Proceedings of the workshop; Cadmium in Shellfish from the Pacific Northwest: Status and Health Concerns. Prepared by L.I. Bendell, Kayi Chan, Toby St. Clair and Hazel Walling. Sponsors Table of Contents Acknowledgements 3 Introduction 4 Presentations 6 Round Table Discussion 19 Next Steps 23 Appendices 24 I. References cited II. On site programme III. List of participants and affiliations 3 Acknowledgements This workshop would not have been possible without the support and experience provided by Dr.
Patricia Gallaugher, Director and Laurie Wood, Program Coordinator, with the Centre for
Coastal Studies at Simon Fraser University. Thanks to all the participants who volunteered their
time and contributed to the discussions. The workshop was sponsored by the Ocean
Management Research Network and the Faculty of Environment at Simon Fraser University.
We are grateful to these organizations for their generous contributions.
4 Introduction In 1998, the federal and provincial governments in partnership with industry began to expand shellfish aquaculture on both the east and west coasts of Canada to promote economic gain. Plans for the rapid expansion of this industry on the Pacific coast were arrested, however, when in 1999 safety inspectors from the Hong Kong market rejected three shipments of BC oysters because they exceeded the cadmium (Cd) safety guidelines of 2 µgg‐1 wet weight (Kruzynski et al. 2002, Kruzynski 2004). A subsequent survey by the Canadian Food Inspection Agency (CFIA) revealed that, on average, BC oysters contain 2.6 µgg‐1 Cd wet weight, an amount that also exceeds the European Community export market guideline of 1 µgg‐1 wet weight. These high cadmium levels prompted Health Canada to issue consumption guidelines of 460 grams of oysters per month for adults and 60 grams per month for children (Canadian Food Inspection Agency, 2003). Recent research findings have shown that this guideline is not stringent enough, especially for target populations such as First Nations (Cheng and Gobas 2007, Widmeyer and Bendell‐Young 2008). Scientists conducted a number of studies to identify possible cadmium sources so that oysters could be farmed without high‐level cadmium contamination. Although spatial and temporal patterns were indicated (Bendell and Feng 2009) as well as additional insights as to whether oysters were obtaining cadmium via food or water (Lekhi et al., 2008, Christie and Bendell 2009), the source(s) of cadmium to oysters from the Pacific Northwest has yet to be identified. Recent research findings (Saratug et al. 2010) indicating that the toxicity of cadmium to humans occurs at much lower levels of exposure than currently thought led us to pose the question: Under these circumstances, should the Province of BC continue to promote expansion of the shellfish industry? To further complicate this issue the Federal Ministry of Health recently implied that “cadmium levels in BC oysters are declining”, and that Health Canada will be reassigning consumption guidelines for this product. Clearly, this statement runs contrary to research findings reported in the scientific literature with respect to cadmium levels in BC shellfish. Therefore, it was identified that there was a need to: 1) based on the most recent studies, establish cadmium concentrations and trends of these concentrations in shellfish from the Pacific Northwest and 2) address the health risks posed to First Nations and other high risk populations that consume such cadmium concentrations in shellfish. To address these data gaps a one‐day workshop entitled; Cadmium in BC shellfish: status and related health concerns was held May 3rd 2010 at the Halpern Centre, Simon Fraser University, Burnaby. The focus of this workshop was on the Pacific oyster (Crassostrea gigas). 5 Format The morning sessions were devoted to presentations (15‐30 min duration) by researchers involved in some aspect of study on levels of cadmium in shellfish from the Pacific Northwest and the health risks associated with such levels of cadmium in shellfish. The afternoon session was a roundtable discussion which drew on the information presented in the morning sessions, and addressed the two data gaps: 1) cadmium concentrations and trends in BC shellfish and 2) health risks posed to First Nations and other consumers of shellfish from such cadmium concentrations. These proceedings summarize the workshop presentations and outcomes of the roundtable discussions. It is hoped that outcomes of this workshop will provide the most up to date information on cadmium levels in shellfish such that appropriate decisions with respect to safe consumption levels can be made. Proceedings, presentations and a resource base with relevant background materials can be found at http://www.sfu.ca/cs/science/cadmium.htm. Presentations 6 1. Cadmium in Shellfish (101) A crash course in the politics of science: Dr. George Kruzynski. Research Scientist Emeritus, Department of Fisheries and Oceans. http://www.sfu.ca/cs/science/resources/cadmium/1_SFU_Cd_GMKF.pdf Funding cuts that occurred through the mid‐80’s to date severely limited the ability of the Department of Fisheries and Oceans to access operating funds, especially for research that might generate results not necessarily friendly to current government policies. Within this funding environment, DFO was requested to determine the sources of cadmium to oysters in BC. This request was triggered by the rejection of several shipments of oysters by the Hong Kong Health Authority (1999). Through collaborative efforts with * academic institutions such as UBC and SFU, research addressing the source of cadmium to BC oysters was completed and several studies are now in the Table 1. literature. However, several obstacles were encountered which prevented solid funding for the required research including governments “facilitating” of aquaculture (Table 1). *(OCAD; Office of the Commissioner for Aquaculture Development which operates at the federal level). In some cases industry was also an obstacle to this research for complementary reasons (Table 2). Relations between researchers and industry were further strained, when at a community Town Hall meeting held January of 2002, Dr. Kruzynski presented data that indicated based on CFIA‐determined cadmium concentrations in BC oysters (2.63 µgg‐
1), to meet the international Table 2. Provisional Tolerable Weekly Intake (PTWI) of 420‐490 µg Cdweek‐1, oyster consumption should be limited to 3 oysters per week. 7 The PTWI was revaluated by the European Food Safety Authority in 2009 and is now 0.36 of existing PTWI for a TWI of ca. 160 µg Cd week‐1 implying that a safe level of consumption for an oyster with an average cadmium value would be 1 week‐1 for adults and 12 year‐1 for children (Figure 1). Micrograms of Cadmium
Health Canada Consumption Advisory based on CFIA
BC average Cadmium concentration of 2.63 ppm
1200
1100
1000
900
800
700
600
500
400
300
200
100
0
2009 PTWI
175
WHO/FAO PTWI
adults
Weekly intake of Cadmium
non smoker, no shellfish
children
0
1
2
3
4
5
6
7
8
9
10
11
Number of Oysters per Week
GK ~ 10 years ago
(60kg female; 70kg male @1 µgCd/kg bwt/day
PTWI 420-490 µg Cd per week
Figure 1. Health Canada Consumption Advisory and the revised European PTWI Where we are now as compared to 10 years ago? We have: 
New data on sources/pathways of cadmium to BC oysters 
Updates on understanding of health effects of chronic cadmium exposure and the PTWI 
An understanding of the implications of high cadmium in BC oysters in some communities 8 
Recognition of the importance of shellfish culture species and site selection 
Recognition of the marketability of First Nation shellfish endeavours 
Recognition that Health Canada advisories still do not mention cadmium in consumption guidelines. 9 2. Cadmium in Pacific Oysters (Crassostrea gigas): A survey of the United States West Coast. Aimee Christy, Pacific Shellfish Institute. http://www.sfu.ca/cs/science/resources/cadmium/2_Christy_Workshop_1.pdf Similar to the experience in British Columbia where several shipments of oysters were rejected from international markets, so too were oysters from the US West Coast rejected from the Asian market for containing cadmium concentrations in excess of safe health guidelines. As with the BC experience, research was initiated to: 1. Evaluate cadmium distribution in US West Coast oysters 2. Identify factors that influence cadmium concentrations in oysters utilizing both field and laboratory studies, and 3. Identify ways to reduce concentrations in the final product. To meet these objectives, during September of 2004, 39 sites (117 composites) were sampled (Figure 2), with seasonal sampling occuring at an additional 7 sites (noted by ). Geographic Distribution
2.0
Figure 2. Sampling Station Locations. Figure 3. Geographic Distribution 10 Overall conclusions included that there was some spatial dependence with regional similarities, notably with high cadmium concentrations for sites in Washington State (Hood Canal) and Alaska (Figure 3). No clear south to north trend was noted, as samples from California also had high cadmium residues (Figure 3). Sampling directed at determining trends in cadmium concentrations with oyster weight noted a significant correlation (p<0.01), with the correlation being attributed to “growth dilution”. Figure 4. Seasonal Distribution Seasonal affects were also reported with oysters sampled during summer months containing lower concentrations as compared to winter months (Figure 4). The aquaculture practices, aqua purses and ploidy were also considered. Aqua purses yielded elevated cadmium levels in 2 of 4 sites with no difference detected for ploidy. Of importance for local shellfish farmers was the finding that locations with fast growth rates and good circulation tended to favour lower cadmium tissue levels. 11 3. Cadmium in oysters from the Pacific Northwest; British Columbia, Canada. Leah Bendell, Simon Fraser University; Faculty of Environment http://www.sfu.ca/cs/science/resources/cadmium/3_BendellMay3rd.pdf In 2001, in collaboration with the federal Department of Fisheries and Oceans and BC Ministry of Agriculture and Lands, researchers at SFU initiated a 3 year grow out study with Pacific oysters. The objective was to determine spatial and temporal trends in cadmium uptake. This information would then be used to identify regions or hotspots where cadmium uptake was the greatest. 5
-1
month
3
2 ppm -1
g cadmium oyster
4
2
1
0
-1
Sa So
ns ok
um e
B
W N as
eb ar in
st rro
er w
Po Is l s
et and
tN
oo
k
U
I -1
U
I -2
U
I -3
U
IKe
nd U 4
Tl rick I-5
up I
Tr an nle
ev a t
en Inl
T en et
Te hor Ba
ak s C y
R ern ove
ed e
G on Ar
or d m
ge a
B
O Ha ay
rc rb
h
H ar our
ec d
at Ba
R eC y
R ive ov
en rs e
n
I
Sk ell nle
S t
H idg ou
um at nd
e
La pba Inl
x ck et
K
M 'w Ba
et al y
la aa
ka m
tla s
Ba
y
Sample location
2.8 ug * 36 months / 7.5 gram dry weight oyster
Figure 5. Sites with the greatest rates of Cd uptake by BC oysters. Such information in turn could then be included by industry as one of the site selection criteria which would facilitate farming without high cadmium tissue residues. 12 String cultures at 25 locations along the BC west coast were deployed and sampled on a bimonthly basis for 3 years. Combining both spatial and temporal aspects where cadmium uptake by the oyster was expressed as a µg Cd accumulated per oyster per month, specific sites were identified where cadmium uptake by the oyster was the greatest (Figure 5). 1.Sooke Basin
2. Sansum Narrows
3. Webster Island
4. Poett Nook
5. Uselet Inlet (UI‐1‐UI‐5)
10. Kendrick Inlet
11. Tlupana Inlet
12. Trevenen Bay
13. Thor’s Cove
14. Teakerne Arm
15. Redonda Bay
16. Gorge Harbour
17. Orchard Bay
18. Hecate Cove
19. Rivers Inlet
20. Rennell Sound
21. Skidgate Inlet
22. Humpback Bay
23. Lax K’walaams
24. Metlakatla Bay
Slide 8 Figure 6. Locations along the BC west coast where rates of Cd uptake by the oyster are the greatest. 13 It was recommended that siting of the oyster lease was key to ensuring low cadmium concentrations in oysters. Locations along the west coast of BC where oyster cadmium concentrations would likely reach more than 2 ppm wet weight in a 3 year period included Effingham Inlet (site 3 on Figure 6), and various sites within Desolation Sound including, 12. Trevenen Bay, 13.,Thor’s Cove, 14. Teakerne Arm, 15. Redonda Bay and 17. Orchard Bay. 14 4. Sources of Cadmium to BC Oysters: Field observations and isotopic tracers. Kristin J. Orians. Earth and Ocean Sciences, University of British Columbia. http://www.sfu.ca/cstudies/science/resources/cadmium/4_ORIANS_SFU_Oyster_Wo
rkshop_2010.pdf The primary objective of the study was to determine the sources of cadmium to BC oysters; specifically dissolved versus particulate. Potential sources identified were “natural” (upwelling and local mineralogy) and “anthropogenic” (e.g., mine drainage, incinerators, metal smelters, phosphate fertilizers, sewage treatment plants and pulp mills). Dissolved cadmium is naturally high in the North Pacific as a consequence of “ocean conveyor belt” which results in cadmium enrichment in older intermediate waters of the North Pacific Ocean and oceanic upwelling (Figure 7) Figure 7. Upwelled Cd­ California Coast This in turn could also lead to cadmium enriched particulates. Figure 8. Published results: Lekhi et al. 2008. Based on two sampling locations, Deep Bay and Lemmen’s Inlet, the main conclusions of the studies of Lehki et al. 2008 aimed at determining whether particulates or dissolved cadmium was the primary source of cadmium to oysters (Figure 8) included:  There was an annual cycle; oyster cadmium high in winter, low in the summer for Deep Bay (east side of Vancouver Island)  Dissolved cadmium was the main source for oysters in Deep Bay  Particulate cadmium was a sink not a source  Oyster growth dilutes oyster cadmium concentrations in the summer 15  Environmental factors such as temperature and salinity resulted in a strong seasonal effect. Data obtained from Baynes Sound are now being used to develop a “predictive model” of cadmium uptake by oysters which could be highly useful for oyster growers. A general model would be ideal, but probably difficult due to the variable role of phytoplankton as a source/sink of cadmium. The complexity of the issue was recognized with phytoplankton interactions, dissolved cadmium, oceanographic processes, seasonality, and oyster physiology (growth and reproduction) all contributing to observed cadmium concentrations. Complementing the work of Lekhi et al. (2008) are the isotope studies of Alyssa Shiel and Dominique Weis. Using oyster tissue samples provided by Bendell and Feng (2009) no relationship between cadmium content of BC oysters and cadmium isotopes was found. It was noted that the BC mainland coast had a tendency to lighter cadmium signatures compared with the west coast of Vancouver Island, on average which could be possibly related to pollution (Figure 9). The main conclusions from the study of cadmium isotopes in BC Figure 9. Cd Isotopes in oysters. oysters were that cadmium isotopes were consistent with North Pacific seawater, but slightly lighter, possibly as a consequence of biogenic fractionation or from an as yet unidentified anthropogenic source. Overall conclusions included: 
High cadmium natural in North Pacific (seawater and bivalves) 
For BC oysters: ‐cadmium mostly from dissolved sources ‐cadmium mostly from natural sources 
Phytoplankton takeup dissolved cadmium and increase oyster growth (a sink for cadmium) 
Phytoplankton composition is important 16 
There is a complex annual cycle; however we may be able to predict oyster cadmium based on simple variables. 
Cadmium isotopes can be used to detect pollution, but mostly it is natural cadmium in BC oysters. 17 5. How much Cadmium is safe? Dr. Soisungwan Satarug. Visiting Professor. Dept. of Pathology, School of Medicine and Health Sciences, University of North Dakota, Grand Forks ND (presented by George Kruzynski) http://www.sfu.ca/cs/science/r
esources/cadmium/5_SoisSarat
ung.pdf How Much Cadmium is Safe?
Dr. Satarug has recently (1993) FAO/WHO guidelines
completed a comprehensive 1 µg/Kg body weight/day
review on cadmium, 70 µg Cadmium/day for a 70 kg person
environmental exposure, and health outcomes which is UPDATE
available through the dedicated (2009) European Food Safety Agency
website under Resources at 0.36µg/Kg body weight/day
http://www.sfu.ca/cs/science/
25 µg Cadmium/day for a 70 kg person
resources/cadmium/, and is listed in the Reference section (Appendix 1; Satarug et al. 2010. Environmental Health Perspectives 118 (2): 182‐190). Figure 10. How much cadmium is safe? Cadmium is a multi‐tissue carcinogen with lung, pancreas, breast, endometrium, prostrate and bladder cancers all having been linked to cadmium exposure. Safe levels have since been redefined from the 1993 FAO/WHO guidelines by the European Food Safety Agency, which place this value at about one third of its current guideline (Figure 10.). Note was made of vulnerable groups who include: 
People with diabetes 
People with diabetes and albuminuria 
People with diabetes, albuminuria, hypertension and high fat/low micronutrient diet 
Women with all of the above, also smoke, eat lots of high cadmium foods (e.g., organ meats) and may have iron depletion through many pregnancies. 18 6. Health Canada’s 2002 HRA for Cadmium in Commercially­Harvested Pacific Oysters. Elizabeth Elliott, Bureau of Chemical Safety, Food Directorate. Health Canada is currently updating the toxicological reference value and undergoing a revised exposure assessment and risk characterization. Once completed, a link will be provided to the update and information. The existing fact sheet can be found at: http://www.inspection.gc.ca/english/fssa/concen/specif/bivalvee.shtml 19 7. Shellfish Safety: Tim Kulchyski. Coordinator; Cowichan/Kuper study http://www.sfu.ca/cs/science/resources/cadmium/6_
Tim_Kulchyski.pdf Shellfish Safety: Tim Kulchyski
To address safety concerns regarding consumption of shellfish, First Nations (Cowichan Tribe) in collaboration with Health Canada, First Nations and Inuit Health and Environment Canada undertook a “food basket” survey to; 
Determine levels of cadmium, paralytic shellfish poisoning (PSP), and organochlorines consumed by First Nations 
Based on the above information, determine safe shellfish consumption levels 
Improve overall knowledge of FN fisheries staff and community. Table 3. Cadmium in shellfish. To meet these objectives, a health survey which included interviews regarding amounts of shellfish consumed and laboratory tests that measured iron levels in blood and urine (to assess kidney damage) were run in parallel with shellfish testing for PSP, cadmium and organochlorines. Only Cadmium data is presented here (Table 3). Oysters, and to a lesser extent mussels, contained high cadmium residues. Other shellfish including the Cockle, Littleneck, Butter, Manila, Horse and Dungeness crab were well below 1 µgg‐1 wet weight. Complementary data to put cadmium shellfish concentrations into context were estimates of amounts of shellfish ingested day (gd‐
1). The feeding patterns of two tribes were assessed; overall one tribe ate about 2 tbsp of shellfish daily whereas the second about ¼ cup shellfish daily. For the second tribe about 40% of this ¼ cup is comprised of oysters. No mussels were eaten by either tribe. An important complementary metric that was included in the study included iron status of the participants. Perhaps not surprisingly, given known information on females tending towards iron deficiency, for both tribes combined 58% of the females had low iron as defined by serum ferritin levels of less than 30 µgL‐1. 20 Based on known shellfish consumption patterns and known levels of cadmium in shellfish the following recommendations were reached: 

Levels of cadmium in oysters are lower in Hul’qumi’num territory than elsewhere in BC On a weekly basis, it is safe for adults to eat 1 cup of shucked oysters harvested locally (about 4‐5 oysters weekly or 200 per year). A key outcome from this study was the publication of “Education Materials” to help educate First Nations about shellfish safety. Round Table Discussion 21 Following the morning session presentations all participants engaged in a “round table discussion” that addressed two key questions: 1) What are the cadmium concentrations and trends of the concentrations in BC oysters? 2) What are the health risks posed to First Nations from such cadmium concentrations? Participants addressing these two questions were asked to recognise the political/economic aspects of the issue and acknowledge there will be consequences to coastal communities as a result of the workshop outcomes. A summary of the dialogue follows. Concentrations and trend in concentrations in BC oysters The average concentrations “right now” for BC oysters lies between the range of 1‐4 µgg‐1 wet weight. There are distinct site specific patterns in oyster cadmium concentrations. Some seasonal influence is evident, with concentrations lower in summer months. This pattern was not observed for oysters sampled from Alaska. As well, when cadmium in oysters is expressed as a burden (µg oyster‐1), this trend is no longer apparent. Limited historical data has hampered the ability to determine temporal trends; however it was noted that oceanic dissolved cadmium concentrations are expected to stay steady. If dissolved cadmium is the primary route of cadmium exposure, then it follows that cadmium levels in oysters from the Pacific Northwest will stay constant as well. Health risks In evaluating health risks, there are two separate issues: the First Nations harvest and the shellfish farming industry. It was suggested that many First Nations communities do not consume oysters as clams are preferred. (Note that the presentation by Tim Kulchyski does not support this comment and that oysters can comprise an important part of the First Nations diet). The elevated cadmium levels in shellfish are a risk to everybody and everyone needs to be aware of safe levels of consumption. Community dependence on the economies of oyster farming needs to be recognized and care needs to be taken when warning communities about safe consumption guidelines. It was also noted that testing for cadmium exposure in high risk communities should be undertaken. Education and availability of information available are key, so that the consumer can choose the amounts of shellfish they wish to consume. The question “Who takes responsibility for advising the public on consumption guidelines?” was raised: It was agreed that it is Health Canada’s mandate to provide the information. 22 23 Next Steps A dedicated website is to be made available with all presentations posted plus relevant resource material. Proceedings of the workshop will be made available on‐
line once reviewed and edited by all participants. Health Canada is now reviewing and will revise existing guidelines based on recent data presented at the workshop. Appendices I. References cited 24 Bendell LI, Feng C. 2009. Spatial and temporal variation in cadmium concentrations and burdens in the Pacific oysters (Crassostrea gigas) sampled from the Pacific Northwest. Marine Pollution Bulletin. 58: 1137‐1143. Canadian Food Inspection Agency. 2003. Food safety facts on bivalve shellfish in British Columbia. Canadian Food Inspection Agency Fact Sheet. <http:// www.inspection.gc.ca.proxy.lib.sfu.ca/english/corpaffr/foodfacts/bivalvee.pdf>. Cheng WW, Gobas, FAPC. 2007 Assessment of human health risks of consumption of cadmium contaminated cultured oysters. Human and Ecological risk assessment. 13: 370‐382 Christie, J, Bendell LI. 2009. Sources of dietary cadmium to the Pacific oysters Crassostrea gigas. Marine Environmental Research. 68: 97‐105. Kruzynski G. 2004. Cadmium in oysters and scallops: the BC experience. Toxicology Letters. 148:159–169. Kruzynski G, Addison R, Macdonald R. 2002. Possible pathways of cadmium into the Pacific Oyster (Crassostrea gigas) as cultured on the coast of British Columbia, Institute of Ocean Sciences, March 6‐7, 2001. Canadian Technical Report of Fisheries and Aquatic Sciences. 2405, vi + 65pp. Lekhi P, Cassis D, Pearce C, Ebell N, Maldonado M, Orians, K. 2008. Role of dissolved and particulate cadmium in the accumulation of cadmium in cultured oysters (Crassostrea gigas). Science of the Total Environment. 393: 309‐325. Satarug, S., Garrett, S.H., Sens, M.A. and D.A. 2010. Cadmium, Environmental Exposure and Health Outcomes. Environmental Health Perspectives. Environ Health Perspect 118(2): 182‐109. Widmeyer J, Bendell‐Young L. 2008. Heavy Metal Levels in Suspended Sediments, Crassostrea gigas, and the Risk to Humans. Arch Environ Contam Toxicol. 55: 442‐
452. II. On site Programme III. List of participants Bendell, Leah Chan, Kayi Cheney, Dan Christy, Aimee Elliott, Beth Gallaugher, Patricia Heath, Bill Kemp, Vern Kodama, Dave Kruzynski, George Kulchyski, Tim Nazar, Steve Nicolson, Midori Orians, Kristin Schmidt, Dave Silver, Jennifer St. Clair, Toby Stevenson, Roberta Stupakoff, Ian Walling, Hazel Wood, Laurie Christie, Jeff Satarug, Soisungwan SFU ­ Biological Sciences SFU ­ Biological Sciences Pacific Shellfish Institute Pacific Shellfish Institute Health Canada SFU ­ Coastal Studies BC Ministry of Agriculture and Lands Alliance for Responsible Shellfish Farming MSc Candidate, UBC , School of Environmental Health Retired, DFO Coordinator/Cowichan/Kuper study Nazar Associates Inc. Dzawadaacenuxw First Nation Kingcome Inlet Biologist UBC ­ Earth and Ocean Sci Biologist Quatsino First Nation SFU ­ REM SFU ­ Biological Sciences BC Shellfish Growers Association Integral Consulting Inc. SFU ­ Biological Sciences SFU ­ Coastal Studies O'Connor Consultancy