Non-Essential Trace Elements Dietary Exposure in French Polynesia: Intake Assessment, Nail Bio Monitoring and Thyroid Cancer Risk

Background: In French Polynesia, thyroid cancer mortality and incidence is reported to be the highest in the world. Excessive levels of non-essential trace elements (nETE) in the body are associated with several types of cancer. Objective: The present study aims to provide quantitative information on food contamination by mercury (Hg), lead (Pb), arsenic (As) and cadmium (Cd) in French Polynesia and its potential correlation with measurements performed in fingernails of Polynesians, and then to investigate the potential association between these nETE and different thyroid cancer risks. Methods: The study population included 229 interviewed cases and 373 interviewed controls We performed a descriptive analysis of Polynesian food and examined the association between thyroid cancer risk and daily intake levels of nETE and with fingernail nETE levels. Results: Hg contamination was mainly present in sea products, Pb contamination was present in almost all samples, Cd was detectable in starchy food and As was detectable in all sea products. No patient exceeded dietary contamination WHO limits for Pb, 2 participants exceeded it for Hg and 3 individuals (0.5%) for cadmium. In fingernail clippings, the most detectable pollutant was Pb (553 participants), then Hg (543 participants) then Cd (only in 130 participants). Thyroid cancer risk was increased more than 4 times by Pb daily intake in patients with a history of cancer in first-degree relatives than in ones without (p for interaction =0.01), and 2 times more in women with more than 3 pregnancies than in those with none or less (p for interaction =0.005); it was also increased following As intake by more than 30% in patients with a history of cancer in first-degree relatives than in ones without (p for interaction =0.05). Conclusion: Locally produced foods are not a source of nETE exposure in French Polynesia. Dieatry nETE exposure and fingernail nETE concentration are not associated to differentiated thyroid cancer risk. No correlation found between nETE dietary exposure and fingernail nETE concentration.

Determination of total iodine in French Polynesian foods: method validation and occurrence data.

Pacific Island populations show some of the highest incidences of thyroid cancer in the world, and iodine deficiency is suspected to play a role. Iodine content was determined in 124 different French Polynesian food samples using inductively coupled plasma-mass spectrometry after alkaline digestion. For samples containing starch, the method was optimised by including an additional enzymatic treatment step. This analytical method was validated with an accuracy profile approach, using certified reference materials with iodine contents ranging from 0.027 to 4.95mgiodinekg(-1) dry weight. The trueness bias ranged from -5.8% to 22.4% and the highest observed intermediate precision coefficient of variation CVR was 11% in starchy materials. Tested Polynesian foods showed large variation in iodine content, with values of 0.014-0.032mgkg(-1) for fruits, 0.014-0.081mgkg(-1) for starchy samples, 0.027-1.85mgkg(-1) for green vegetables, 0.222-5.19mgkg(-1) for fish, 6.51-85.6mgkg(-1) for shellfish, and 0.004-1.39mgkg(-1) for beverages.

Risk assessment after internal exposure to black sand from Camargue: uptake and prospective dose calculation.

Some beaches in the south of France present high levels of natural radioactivity mainly due to thorium (Th) and uranium (U) present in the sand. Risk assessment after internal exposure of members of the public by either inhalation or ingestion of black sand of Camargue was performed. This evaluation required some information on the human bioavailability of U and Th from this sand. In vitro assays to determine the solubility of U, Th and their progeny were performed either in simulated lung fluid, with the inhalable fraction of sand, or in both simulated gastric and intestinal fluids with a sample of the whole sand. The experimental data show that the bioavailability of these radionuclides from Camargue sand is low in the conditions of the study. Prospective dose assessment for both routes of intake show low risk after internal exposure to this sand.