Fluoride exposure and pediatric kidney health in dry, wet and intermediate climatic zone communities in Sri Lanka: Implications from urinary Cystatin-C, and albumin-creatinine ratio.

Abstract

Highlights

Fluoride exposure is supposed as a potential risk factor of kidney injury in tropical regions.
Pediatric renal outcomes associated with fluoride exposure is not properly understood.
This study investigates effects of fluoride exposure on renal health using cystatin-C as a marker.
Here we present baseline evidence for risk of pediatric kidney injury with high fluoride exposure.

Background

High fluoride exposure is increasingly discussed attributing to kidney injury as a causative factor. Depending on geochemistry, differential fluoride levels in drinking water are identified in different regions in Sri Lanka. However, the levels of fluoride exposure, and associations with kidney health has not been adequately studied in Sri Lanka, particularly in pediatric communities. Hence, the present study aimed to assess fluoride exposure in selected pediatric communities in the dry, wet and intermediate climatic zones in Sri Lanka, along with an assessment of renal health using urinary Cystatin-C (uCys-C), and albumin-creatinine ratio (uACR).

Methods

We conducted a cross-sectional study with school students in selected education zones representing dry (N = 331), wet (N = 152), and intermediate (N = 292) climatic zones in Sri Lanka. Fluoride contents in urine and drinking water were assessed as measures of fluoride exposure.

Results

The median (interquartile distance) urinary fluoride levels of participants in the dry, wet and intermediate zones were 1.63(1.04–2.85), 1.29(0.85–2.21), and 1.07(0.61–1.98) mg/gCr while the fluoride contents of drinking water samples were 1.76(1.36–2.30), 0.25(0.18–0.37), and 0.43(0.26–0.63) ppm respectively with significant differences among the three groups. Median uCys-C level (ng/mgCr) of the participants in intermediate zone [30.26(8.49–71.44)] was significantly low (p < 0.05) compared to that of the participants in dry zone [56.19(7.08–211.8)], and wet zone [66.29(30.43–125.20)]. The incidences of elevated uCys-C levels above reference intervals in participants of dry zone (47.7%), and wet zone (50.0%) were significantly high (p < 0.001) compared to the intermediate zone (26.4%).

Conclusion

Relatively high fluoride exposure is likely in dry and wet zone communities compared to the intermediate zone along with significantly higher incidence of uCys-C levels above reference intervals in study groups with higher fluoride exposure. However, to conclude a clear link between fluoride exposure and kidney health we need in-depth studies.

Graphical Abstract

Section snippets

Study participants

The present study was conducted focusing children and adolescents residing within the dry, wet and intermediate climatic zones in Sri Lanka. Education zones within each climatic zone were selected for the study based on multi-stage random sampling. Padavi Sripura (Trincomalee district, North Central Province) and Uhana (Ampara district, Eastern province) education zones were selected from the dry climatic zone. Udunuwara (Kandy district, Central Province) education zone was selected from the…

Characteristics of the participants

Adhering to the inclusion and exclusion criteria, data of 775 students were considered for analysis. An overview of the key socio-demographic and clinical characteristics of the participants is given in Table 1.

Certain manifestations of urinary system including nephrolithiasis, and pain when passing urine were identified in study participants, and the incidence rates did not show significant variation across the regions. In particular, dental fluorosis (0.9%) was identified only in the dry…

Discussion

In Sri Lanka, communities within the dry climatic zone have been identified to have relatively higher fluoride exposure compared to the wet zone communities [14], [32]. Even though multiple studies have focused different communities within the dry climatic zone in Sri Lanka for assessment of fluoride exposure [33], [34], [35], [36], fluoride exposure of pediatric communities particularly in the wet and intermediate climatic zones has not been studied adequately. Hence, the main focus of the…

Conclusions

Significantly higher drinking water fluoride contents, and elevated urinary fluoride levels indicate potential likelihood of high fluoride exposure for children and adolescents in dry climatic zone. Within the context of the findings of the present study, a strong association between fluoride exposure and adverse kidney health outcomes in the study participants is not evident. However, significantly high incidence of elevated uCys-C levels in study groups with higher fluoride exposure levels…

Abstract online at https://www.sciencedirect.com/science/article/abs/pii/S0946672X23002432

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