Atmospheric mercury in Changbai Mountain area, northeastern China I. The seasonal distribution pattern of total gaseous mercury and its potential sources

An intensive field campaign for the measurement of total gaseous mercury (TGM) concentrations in ambient air was conducted in Changbai Mountain area from 5 August 2005 to 5 July 2006 using an automatic atmospheric mercury analyzer (Tekran 2537A), which was the first time TGM was monitored at a remote area in northeastern China. 99% of the hourly TGM concentrations fell between 1.28 and 9.49 ng m⁻³ with an annual arithmetic mean of 3.58±1.78 ng m⁻³, which was significantly elevated compared to values obtained in remote areas of Europe and North America. Seasonal mean TGM concentrations displayed a descending trend as follows: winter, spring, fall, and summer. Compared to spring/winter, TGM concentrations were lower in the summer/fall but the standard deviation (SD) of TGM levels was higher and indicated a correlation with anthropogenic emissions. TGM concentrations showed seasonal differences with respect to meteorological parameters: TGM levels in spring/winter were most correlated with wind speed, and correlated with solar radiation only in the winter, while TGM levels in summer/fall periods were most correlated with air temperature. There was a strong diurnal variation of seasonal TGM with significantly higher concentrations in daytime/nighttime compared to the early morning. The seasonal diel TGM pattern indicated regional biofuel and coal combustion were the primary mercury sources.     

Atmospheric distribution and deposition of mercury in the Idrija Hg mine region, Slovenia

The atmospheric distribution and deposition of Hg in the area of the former Idrija Hg-mine, Slovenia, were investigated. Mapping of air Hg⁰ concentrations was performed to assess the spatial distribution and major sources of mercury to the atmosphere in the area. In addition, analyses of mercury speciation in the air over Idrija were performed during a 4-day sampling campaign in September 2006 to better understand the fate and transformation of Hg in the atmosphere of this specific mercury polluted site. The speciation results were then compared to the results of mercury speciation in the wet and throughfall deposition sampled on a precipitation event basis from October 2006 to September 2007. The Hg⁰ concentration in air was mostly below 10 ng m⁻³, with the highest concentration in the area of the former smelter complex exceeding 5000 ng m⁻³. Mercury-bearing airborne particles (TPM) seem to dominate the atmospheric Hg deposition, which revealed noticeable variations between precipitation events (11–76 ng m⁻² day⁻¹), mostly as a function of the amount of precipitation. Hg in precipitation was largely (∼50%) associated with the particulate phase (THg_P). No correlation was found between the THg_P and the dissolved phases (THg_D), suggesting that particulate phase Hg is mostly the result of dry deposition. In the throughfall, significantly higher (2–10 fold) Hg concentrations than in associated event precipitation were observed, mostly due to Hg in the particulate phase (∼70% THg). As shown by SEM/EDXS microscopy, an important amount of mercury in the precipitation and throughfall samples is due to the presence of cinnabar particles as a result of the aeolian erosion of cinnabar-containing surfaces in the area.     

Hair mercury concentration and fish consumption: Risk and perceptions of risk among women of childbearing age

The purposes of this study were to assess the hair mercury concentration of women of childbearing age in Taiwan, and to calculate a hazard quotient (HQ) to evaluate the risk of fish consumption for these women. We also examined perceptions of risk associated with fish consumption and whether women in our study changed their habits in response to such risks. The average concentration of mercury was 1.73±2.12 μg g⁻¹ (range: 0.02-16.34 μg g⁻¹), exceeding the US EPA reference dose of 1 μg g⁻¹ in 52.9% of study subjects. The WHO tolerance limit of 10 μg g⁻¹ was exceeded in 1.5% of study subjects. Hair mercury concentration in groups who consumed fish was significantly higher than in groups who never consumed fish (p<0.05). The hazard quotient (exposure estimate/oral reference dose) exceeded 1.0 for 29% of subjects, based on the US EPA’s reference dose (0.1 μg kg⁻¹ d⁻¹), and the average HQ equaled 1.26. When told that some fish contain high levels of mercury that may be harmful for unborn babies, 67.6% of women still indicated that they would not change their amount of fish intake. The high hair mercury concentrations among women of childbearing age in Taiwan are a cause for concern, due to the effect on babies’ brain development. The government should provide specific information about risks and benefits of fish consumption for women to make risk-balancing decisions.     

Human co-exposure to mercury vapor and methylmercury in artisanal mercury mining areas, Guizhou, China

Mercury (Hg) concentrations were determined in human urine and hair samples from Gouxi (GX, n=25) and Laowuchang (LWC, n=18), Tongren, Guizhou, China, to evaluate human exposure from artisanal Hg mining. Geometric means of urinary Hg (U-Hg) were 216 and 560 μg g⁻¹ Creatinine (μg g⁻¹ Cr) for artisanal mining workers from GX and LWC, respectively, and clinical symptoms (finger tremor) were observed in three workers. The means of hair Me-Hg concentrations were 4.26 μg g⁻¹ (1.87-10.6 μg g⁻¹) and 4.55 μg g⁻¹ (2.29-9.55 μg g⁻¹) for the population in GX and LWC, respectively. Significant relationship was found between estimated rice Me-Hg intake and hair Me-Hg levels (r=0.73, p<0.001). Co-exposure to Hg vapor and Me-Hg may pose health risks for the study population.     

Mercury concentrations are low in commercial fish species of Lake Ziway, Ethiopia, but stable isotope data indicated biomagnification

Stable isotope ratios of nitrogen (δ¹⁵N) and carbon (δ¹³C), complemented by stomach content data, were used to assess the food web structure and trophic transfer of mercury (Hg) in four commercial fish species of Lake Ziway, Ethiopia: Nile tilapia (Oreochromis niloticus), catfish (Clarias gariepinus), Tilapia zillii, and golden carp (Carassius auratus). Total mercury (THg in mg kg⁻¹, ww) concentrations were low, with mean values of 0.033, 0.034, 0.025, and 0.011, in C. gariepinus, T. zillii, C. auratus, and O. niloticus, respectively. The relationships between mercury concentrations against total length (TL) and total weight (TW) were positive and significant in T. zillii, C. auratus, and C. gariepinus (P<0.01), but not in O. niloticus, which even showed a decreasing tendency with increase in TL and TW. Regression of log THg vs. δ¹⁵N among all fish species showed a significant correlation, indicating that mercury is biomagnifying along the food web of Lake Ziway. Isotope ratios indicated that C. gariepinus occupied the highest trophic level of the food web of Lake Ziway; but contained similar THg concentrations as T. zillii, which is located at a lower trophic level, probably due to a faster growth rate of C. gariepinus, and thus an example of biodilution.     

Human exposure to mercury in the vicinity of chlor-alkali plant

The main objectives of our study were to estimate the impact of a mercury cell chlor-alkali (MCCA) complex in Rosignano Solvay (Tuscany, Italy) on the local environment and to assess mercury exposure of inhabitants living near the plant. Measurement campaigns of atmospheric Hg near the MCCA plant showed that the impact of the emitted Hg from the industry on the terrestrial environment is restricted to a close surrounding area. Total gaseous mercury concentrations in ambient air of inhabited area around the MCCA plant were in the range of 8.0-8.7 ng/m³ in summer and 2.8-4.2 ng/m³ in winter. Peaks of up to 100 ng/m³ were observed at particular meteorological conditions. Background levels of 2 ng/m³ were reached within a radius of 3 km from the plant. Reactive gaseous mercury emissions from the plant constituted around 4.2% of total gaseous mercury and total particulate mercury emission constituted around 1.0% of total gaseous mercury emitted. Analysis of local vegetables and soil samples showed relatively low concentrations of total mercury (30.1-2919 μg Hg/kg DW in the soil; <0.05-111 μg Hg/kg DW in vegetables) and methylmercury (0.02-3.88 μg Hg/kg DW in the soil; 0.03-1.18 μg Hg/kg DW in vegetables). Locally caught marine fish and fresh marine fish from the local market had concentrations of total Hg from 0.049 to 2.48 μg Hg/g FW, of which 37-100% were in the form of methylmercury. 19% of analysed fish exceeded 1.0 μg Hg/g FW level, which is a limit set by the European Union law on Hg concentrations in edible marine species for tuna, swordfish and shark, while 39% of analysed fish exceeded the limit of 0.5 μg Hg/g FW set for all other edible marine species. Risk assessment performed by calculating ratio of probable daily intake (PDI) and provisional tolerable daily intake (PTDI) for mercury species for various exposure pathways showed no risks to human health for elemental and inorganic mercury, except for some individuals with higher number of amalgam fillings, while PDI/PTDI ratio for methylmercury and total mercury exceeded the toxicologically tolerable value due to the potential consumption of contaminated marine fish.     

Total and methyl-mercury in hair and milk of mothers living in the city of Porto Velho and in villages along the Rio Madeira,Amazon, Brazil

High fish consumption and extended breastfeeding are hallmarks of traditional lifestyle in Western Amazonia. We studied sources of mercury exposure, fish-methylmercury (meHg) and dental-amalgam filling, in 75 urban and 82 rural lactating mothers. Total mercury was determined in all samples while meHg concentrations were determined in subsamples of milk (45) and hair (27) of urban mothers living in Porto Velho (PV) and in hair (46) and milk (37) of mothers living in traditional communities (TC) of the Rio Madeira. The TC mothers showed significantly higher median hair-Hg concentrations (8.2 μg g⁻¹) than PV mothers (1.3  μg g⁻¹). Median total Hg in milk of PV mothers (0.36 ng g⁻¹) was significantly lower (p = 0.0000) than that found in milk of TC mothers (2.30 ng g⁻¹). The median meHg concentrations in milk of TC mothers were also significantly higher (1.0 ng g⁻¹) than in milk of PV mothers (0.07 ng g⁻¹). For urban mothers with low fish consumption rates (and relatively higher dental amalgam fillings) the proportion of inorganic Hg in milk was higher (85%) than in TC (62%). In TC mothers 51% of breast milk Hg concentrations were above 2 ng g⁻¹ (world median concentrations), contrasting with 8% in PV mothers. Despite this, there was no significant correlation between total Hg concentrations in milk and either amalgam filling or daily fish consumption. Socioeconomic changes occurring in Western Amazonia are causing changes in fish-eating habits of urban mothers. However, traditional lifestyle and attendant high fish consumption in riverine populations can still impact total Hg and methylmercury concentrations in mothers’ milk and hair.     

High exposure of Chinese mercury mine workers to elemental mercury vapor and increased methylmercury levels in their hair

Objective The aim of this study was to determine the level of exposure of mercury (Hg) miners and smelter workers to elemental mercury (Hg⁰) vapor in China, who work in Hg mines without using protective equipment against Hg⁰ vapor. In addition, the level of methylmercury (MeHg) intake by the workers was estimated from the MeHg concentration in their hair. Methods Urinary total mercury (THg) and hair THg and MeHg concentrations were measured in 26 Hg miners and smelter workers (i.e., exposed group), and 48 unexposed people (unexposed group). Results The exposed group showed high geometric mean THg concentrations in urine (258 ng/ml, 226 μg/g creatinine) and hair (20.0 μg/g). The urinary THg concentration of the smelter workers in particular was extremely high (338 μg/g creatinine in urine). The highest urine THg concentration reached 4577 μg/g creatinine. THg concentrations in urine and hair showed a significant correlation in the exposed group (r=0.62), indicating the adhesion of Hg⁰ vapor to hair. However, no such significant correlation was found in the unexposed group. Hair MeHg concentration in the exposed group (1.97 μg/g) was about threefold higher than that in the unexposed group (0.60 μg/g). Conclusions This study shows that smelter workers in a Chinese Hg mine are exposed to extremely high levels of Hg⁰ vapor, and that Hg miners are exposed to higher levels of MeHg than the unexposed subjects. Further study is needed to determine the cause of the higher hair MeHg concentration in the exposed group.     

The effect of outdoor air and indoor human activity on mass concentrations of PM(10), PM(2.5), and PM(1) in a classroom

The 12-h mass concentration of PM₁₀, PM_2.5, and PM₁ was measured in a lecturing room by means of three co-located Harvard impactors. The filters were changed at 8 AM and at 8 PM to cover the periods of presence and absence of students. Concentrations were assessed by gravimetry. Ambient PM₁₀ data were available for corresponding 12-h intervals from the nearest state air-quality-monitoring network station. The data were pooled into four periods according to the presence and absence of students—Monday-Thursday day (workday daytime), Monday-Thursday night (workday night), Friday-Sunday day (weekend daytime), and Friday-Sunday night (weekend night). Average indoor workday daytime concentrations were 42.3, 21.9 and 13.7 μg m⁻³, workday night were 20.9, 19.1 and 15.2 μg m⁻³, weekend daytime were 21.9, 18.1 and 11.4 μg m⁻³, and weekend night were 24.5, 21.3, and 15.6 μg m⁻³ for PM₁₀, PM_2.5, and PM₁, respectively. The highest 12-h mean, median, and maximum (42.3, 43.0, and 76.2 μg m⁻³, respectively) indoor concentrations were recorded on workdays during the daytime for PM₁₀. The statistically significant (r=0.68,P<0.0009) correlation between the number of students per hour per day and the indoor coarse fraction calculated as PM_10−2.5 during daytime on workdays indicates that the presence of people is an important source of coarse particles indoor. On workdays, the daytime PM₁₀ indoor/outdoor ratio was positively associated (r=0.93) with an increasing indoor coarse fraction (PM_10-2.5), also indicating that an important portion of indoor PM₁₀ had its source inside the classroom. With the exception of the calculated coarse fraction (PM_10-2.5), all of the measured indoor particulate matter fractions were significantly highly correlated with outdoor PM₁₀ and negatively correlated with wind velocity, showing that outdoor levels of particles influence their indoor concentrations.     

Spring snowmelt and mercury export from a forested catchment in the Czech Republic, Central Europe

The annual output of filtered mercury (Hg) from Lesni potok catchment, a forested ecosystem in central Europe, was estimated at 0.87 μg m⁻². More than 70% of the annual mercury output flux occurred during the spring snowmelt period. The snowmelt period is the most important part of the hydrological year in central European forested ecosystems. Average filtered concentrations of mercury (17.8 ng L⁻¹) and DOC (10.5 mg L⁻¹) in the stream water during snowmelt were greater than average values for the rest of the hydrological year. Omitting frequent daily or bi-daily filtered mercury analysis during the snowmelt caused underestimation of the annual mercury output flux (0.79 μg m⁻²) and decreased the accuracy of flux calculations.     

Sequential hair mercury in mothers and children from a traditional riverine population of the Rio Tapajós, Amazonia: Seasonal changes

Riverine populations of the Brazilian Amazon depend on fish for their principal source of protein, which changes in availability with seasonal fluctuations in the aquatic ecosystem. We report seasonal (high and low waters) and interannual changes in total mercury and methylmercury concentrations in hair of subsistence fish-eaters from a traditional riverine village on the banks of the Rio Tapajós in the Brazilian Amazonia. Retrospective exposure assessment was conducted from hair concentrations in segments representative of 2 years. A total of 32 mothers and their 51 children were studied. They reported high fish consumption (4-14 times a week). Ranges of total mercury and methylmercury concentrations in hair were 1.0-51.0 and 0.5-41.4 μg g⁻¹, with means of 12.4 and 10.2 μg g⁻¹, respectively. The relative mean value for methylmercury was 80%. There was a significant correlation between mothers and children for both total-Hg (r=0.4826; P=0.003) and methyl-Hg (r=0.5214; P=0.004). Mercury concentrations along hair strands of individuals showed significant variation coinciding with seasonal high and low waters. The changes in the aquatic environment impacted fish species availability, which is reflected in the total and MeHg concentrations in hair.     

Bioconcentration and immunotoxicity of an experimental oil spill in European sea bass (Dicentrarchus labrax L.)

The effects of Polycyclic Aromatic Hydrocarbons (PAHs) resulting from a water soluble fraction (WSF) of an Arabian crude oil were tested in vivo on the bioconcentration in muscles and on immune parameters in sea bass, Dicentrarchus labrax. After 15 days of acclimation, fish were acutely exposed (48 h) to the WSF of 25 g of oil, and then returned to clean sea water for a 15 day recovery period. PAH concentration in the WSF at the beginning of the exposure was estimated to 773±187 ng L⁻¹ similar to that observed in the marine environment after an oil spill. The WSF in the experimental system was composed by lightest PAH compounds and did not remain constant during the two days of exposure. Just after exposure to the WSF, a total mean concentration of 148±46 μg kg⁻¹ of PAHs was found in contaminated fish muscle, composed of parent and alkylated naphthalene compounds (86.5%), benzo[a]pyrene (10.1%) and benzo[b+k]fluoranthene (3.4%). In addition, a decrease of leucocytes counts due to a lymphopenia and granulopenia and an increase of the haemolytic activity of the alternative pathway (ACH₅₀) were noted. After a 15 day recovery period, haematocrit was decreased whereas effects on the blood granulocytes of fish seemed to be reversible, contrary to the specific immune system and quality of flesh. In fact, contaminated fish had still less lymphocyte cells compared to controls fish and their flesh were still contaminated by naphthalene and benzo[a]pyrene creating a risk for human consumers.     

Biomarkers of low-level mercury exposure through fish consumption in pregnant and lactating Slovenian women

In order to assess the mercury exposure of pregnant and lactating women in Slovenia, levels of total mercury (THg) and methylmercury (MeHg) were determined in hair, cord blood and breast milk. In addition, the frequency of fish consumption was estimated, because fish is generally the main pathway for human exposure to MeHg. Hair samples were collected from 574 women participating in this study, while cord blood and breast milk samples were collected from 446 and 284 women, respectively. As expected, the levels of THg in hair (median (Med)=297 ng/g, 10th percentile (P10)=73 ng/g, 90th percentile (P90)=781 ng/g), cord blood (Med=1.5 ng/g, P10=0.5 ng/g, P90=4.2 ng/g) and breast milk (Med=0.2 ng/g, P10=0.06 ng/g, P90=0.6 ng/g) were low, due to low consumption of fish (X=25 g/day). A significant linear correlation was found between levels of ln THg in hair and ln THg in cord blood (r=0.87, 95% confidence interval (CI): 0.84–0.89), between levels of ln THg in hair and ln MeHg in cord blood (r=0.94, 95% CI: 0.90–0.96) and between ln THg levels in cord blood and ln THg levels in breast milk (r=0.36, 95% CI: 0.25–0.47). Spearman's rank correlations between the frequency of fish consumption and THg in hair (r_s=0.35, 95% CI: 0.28–0.42), and between the frequency of fish consumption and THg in cord blood (r_s=0.43, 95% CI: 0.36–0.51) or MeHg in cord blood (r_s=0.31, 95% CI: 0.06–0.52) were weak. This could be due to the approximate information on fish consumption obtained from the questionnaires, the high variability of MeHg concentrations in fish and a relatively high proportion of inorganic mercury in the biomarkers which originates from sources other than fish. In conclusion, THg levels in cord blood, THg levels in hair and MeHg levels in cord blood are suitable biomarkers of low-level Hg exposure through fish consumption. Compared to cord blood, hair samples are easy to collect, store and analyse.     

Urinary mercury and biomarkers of early renal dysfunction in environmentally and occupationally exposed adults: a three-country study

We conducted a cross-sectional study in Sweden, Italy and Poland to assess environmental and occupational exposure to mercury from chloralkali (CA) plants and the potential association with biomarkers of early renal dysfunction. Questionnaire data and first-morning urine samples were collected from 757 eligible subjects. Urine samples were analysed for mercury corrected for creatinine (U-HgC), alpha-1-microglobulin (A1M), N-acetyl-β-glucosaminidase (NAG) and albumin. Determinants of urinary mercury excretion were examined. Levels of kidney markers were compared in three U-HgC categories, and differences were tested taking age and other covariates into account. In the general population, the median U-HgC was higher in Italian (1.2 μg/g C) than in Polish (0.22 μg/g C) or Swedish (0.21 μg/g C) subjects, and no effect of living close to CA plants could be shown. Dental amalgam, chewing on amalgam, and fish consumption were positively associated with U-HgC. In subjects from the general population, no effects on the kidney markers could be detected, while in men, including workers occupationally exposed to mercury, U-HgC was positively associated with the kidney markers, especially with NAG, but to some extent also with A1M and albumin. Differences in urinary mercury and kidney markers in the general population between three studied countries could possibly be due to dietary factors, increased susceptibility to mercury at low selenium intake or co-exposure to other nephrotoxic metals.     

Comparison of carotenoid and anthocyanin profiles of raw and boiled Solanum tuberosum and Solanum phureja tubers

Tubers of the closely related species Solanum tuberosum (potatoes) and Solanum phureja belong to the staff of life for humans. The coloration of the often very colorful tubers is caused by carotenoids (especially xanthophylls) and anthocyanins. The new S. phureja cultivars Mayan Gold and Mayan Twilight, the new S. tuberosum cultivar Red Laura and the traditional S. tuberosum variety Shetland Black were analyzed for their pigment content. The dominant anthocyanin in the red-skinned cultivars Red Laura and Mayan Twilight was characterized as pelargonidin-3-coumarylrutinoside-5-glucoside by LC-ESI-MS. The blue pigment of the Shetland Black cultivar was petunidin-3-coumaroylrutinoside-5-glucoside. Red Laura contained 10 mg anthocyanins g⁻¹ dry weight and Shetland Black 31 mg anthocyanins g⁻¹ dry weight. The main carotenoids in raw tubers are 9-cis-violaxanthin, lutein and one unidentified carotenoid in all S. tuberosum and S. phureja cultivars. Minor compounds were identified as neoxanthin and neochrome. Additionally, zeaxanthin and one further unidentified carotenoid could be found in Red Laura and Mayan Gold. No differences in the carotenoid composition between peel and parenchyma could be found. Total carotenoid content ranged from 2.57 ± 0.53 μg g⁻¹ dry weight in Shetland Black to 14.77 ± 2.22 μg g⁻¹ dry weight in Red Laura (calculated as β-carotene-equivalents). In heat processed tubers, high amounts of carotenoids either changed from all-trans to 9-cis and 13-cis-isomeric form or was degraded. The total pigment content was decreased by heat processing in all cultivars. 8.23 ± 2.98 μg g⁻¹ dry weight could be found in Mayan Twilight and 1.51 ± 0.31 μg carotenoids g⁻¹ dry weight in Shetland Black.     

Residues of organochlorine pesticides (OCPs) in upper reach of the Huaihe River, East China

Residues of HCHs and DDTs in surface water and suspended particulate matter (SPM) from upper reach of the Huaihe River, East China, were investigated. Levels of total HCHs (∑HCH) and total DDTs (∑DDT) in water detected by GC-ECD ranged from 0.85 to 12.77 ng L⁻¹ and from 3.54 to 33.59 ng L⁻¹, respectively. According to European and America water quality guidelines, HCHs were within safe levels while DDT would pose adverse biological effects. Distribution of OCPs in water indicated that input of tributaries was important factor for the Huaihe River. For OCPs in SPM, concentrations varied from 1.01 to 25.22 ng g⁻¹ for ∑HCH and not detected to 4.74 ng g⁻¹ for ∑DDT. Compared with sediment quality guidelines, HCHs and DDTs might have an ecological risk. The main reason for OCPs residues in the Huaihe River was usage of lindane and technical DDT. Furthermore, composition of DDTs reflected fresh inputs of dicofol mixture in some sites.     

Metallothionein role in the kinetic model of copper accumulation and elimination in the clam Ruditapes decussatus

In order to clarify the role of metallothioneins (MT) in copper (Cu) toxicity, this work aimed to assess the involvement of this protein in the accumulation and elimination strategies of Cu in the clam Ruditapes decussatus exposed to two sublethal concentrations (25 and 50 μg Cu l⁻¹). The behaviour of MT in three different tissues of clams during the accumulation and depuration processes was also followed by gel-filtration chromatography to assess if Cu was bound to MT or to other cytosolic components.The 96 h LC₅₀ for water-borne copper was 715 μg L⁻¹ in R. decussatus. The Cu accumulation pattern was dependent on Cu exposure concentrations. In clams exposed to 25 μg l⁻¹, total Cu accumulation in the three tissues increased linearly during the exposure period, while in those exposed to 50 μg l⁻¹ it followed the first order kinetic model. The greatest amount of Cu accumulated in all tissues is associated to the low molecular weight cytosolic fraction (>50%). The chromatographic assay indicated that Cu in the cytosolic fraction is bound to MT and MT levels increase with the increase of Cu exposure confirming the binding affinity of Cu to MT in all tissues. However, a smaller percentage of Cu seems to be bond to other ligands, such as GSH. Copper was exponentially eliminated (only studied in clams exposed to 25 μg l⁻¹) and the estimated half-life was tissue dependent (9, 5 and 14 days for the gills, digestive gland and remaining tissues, respectively). Copper bound to the thermostable compounds was eliminated more quickly (t_1/2=4-7 days) in all tissues than those bound to the thermolabile compounds (t_1/2=7-18 days). Interestingly, MT is rapidly degraded (t_1/2=7 and 18 days), suggesting that this protein is actively involved in the elimination of this metal, through the Cu-MT complex since MT and Cu are turning over simultaneously.Therefore, when Cu exposure is low, the clam can cope efficiently with the excess of Cu levels by increasing MT induction as well as rapidly eliminating this metal via the MT-Cu complex. Copper toxicity in the clam R. decussatus is associated to the limited capacity of MT induction at higher and environmental unrealistic Cu exposures especially in the gills and remaining tissues.     

Elemental mercury in urine from workers exposed to mercury vapor

Summary Elemental mercury (Hg°) in urine samples from workers in thermometer manufacturing factories was determined. In a factory in which the mercury level in the ambient air averaged more than 0.1 mg Hg m^–3, the Hg° concentration in the workers' urine ranged between 0.05 and 1.7 g Hg 1^–1 and constituted less than 1% of the inorganic mercury (In-Hg) in urine. Higher amounts of Hg° could be detected in urine on the day of the filling operation when thermometer blanks were filled with metallic mercury and on the following day when compared with other days. During this operation, the workers were exposed to mercury vapor levels with as much as 0.47–0.67 mg Hg m^–3. Our findings suggest that Hg° appears in urine quite rapidly after the worker's exposure to unusually high mercury levels.     

Study of selenium intake and disposition in various matrices based on mathematical algorithms derived from pooled biomonitoring data

Biomonitoring is increasingly used to assess exposure to selenium (Se) in the population. However, there is little harmonization among protocols used in the different studies (varying biological matrices, differences in expression of results (concentrations versus amounts, units)). This makes inter-comparison of biomonitoring results across studies difficult. From a public health risk perspective, it also becomes challenging to estimate baseline levels in biological matrices for populations exposed by various sources. The aim of this study was thus to perform a systematic analysis of the relationship between Se intakes and biological concentrations based on published data. Inclusion and exclusion criteria were used and led to select 75 published biomonitoring data in humans from an extended review of Se biomonitoring studies. This represents 8 628 individuals who provided biological samples aiming at documenting Se exposure and/or Se concentrations in two or more biological matrices. Mathematical algorithms that relate Se intakes to biological concentrations and establish matrix-to-matrix associations were derived from these pooled biomonitoring data. Logarithmic regressions showed good correlations between Se intakes and whole blood concentrations (R² = 0.884), plasma concentrations (R² = 0.863) and urinary excretion rates (R² = 0.958). Blood and plasma concentrations were also strongly related (R² = 0.874), as were whole blood concentrations and urinary excretion rates (R² = 0.953). The interpretation of the log-regression coefficients allowed illustrating Se physiology. Se concentrations in plasma tend to plateau when daily intake exceed 150 μg/d, whereas Se in urine increases rapidly above this threshold. The application of the algorithms to other independent data sets in order to reconstruct past Se intakes confirmed that interpretation of results on the basis of Se in integuments may be misleading if external contamination is not avoided. This approach based on pooled data covered a wide range of exposure and the large number of data integrated increased the level of confidence of results.     

Chitobiase activity as an indicator of altered survival, growth and reproduction in Daphnia pulex and Daphnia magna (Crustacea: Cladocera) exposed to spinosad and diflubenzuron

Chitobiase is involved in exoskeleton degradation and recycling during the moulting process in arthropods. In aquatic species, the moulting fluid is released into the aqueous environment, and chitobiase activity present therein can be used to follow the dynamics of arthropod populations. Here, chitobiase activity was used for monitoring the impact of mosquito candidate larvicides on Daphnia pulex and Daphnia magna under laboratory conditions. Both species were exposed to spinosad (2, 4, 8 μg L⁻¹) and diflubenzuron (0.2, 0.4, 0.8 μg L⁻¹) for 14 days. Bacillus thuringiensis var. israelensis (Bti; 0.25, 0.5, 1 μL L⁻¹) was used as the reference larvicide. Chitobiase activity, adult survival, individual growth and fecundity, expressed as the number of neonates produced, were measured every 2 days. Average Exposure Concentrations of spinosad were ten-fold lower than the nominal concentrations, whereas only a slight deviation was observed for diflubenzuron. In contrast to Bti, spinosad and diflubenzuron significantly affected both species in terms of adult survival, and production of neonates. As compared to D. pulex, D. magna was more severely affected by diflubenzuron, at low and medium concentrations, with reduced adult growth and much lower chitobiase activity. Chitobiase activity was positively correlated with the individual body length, number of neonates produced between two consecutive observation dates, and number of females and neonates. In addition, the significant positive correlations between chitobiase activity measured on the last sampling date before the first emission of neonates and the cumulative number of neonates produced during the whole observation period strongly support the potential of the activity of this chitinolytic enzyme as a proxy for assessing the dynamics of arthropod populations exposed to larvicides used for mosquito control.