Mean Mercury Concentrations Research Articles

Spatiotemporal variation in fish mercury contamination: Comparing approaches for crafting consumption advisories and assessing impairment

Mercury in fish is a serious human health concern. Mercury is a widespread contaminant that exceeds health effect thresholds in many fish species and waterbodies. The objectives were to determine the spatiotemporal variation of mercury in fish tissue for several fish species across thousands of lakes and to assess the potential use of fish length standardization and statistical models to improve fish consumption guidelines and impairments determinations in lake-rich areas. The results showed that fish length, species, ecoregion, lake size, latitude, color dissolved organic matter, water clarity, and zebra mussel presence influenced mercury concentrations. Fish mercury concentrations were generally higher from 1967 to 1990, and since 1990 there was no obvious trend. We found that a statistical model provided estimates of mean mercury concentrations by fish total length that were unbiased and with greater confidence than those based solely on sample statistics. The use of fish length standardization and inclusion of predictive models could improve precision and consistency of fish consumption guidelines and impairments determinations.

Association of maternal blood mercury concentration during the first trimester of pregnancy with birth outcomes.

Exposure to mercury has been associated with adverse effects on pregnancy outcomes. However, there is limited literature on mercury exposure and pregnancy outcomes in Chinese pregnant women. Our study was to investigate the possible association between maternal mercury exposure and spontaneous preterm birth and birth weight. This study was a nested case-control study. The association between blood mercury concentration and both spontaneous preterm birth and birth weight was analyzed using conditional logistic regression and linear regression adjusted for the potential confounding factors, respectively. The dose-response relationship between mercury concentration and birth outcomes was estimated using restricted cubic spline regression. The mean concentration of mercury was 2.8 ± 2.2µg/L. A positive relationship was observed between maternal blood mercury concentration and SPB when analyzed as a continuous variable. However, it was not found to be statistically significant (adjusted OR = 1.10, 95% CI = 0.95-1.26, P = 0.202). Moderate mercury exposure was associated with a higher risk of SPB (Q3 vs. Q1: crude OR = 2.50, 95% CI = 1.16-5.41, P = 0.02; adjusted OR = 3.49, 95% CI = 1.33-9.11, P = 0.011). After considering the combined effects of chemicals other than mercury exposure (including lead, selenium, and cadmium), the results remained consistent. There was no statistically significant association between blood mercury levels and birth weight (adjusted coefficient = 18.64, P-value = 0.075). There were no statistically significant dose-response associations between mercury concentration and birth outcomes (SPB: P = 0.076; birth weight: P = 0.885). Public health policies should focus on reducing environmental releases of mercury, improving food safety standards, and providing education to pregnant women about the risks of mercury exposure and preventive measures.

Egg Mercury Concentration and Egg Size Varies with Position in the Laying Sequence in two Songbird Species.

In birds, mercury embryotoxicity can occur through the transfer of mercury from the female to her eggs. Maternal transfer of mercury can vary by egg position in the laying sequence, with first-laid eggs often exhibiting greater mercury concentrations than subsequently laid eggs. We studied egg mercury concentration, mercury burden (total amount of mercury in the egg), and egg morphometrics by egg position in the laying sequence for two songbirds: tree swallows (Tachycineta bicolor) and house wrens (Troglodytes aedon). Egg mercury concentration in the second egg laid was 14% lower for tree swallows and 6% lower for house wrens in comparison with the first egg laid. These results indicate that in both species, after an initial relatively high transfer of mercury into the first egg laid, a smaller amount of mercury was transferred to the second egg laid. This lower mercury concentration persisted among all subsequently laid eggs (eggs three to eight) in tree swallows (all were 14%-16% lower than egg 1), but mercury concentrations in subsequently laid house wren eggs (eggs three to seven) returned to levels observed in the first egg laid (all were 1% lower to 3% greater than egg 1). Egg size increased with position in the laying sequence in both species; the predicted volume of egg 7 was 5% and 6% greater than that of egg 1 in tree swallows and house wrens, respectively. This change was caused by a significant increase in egg width, but not egg length, with position in the laying sequence. The percentage of decline in mercury concentration with position in the laying sequence was considerably lower in tree swallows and house wrens compared with other bird taxonomic groups, suggesting that there are key differences in the maternal transfer of mercury into songbird eggs compared with other birds. Finally, we performed simulations to evaluate how within-clutch variation in egg mercury concentrations affected estimates of mean mercury concentrations in each clutch and the overall sampled population, which has direct implications for sampling designs. Environ Toxicol Chem 2024;43:1844-1854. Published 2024. This article is a U.S. Government work and is in the public domain in the USA.

No Increased Mercury Release from Dental Restorations at 1.5T, 3T, or 7T MRI.

Dental amalgam contains mercury and is commonly used in dental restorations. The impact of MRI on mercury excretion from dental amalgam is not well understood across clinical field strengths, especially 7T. We investigated the effects of MRI exposure on mercury excretion using fresh, lab-created dental amalgam restorations and in extracted teeth with old, pre-existing restorations. Donated, unfilled human teeth (n = 120) were restored with amalgam before being stored in saline, artificial saliva, or a dry box prior to MRI scanning. The teeth were placed in individual tubes of fresh artificial saliva and scanned at 1.5T, 3T, or 7T or left unscanned as controls. Mercury concentrations were measured 24-30 h later. Donated teeth with pre-existing restorations (n = 40) were stored in artificial saliva, scanned at 7T or left unscanned as controls, and mercury concentration tested. For teeth extracted and restored in a laboratory, no significant difference was found (F = 2.42, P = 0.072) between mean mercury concentrations of unscanned teeth (13.72 μg/L) and teeth scanned at 1.5T (10.88 μg/L), 3T (12.65 μg/L), or 7T (8.88 μg/L). For teeth extracted with previously placed restorations, no significant difference (P = 0.288) was found between unscanned controls (4.28 μg/L) and teeth scanned at 7T (6.63 μg/L). MRI of dental amalgam does not significantly increase mercury excretion at 1.5T, 3T, or 7T compared to unscanned teeth. This holds true for controlled laboratory restorations as well as for those placed and lived with prior to extraction and scanning, demonstrating no added risk to the clinical patient or research subject.

Maternal blood concentrations of toxic metal(loid)s and trace elements from preconception to pregnancy and transplacental passage to fetuses

Intrauterine exposure to heavy metals may adversely affect the developing fetus and health later in life, while certain trace elements may be protective. There is limited data on their dynamic fluctuation in circulating concentration of women from preconception to pregnancy and the degree of transplacental passage to fetus. Such information is critically needed for an optimal design of research studies and intervention strategies. In the present study, we profiled the longitudinal patterns and trajectories of metal(loid)s and trace elements from preconception to late pregnancy and in newborns. We measured whole blood metal(loid)s in women at preconception, 16, 24 and 32 weeks of gestation and in cord blood in 100 mother-newborn pairs. Our data showed that the mean concentrations of mercury (Hg), lead (Pb), rubidium (Rb), manganese (Mn), and iron (Fe) were lower during early-, mid-, and late-pregnancy than at preconception. Copper (Cu), and calcium (Ca) concentrations increased after pregnancy (Cu 798 versus 1353, 1488, and 1464 μg/L). Concentrations at preconception were correlated with those during pregnancy for all examined metal(loid)s. Maternal Hg, Pb, and Se concentrations at late-pregnancy were correlated with those in newborn cord blood in various degrees (correlation coefficients: Hg 0.66, Pb 0.29, Se 0.39). The estimated placental transfer ratio for toxic metal(loid)s ranging from 1.68 (Hg) to 0.18 (Cd). Two trajectory groups were identified for Hg, Pb, Cd, Se concentrations. Hg concentrations may be correlated with maternal education levels. The study is the first to present longitudinal circulating concentration trajectories of toxic metal(loid)s and trace elements from preconception to pregnancy stages. A high degree of transplacental passage was observed in toxic metals Pb and Hg which may pose hazards to the developing fetus.

Evaluation of a gold-nanoparticle-modified carbon-fiber microelectrode to quantify mercury in canned tuna sold in Ecuador

Seafood consumption is the primary exposure route for trace metals like mercury. Accordingly, canned tuna meat has been focused on by researchers because of the potential bioaccumulation of high amounts of mercury. This study aimed to test a novel and reliable electroanalytical method employing a working electrode consisting of gold-nanoparticle-modified carbon microfibers to quantify total mercury in canned tuna samples. Determination was achieved via differential pulse anodic stripping voltammetry. The proposed method had a limit of detection of 3.9781 ± 0.0001 μg L−1 and a limit of quantification of 33.6634 ± 0.0001 μg L−1, with a sensitivity of 0.3275 nA μg L−1. The modified electrode was evaluated in samples taken from three canned tuna brands sold in the Sangolquí parish in Rumiñahui, Ecuador. These brands, coded A, B, and C, represent 47.92%, 27.08%, and 11.98% of all canned tuna sold in the Ecuadorian market, respectively. The resulting respective total mercury concentrations were 0.5999 ± 0.0001 mg kg−1; 0.9387 ± 0.0001 mg kg−1; and 0.3442 ± 0.0001 mg kg−1 for A, B, and C. Method accuracy was determined through the recovery percentages of ≥98%, which indicated acceptable accuracy for the final optimized method. Mean mercury concentrations for all samples did not represent a carcinogenic risk for consumers. However, the values obtained for potential no-carcinogenic risk and daily consumption rate suggest that consumers of tuna canned in water, particularly brand C, may be at risk.

Levels of mercury in hair among pregnant women in Iceland

To limit exposure to methylmercury several countries have implimented specific advice on fish intake to pregnant women as well a measuring compliance through regular human biomonitoring. Despite fish intake being relatively high in Iceland, human biomonitoring data on mercury is scarce. We measured mercury in hair from 120 pregnant women recruited in 2021 from the the Reykjavik Capital area. At recruitment, information on fish intake during the past four months was recorded. Hair mercury concentrations were compared to existing health based guidance values and associatons with fish intake was explored. Mean (standard deviation) mercury concentration in hair was 0.48 μg/g (0.33). All participants had concentrations in hair below 1.8 μg/g, which corresponds to the hair value that the tolerable daily intake set by the European Food Safety Authority is derived from, while 5% had concentrations above 1.1 μg/g, which corresponds to the hair value that the US-EPA reference dose is derived from. Mean mercury concentrations in hair increased in a dose dependent manner (p for trend p<0.001) from 0.25 μg/g among women who consumed fish ≤ 3/month (n=24) and up to 0.80 mg/g among those consuming fish 3-4/ week (n=16). The few (n=3) women who reported to have eaten shark (p<1/month) were all at the higher end of the exposure distribution. Our results suggest that exposure is generally below the tolerable daily intake set by EFSA but may in some women exceed the reference dose established by the US-EPA.

Geochemical variations of major, trace, rare earth elements in some Gondwana and Eocene coals of India with a comparison of their germanium, lithium, and mercury content

The geochemistry of major, trace, rare earth elements (REEs), with special reference to Ge, Li, and Hg in selected Gondwana and Eocene coals, has been studied. Major oxide and trace element ratios have been utilised to compare the tectonic setting, provenance of source rocks, and paleoweathering conditions that prevailed the during formation of these coals. The Gondwana coals have a higher mean mercury and ash content (244.5 μg/kg and 17.2 %, respectively) than the Eocene coals (142.1 μg/kg, 8.9 % respectively). The major oxides, SiO2, Fe2O3, and Al2O3, in Gondwana and Eocene coals, are enriched relative to the upper continental crust (UCC), Chinese and American coals. The UCC normalized trace element concentration coefficients of the Gondwana and Eocene coals show enrichment in Ge, Se, Th, Co, Mo, Sn, W, and Li. The mean Ge and Li concentrations (mg/kg) in Gondwana (106.7, 154.7) and Eocene (120.0, 252.6) exceed the corresponding values in world coal (2.2, and 12). The Rajmahal coals have the highest mean Ge concentration (168.8 mg/kg) among the Gondwana coals while Eocene coals from East Jaintia Hills have the highest mean value (343.7 mg/kg). The Gondwana coals have a higher mean As concentration (3.5 mg/kg) in comparison to the Eocene coals (1.9 mg/kg). The mean of the rare earth elements in Gondwana (24.1 mg/kg) is higher than that in Eocene coals (11.3 mg/kg) and these values are less than the World coals (68.5 mg/kg). Both the Gondwana and Eocene coals are enriched in light rare earth elements (LREEs). However, among the Eocene coals, the Meghalayan coals show REE enrichment in comparison to Assam coals. Both the Gondwana and Eocene coals were formed in warm and humid climates under oxic conditions with moderate weathering of the source rocks.

Assessment of the chemical and radiological safety of wild mushrooms and berries growing in the Arkhangelsk region

AIM: To analyze the levels of contamination with heavy metals and radionuclides of wild mushrooms and berries growing in the Arkhangelsk region.&#x0D; METHODS: Data on the content of heavy metals (cadmium, mercury, lead, arsenic) and radionuclides (cesium-137 and strontium-90) in berries and mushrooms were studied in accordance with the protocols of the Agrochemical Service Station Arkhangelskaya and the Center for Hygiene and Epidemiology in the Arkhangelsk Region and the Nenets Autonomous Okrug during the period of 20152021. Total 201 samples of mushrooms and 175 samples of berries were analyzed.&#x0D; RESULTS: The levels of heavy metals did not exceed the maximum permissible concentrations in 94% of the studied samples of mushrooms and 86% of the studied samples of berries. All samples of mushrooms and berries corresponded the hygienic standards for the content of radionuclides. The mean concentrations of mercury (0.013 mg/kg) and cadmium (0.040 mg/kg) in mushrooms were higher than the average concentrations of these metals in berries by 2.1 (p=0.002) and 1.8 times (p 0.001), respectively. At the level of median concentration and 90th percentile, the content of mercury in tubular mushrooms (0.036 and 0.047 mg/kg, respectively) was 3.2 times higher in comparison to plate mushrooms (p=0.003). The highest content of arsenic (0.067 and 0.24 mg/kg, respectively) and lead (0.088 and 0.15 mg/kg) were found in the berries of the large-sized shrubs at the level of average concentration and the 90th percentile compared to other shrub species, but the differences were not statistically significant.&#x0D; CONCLUSION: The comparative analysis concluded that although mushrooms and berries from the Arkhangelsk region contain low concentrations of heavy metals and radionuclides, mushrooms tend to accumulate higher concentration of heavy metals and radionuclides in comparison to berries.

Assessment of mercury and lead contamination using the bivalve Anadara tuberculosa (Arcidae) in an estuary of the Colombian Pacific

Buenaventura Bay is considered the main estuary on the Pacific coast of Colombia, because of port and industrial activities. Mining and agriculture are major sources of contamination in the estuary. This study used the bivalve Anadara tuberculosa to evaluate the presence of mercury and lead in the Dagua River estuary (Colombia), one of the main tributaries coming into the bay. Five samplings for sediments and six for tissues of A. tuberculosa were carried out between 2016 and 2017. Additionally, a series of bioassays were conducted to determine its ability to bioaccumulate metals. A mean mercury concentration of 0.57 ± 0.74 mg*kg−1 and lead concentration of 0.87 ± 0.68 mg*kg−1 in sediment were found. Bioassays allowed us to conclude that at low mercury exposure concentrations (0.25 mg*kg−1), lesions are generated in animal tissue, mainly in sexual cells. The high concentrations of mercury found in organisms exceed the maximum permitted concentration established in Colombia. In addition, the contamination factors for mercury and lead were considered very high. This research aims at contributing to the use of Anadara tuberculosa, as prospective bioindicator for pollution biomonitoring in mangrove coastal ecosystems.

Determination of some heavy metals and microbial profile of raw Sugar samples collected from Sudanese Sugar Industries in season 2017 in relation to EU.1998 and ICUMSA,1974 standards

The study was conducted in Sudanese Sugar Industries during the period 2017 to aim the determination some heavy metals and microbial profiles of raw Sugar samples collected from Sudanese Sugar Industries in season 2017 in relation to EU.1998 and ICUMSA,1974 standards. The samples were obtained from all Sudanese Sugar Industries namely, (Kenana, White Nile, Assalaya, Sennar, Guneid, and New Halfa). After that the samples were transferred to the laboratory to assess the quality parameters of raw sugar which include the determination of some heavy metals content of sugar cane per mg/kg in Sudanese sugar companies which include Mercury, Cadmium, Lead, and Arsenic, Determination Microbial analysis for final sugar which includes Detection of Thermopolis Bacteria (Sporeforming Bacteria, Bacteria producing H2S and H2 swell) and Determination Methophilic Bacteria (Total Count of bacteria CFU/10 gm, Determination Coliform Bacteria CFU/ 10 gm, Determination of Leuconstoc Mesenteroides Bacteria CFU/10 gm. and Enumeration of Yeasts and Moulds CFU/ 10 gm and Determination the concentration of Dextran. and the data were analyzed by using a Statistical system Complete Randomized Design (CRD) and analysis of variance technique by Least Significant Different Test (LSD) according to Fisher’s LSD method, 2010 at (Probability 0.05). Was applied to compare differences between means. The results showed that the mean concentration of Mercury, Cadmium, Lead and Arsenic was (0.02 mg/ kg grams of sugar), (0.62 mg/ kg sugar), (6.74 mg/ kg sugar), and (2.73mg/ kg sugar). These results Indicate all sample industries were agreeable with critical limit maximum value. It was concluded that the total count of Bacteria for raw Sugar White Nile and Sennar agreed with recommended limit. In the case of total yeasts, Sporeforming Bacteria, and Dextranium Bacteria all samples Industries were highest than the critical limit. While the total Moulds and Bacteria Production H2S all samples Industries were less than the critical limit except Kenana and Guneid respectively. Concerning the Total Count of Leuconstoc Mesenteroides Bacteria in sugar, the results revealed all samples Industries were higher than the recommended limit. And the samples Industries were online with the recommended limit concerning the dextran concentration except Guneid industry was highest than the critical limit (75 ppm). The study recommended that the Sudanese Sugar Industry needs to establish proper quality assurance laboratories to help in monitoring the quality and safety of raw materials and end products.In conclusion, the grain yield of maize increased with increasing N rate and plant density up to the optimum. Therefore, it’s possible to recommend using a high N rate with both low and medium plant density (&lt; 45,000 plants ha-1) and (45,000 to 65,000plants ha-1) to harvest high grain yield.

Fish consumption habits of pregnant women in Itaituba, Tapajós River basin, Brazil: risks of mercury contamination as assessed by measuring total mercury in highly consumed piscivore fish species and in hair of pregnant women.

The Tapajós River basin in the Amazon region, Brazil is one of the most active gold mining areas in the world. In this study, we evaluated fish consumption habits and mercury exposure in 110 pregnant women in the city of Itaituba by measuring their total hair mercury concentrations. In addition, we investigated seasonal differences in mercury concentrations in two highly consumed piscivorous fish species, tucunaré (Cichla spp.) and pescada (Plagioscion squamosissimus). Total fish mercury concentrations (THg) during the dry season were 0.62±0.07 mg/kg for Cichla spp. and 0.73±0.08 mg/kg for P. squamosissimus. During the rainy season they were 0.39±0.04 and 0.84±0.08 mg/ kg, respectively. Of our participants 44 % declared that they ate Cichla spp. and 67 % P. squamosissimus. Mean mercury concentration in their hair was 1.6±0.2 mg/kg and was above the US Environmental Protection Agency (US EPA) reference dose of 1 mg/kg in 48 % of them. Mean fish THg concentrations were also above the joint Food and Drug Administration and US EPA safety limit of 0.5 mg/kg for P. squamosissimus during both seasons and for Cichla spp. during the dry season only. These results show that pregnant women should avoid consumption of these piscivorous fish species during pregnancy and call for a regular programme to monitor Hg levels in that area.

Environmental distribution and risk of exposure of Heavy Metal Pollutants from Lolgorian Artisanal Gold Mining in Kenya.

The aim of the study was to assess the distribution of heavy metals in the environmental compartments from artisanal and small-scale gold mining (ASGM) activities from Lolgorian, Kenya. The investigation was carried out using Inductively-Coupled Plasma-Optical Emission Spectrometry (ICP-OES). Mercury (p > 0.05) (p = 0.755), arsenic (p = 0.182), and lead (p = 0.430) mean concentrations in soil, water, sediments, and ore were not significantly different. The mean mercury, lead, and arsenic concentrations in the water were 0.66mg/L, 0.46mg/L, and 1.25mg/L, respectively. In sediments, the mean values of Cr (66.65mg/kg), Zn (45.62mg/kg), Hg (24.63mg/kg), Pb (22.35mg/kg), Cd (0.90mg/kg), and Mn (613.10mg/kg) were found to be significantly higher. A positive correlation between ore-tailings (r = 0.971109), tailings-sediment (r = 0.9441036), and ore-sediment (r = 0.9441036), was observed indicating the presence of harmful heavy metals in the environment in excess of national and World Health Organization (WHO) recommended threshold, posing a high risk of multiple human exposure pathways.

Distribution of Hg and Se in Muscle and Liver of the Thornback Guitarfish Platyrhinoidis triseriata from the Eastern Pacific Ocean.

Human consumption of the thornback guitarfish (Platyrhinoidis triseriata) is concentrated in coastal populations of the Pacific coast of Mexico as its meat is prized for its high quality. This study analyzes the distribution of mercury and selenium in the muscle and liver of Platyrhinoidis triseriata and the risk to human health associated with its consumption. In order to conduct these estimates, specimens were collected from the Eastern Pacific Ocean in 2015 and 2016 and found mean concentrations (µg g-1 wet weight) of mercury ranging from 0.02 to 0.58 in muscle and 0.10 to 0.31 in liver. Selenium ranged from 0.14 to 1.31 in muscle and from 0.93 to 4.52 in liver. Mercury levels in the muscle of P. triseriata were significantly correlated (positive correlation) with the total length of the specimens. The predominant prey of P. triseriata was the shrimp Pleuroncodes planipes and according to the biomagnification factor, only mercury was biomagnified. The risk to consumers associated with the simultaneous presence of mercury and selenium in the muscle and liver of rays under the selenium health benefit value approach indicated that consumption of P. triseriata from this area is beneficial to human health.

Influence of environmental and social factors on mercury accumulation in the hair of residents of the Northwest Russia

Abstract. Mercury is a global pollutant. The main source of mercury in the human body is seafood and freshwater fish. More than 90% of methylmercury from total mercury is found in fish muscles. The main aim of this study was to investigate the mercury levels in the hair of the population of the Vologda Oblast, Northwest Russia, where the heterogeneous distribution of rivers and lakes is the resource base of fishing. The mean mercury concentration in the hair of residents of the Vologda Oblast was 0.445 0.018 mg/kg. 10.7% of the samples studied had mercury concentrations exceeding 1 mg/kg. The minimum mercury concentrations were detected in residents of Cherepovets and the eastern districts of the Vologda Oblast. Residents of western districts, where local reservoirs are the main sources of commercial fish, had the maximum concentrations. There were no differences in the amount of this metal between men and women. At the same time, mercury concentrations in men and women from the western districts of the Vologda Oblast had a higher percentage of exceeding the recommended standards.

Air mercury monitoring in the Baikal area (2011-2021)

Abstract. We present long-term (2011 2021) data on air mercury monitoring that was started within the GMOS (Global Mercury Observation System) project (2011-2015) at the Listvyanka station located on the shore of Lake Baikal, Siberia. Monitoring shows an obvious seasonal variation in the background mercury concentration in the air, which increases in the cold season and decreases in the warm season. Short-term anomalies are associated with the wind carrying air from industrial areas where several large coal-fired power plants are located (Irkutsk and Angarsk). A positive correlation between mercury, SO2 and NO2 concentrations is observed both in short-term variations and in average monthly concentrations. The analysis of the forward and backward trajectories obtained with the HYSPLIT model demonstrates possible mercury emission sources. Concentration-weighted trajectory (CWT) analysis has revealed potential remote regions of mercury emissions from where mercury can be transported by air masses to the area of Lake Baikal, including the territories of Transbaikalia and Mongolia (Erdenet). During the 2018 cruise, the continuous air mercury survey above Lake Baikal covered 1800 km. The mean mercury concentration above Lake Baikal is significantly lower than the mean value obtained at the onshore Listvyanka station during the same days of the cruise. That can lead to the conclusion that Lake Baikal is a sink of atmospheric mercury.

Distribution, sources and forms of mercury occurrence in the street dust of Mezhdurechensk (Kemerovo Region)

Abstract. The aim of this study was to investigate mercury concentration and forms of its occurrence in the dust component of the atmospheric air (street dust) to assess the geo-ecological condition of the area where coal is mined, processed and transported. The mean mercury concentration of 29 street dust samples collected along a uniform network throughout the city was 36.4 4.7 ng/g, with a minimum (4.6 ng/g) and a maximum (104.6 ng/g) value, respectively. This value was much lower than the mean concentration in soil samples taken previously at the same sites (58.4 ng/g) but higher than the mean concentration in snow solids (29.8 ng/g), which was likely due to precipitation that washed out mercury from the street dust and to the wind blowing. The method of successive chemical extraction revealed a weakly bonded water-soluble form, inorganic poorly sorbed mercury compounds, an organic form of mercury, and mercury associated with minerals. The proportion of each fraction accounted for on average 10.94%, 10.32%, 44.76%, and 33.97%, respectively. Water-soluble and acid-soluble mercury forms were less common. The bulk of mercury had metal-organic and sulfide forms. The study of mercury distribution based on particle size indicated that the mercury concentration increased as the diameter of the grains of dust material decreased. The fine fraction with a diameter of 20 to 50 m contained the bulk of mercury, which stayed in suspension form for a long time before settling on the surface.

Correlation of Mercury Occurrence with Age, Elemental Composition, and Life History in Sea-Run Food Fish from the Canadian Arctic Archipelago’s Lower Northwest Passage

As mercury emissions continue and climate-mediated permafrost thaw increases the burden of this contaminant in northern waters, Inuit from a Northwest passage community in the Canadian Arctic Archipelago pressed for an assessment of their subsistence catches. Sea-run salmonids (n = 537) comprising Arctic char (Salvelinus alpinus), lake trout (S. namaycush), lake whitefish (Coregonus clupeaformis), and cisco (C. autumnalis, C. sardinella) were analyzed for muscle mercury. Methylmercury is a neurotoxin and bioaccumulated with fish age, but other factors including selenium and other elements, diet and trophic level as assessed by stable isotopes of nitrogen (δ15N) and carbon (δ13C), as well as growth rate, condition, and geographic origin, also contributed depending on the species, even though all the fish shared a similar anadromous or sea-run life history. Although mean mercury concentrations for most of the species were ~0.09 µg·g−1 wet weight (ww), below the levels described in several jurisdictions for subsistence fisheries (0.2 µg·g−1 ww), 70% of lake trout were above this guideline (0.35 µg·g−1 ww), and 19% exceeded the 2.5-fold higher levels for commercial sale. We thus urge the development of consumption advisories for lake trout for the protection of pregnant women and young children and that additionally, periodic community-based monitoring be initiated.

Hair to blood mercury concentration ratios and a retrospective hair segmental mercury analysis in the Northwest Territories, Canada

Concentrations of total mercury were measured in blood and hair samples collected as part of a human biomonitoring project conducted in First Nations communities of the Mackenzie Valley, Northwest Territories, Canada. Hair (n = 443) and blood (n = 276) samples were obtained from six communities in the Dehcho region and three communities in the Sahtú region of the Mackenzie Valley. The aim of this paper was to calculate hair to blood mercury ratios (for matched samples) and determine if: 1) ratios differed significantly between the two regions; 2) ratios differed from the 250:1 ratio proposed by the WHO; and, 3) point estimates of hair to blood mercury ratios could be used to estimate blood mercury concentrations. In addition, this paper aims to determine if there were seasonal patterns in hair mercury concentrations in these regions and if so, if patterns were related to among-season variability in fish consumption.The majority of mercury levels in hair and blood were below relevant health-based guidance values. The geometric mean hair (most recent segment) to blood mercury ratio (stratified by region) was 619:1 for the Dehcho region and 1220:1 for the Sahtú region. Mean log-transformed hair to blood mercury ratios were statistically significantly different between the two regions. Hair to blood ratios calculated in this study were far higher (2–5 times higher) than those typically reported in the literature and there was a large amount of inter-individual variation in calculated ratios (range: 114:1 to 4290:1). Using the 250:1 ratio derived by the World Health Organisation to estimate blood mercury concentrations from hair mercury concentrations would substantially over-estimate blood mercury concentrations in the studied regions. However, geometric mean site-specific hair to blood mercury ratios can provide estimates of measures of central tendency for blood mercury concentrations from hair mercury concentrations at a population level.Mercury concentrations were determined in segments of long hair samples to examine exposure of participants to mercury over the past year. Hair segments were assigned to six time periods and the highest hair mercury concentrations were generally observed in hair segments that aligned with September/October and November/December, whereas the lowest hair mercury concentrations were aligned with March/April and May/June. Mean log-transformed hair mercury concentrations were statistically significantly different between time periods. Between time periods (e.g., September/October vs. March/April), the geometric mean mercury concentration in hair differed by up to 0.22 μg/g, and the upper margins of mercury exposure (e.g., 95th percentile of hair mercury) varied by up to 0.86 μg/g. Results from self-reported fish consumption frequency questionnaires (subset of participants; n = 170) showed total fish intake peaked in late summer, decreased during the winter, and then increased during the spring. Visual assessment of results indicated that mean hair mercury concentrations followed this same seasonal pattern. Results from mixed effects models, however, indicated that variability in hair mercury concentrations among time periods was not best explained by total fish consumption frequency. Instead, seasonal trends in hair mercury concentrations may be more related to the consumption of specific fish species (rather than total wild-harvested fish in general). Future work should examine whether seasonal changes in the consumption of specific fish species are associated with seasonal changes in hair mercury concentrations.

Mercury and neurochemical biomarkers in multiple brain regions of five Arctic marine mammals

Mercury is a neurotoxic chemical that represents one of the greatest pollution threats to Arctic ecosystem health. Evaluating the direct neurotoxic effects of mercury in free ranging wildlife is challenging, necessitating the use of neurochemical biomarkers to assess potential sub-clinical neurological changes. The objective of this study was to characterize the distribution and speciation of mercury, as well as exposure-associated changes in neurochemistry, across multiple brain regions (n = 10) and marine mammal species (n = 5) that each occupy a trophic niche in the Arctic ecosystem. We found consistent species differences in mean brain and brain region-specific concentrations of total mercury (THg) and methyl mercury (MeHg), with higher concentrations in toothed whales (narwhal, pilot whales and harbour porpoise) compared to fur-bearing mammals (polar bear and ringed seal). Mean THg (μg/g dw) in decreasing rank order was: pilot whale (11.9) > narwhal (7.7) > harbour porpoise (3.6) > polar bear (0.6) > ringed seal (0.2). The higher THg concentrations in toothed whales was associated with a marked reduction in the percentage of MeHg (<40 %) compared to polar bears (>70 %) that had lower brain THg concentrations. This pattern in mercury concentration and speciation corresponded broadly to an overall higher number of mercury-associated neurochemical biomarker correlations in toothed whales. Of the 226 correlations between mercury and neurochemical biomarkers across brain regions, we found 60 (27 %) meaningful relationships (r>0.60 or p < 0.10). We add to the growing weight of evidence that wildlife accumulate mercury in their brains and demonstrate that there is variance in accumulation across species as well as across distinct brain regions, and that some of these exposures may be associated with sub-clinical changes in neurochemistry.