EPIDEMIOLOGY OF FLUOROSIS

Abstract

Fluorosis, a disease due to high fluoride intake by communities is distributed world-wide. It is mostly associated with water supplies whose fluoride levels exceed 1mg/l. Chronic Fluorosis causes brownish discoloration of the teeth and further exposure leads to bone malformations with osteosclerosis. The excess fluoride in the body is excreted in urine. It is endemic in some communities in Nigeria, notably Sokoto, Kano, Bauchi and Plateau States, but no epidemiological data is available. The study is community based, cross-sectional and exploratory in design. The aims of the study were to:- determine the prevalence and distribution of fluorosis in Langtang community, measure the fluoride content of drinking water sources, compare the urinary fluoride content of subjects with and without clinical fluorosis, find out the impact of water supply from the metropolitan Dam built in 1982 on prevalence of fluorosis. The study will provide appropriate recommendations to the concerned authorities. Questionnaire survey, clinical examination respondents and laboratory analysis of drinking water and urine samples for fluoride were carried out.

For the prevalence survey 475 subjects were proportionately drawn from the towns population of 7,500 using a systemic random sampling technique in which every 15th house was chosen. One hundred and twenty four subjects out of 475 had fluorosis giving a general prevalence rate of 26.1%. The age group affected with fluorosis ranged from 5-59 years. The worst affected age group being 10-19 years age which constituted 41.1% of all cases. The age specific prevalence of fluorosis in the age group less than 15 years (children born after building the metropolitan water supply dam in 1982) was 37.5% while the rate among age group 15-29 years (born before the dam) was 41.8% indicating that the introduction of the metropolitan water supply has not controlled fluorosis which is a major public health problem of the community. Fourteen of the 124 cases with fluorosis were lost to follow-up leaving 110. The 110 subjects with fluorosis referred to as cases were further investigated on associated factors on fluorosis such as their sources of drinking water, age, urine fluoride levels, knowledge, attitudes and practices (KAP) and affected family relations. These associated factors were compared against a comparative or control group of 100 volunteers out of 475 who did not have clinical fluorosis of teeth.

Of the 110 cases 25(22.7%) had bilateral genu valgum compared to three only 3(3%) bilateral genu valgum from the 100 controls. This difference is statistically significant. (P.value <0.05) thus the association of fluorosis and genu valgum. The most affected family relations among the 100 cases are 56(50.1%) bothers and 52(47.25%) sisters compared to 13(13%) brothers and 15(15%) sisters among the 100 controls. This associated factor is statistically significant (P .value < 0.05). Twenty-four (21.8%) of the 110 subjects with fluorosis know that fluorosis is associated with water but 86(77.5%) did not know while 22(22%. of the 100 controls associated fluorosis with water, 78(78%) of the controls do not know Eighty (72.7% of the 110 cases of fluorosis and 70(70%) 100 controls perceive fluorosis as a serious disease that needs treatment. Of the 110 cases of fluorosis 36(32.7%) had used stream water before they developed teeth mottling while 74(67.2) had used wells and pipe water compared to 7(7%) subjects in 100 controls who used stream water and 93(93%) who had used pipe water. This difference is statistically significant most probably an indication of stream water as a possible risk factor in developing fluorosis. A total of 136 water sources were sampled from 2 Dams, 71 wells, 3 Bore holes, 10 streams and 54 Taps for fluoride contents.

The fluoride levels ranged from 0.69-3.96mg/1. The levels were, highest in stream waters. The pipe water ranged from 0.69-0.95mg/1, Bore holes 1.0-1.2mg/l , Stream 2.1-3.86mg/l, Wells 2.0 2.3mg/1. The fluoride levels of the raw water from the metropolitan Dam was 1.68mg/1 while the post chlorinated water ready for distribution was 0.78mg/1. The acceptable standards of drinking water by WHO is 0.8mg/l to 1.2mg/1. The permissible maximum is 1.5 mg/1. The analysis of urine fluoride was limited to 55 out of the 110 cases with fluorosis and 74 of the 100 controls because of cost of analysis and unwillingness of some respondents to give urine samples. The urine fluoride levels from 55 of the 110 and 74 of the 100 controls had a mean of 130 mg (range 0.72-730 mg/1) and 171 mg /1 (range 14.8-635 mg/1) respectively. The scatter graph of mean fluoride level versus age above shows a decrease as age advances among the 55 cases with fluorosis while the 74 controls show a slight increase as age advances This difference is marginally significant (P-value <0.492). with respect to treatment of clinical fluorosis of the teeth, 10(9%) out of the 110 cases chose to consult a medical Doctor. One(0.9%) consulted a nurse, 1(0.9%) consulted a village

health worker and 94(85.5%) consulted no one while 4(3.7%) are :contented with traditional scraping methods. This study has provided baseline data on the prevalence, associated factors of fluorosis in Langtang town. This will likely be of assistance to the Ministry of Health and water board in evaluating the efficiency of the metropolitan water supply in solving the basic problem of fluorosis in Langtang town. Finally the data has provided. opportunity for further research on the problem of fluorosis in the state in particular and country in general.