The Assessment of Contemporary and Recent Biological Markers of Human Exposure to Fluoride

  • Oladipo Idowu

Student thesis: Doctoral Thesis


Background: Excessive or deficient intake of biologically available fluoride (F) can be primarily monitored using fluoride biomarkers such as urine, plasma, saliva for short-term exposure and hair and nails for long-term exposure, however, these biomarkers have not been fully investigated.

Main aim: The overall aim of the study was to find the most acceptable, feasible and reliable biomarkers of exposure to fluoride among contemporary and recent biological markers. The overall aim was investigated by undertaking two separate studies.

Methods: In the UK, children aged 4-5 years and their parents were selected through primary
schools in Middlesbrough and Teesside University as well as Newcastle University. Participants completed either a hard copy of questionnaire or participated in an online survey. A few of the participants consented to provide samples of the biological marker which was analysed for fluoride. In Nigeria, sixty healthy children (4-5y) and their parents (≥20y) in low- and high- F water areas (LFA, HFA, respectively) participated. Total daily dietary F intake (TDDFI) was assessed by food frequency questionnaire coupled with analysis of F content of food and drinks consumed by either a direct method (Martinez-Mier et al., 2011) or an indirect method (Whitford, 1996). Toothpaste ingestion was assessed through questionnaires. Total Daily F Intake (TDFI) was calculated from TDDFI and toothpaste ingestion. Biomarker samples including 24-h urine, plasma, saliva, hair, fingernail and toenail clippings were collected, prepared and analysed for F contents. Participants also completed Biomarker Acceptability Questionnaire (BAQ) questionnaires for themselves and their children. Data obtained were analysed using SPSS.

Results: For the qualitative study, in the UK, a combined 59%, 60%, 47%, 67%, 71%, 71% and 32% would find collection of samples of 24-h urine, spot urine (one day), spot urine (2 days), saliva, blood, nails and hair, respectively, perfectly acceptable or slightly acceptable among adults whereas for children a combined 37%, 52%, 42%, 50%, 38%, 73% and 50% was found. However, in Nigeria, participants were indifferent about the acceptability of the various biological markers to use in measuring exposure to fluoride among adults and children. However, based on behavioural interest to future use among adults and children, they were more likely to provide blood samples. For the quantitative study conducted in Nigeria, the mean (SD) TDFI among children was 0.075 (0.036) and 0.277 (0.184) mg/kgbw/d in low- and high- fluoride water areas, respectively, while the corresponding values in adults were 0.036 (0.020) and 0.125 (0.093) mg/kgbw/d. The contribution to the TDFI was mostly from the diet in the low- and high- fluoride water areas. In children, there was a strong correlation between TDFI and DUFE as well as with plasma fluoride concentration, a moderate relationship between TDFI and fingernail as well as with toenail fluoride concentration, and a weak correlation between TDFI and saliva as well as with hair fluoride concentration. In adults, there was a strong correlation between TDFI and DUFE, plasma and hair fluoride concentration, a moderate correlation between TDFI and fingernail as well as with toenail fluoride concentration.

Conclusion: For the qualitative study, in Nigeria blood was perceived the most acceptable biomarker of exposure to fluoride among adults and children whereas in the UK, nail was perceived as the most acceptable biomarker of fluoride exposure for both age groups. However, adults in the UK would still be willing to provide blood samples due to previous experience in giving such sample. For the quantitative study, among contemporary and recent biomarkers, plasma is a more reliable biomarker since it reflects total daily fluoride intake in both children and adults even when exposure is very low. Although, the urine sample can be considered in place of plasma where there is difficulty in obtaining samples. Whole saliva is not a good biomarker of exposure to fluoride in adults and children. For long-term exposure, nail sample could be more reliable in both children and adults.
Date of Award19 Oct 2019
Original languageEnglish
Awarding Institution
  • Teesside University
SupervisorVida Zohoori (Supervisor)

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