.9 6.8 11.3 18.5 165.3 9.9
7 15 11 13 25 13 86t
Rate/10,000 white births 3.8 4.0 4.1 11.0 45.8 85.1 8.5
X2*
1.98 2.93 1.78 0.01 7.42 3.67 1,41
Fluoride (234,300 total births) No. cases 8 19 22 18 20 28 115
Rate/10,000 white births 3.2 2.2 3.6 5.1 10.0 48.3 4.9
Nonfluoride (1,032,100 total births) No. cases 30 75 76 76 126 141 524
Rate/10,000 white births 2.3 2.0 2.8 4.8 16.4 57.3 5.1
*1 degree of freedom corrected for continuity; P 0.05=3.84. flncludes two cases of unknown maternal age. Erickson— others: FLUORIDATION AND CONGENITAL MALFORMATIONS: NO ASSOCIATION ■ 983
X2*
0.0< o.os 0.7/ 0.0( 1.9: 0.3( 0.0Î
idated and nonfluoridated areas are lower than those found in Atlanta. The comparability of the rates for fluoridated and nonfluoridated areas, rather than the abso lute level of the rates, is the important element. Thus, our comparisons are made only within the data for the metropolitan Atlanta area and with in the data for the N IS areas. In any event, under ascertainment could lead to false conclusions only if the reporting o f defects were biased with respect to the fluoride content o f water supplies. But the apparent randomness o f the rank order o f total malformation rates (a measure o f the completeness o f ascertainment) suggests no bias in the reporting o f defects with respect to the fluoridation or nonfluoridation of water sup plies. For the N IS areas, the rank order is Los Angeles (nonfluoridated) > Baltimore (fluori dated) > Philadelphia (fluoridated) > N ew York (nonfluoridated) > San Francisco (fluoridated). The order for the Atlanta area counties is DeKalb (fluoridated) > Fulton (nonfluoridated) > Fulton (fluoridated) > Clayton (fluoridated) > Gwinnett (nonfluoridated) > Cobb (fluoridated). The generally quoted crude incidence rate for D ow n’s syndrome is 1.5 per 1,000 births,8 where as the rate in Atlanta was found to be about 1.0 per 1,000 births. This seemingly low rate may be attributed to the retrospective ascertainment o f children with this syndrome, bom during the years 1960 through September 1967, and the low average maternal age in Atlanta. Since the risk of having a child with D ow n’s syndrome rises with maternal age, a population such as that for me tropolitan Atlanta, with a high proportion of
984
■ JADA, Vol. 93, November 1976
young mothers, would be expected to have a lower than “ usual” crude rate. The approxi mate equality o f the incidence of D ow n’s syn drome by five-year age groups in Atlanta and in areas having high crude rates6 would seem to confirm this notion.
We thank the many people who, over several years, have con tributed to collecting data used in this report. We particularly thank Allen J. Ebbin, MD, and Suzanne Shimpler, RN, who col lected the data on the incidence of Down’s syndrome in Atlanta for the years 1960 to 1967. Dr. Erickson, Dr. Oakley, and Dr. Flynt are with the Birth Defects Branch, Bureau of Epidemiology, Center for Disease Control, Atlanta, 30333. Miss Hay was formerly with the Congenital An omalies Section, Epidemiology Branch, Dental Health Center, San Francisco. Address requests for reprints to Dr. Erickson. 1. Rapâport, I. Contribution à l’e'tude de mongolisme: role pathoge'nique du fluor. Bull de I’Acad Nat de Med, Nov 6, 1956, p 529. 2. Berry, W.T.C. A study of the incidence of mongolism in rela tion to the fluoride content of water. Am J Ment Defic 62:634 Jan 1958. 3. Needleman, H.L.; Pueschel, S.M.; and Rothman, K.J. Fluor idation and the occurrence of Down's syndrome. N Engl J Med 291:821 Oct 17, 1974. 4. Flynt, J.W., Jr., and others. In Hook, E.B.; Janerich, D.T.; and Porter, I.H., eds. Monitoring birth defects and environment; the problem of surveillance. New York Academic Press, 1971, p 155. 5. Greene, J.C.; Vermillion, J.R.; and Hay, S. Utilization of birth certificates in epidemiologic studies of cleft lip and palate. Cleft Palate J 2:141 April 1965. 6. Lilienfeld, A.M. Epidemiology of mongolism. Baltimore, Johns Hopkins Press, 1969, p 27. 7. Chung, C.S., and Myrianthopoulos, N.C. Racial and prenatal factors in major congenital malformations. Am J Hum Genet 20:44 Jan 1968. 8. Smith, D.W. Recognizable patterns of human malformation: genetic, embryologie, and clinical aspects. Philadelphia, W. B. Saunders Co., 1970, p 33.
