Determination of methylmercury and inorganic mercury in human hair

Overview

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Key numbers

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• Hg species-specific human hair samples (N = 96), mostly non-directly occupied in ASGM tasks, from the six most relevant gold
• double spiking species-specific isotope dilution mass spectrometry (IDMS) and GC-ICP-MS. Only 16.67% of
• Amazonian participants were involved at some point in AGSM works and fish consumption ranged from 3 to 7 times/week,
• higher than the reference dose weekly acceptable of MeHg intake established by the EPA (1 ppm), whereas a 25%
• were more than 4 times higher than the WHO level (2.2 μg Hg g− 1). Median THg value of individuals consuming
• g− 1). Most of the samples presented a % of MeHg relative to THg higher than 80%. The average % of Hg(II)/THg
• was 11% and only 10 individuals presented a Hg(II) content over 30%. No significant differences (p > 0.05) were
• account for almost 38% of the total Hg release to the biosphere (Fuentes-Gandara et al., 2018), thus, consumption of contaminated fish
• Some of these methods only allow the determination of one Hg species at lutions were prepared daily in 2% sub-boiled HCl (Sigma-Aldrich, St.
• set-up (Montuori et al., 2004, 2006). In such cases, a second analysis is at − 18 ◦ C. 25% tetramethylammonium hydroxide (TMAH) (Sigma-Al­
• 2017). Agilent J&W Scientific (cross-linked 5% diphenyl, 95% dimethylsilox­
• sumption and the Hg(II) absorbed into hair by direct exposure to Hg More detailed instrumental parameters can be found in Table S1.
• focused microwave unit at a fixed power of 75 W during 4.5 min, after Most of the participants (N = 96) in the study were women (77.08%,
• the addition of 3 mL of 25% TMAH and a magnetic stir bar to the vial. N = 74). The mean age was 36.92 years. Only 12.50% of the surveyed
• buffer. Sample derivatization was carried out by manual shaking for 5 dividuals (79%) had low educational levels, as 73 adults had grades
• involved in mining tasks. Only 16.67% of participants were involved
• Hg species-specific isotope abundances were calculated for MeHg and described in Table 1. In general, consumption of fish ranged from 3
• instrumental parameters are given in Table S1. For statistical analyses, and Table S4 According to MeHg median values, departments followed
• tween groups were tested using Kruscal-Wallis. Statistical significance (13.75 μg Hg g− 1, IQR 9.84–26.29). MeHg median value in Vaupés was
• was set at p < 0.05. The median and the interquartile range (IQR, 25th statistically different from the other departments (p < 0.05) and no
• 3. Results (p < 0.05). Males had a median value of 8.8 μg Hg g− 1 (IQR 0.78–16.26)
• 3.1. Quality control of the measurements had a median value of 1.05 μg g− 1 (IQR 0.54–2.74) and a maximum
• terial IAEA-086. The average results from all measurement sessions are Amazon (Crespo-Lopez et al., 2021), most of the samples presented a %
• shown in Table S2. As it can be observed, the experimental values ob­ of MeHg relative to THg higher than 80% as shown in Fig. S2. Statistical
• although the IAEA-086 material is not certified for Hg(II), the experi­ MeHg/THg (%) when workers in ASGM were compared with people not
• six procedural blanks are shown in Table S3. LOD and LOQ values were 3.4. Inorganic mercury in the hair samples
• The interconversion factors determined for the reference material and Table S4. A much lower median value than that of MeHg was ob­
• shown in Fig. S1. MeHg demethylation factor (F2) was the most relevant median Hg(II) value (0.86 μg Hg g− 1), being again statistically different
• factor in agreement with previous results (Queipo Abad et al., 2017; from the other departments. Antioquia and Bolívar had the same median
• Suárez-Criado et al., 2022). For most real samples, F2 (%), was lower value of 0.11 μg Hg g− 1 (IQR 0.06–0.43 and 0.05–0.11, respectively).
• than 5 (IQR values between 1.7% and 3.1%), except for one particular The order of the departments, according to median values for Hg(II) was
• sample in which a value of 29.2% was reached. Hg(II) methylation Vaupés > Antioquia = Bolívar > Nariño > Sucre > Chocó.
• reactions were considered for the calculation of the Hg species specific < 0.05). A 4-times greater median value (0.44 μg Hg g− 1) was obtained
• Descriptive variables of Colombian individuals (n = 96) distributed by departments.
• All Departments (n = 96) Chocó (n = 20) Sucre (n = 5) Nariño (n = 22) Bolívar (n =12) Antioquia (n = 6) Vaupés (n = 31)
• Gender, female (%) 77.08 75.00 60.00 90.91 83.33 100.00 64.52
• AGSM or Hg involving tasks (%) 16.67 15.00 – 50.00 – 33.33 –
• 11% and only 10 individuals had a Hg(II) content over 30%. No sig­
• in AGSM tasks showed 1.7 times higher Hg(II)/THg (%) vs. people not
• summarized in Fig. 1 and Table S4. Median THg values were under the
• In all departments there was at least one individual above the WHO Fig. 2. Ratio of Hg(II)/THg (%) in hair of the Colombian individuals in relation
• weekly acceptable MeHg intake. The THg concentration values of 25% to Hg involving tasks including Vaupés (A), not including Vaupés (B).

Methods (brief)

• samples of individuals from Colombian gold mining regions by double
• spiking isotope dilution and GC-ICP-MS
• Hg species-specific human hair samples (N = 96), mostly non-directly occupied in ASGM tasks, from the six most relevant gold
• double spiking species-specific isotope dilution mass spectrometry (IDMS) and GC-ICP-MS. Only 16.67% of
• Colombia which is between medium and high intake levels. The median concentration of THg obtained from all samples is
• g− 1). Most of the samples presented a % of MeHg relative to THg higher than 80%. The average % of Hg(II)/THg
• Hg(II)/THg vs. inhabitants uninvolved. This suggest that Hg(II) determination by IDMS-GC-ICP-MS could be a
• With the aim of knowing the effects of Hg in ASGM communities of tives and scope of the study. After permission, hair samples of 96 sub­
• Colombia, their species can be determined in several biomarkers (Poulin jects were collected from the occipital area with stainless steel scissors.
• and Gibb, 2008). Hair is preferred over blood and urine due to the easier Then, the hair samples were stored and properly identified. Data from all
• amos et al., 2021; Crespo-Lopez et al., 2021; Díez et al., 2011). Tradi­ habits and employment were also collected. The questionnaire included
• a time. For example, acid digestion step prior to the aqueous-phase Louis, MO, USA) in Milli-Q water (≥18 MΩ cm). MeHg working solu­
• atomic fluorescence spectrometry (GC-CVAFS) GC-CVAFS interface Germany) and methanol (Sigma-Aldrich) and stored in dark conditions
• required to determine THg concentration, for example by sample cata­ drich) was used for the digestion of the samples. A pH 4 buffer was
• desorption, and atomic absorption spectrometry (AAS) (Díez et al., Hexane (Sigma-Aldrich) was used to extract the mercury derivatized
• during sample preparation steps (Monperrus et al., 2008). To do so, the organic phase.
• phenated to inductively coupled plasma-mass spectrometry (ICP-MS) for The separation of the Hg species was carried out with a gas chro­
• neously determined by double spiking IDMS and GC-ICP-MS in human at 270 ◦ C was used to couple the GC to an Inductively Coupled Plasma

Implications

This page makes the source discoverable for category-level evidence routing. Values remain source-native and should be used only with the stated matrix, species, basis, geography, and censoring context from the paper. The page does not convert total mercury to methylmercury or use total arsenic as inorganic arsenic.

Wiki pages this source may touch

• Fish — marine, non-predatory (sardines, anchovies, salmon, cod)
• Mercury
• Mercury

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Update history

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