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Results
The sample size was 107 subjects for Sirablo and 94 for Woloni. Age and sex distribution in the two populations was close to normal and the two did not differ significantly. The average age was 22 years (SD = 12) at Sirablo and 24 years (SD = 14) at Woloni ; there was no statistically significant difference between the sex ratios of the two villages. Ethnic structure (Bambara and Malinke) and eating habits were similar ; in both villages, diet is based exclusively on local resources.
Table 1 shows the comparative results for iodine content over the course of time. Before the start of the study, the water supply to the villages had a very low iodine content : the average of eight samples was 4 µg/L and content did not differ significantly between the two villages. Iodine release from the elastomer system in the test village was observed from the 2nd day onward and was continuous throughout the day and constant over the 12-month period ; the average concentration for all the assays carried out was 163.2 µg/L (range = 34 to 390 µg/L). The iodine content in the control village water remained unchanged (range = 0 to 7 µg/L).
Table 2 shows the changes in urinary concentrations in the two villages over the course of time. Before the start of the study (day 0), urinary iodine values were low and were not significantly different between the two villages, whether the comparison concerned urinary iodine or the iodine :creatinine ratio. These levels showed that, on average, three quarters of the subjects in the two villages had "severe deficiency," according to the World Health Organization classification.11
Figure 2 shows the changes that occurred in urinary iodine levels in the test and control villages according to the degree of deficiency described by the World Health Organization classification. Thus, from 6 months after the installation of the elastomer system until the end of the study, 90.29% of the subjects had "no deficiency" and 9.71% had "slight deficiency" ; "moderate" and "severe" deficiencies disappeared at 6 months. There was no significant modification in the control village over the same period.
At the beginning of the study, overall goiter frequency was comparable in the test (53.2%) and control villages (56.5%) (P = .351, not significant [NS). Goiter frequency in males was 40.1% and 39.4% (P = .894, NS) in the test and control villages, respectively, and that in females was 66.7% and 68.5% (P = .666, NS), respectively. The higher frequency of goiter in females is usual. Twelve months later, the overall frequency of goiters in the test village significantly decreased to 29.2% (P < .001). Frequency decreased in both males (16.1%, P < .001) and females (44.7%, P = .04). Severe forms (GIb and GII) were particularly affected ; their frequency relative to all goiter forms fell from 78.4% to 57.3% ( P< .001). This favorable development was observed as of month 6.
For fibrous GIII goiters, frequency was unchanged. In the control village, no change in goiter frequency was observed. Figures 3A and 3B show the course over time of the various goiter stages, by sex, in the test and control villages.
The elastomer system was easily installed in the boreholes during annual maintenance of the pumping system as recommended by the manufacturers. The device was completely accepted by all the villagers throughout the study. No fears or criticisms were expressed about the device or about the odor or palatability of the water. No clinically detectabte adverse effect was noted. No drug containing iodine was introduced into the villages during the entire length of the study.
