Claire Vanier

Ecosystem matters: Fish consumption, mercury intake and exposure among fluvial lake fish-eaters

Many studies use the number of fish meals as an estimate of Hg intake, although fish Hg concentrations, even within the same species, can greatly vary. Furthermore, most freshwater advisories only refer to local catch, while market fish advisories only focus on market fish, although both can contribute to Hg body burden. The present study, carried out in lakeside communities from 2 ecosystems in Quebec, Canada, sought to (i) estimate Hg intake from local freshwater sources, hunted waterfowl and market fish and seafood, and (ii) examine the relations between fish consumption, estimated Hg intake and biomarkers of exposure. A total of 238 adults (18-74 years), who had consumed local catch within the past three months, responded to an extensive interview-administered fish and waterfowl frequency questionnaire. Anthropometric measures were taken and a self-administered questionnaire was used to obtain socio-demographic information. Hg intake was estimated as microg Hg/kg body weight/day. Blood and hair samples were analyzed for Hg content. Results showed that persons from one ecosystem ate significantly more fish compared to those from the other (median: 52.1 g/day vs 38.9 g/day), but presented significantly lower concentrations of hair Hg (median: 448.0 ng/g vs 730.5 ng/g), blood organic Hg (median: 1.1 microg/L vs 3.4 microg/L) and inorganic Hg (median: 0.4 microg/L vs 0.8 microg/L). Median daily total Hg intake was 0.080 microg/kg bw/day for the former community and 0.141 microg/kg bw/day for the latter. Overall, 59.5% from the first ecosystem and 41.0% from the other, exceeded the US EPA RfD (0.1 microg/kg bw/day), while 13.2% and 6.0%, respectively, exceeded the Canadian tolerable daily intake (0.47 microg/kg bw/day) for adults. For the two groups, freshwater fish consumption frequency, but not total fish, was positively associated with bioindicators of Hg while estimated Hg intake from freshwater catch as well as from total fish consumption were positively related to Hg biomarkers. There was a positive relation between consumption and estimated Hg intake from freshwater fish and blood inorganic Hg. These findings indicate that the number of fish can be a poor surrogate for Hg exposure. The differences observed here for Hg intake and exposure reflect ecosystem disparities in fish diversity and Hg bioaccumulation. Studies and advisories need to consider Hg fish concentrations and fish-eating patterns in different ecosystems, as well as the contribution of market fish. The relation between fish consumption and inorganic Hg exposure, reported as well in other studies, needs to be further investigated.

Persistence and fate of PCBs in sediments of the Saint Lawrence River

Abstract Polychlorinated biphenyl (PCB) congener concentrations and composition were determined in sediments from three sections of the St. Lawrence River that have been exposed to high PCB contamination. In at least one sampling station in each river section (upper Lac St-Francois (LSF) and two sections in metropolitan Montreal, Canada), high PCB concentrations were found in the top 10 cm of sediments (respectively 16.2, 9.8 and 3.8 mg/kg d.w. of Aroclor 1248 equivalents). In the case of sediments along the south shore of LSF, both PCB concentrations (regression analysis) and composition (correspondence analysis) were related to the distance of sampling sites downstream from the local source area. In the most contaminated station of the lake, located near an industrial facility, analysis of sediment core profile dated by 137 Cs revealed a relatively constant input of PCBs since ∼ 1982. The di- and tri-chlorinated congeners accounted for more than 70% of the quantified congeners in surface sediments of this station, whereas these congeners made up less than 30% of the PCBs found in less contaminated St. Lawrence River sediments. The PCB concentrations and compositions found in the river sediments suggest that local point sources, river hydrology, physicochemical processes and microbial dechlorination were major factors explaining the fate of PCB congeners in St. Lawrence River sediments.

An Ecosystem Approach to Describe the Mercury Issue in Canada: From Mercury Sources to Human Health

It has been decades now since the international scientific community initially raised the issue of mercury (Hg) contamination in the global environment. The presence of Hg in ecosystems is ubiquitous, even in the absence of local/regional contamination point sources. Almost all fish consumers (occasional or frequent) are exposed to this contaminant. Governments of the industrialized countries have invested considerable financial and human resources, in order to better understand the biogeochemical behavior and cycling of Hg and its impacts on the health of populations. Indeed, our knowledge of the sources and fate of this pollutant has greatly evolved since these early reports. Numerous protocols, technical documents, epidemiological and clinical studies, detailing precise aspects of the Hg cycle have been published. However, given the complexity of environmental processes leading to the accumulation of Hg in fish tissue, and the relative importance of fish as a protein source among communities, most available literature fails to fully evaluate the level of risk to health (and/or the health benefits related to fish consumption) encountered by fish consumers in their daily lives. This paper summarizes the learning acquired through a wide-scale integrated study of the mercury (Hg) pathways in lake environments of three distinct regions located in Eastern Canada : Lake St. Pierre (LSP), Labrador (Lab), and Abitibi (Ab). This research was accomplished by a multidisciplinary team of researchers assembled under the auspice of the Collaborative Mercury Research Network (COMERN), a major Canadian initiative supported by numerous universities and government agencies throughout the country. The prime focus of the study was to link human exposure to Hg with particular local/regional environmental and socioeconomic characteristics and settings. Two conditions must co-occur to define a situation where higher Hg exposure can be identified for populations/sub-populations/ groups : Frequent fish consumption;Mercury levels of concern in the edible fish resource.