The toxicity of mercury is dependent on its chemical composition at its point of entry and site of toxicity. Differences in toxicity indicate that inorganic mercury (iHg) and methylmercury (MeHg) mediate adverse reactions via different mechanisms. Based on the available toxicity data, demethylation of MeHg to iHg has proven detrimental as it increases the severity of toxic insult. Accordingly, an in vitro system was established in order to characterize the demethylation reaction using primary astrocytes from neonatal rat cerebellum. Incubation of MeHg with a pro-oxidant increased the rate of demethylation (control vs. rotenone = -1.86±5.57 vs. 16.27±2.68%, p<0.05) and accumulation (control vs. rotenone = 86.53±4.13ng/mg vs. 23.6±3.80ng/mg, p<0.001) relative to control. These findings suggest that demethylation is not only harmful as a result of increased iHg levels, but also because total mercury is increased. In light of rising atmospheric mercury levels, it is important that this pathway be fully characterized.
Human exploitation of earth's ecosystems has impacted the flow of ecological services, many with complex links to human health and well-being. The need to understand and plan for these impacts in an integrative manner is today an imperative. Yet, their integration into the planning process has been largely unsuccessful. In Canada, the Canadian Environmental Assessment Act (CEAA) was established to achieve this integration. Yet, despite decades of effort there has been limited progress in practice. Thus, the aim of this research was to contribute new knowledge and insights to the challenge of integrating a broad range of social and ecological concerns into the environmental planning and management process, focussing on pragmatic solutions. A scoping review of the literature revealed key underlying issues affecting integration. These were discussed and contextualized to the CEAA mandated Environmental Assessment (EA) process, and a number of recommendations made for improved integration. The integration challenge was then examined within a spatial context. Two approaches to integrated spatial analyses were investigated. The first approach focussed on available marine spatial social, ecological, economic and protection legislation data analyzing the data both singly to detect statistically significant clustering of high value or high incidence data (hotspots) and collectively to detect areas of agreement (overlaps). The analyses provided a perspective on the spatial distribution of marine social-ecological-economic hotspots. The integration was, however, challenged by the characteristics of the underlying data including differing approaches to data collection and units of measure. The second approach to integrated spatial analysis was based on expert spatial knowledge of the social-ecological system, and was termed expert informed geographic information systems (xGIS). Important social-ecological spaces were similarly detected using xGIS. It was found that xGIS allowed for a broader range of values to be co
Fish can accumulate high levels of mercury (Hg) and become a human health concern if consumed. The purpose of this study was to develop a risk assessment tool to determine which water bodies from certain areas in Northern British Columbia contain fish with high Hg concentrations. Raw and published data were collected from Health Canada and Ministry of Environment and amalgamated to form a large data set (3097 fish samples from 34 distinct areas between 1974 and 2000). Fish weight was standardized and a cut-off point was determined for each species for high Hg levels. This was used to develop a risk assessment tool unique to the study area to identify which species/water body combinations were high in Hg and how fish consumption strategies can be adapted to minimize exposure. Although high Hg levels were widespread, the majority of contaminated samples were form Pinchi Lake and the Williston Lake area. --Leaf ii.
Exposure to contaminants during pregnancy is associated with certain adverse birth outcomes that require further investigation. Community reproductive and environmental health risk maps were produced utilizing birth data obtained from the B.C. Perinatal Health Program and environmental contaminant data from the National Pollutant Release inventory and other national and provincial sources. Geographical information systems (GIS) were utilized to spatially relate perinatal and environmental hazard data, and the risk of adverse birth outcomes was tested using watersheds as the ecological aggregation unit adjusting for individual-level risk factors. The perinatal data included birth outcomes (low birth weight, prematurity, inter-uterine growth restriction, congenital anomalies, stillbirths) and numerous maternal and antenatal risk factor data for all singleton births in B.C. from 2001 to 2006. Small but significant increased risks of adverse birth outcomes were found in high and intermediate hazard watersheds compared to low hazard watersheds. This suggests a possible environmental effect on these reproductive outcomes, however, further studies are needed to corroborate these results. --P.ii.
Methylmercury (MeHg) is a well-known neurotoxicant but the diverse mechanistic events associated with MeHg neurotoxicity have yet been fully elucidated. In this study, we explored the mechanisms of MeHg neurotoxicity particularly its possible roles in neurodegenerative diseases like Parkinson’s disease (PD) using dopaminergic neuronal cells and a non-human primate model. In the cell culture model, we compared effects of MeHg to those induced by 1-methyl-4-phenylpyridinium (MPP⁺), a well-established drug that can induce Parkinsonism-like symptoms. A proteomic approach was used to identify and analyze MeHg affected proteins and their biological functions and associated pathways in both the cellular and marmoset models. Our results showed that MeHg induced changes of gene/protein profiles are similar to the effects as MPP⁺. Evidence from proteomic results suggested MeHg caused neurodegenerative effects not only associated with PD but also other neurodegenerative disorders such as Huntington’s disease (HD), Alzheimer’s disease (AD), and amyotrophic lateral sclerosis (ALS). We also found brain regional specific response to MeHg stimuli, based on the protein profiles affected in the following order: cerebellum > occipital lobe (OL) > frontal lobe (FL) of the cerebrum. In the cerebellum, carbohydrate derivative metabolic process, synaptic transmission, cell development and calcium signalling are dominant functions and pathways contributing to the motor deficit in MeHg-treated marmoset. MeHg was found to selectively target membrane proteins in the cerebellum particularly in synaptic membranes. MeHg affected proteins involved in energy metabolism in both OL and FL of the cerebrum through different proteins and biochemical pathways. In the OL, proteins were enriched in functions of carbohydrate metabolic process, lipid metabolic process, cellular amino acid metabolic process, homeostatic process, transportation, and regulation of body fluid level. In the FL, differentially expressed proteins were mainly involved in the cell cycle and cell division, glycerolipid metabolic process, sulfur compound metabolic process, cellular amino acid metabolic process, microtubule-based process, and proteolysis. The dyshomeostasis of water transport and associated pathways observed in OL and FL was found to be the underlying mechanism for brain edema observed in the MeHg exposed marmoset. Novel proteins such as DLG4 (PSP95) in the cerebellum and APOE in OL were exhibited to be core proteins in linking multifunction targeted by MeHg. This study provides a new perspective upon understanding mechanisms behind MeHg mediated neurotoxic deficits, and suggests potential links between MeHg exposure and neurodegenerative disorders in humans.
Mercury (Hg) is a widespread neurotoxin, therefore it is important to identify a biomarker of effect in populations that could be at risk of Hg exposure. Platelet monoamine oxidase (MAO) could be a biomarker since animal studies indicate that brain and platelet MAO activity decreases as blood Hg increases. This study examined the relationship between blood Hg and platelet MAO activities among Inuit in the Canadian Arctic. This study found an increase in platelet MAO activities as blood Hg levels increased, which could be due to the high selenium (Se) in the population. This study then examined the relationship between Hg and MAO activities in an established cell line (SH-SY5Y) and found that Hg treated cells had an increase in MAO activities, but no changes occurred in MAO-A mRNA levels. Discrepancies between animal studies and these in vitro results could be due to differences between cell lines and whole organisms. --P.ii.
Traditional foods are central to the well-being of Aboriginal communities however there is a trend of decreasing traditional food use which can pose health risks when the replacement foods are low in nutrients and high in carbohydrates and saturated fats. This study collected information on the frequency and quantity of traditional food consumption as well the level of food security of 29 adults in the Vuntut Gwitchin First Nation community of Old Crow and 33 adults in the Tlingit community of Teslin, both of Yukon, Canada. In each community traditional foods were shown to be an important part of the diet, although challenges in access to and availability of foods were reported. Chemical contamination is another challenge in the context of food security. There is limited data on mercury levels in caribou, a principal food source for the Vuntut Gwitchin First Nation. Seventy-five caribou muscle, 63 kidney and 3 liver samples were analyzed for total mercury and combined with reported dietary information to calculate estimated total mercury and methylmercury exposure. Nutrient intake was calculated by combining data from the Canada Nutrient File and supplemented by Kuhnlein et al. (2006) and Hidiroglou et al., (2008) with the collected dietary information. Caribou issues were found to contribute high levels of important nutrients to the diet and pose minimal health risk from mercury exposure.
