Rachael Fletcher

Influence of fish size and sex on mercury/PCB concentration: importance for fish consumption advisories.

Fish advisories for polychlorinated biphenyls (total-PCBs) and mercury are often given on a length-specific basis and fish sex is usually not considered. The relationship between concentration and length is well established for mercury, however its suitability for total-PCBs and the influence of sex over the large scale covered by most monitoring programs is not well known. Here we use what is perhaps the largest consistent sport fish contaminant dataset to evaluate the relationship between total-PCB/mercury and length and sex. We evaluated seven of the most commonly consumed fishes from the Canadian Great Lakes and two Ontario (Canada) inland lakes. For mercury, the relationship between concentration and length was significant (p<0.05) in most fish species and locations. For total-PCB, this relationship was also generally significant in Chinook salmon and lake trout, which are the species with the most advisories for this compound. In contrast, significant relationships were found less often for whitefish, northern pike, smallmouth bass, walleye, and especially yellow perch. However, mercury usually drives fish consumption advisories for these species. Overall, our results support the protocol of issuing contaminant advice on a length-specific basis in fish monitoring programs with reasonable confidence when at least a moderate number of samples over the natural size range of a species are included in the analysis. Sex differences were common for walleye (males>females, p<0.05) but not other species, suggesting that an equal number of male and female walleye should be used in deriving fish advisories for walleye.

Long-term environmental fate of perfluorinated compounds after accidental release at Toronto airport.

Perfluorooctane sulfonate (PFOS; a perfluorinated compound or PFC), its salts, and perfluorooctane sulfonyl fluoride have recently been listed in Annex B of the Stockholm Convention due to their widespread presence, persistence, and toxicity. Because of the persistent nature of PFCs, it is generally presumed that the impact of direct discharges of these chemicals on a receiving environment would be long-lasting. However, long-term environmental fate studies based on field measurements are rare. We examined spatial and long-term (9 year) temporal trends of PFCs in water, sediment, fish, and fish liver collected in 2003, 2006, and 2009 from 10 locations spanning ∼20 km in Etobicoke and Spring Creeks, where an accidental release of fire fighting foam containing PFOS from nearby Toronto International Airport occurred in 2000. Even a decade after the spill, sediment PFOS concentrations are still elevated in Spring Creek Pond which received the foam discharge; however, the major impact is relatively localized likely due to the stormwater management nature of the pond and the diluting effect of Etobicoke Creek. Fish and fish liver PFOS concentrations at a Spring Creek location downstream of Spring Creek Pond declined by about 70 and 85%, respectively, between 2003 and 2009. PFOS in water at locations further downstream in Etobicoke Creek have declined by >99.99% since the spill; however, the 2009 water and fish levels were ∼2-10 times higher than upstream locations likely due to the long-term impact of the spill as well as urbanization. The decrease in the upstream PFOS concentrations likely reflects the reduction of PFOS sources due to phased out production by 3M and regulations on the use of PFOS in fire fighting foams. Field-based sediment/water distribution coefficients (K(D)) and bioaccumulation factors (BAF) were calculated from environmental measurements. Log K(D) values were 0.54-1.65 for perfluoroalkyl sulfonates (PFASs) and 1.00-1.85 for perfluorocarboxylates (PFCAs). Log BAF(fish) ranged from 1.85 to 3.24 for PFASs and 0.88-3.47 for PFCAs, whereas log BAF(fish liver) ranged from 2.1-4.3 for PFASs and 1.0-5.0 for PFCAs.

Algal blooms in Ontario, Canada: Increases in reports since 1994

Abstract The Ontario Ministry of the Environment provides an algal identification service as part of the Ministrys response to algal bloom events, and we have been tracking the reports since 1994. From 1994 through 2009, we noted a significant increase in the number of algal blooms reported each year (P < 0.001). There was also an increase in the number of blooms in which cyanobacteria were dominant (P < 0.001), with these samples making up >50% of the total during peak years. The most common taxa of cyanobacteria identified were Anabaena, Aphanizomenon, Microcystis, Gloeotrichia, and various Oscillatoriales. The remaining samples were dominated by filamentous green algae, or occasionally by chrysophytes. We also noted geographic and seasonal trends in the bloom reports. Most of the increase in the number of cyanobacterial bloom reports was accounted for from lakes on the Canadian Shield (located within the boundary of the Ministrys Northern Region). Algal blooms are now being reported later into the fall than they were during the 1990s; bloom reports have extended well into November in recent years. We attributed these trends to (1) increased nutrient inputs in some areas, which promote the growth of algae; (2) factors associated with climate warming, which may exacerbate bloom conditions; and (3) an increase in public awareness of algal issues. An increase in algal bloom reports is a management issue in Ontario, and blooms of potentially toxin-producing cyanobacteria prompted a formal response protocol to be followed.

Temporal trends and spatial distribution of dioxins and furans in lake trout or lake whitefish from the Canadian Great Lakes.

Concentrations of the seventeen 2,3,7,8-substituted, most toxic congeners of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) were measured in lake trout (Salvelinus namaycush) or lake whitefish (Coregonus clupeaformis) collected between 1989 and 2003 from the Canadian Great Lakes as a part of the on-going Sport Fish Contaminant Monitoring Program of the Ontario Ministry of the Environment. These monitoring data were used to assess temporal trends and spatial variations of these compounds in the Canadian Great Lakes. Toxic equivalents (TEQs) were calculated using the measured congener concentrations and toxicity equivalency factors (TEFs) published by the World Health Organization in 1998. Five congeners, namely 2,3,7,8-TCDD, 2,3,7,8-TCDF, 1,2,3,7,8-PeCDD, 1,2,3,7,8-PeCDF, and 2,3,4,7,8-PeCDF, were the most dominant congeners among the 17 congeners analyzed. The highest TEQs were found for Lake Ontario lake trout (22-54 pg g(-1)) while the TEQs for the other Canadian Great Lakes were 60-95% lower. Non-parametric Mann-Kendall and Sens tests performed on TEQs and PCDD/Fs standardized at a mean lake trout length of 60 cm suggest a linearly decreasing trend for PCDD/Fs in lake trout from Lakes Ontario and Huron. There was no monotonously increasing or decreasing trend found for Lake Superior lake trout. The ratios of 2,3,7,8-TCDD to 2,3,7,8-TCDF concentrations were generally constant during the 1989-2003 period with the values being in the order of Lakes Superior (0.05-0.3) <or= Huron (0.16-0.25)<<Ontario (0.56-0.88). These spatial differences observed in the relative abundance of TCDD and TCDF suggest that the sources of dioxins and furans differ between the upper and lower Great Lakes.

Converting Toxic Equivalents (TEQ) of dioxins and dioxin-like compounds in fish from one Toxic Equivalency Factor (TEF) scheme to another.

Toxic Equivalency Factors (TEFs) are an essential part of the Toxic Equivalent (TEQ) concept and have evolved for dioxins/dioxin-like compounds over the last two and half decades. Therefore, it is difficult to compare past and current TEQs that are reported using different TEFs without explicitly mentioning underlying congener concentrations. Using what likely is the largest known dioxin/furan (PCDD/F) and dioxin-like polychlorinated biphenyl (dl-PCB or DLP) fish database, here we present regression models that can facilitate conversion of a fish TEQ from an old to a newer TEF scheme. The results show that the mammalian PCDD/F-TEQ based on the latest TEF(WHO-05) is about 7.5% lower than that based on TEF(WHO-98). The mammalian DLP-TEQ(WHO-05) is on average 25-26% lower than almost identical DLP-TEQ(WHO-94) and DLP-TEQ(WHO-98). Total-TEQ(WHO-05) is on average 22% lower than Total-TEQ(WHO-98). According to the current toxicological standards for dioxins/furans, all previous major TEF schemes except TEF(Germany-85) and TEF(USEPA-87) were conservative (i.e., higher) in estimating TEQs. The major (> 75%) contribution to PCDD/F-TEQ(WHO-05) is from 2,3,7,8-TCDD (33%), 1,2,3,7,8-PCDD (26%), 2,3,7,8-TCDF (10%), and 2,3,4,7,8-PCDF (9%). The DLP-TEQ(WHO-05) is dominated by PCB-126 which on average contributes about 88%. The DLP-TEQ generally contribute > 70% of Total-TEQ. When reporting TEQs, we recommend that the underlying congener specific concentrations are presented, TEF scheme used is clearly stated, names of compounds included are explicitly expressed, and TEQs are identified accordingly (e.g., DLP-TEQ, PCDD/F-TEQ, Total-TEQ).

Temporal and spatial trends of organochlorines and mercury in fishes from the St. Clair River/Lake St. Clair corridor, Canada

ABSTRACT The temporal and spatial relationships of a suite of organochlorine contaminants and mercury were examined in various fish species of the St. Clair River/Lake St. Clair corridor, Canada, in order to evaluate the effectiveness of remediation efforts and to assess the risk to human and wildlife fish consumers. In Lake St. Clair, fish tissue concentrations of mercury, polychlorinated biphenyls (PCBs), octachlorostyrene (OCS), hexachlorobenzene (HCB), and dichlorodiphenyltrichloroethane (DDT) decreased consistently from the 1970s until the 1980s and 1990s, after which the rate of contaminant decline slowed or concentrations stabilized. This trend was consistent in up to 13 species (both young-of-the-year and adult fishes) comprising different trophic positions and dietary habits, suggesting that the changes were reflective of ambient conditions rather than food web processes. Elevated concentrations of mercury, PCBs, OCS, HCB, and DDT were detected in St. Clair River young-of-the-year spottail shiner compared with fish from Lake Huron, indicating that non-atmospheric inputs of these chemicals, likely originating from sediment, remain in the St. Clair River. Current concentrations of mercury and PCBs, and mercury, PCBs, and DDT remain of concern to human and wildlife fish consumers, respectively. Given that contaminant decreases have generally stabilized in fish, we suggest that further natural recovery of contaminants in St. Clair corridor fishes will be slow since contaminants will likely continue to be influenced by sediment levels.

Long-term changes in fish mercury levels in the historically impacted English-Wabigoon River system (Canada)

The English-Wabigoon River system in Northwestern Ontario, Canada, was one of the most heavily mercury-contaminated waterways in the world due to historical discharges in the 1960s from a chlor-alkali plant. This study examines long-term (1970-2010) monitoring data to assess temporal trends in mercury contamination in Walleye, Northern Pike and Lake Whitefish, three species important for sport and subsistence fishing in this region, using dynamic linear modeling and piecewise regression. For all lakes and species, there is a significant decline (36-94%) in mercury concentrations through time; however, there is evidence that this decline is either slowing down or levelling off. Concentrations in the English-Wabigoon fish are elevated, and may still present a potential health risk to humans consuming fish from this system. Various biotic and abiotic factors are examined as possible explanations to slowing rates of decline in mercury concentrations observed in the mid-1980s.

Estimating sediment quality thresholds to prevent restrictions on fish consumption: Application to polychlorinated biphenyls and dioxins–furans in the Canadian Great Lakes

Sediment quality thresholds (SQTs) are used by a variety of agencies to assess the potential for adverse impact of sediment-associated contaminants on aquatic biota, typically benthic invertebrates. However, sedimentary contaminants can also result in elevated fish contaminant levels, triggering consumption advisories that are protective of humans. As such, SQTs that would result in fish concentrations below consumption advisory levels should also be considered. To illustrate how this can be addressed, we first calculate biota sediment accumulation factors (BSAFs) for polychlorinated biphenyls (total PCB) and polychlorinated dioxins-furans (PCDD/Fs) in the Canadian Great Lakes using measured lake sediment and fish tissue concentrations in 4 fish species, namely, lake trout, whitefish, rainbow trout, and channel catfish. Using these BSAFs and tissue residue values for fish consumption advisories employed by the Ontario Ministry of the Environment (OMOE, Canada), we derive fish consumption advisory-based SQTs (fca-SQTs) that are likely to result in fish tissue residues that are safe to eat without restriction. The PCDD/Fs fca-SQTs ranged from 6 to 128 pg toxic equivalents (TEQ)/g dry weight (dw) and were above the Canadian Council of the Ministers of the Environment (CCME) threshold effect level (TEL) of 0.85 pg TEQ/g dw. In contrast, the total PCB fca-SQTs ranged from 1 to 60 ng/g dw and were generally below the CCMEs TEL of 34.1 ng/g and OMOEs lowest effect level (LEL) of 70 ng/g; however, they were consistent with the OMOEs no effect level (NEL) of 10 ng/g. The fca-SQTs derived using the BSAF as well as food chain multiplier (FCM) approach for a smaller scale system (Hamilton Harbour in Lake Ontario) corresponded well with average lakewide Lake Ontario fca-SQTs. This analysis provides approximate sediment concentrations necessary for reducing fish consumption advisories for each of the Canadian Great Lakes and emphasizes the impacts of historical lake sediment contamination on fish advisories. We believe that this approach merits consideration in sediment guideline development.