Anthropogenic contributions to mercury levels in present-day Arctic animals—A review

Background

Because of concern about the recently increasing levels of biological Hg in some areas of the Arctic, we examined the literature concerning the long-term changes of Hg in humans and selected Arctic marine mammals and birds of prey since pre-industrial times (i.e. before 1800 A.D.), to determine the anthropogenic contribution to present-day Hg concentrations and the historical timing of any changes.

Methods

Mercury data from published articles were extracted on historical and pre-industrial concentrations as percentages of the recent maximum, as well as the man-made contribution was calculated and depicted in a uniform manner to provide an overview of the development over time.

Results and discussion

Trends of [Hg] in hard tissues such as teeth, hair and feathers consistently showed that there had been an order-of-magnitude increase of [Hg] in Arctic marine foodweb-based animals that began in the mid- to late-19th Century and accelerated in the 20th Century. The median man-made contribution to present-day Hg concentrations was 92.4% ranging from 74.2 to 94.4%. Confidence in our data was increased by accompanying data in some studies on stable isotopes (δ¹³C, δ¹⁵N), which allowed us to normalize where necessary for changes in animal trophic position and feeding location over time, and by careful attention to the possibility of sample chemical diagenesis (Hg contamination or loss) which can alter the Hg content of ancient hard tissues.

Conclusions

Wildlife hard tissue matrices provide consistent information with respect to the steep onset of Hg exposure of Arctic wildlife beginning in the latter half of the 19th Century. Today the man-made contribution was found to be above 92%. Stable isotope analyses provide important information to normalize for possible changes in diet over time, and are highly relevant to include when interpreting temporal trends, baseline concentrations as well as man-made anthropogenic contribution of Hg.     

Methyl mercury production and loss in Arctic soil

Mercury has been found in polar bears and other top predators in the Arctic at concentrations that pose a risk to the indigenous population, however, the means by which this occurs is uncertain. There has been extensive research on the atmospheric cycling of mercury but little is known about mercury cycling in Arctic terrestrial ecosystems. The objective of this study was to determine whether wet sedge meadow soils within the Truelove Lowlands, Devon Island, NT, Canada (75° 33′N, 84° 40′N) were acting as sources or sinks for methylmercury (MeHg). Over the course of an Arctic summer, MeHg concentrations and other biophysical characteristics were measured at four wet sedge meadows over a 19 day study period that commenced approximately 1 month after snowmelt. Soil MeHg concentrations declined during the study period, indicating a net loss of MeHg over the summer. The dominant ligand in solution appeared to be dissolved organic matter, little sulfide was detected, and it would seem that most of the mercury was unavailable for methylation during the summer sampling period. In soil microcosms, spiked with 5.0 nmol g^− 1 (1 µg g^− 1) HgCl₂, the soil did methylate mercury suggesting that there is the potential for mercury methylation. We also noted significant spatial variability in MeHg concentrations between catenas that could not be explained by other biophysical parameters, which are known to affect methylation. Given our data and previous geochemical data collected from suprapermafrost groundwater during snowmelt, it seems likely that methylation may occur during the spring melt period in the arctic. Furthermore the geochemical variability of the melt water may lead to the spatial variability observed in MeHg concentrations in this study.     

Impact of cement factory operations on air quality and human health in Ewekoro Local Government Area,South-Western Nigeria

The concentrations of pollutants associated with cement production and the effects on ambient air and community health were assessed in this study. Suspended particulates were monitored using a Negretti 1000^TM air sampler. Additionally, an Ogawa^TM sampler was employed to assess levels of selected gaseous pollutants at selected sites. To collect data on health status, a questionnaire survey was used for selected neighbouring communities and clinic records for industry workers. The data were analysed with the aid of percentage, variation test, correlation and regression statistics. Mean concentrations of particulate matter of 10?μ (74–338?μg/m³) and 2.5?μ (28–116?μg/m³) were significantly higher than permissible limits (50?μg/m³ and 10?μg/m³) within and around the production plant. At all sites, levels of sulphur dioxide (0.1–12?ppb), nitrogen dioxide (0.1–13?ppb) and carbon monoxide (0.1–1.7?ppm) were below the allowable limits for human exposure. Analysis of variance showed significant spatial variations (p?相似文献   

The short-term effect of air pollution on cardiovascular mortality in Tianjin, China: comparison of time series and case-crossover analyses

Background

Many studies have illustrated that ambient air pollution negatively impacts on health. However, little evidence is available for the effects of air pollution on cardiovascular mortality (CVM) in Tianjin, China. Also, no study has examined which strata length for the time-stratified case-crossover analysis gives estimates that most closely match the estimates from time series analysis.

Objectives

The purpose of this study was to estimate the effects of air pollutants on CVM in Tianjin, China, and compare time-stratified case-crossover and time series analyses.

Method

A time-stratified case-crossover and generalized additive model (time series) were applied to examine the impact of air pollution on CVM from 2005 to 2007. Four time-stratified case-crossover analyses were used by varying the stratum length (Calendar month, 28, 21 or 14 days). Jackknifing was used to compare the methods. Residual analysis was used to check whether the models fitted well.

Results

Both case-crossover and time series analyses show that air pollutants (PM₁₀, SO₂ and NO₂) were positively associated with CVM. The estimates from the time-stratified case-crossover varied greatly with changing strata length. The estimates from the time series analyses varied slightly with changing degrees of freedom per year for time. The residuals from the time series analyses had less autocorrelation than those from the case-crossover analyses indicating a better fit.

Conclusion

Air pollution was associated with an increased risk of CVM in Tianjin, China. Time series analyses performed better than the time-stratified case-crossover analyses in terms of residual checking.     

Mercury pollution in an estuarine region and its effect on a coastal population

Studies were conducted on sediments and organisms from two estuarine regions, viz. Thana Creek and Ulhas Estuary, for Hg pollution. Higher concentration of Hg were recorded in surface sediments at stations situated nearby the effluents discharge points of major industries. Levels of Hg in sediments decreased from head to mouth region. Hg concentration in organisms was found to be highest in benthic filter feeders and detritus feeders. The concentration ratio of Hg in organisms was observed to be very high in prawn, fish, crab and bivalves. The blood Hg level in people in the region showed a strong dependence on quantitative consumption of fish by the individuals. The study revealed a 3 to 4‐fold increase in blood Hg content of fish eaters over non‐fish eaters.     

Mercury and methylmercury concentrations in high altitude lakes and fish (Arctic charr) from the French Alps related to watershed characteristics

Total mercury (THg) and methylmercury (MeHg) concentrations were measured in the muscle of Arctic charr (Salvelinus alpinus) and in the water column of 4 lakes that are located in the French Alps. Watershed characteristics were determined (6 coverage classes) for each lake in order to evaluate the influence of watershed composition on mercury and methylmercury concentrations in fish muscle and in the water column. THg and MeHg concentrations in surface water were relatively low and similar among lakes and watershed characteristics play a major role in determining water column Hg and MeHg levels. THg muscle concentrations for fish with either a standardized length of 220 mm, a standardized age of 5 years or for individualuals did not exceed the 0.5 mg kg^− 1 fish consumption advisory limit established for Hg by the World Health Organization (WHO, 1990). These relatively low THg concentrations can be explained by watershed characteristics, which lead to short Hg residence time in the water column, and also by the short trophic chain that is characteristic of mountain lakes. Growth rate did not seem to influence THg concentrations in fish muscles of these lakes and we observed no relationship between fish Hg concentrations and altitude. This study shows that in the French Alps, high altitude lakes have relatively low THg and MeHg concentrations in both the water column and in Arctic charr populations. Therefore, Hg does not appear to present a danger for local populations and the fishermen of these lakes.     

Temporal trends of Hg in Arctic biota, an update

A statistically robust method was applied to 83 time-series of mercury in Arctic biota from marine, freshwater and terrestrial ecosystems with the purpose of generating a ‘meta-analysis’ of temporal trend data collected over the past two to three decades, mostly under the auspices of the Arctic Monitoring and Assessment Program (AMAP). Sampling locations ranged from Alaska in the west to northern Scandinavia in the east. Information from recently published temporal trend studies was tabulated to supplement the results of the statistical analyses. No generally consistent trend was evident across tissues and species from the circumpolar Arctic during the last 30 years or so. However, there was a clear west-to-east gradient in the occurrence of recent increasing Hg trends, with larger numbers and a higher proportion of biotic datasets in the Canadian and Greenland region of the Arctic showing significant increases than in the North Atlantic Arctic. Most of the increasing datasets were for marine species, especially marine mammals. A total of 16 (19%) out of the 83 time-series could be classified as “adequate”, where adequate is defined as the number of actual monitoring years in a time-series being equal to or greater than the number of years of sampling required to detect a 5% annual change in Hg concentrations, with a significance level of P < 0.05 and 80% statistical power. At the time of the previous AMAP Assessment, only 10% of the Hg time-series were deemed adequate. If an additional 5 years of data were to be added to the current set of time-series, it is predicted that 53% of time-series would become adequate.     

Mercury in the Mackenzie River delta and estuary: Concentrations and fluxes during open-water conditions

Estimates of mercury (Hg) loadings to the Arctic Ocean from circumpolar rivers have not considered biogeochemical changes that occur when river water is temporarily stored in large deltas (delta effect). There are also few data describing Hg changes across the freshwater-saltwater transition zone (FSTZ) of these rivers. We assessed temporal changes in unfiltered total mercury (THg) and methylmercury (MeHg) concentrations during open-water 2004 in the Mackenzie River upstream of the Mackenzie River delta, and in 6 floodplain lakes across an elevation gradient. These data were used to calculate Hg fluxes from the Mackenzie River and to evaluate a delta effect on Hg using an estimate of delta river water storage and a mixing analysis. Mean THg concentrations were highest in river water (9.17 ± 5.51 ng/L) and decreased up the lake elevation gradient. Mean MeHg concentrations were highest in lakes periodically connected to the river (0.213 ± 0.122 ng/L) and MeHg concentrations in elevated lakes showed a mid-summer peak. Results from the mixing analysis showed that the delta effect may be large enough to affect Hg loadings to the Arctic Ocean. THg concentrations exiting the delta (10.2 ng/L) were 16% lower than those entering (12.1 ng/L), whereas MeHg showed little change. We calculated 2.5-month (open-water) THg and MeHg fluxes from the Mackenzie River of 1208 and 8.4 kg. These fluxes are similar in magnitude to previous annual estimates in the arctic literature suggesting that previously published annual Hg fluxes from the Mackenzie River may be large underestimates. We also assessed changes in Mackenzie River water THg and MeHg concentrations as it crossed the FSTZ during an open-water cruise. THg decreased non-conservatively across the estuary from 3.8-0.6 ng/L, possibly due to mixing and particle settling. MeHg concentrations were variable and near detection. Our results show that the Mackenzie River estuary is a dynamic environment and may have important controls on Hg delivered to the Arctic Ocean.     

Application of land use regression to regulatory air quality data in Japan

A land use regression (LUR) model has been used successfully for predicting traffic-related pollutants, although its application has been limited to Europe and North America. Therefore, we modeled traffic-related pollutants by LUR then examined whether LUR models could be constructed using a regulatory monitoring network in Shizuoka, Japan. We used the annual-mean nitrogen dioxide (NO₂) and suspended particulate matter (SPM) concentrations between April 2000 and March 2006 in the study area. SPM accounts for particulate matter with an aerodynamic diameter less than 8 μm (PM₈). Geographic variables that are considered to predict traffic-related pollutants were classified into four groups: road type, traffic intensity, land use, and physical component. Using geographical variables, we then constructed a model to predict the monitored levels of NO₂ and SPM. The mean concentrations of NO₂ and SPM were 35.75 μg/m³ (standard deviation of 11.28) and 28.67 μg/m³ (standard deviation of 4.73), respectively. The final regression model for the NO₂ concentration included five independent variables. R² for the NO₂ model was 0.54. On the other hand, the regression model for the SPM concentration included only one independent variable. R² for the SPM model was quite low (R² = 0.11). The present study showed that even if we used regulatory monitoring air quality data, we could estimate NO₂ moderately well. This result could encourage the wide use of LUR models in Asian countries.     

Assessing air quality in Hong Kong: A proposed,revised air pollution index (API)

The Environment Protection Department of Hong Kong has been using an air pollution index (API) to report the status of ambient air quality since 1995. Such an index system was first developed by the USA Environmental Protection Authority. The API compares five main air pollutants, i.e. sulfur dioxide (SO₂), respirable suspended particulates (RSP), nitrogen dioxide (NO₂), carbon monoxide (CO) and Ozone (O₃) as sub-indexes, which are calculated separately from a segmented linear function that transforms ambient pollutants concentrations into a normalized scale extending from 0 to 500. The resultant pollution level is described by the maximal value of these five sub-indexes. The limitation of this API system is that it considers only one pollutant with the maximum value at a time but reflects other pollutants concurrently. In this study, a revised air quality index (RAPI) is proposed based on the entropy function, which combines the effect of all pollutants on public health. The design of the revised index is based on database of air pollutants collected at two air quality monitoring stations in Hong Kong, i.e. a roadside station in Mong Kok and a general station in Sha Tin. Compared with the existing API, values of RAPI (calculated from data collected for API) at both stations are at higher levels and provide more information of levels of all pollutants. Therefore, RAPI should be representatively and widely used to provide the public with a better indicator of air quality. In addition, variations and oscillations of pollutants concentrations were also examined and the results show that RSP and NO₂ contribute more to the overall pollution level than other components. It is suggested that more abatement strategies be focused on these pollutants to improve air quality in the future.     

Particulate matter concentrations in residences: an intervention study evaluating stand-alone filters and air conditioners

This study, a randomized controlled trial, evaluated the effectiveness of free-standing air filters and window air conditioners (ACs) in 126 low-income households of children with asthma. Households were randomized into a control group, a group receiving a free-standing HEPA filter placed in the child's sleeping area, and a group receiving the filter and a window-mounted AC. Indoor air quality (IAQ) was monitored for week-long periods over three to four seasons. High concentrations of particulate matter (PM) and carbon dioxide were frequently seen. When IAQ was monitored, filters reduced PM levels in the child's bedroom by an average of 50%. Filter use varied greatly among households and declined over time, for example, during weeks when pollutants were monitored, filter use was initially high, averaging 84±27%, but dropped to 63±33% in subsequent seasons. In months when households were not visited, use averaged only 34±30%. Filter effectiveness did not vary in homes with central or room ACs. The study shows that measurements over multiple seasons are needed to characterize air quality and filter performance. The effectiveness of interventions using free-standing air filters depends on occupant behavior, and strategies to ensure filter use should be an integral part of interventions. PRACTICAL IMPLICATIONS: Environmental tobacco smoke (ETS) increased particulate matter (PM) levels by about 14 μg/m3 and was often detected using ETS-specific tracers despite restrictions on smoking in the house as reported on questionnaires administered to caregivers. PM concentrations depended on season, filter usage, relative humidity, air exchange ratios, number of children, outdoor PM levels, sweeping/dusting, and presence of a central air conditioner (AC). Free-standing air filters can be an effective intervention that provides substantial reductions in PM concentrations if the filters are used. However, filter use was variable across the study population and declined over the study duration, and thus strategies are needed to encourage and maintain use of filters. The variability in filter use suggests that exposure misclassification is a potential problem in intervention studies using filters. The installation of a room AC in the bedroom, intended to limit air exchange ratios, along with an air filter, did not lower PM levels more than the filter alone.     

Mercury recovery in situ of four different dental amalgam separators

Amalgam separators are used to physically remove dental amalgam from waste water in dental clinics. They are thereby supposed to reduce mercury (Hg) emissions to the municipal waste water system to acceptable levels. We here present results from a comparative study in situ of three amalgam separators available on the market, all with a claimed efficiency of 99% according to Danish and ISO protocols, and using sedimentation as the principle of separation. We also present corresponding data for an investigational prototype of an improved separator. The obtained efficiency of the three commercial separators is far below what is stated by the manufacturer and by authorities assumed to be the efficiency in clinical conditions. They reduced Hg emissions by 79 - 91%, leaving an average Hg content in outgoing waste water of 1.5 mg L(-1). However, the prototype separator participating in this study retained 99.9% of the waste water Hg emissions, leaving an average Hg content in outgoing waste water of 0.004 mg L(-1). Physical restrictions prohibit sedimentary type separators to recover the Hg fractions causing the largest damages in wastewater treatment plants. This fraction is not considered in the ISO protocol for testing amalgam separators, which therefore needs to be revised. Abolishing the use of dental amalgam and cleaning the tubing systems is the most efficient long-term solution to reduce Hg emissions from dental clinics. Until then, Hg emissions originating from placing, polishing or removing existing amalgam fillings, should be counteracted by the use of low-emission amalgam separators, already on the market or presently being developed for use alone or together with sedimentary type amalgam separators.     

The delivery of mercury to the Beaufort Sea of the Arctic Ocean by the Mackenzie River

Very high levels of mercury (Hg) have recently been reported in marine mammals and other higher trophic-level biota in the Mackenzie Delta and Beaufort Sea of the western Arctic Ocean. To quantify the input of Hg (particulate, dissolved and methylated) by the Mackenzie River as a potential source for Hg in the ecosystem, surface water and sediment samples were taken from 79 sites in the lower Mackenzie Basin during three consecutive summers (2003-2005) and analyzed for Hg and methylmercury (MeHg). Intensive studies were also carried out in the Mackenzie Delta during the freshets of 2004 and 2005. Large seasonal and annual variations were found in Hg concentrations in the river, coincident with the variations in water discharge. Increased discharges during spring freshet and during the summers of 2003 and 2005 compared to 2004 were mirrored by higher Hg concentrations. The correlation between Hg concentration and riverflow suggests additional Hg sources during periods of high water, potentially from increased surface inundation and increased bank erosion. The increase in the Hg concentration with increasing water discharge amplifies the annual Hg and MeHg fluxes during high water level years. For the period 2003-2005, the Hg and MeHg fluxes from the Mackenzie River to the Beaufort Sea averaged 2.2 tonnes/yr and 15 kg/yr, respectively, the largest known Hg source to the Beaufort Sea. More than half of the mercury flux occurs during the short spring freshet season which coincides with the period of rapid growth of marine biota. Consequently, the Mackenzie River input potentially provides the major mercury source to marine mammals of the Beaufort Sea. The Hg and MeHg fluxes from the Mackenzie River are expected to further increase with the projected climate warming in the Mackenzie Basin.     

Mercury regulation, fate, transport, transformation, and abatement within cement manufacturing facilities: review

The USEPA's 2010 mercury rule, which would reduce emissions from non-hazardous waste burning cement manufacturing facilities by an estimated 94%, represents a substantial regulatory challenge for the industry. These regulations, based on the performance of facilities that benefit from low concentrations of mercury in their feedstock and fuel inputs (e.g., limestone concentration was less than 25 ppb at each facility), will require non-compliant facilities to develop innovative controls. Control development is difficult because each facility's emissions must be assessed and simple correlation to mercury concentrations in limestone or an assumption of ‘typically observed’ mercury concentrations in inputs are unsupported by available data. Furthermore, atmospheric emissions are highly variable due to an internal control mechanism that captures and loops mercury between the high-temperature kiln and low-temperature raw materials mill. Two models have been reported to predict emissions; however, they have not been benchmarked against data from the internal components that capture mercury and do not distinguish between mercury species, which have different sorption and desorption properties. Control strategies include technologies applied from other industries and technologies developed specifically for cement facilities. Reported technologies, listed from highest to lowest anticipated mercury removal, include purge of collected dust or raw meal, changes in feedstocks and fuels, wet scrubbing, cleaning of mercury enriched dust, dry sorbent injection, and dry and semi-dry scrubbing. The effectiveness of these technologies is limited by an inadequate understanding of sorption, desorption, and mercury species involved in internal loop mercury control. To comply with the mercury rule and to improve current mercury control technologies and practices, research is needed to advance fundamental knowledge regarding mercury species sorption and desorption dynamics on materials within cement facilities.     

Short-term impact of particulate matter (PM2.5) on daily mortality among the over-75 age group in Madrid (Spain)

Background

The 2006 World Health Organization Air Quality Guidelines recommend using particulate matter having a diameter of under 2.5 micra (PM_2.5) rather than PM₁₀ as an indicator of air particle concentration, a pattern followed by new European directives. Nevertheless, few studies have analysed this new indicator's impact at a European level on daily mortality among a high-risk group, such as persons aged over 75 years.

Objective

This study sought to analyse and quantify the effect of PM_2.5 on daily cause-specific mortality among the over-75 age group in the city of Madrid.

Methods

Using Poisson regression with Generalized Additive Models (GAM), a longitudinal, ecological time-series study examined the following causes of death: all causes except accidents (International Classification of Diseases-9th revision (ICD 9): 1-799); circulatory causes (ICD 9: 390-459); and respiratory causes (ICD 9: 460-519). These were adjusted for other chemical, biotic and acoustic pollutants. Further control variables considered were: trend; seasonality; influenza epidemics; and autocorrelation between mortality series.

Results

A significant statistical association was detected between daily mean PM_2.5 particle concentrations and all-cause mortality in the city of Madrid. This association was not in evidence for PM₁₀ concentrations. The Relative Risks found for an increase of 25 µg/m³ in PM_2.5 concentrations were as follows: all-cause mortality, 1.057 (1.025-1.088); circulatory-cause mortality, 1.088 (1.041-1.135); and respiratory-cause mortality, 1.122 (1.056-1.189). The Attributable Risks were 5.41%, 8.12% and 10.90% respectively. This effect was observed in the short term (lags 1-2).

Conclusion

Our results indicate a strong impact of PM_2.5 concentrations on daily mortality among the over-75 age group in Madrid, and underscore the need for measures aimed at lowering the concentration levels of this primary air pollutant in large cities, particularly by reducing motor vehicle traffic, the main source of such pollutant emission in urban atmospheres.     

Biomagnification of mercury in selected species from an Arctic marine food web in Svalbard

Concentrations and biomagnification of total mercury (TotHg) and methyl mercury (MeHg) were studied in selected species from the pelagic food web in Kongsfjorden, Svalbard. Twelve species of zooplankton, fish and seabirds, were sampled representing a gradient of trophic positions in the Svalbard marine food web. TotHg and MeHg were analysed in liver, muscle and/or whole specimens. The present study is the first to provide MeHg levels in seabirds from the Svalbard area. The relative MeHg levels decreased with increasing levels of TotHg in seabird tissues. Stable isotopes of nitrogen (δ¹⁵N) were used to determine the trophic levels and the rate of biomagnification of mercury in the food web. A linear relationship between mercury levels and trophic position was found for all seabird species combined and their trophic level, but there was no relationship within species. Biomagnification factors were all > 1 for both TotHg and MeHg, indicating biomagnification from prey to predator. TotHg levels in the different seabirds were similar to levels detected in the Kongsfjorden area in the 1990s.     

An isotopic investigation of mercury accumulation in terrestrial food webs adjacent to an Arctic seabird colony

At Cape Vera (Devon Island, Nunavut, Canada), a seabird colony of northern fulmars (Fulmarus glacialis) congregates and releases nutrients through the deposition of guano to the coastal terrestrial environment, thus creating nutrient-fertilized habitats important to insects, birds, and mammals. Here we determined whether mercury was similarly enriched in various terrestrial food web components in this High Arctic coastal ecosystem due to seabird inputs. Stable isotopes (δ¹⁵N, δ¹³C) were used to identify trophic linkages and possible routes of contaminant transfer in the food web. Values of δ¹⁵N were significantly higher in lichens and certain plants collected closer to the bird colony, demonstrating a gradient of seabird influence, and were higher at Cape Vera than our reference site at Cape Herschel, on eastern Ellesmere Island, an area relatively unaffected by seabirds. In contrast, δ¹³C showed little variation among terrestrial species, suggesting minimal influence by seabirds. Concentrations of total mercury (THg) in primary producers and phyto/zooplankton were not significantly correlated with distance from the seabird colony or δ¹⁵N values, and were similar to other taxa from the High Arctic. Our results provide novel data on THg in several Arctic taxa where concentrations have not been reported previously. Moreover, the analyses indicate that δ¹⁵N is significantly enriched in the adjacent environment by guano fertilization, but our study was unable to show an enrichment of THg and δ¹³C in the terrestrial food web near the seabird colony.     

Ambient air pollution and daily mortality in Anshan, China: a time-stratified case-crossover analysis

Few case-crossover studies were conducted in China to investigate the acute health effects of air pollution. We conducted a time-stratified case-crossover analysis to examine the association between air pollution and daily mortality in Anshan, a heavily-polluted industrial city in northeastern China. Daily mortality, air pollution, and weather data in 2004-2006 in Anshan were collected. Time-stratified case-crossover approach was used to estimate the effect of air pollutants (PM₁₀, SO₂, NO₂ and CO) on total and cardiopulmonary mortality. Controls were selected as matched days of the week in the same month. Potential effect modifiers, such as gender and age, were also examined. We found significant associations between air pollution and daily mortality from cardiovascular diseases in Anshan. A 10 μg/m³ elevation of 2-day moving average (lag 01) concentration in PM₁₀, SO₂, NO₂ and CO corresponded to 0.67% (95% CI: 0.29%, 1.04%), 0.38% (95% CI: −0.06%, 0.83%), 2.11% (95% CI: 0.22%, 4.00%) and 0.04% (95% CI: 0.01%, 0.07%) increase of cardiovascular mortality. The associations for total and respiratory mortality were generally positive but statistically insignificant. The air pollution health effects were significantly modified by age, but not by gender. Conclusively, our study showed that short-term exposure to air pollution was associated with increased cardiovascular mortality in Anshan. These findings may have implications for local environmental and social policies.     

Modelling air pollution for epidemiologic research — Part I: A novel approach combining land use regression and air dispersion

A common limitation of epidemiological studies on health effects of air pollution is the quality of exposure data available for study participants. Exposure data derived from urban monitoring networks is usually not adequately representative of the spatial variation of pollutants, while personal monitoring campaigns are often not feasible, due to time and cost restrictions. Therefore, many studies now rely on empirical modelling techniques, such as land use regression (LUR), to estimate pollution exposure. However, LUR still requires a quantity of specifically measured data to develop a model, which is usually derived from a dedicated monitoring campaign. A dedicated air dispersion modelling exercise is also possible but is similarly resource and data intensive.This study adopted a novel approach to LUR, which utilised existing data from an air dispersion model rather than monitored data. There are several advantages to such an approach such as a larger number of sites to develop the LUR model compared to monitored data. Furthermore, through this approach the LUR model can be adapted to predict temporal variation as well as spatial variation. The aim of this study was to develop two LUR models for an epidemiologic study based in Greater Manchester by using modelled NO₂ and PM₁₀ concentrations as dependent variables, and traffic intensity, emissions, land use and physical geography as potential predictor variables. The LUR models were validated through a set aside “validation” dataset and data from monitoring stations.The final models for PM₁₀ and NO₂ comprised nine and eight predictor variables respectively and had determination coefficients (R²) of 0.71 (PM₁₀: Adj. R² = 0.70, F = 54.89, p < 0.001, NO₂: Adj. R² = 0.70, F = 62.04, p < 0.001). Validation of the models using the validation data and measured data showed that the R² decreases compared to the final models, except for NO₂ validation in the measured data (validation data: PM₁₀: R² = 0.33, NO₂: R² = 0.62; measured data: PM₁₀: R² = 0.56, NO₂: R² = 0.86). The validation further showed low mean prediction errors and root mean squared errors for both models.     

Critical review of mercury fates and contamination in the arctic tundra ecosystem

Mercury (Hg) contamination in tundra region has raised substantial concerns, especially since the first report of atmospheric mercury depletion events (AMDEs) in the Polar Regions. During the past decade, steady progress has been made in the research of Hg cycling in the Polar Regions. This has generated a unique opportunity to survey the whole Arctic in respect to Hg issue and to find out new discoveries. However, there are still considerable knowledge gaps and debates on the fate of Hg in the Arctic and Antarctica, especially regarding the importance and significance of AMDEs vs. net Hg loadings and other processes that burden Hg in the Arctic. Some studies argued that climate warming since the last century has exerted profound effects on the limnology of High Arctic lakes, including substantial increases in autochthonous primary productivity which increased in sedimentary Hg, whereas some others pointed out the importance of the formation and postdeposition crystallographic history of the snow and ice crystals in determining the fate and concentration of mercury in the cryosphere in addition to AMDEs. Is mercury re-emitted back to the atmosphere after AMDEs? Is Hg methylation effective in the Arctic tundra? Where the sources of MeHg are? What is its fate? Is this stimulated by human made? This paper presents a critical review about the fate of Hg in the Arctic tundra, such as pathways and process of Hg delivery into the Arctic ecosystem; Hg concentrations in freshwater and marine ecosystems; Hg concentrations in terrestrial biota; trophic transfer of Hg and bioaccumulation of Hg through food chain. This critical review of mercury fates and contamination in the Arctic tundra ecosystem is assessing the impacts and potential risks of Hg contamination on the health of Arctic people and the global northern environment by highlighting and “perspectiving” the various mercury processes and concentrations found in the Arctic tundra.