Overview of Research Sponsored by Health Canada’s Contaminated Sites Program/ Metal Concentrations in Indoor Dust

Deborah Schoen, Safe Environments Program Quebec Region, Healthy Environments & Consumer Safety Branch, Health Canada, 2nd Floor, St-Laurent Street West, 1001 St-Laurent Street West, Longueuil, Quebec, J4K 1C7, Tel: 450-646-1353, ext 254, Fax: 450-928-4269; Email: deborah_schoen@hc-sc.gc.ca
Pat Rasmussen, Environmental & Occupational Toxicology Division, Safe Environments Program, Health Canada, Ottawa, Ontario
Nellie Roest, Safe Environments Program, Atlantic Region, Healthy Environments & Consumer Safety Branch, Health Canada, 1505 Barrington St. Suite 1817, Halifax, Nova Scotia, B3J 3Y6, Tel: 902-426-5618, Fax: 902-426-4036, Email: Nellie_Roest@hc-sc.gc.ca

The Canadian Federal Contaminated Sites Action Plan (FCSAP) was created to accelerate the assessment and remediation of contaminated sites owned by the federal government.  To date over 4000 federal sites, including mines, military bases, harbours, airports, and lighthouses, have been listed in the federal inventory.  Health Canada, as an Expert Support Department, provides guidance, training, advice, and tools for assessing the human health risks of contaminated sites.  To help meet these responsibilities, Health Canada has initiated and sponsored research on risk assessment methods, toxicological reference values, soil quality guidelines, sampling methodologies, bioavailability, and other health-related issues at contaminated sites. 

One of the FCSAP-sponsored research projects is investigating indoor exposures to toxic metals commonly found in contaminated soils, and the ability to predict indoor exposures from outdoor geochemistry.  The study, which examined 48 homes in the Ottawa area, evaluated indoor/outdoor ratios in the concentrations of lead, cadmium, and nickel.  Indoor (i.e., indoor dust) elemental concentrations were not spatially correlated with outdoor (i.e., garden soil) elemental concentrations.  Moreover, indoor/outdoor ratios of total metal concentration were consistently higher than unity:  5.5 for Pb, 16.4 for Cd, and 3.4 for Ni.  Considering only the migratable fraction, the indoor/outdoor ratios were found to be 24.8 for Pb, 20.7 for Cd, and 40.4 for Ni.  Relative bioavailability factors (migratable/total metal) were also found to be higher in indoor dust as compared to outdoor soil.  The high values appear to be related to the ability of the organic-rich indoor dust matrix to accumulate metals.

The Mutagenic Hazards of Complex PAH Mixtures in Contaminated Soils

Paul White, Mutagenesis Section, Safe Environments Program, Healthy Environments & Consumer Safety Branch, Health Canada, Tunney's Pasture 0803A, Ottawa, Ontario K1A 0K9.  Tel: 613-941-7373; Fax: 613-941-8530; Email: paul_white@hc-sc.gc.ca
Christine Lemieux, Mutagenesis Section, Environmental & Occupational Toxicology Division, Safe Environments Program, Health Canada, Ottawa, Ontario
Iain Lambert, Biology Department, Carleton University, Ottawa, Ontario Rémi Gagné¹, Mutagenesis Section, Environmental & Occupational Toxicology Division, Safe Environments Program, Health Canada, Ottawa, Ontario
Mats Tysklind, Department of Chemistry, University of Umeå, Umeå, Sweden
Staffan Lundstedt, Mutagenesis Section, Environmental & Occupational Toxicology Division, Safe Environments Program, Health Canada, Ottawa, Ontario
George R. Douglas, Mutagenesis Section, Environmental & Occupational Toxicology Division, Safe Environments Program, Health Canada, Ottawa, Ontario

This FCSAP-funded project is evaluating risk assessment methods employed to assess the carcinogenic hazards of PAH mixtures.  Methods for mutagenic carcinogens often employ an assumption of additivity and express total hazard as the cumulative hazard of priority PAHs.  In this study, organic components of PAH-contaminated soils were extracted using pressurized fluid extraction and subsequently separated into polar (e.g., nitroarenes) and non-polar fractions (e.g., PAHs and alkyl-PAHs).  Synthetic mixtures of priority PAHs were prepared using the results of chemical analyses.  The mutagenic potencies of complex soil extracts/fractions, synthetic PAH mixtures, and individual PAHs were evaluated using the Salmonella mutagenicity assay.  All soil extracts/fractions and synthetic PAH mixtures yielded significant mutagenic responses in at least one of Salmonella strains TA98 and TA100; however only 8 of the 16 PAHs yielded a mutagenic response.  The predicted mutagenic hazard of the non-polar fraction, whether based on (a) its synthetic mixture or (b) the sum of the effects expected from the identified PAH constituents, was frequently greater than the mutagenicity of the non-polar PAH-containing fraction.  Furthermore, a significant response was obtained for the polar fraction in Salmonella YG1041, a strain that is sensitive to N-containing heterocyclic compounds.  These results suggest that a targeted risk assessment approach focusing on priority PAHs may provide useful, although conservative, assessments of mutagenic hazard for PAH-contaminated soils.  However, a priority substance approach cannot account for hazards associated with unidentified polar compounds.  Validation of the Salmonella results using an in vitro mammalian cell mutation assay is ongoing.

Dermal Penetration of Carcinogenic PAHs in Contaminated Soils

Richard P. Moody, Systemic Toxicology and Pharmacokinetics Section, Safe Environments Program, Healthy Environments & Consumer Safety Branch, Health Canada, Tunney's Pasture 0803B, Ottawa, Ontario K1A 0K9, Tel: 613-957-1840, Fax: 613- 957-8800, Email: rick_moody@hc-sc.gc.ca

Due to their recreational activites, children are especially vulnerable to dermal exposure to soil contaminants. Our laboratory at Health Canada has recently determined that the carcinogenic PAH benzo[a]pyrene (B[a]P) was quite well-absorbed in human skin exposed to gardening soil spiked with ¹⁴C-B[a]P. This study followed our in-house in vitro dermal absorption test using fresh viable human skin tissue. Teflon^® flow-through type diffusion cells were used to hold skin specimens cut by dermatome to about 0.3-0.4 mm thickness, perfused at 32 ⁰C with a ‘receivor’ solution consisting of Hanks HEPES buffered (pH 7.4) Bold’s basal saline solution (HHBBSS) containing  4% BSA. Including the % of the applied dose detected in the HHBBSS receivor solution summed together with the % in the skin ‘depot’ which contains the ¹⁴C-B[a]P residues remaining in skin following soap washing, the total % absorption was 14.8 + 6.17% (n = 5) and 15.8 + 8.30% (n = 4) after 24 hr and 42 hr exposure to ¹⁴C-B[a]P spiked soil, respectively. For use of such data in risk assessment the concept of the skin depot and the basic essentials of in vitro dermal absorption test methods need to be clearly understood. We will present an overview of our test protocol and briefly discuss the skin depot in relation to the bioavailability of soil contaminants.

The Toxicity of Complex Metal Mixtures in Contaminated Soils  

Wayne J. Bowers, Systemic Toxicology and Pharmacokinetics Section, Safe Environments Program, Healthy Environments & Consumer Safety Branch, Health Canada, Tunney's Pasture 0803B, Ottawa, Ontario K1A 0K9, Tel: 613- 952-3021, Fax: 613- 957-8800, Email:  wayne_J_bowers@hc-sc.gc.ca
Philip W. Wall, Jamie S. Nakai, Al Yagminas, Rudi Mueller, Nanqin Li, and Ih Chu, Environmental & Occupational Toxicology Division, Safe Environments Program, Health Canada, Ottawa, Ontario 

Current guidelines for soil contaminant levels are based on toxicological data from individual contaminants and estimated exposure in humans. There is little data available on combined exposure to metal contaminants found at contaminated sites and little toxicological information on the effects of exposure to mixtures of soil-bound heavy metals. The current study examined the neurotoxicological, systemic and pathological effects of in utero and lactational exposure to a metal mixture in the rodent model. The mixture of metals was based on frequency and cooccurrence of metals found at contaminated sites. Relative concentrations of metals in the mixture were based on current Canadian soil quality guidelines. The metals included: lead, cadmium, chromium, Copper, Zn and Ni. Pregnant rats were dosed with 0.00094, 4.7, and 9.4 mg/kg bw/day from gestation day 1 to PND 21. The lowest dose reflected estimated exposure based on current soil quality guidelines. Reproduction, mortality and weight gains were not affected in mothers or offspring. The highest dose of the mixture produced small alterations in motor coordination at Day 35 but no dose affected any other measure of motor function. Measures of reactivity and sensorimotor integration were not altered by any dose. Similarly, the mixture did not affect measures of learning and memory. Overall, there was no indication that doses at up to 1000 times the estimated exposure from current soil quality guidelines exerted any significant effects on neural system functioning. Analyses are currently underway to evaluate residue levels in mothers and offspring, pathology and systemic toxicity.

Bioaccessibility: Improving Risk Assessments for Contaminated Sites

Megan Lord-Hoyle, Environmental Sciences Group, Royal Military College of Canada, Kingston, Ontario, K7K 7B4, Canada, Tel: 613-541-6000 ext. 6922, Fax: 613-541-6596, Email: Megan.Lord-Hoyle@rmc.ca
Louise Meunier, Environmental Sciences Group, Royal Military College of Canada, Kingston, Ontario, K7K 7B4, Canada
Ken Reimer, Environmental Sciences Group, Royal Military College of Canada, Kingston, Ontario, K7K 7B4, Canada
Chris Ollson, Jacques Whitford Environment Limited, 2781 Lancaster Road, Ottawa, Ontario, Canada
Iris Koch, Environmental Sciences Group, Royal Military College of Canada, Kingston, Ontario, K7K 7B4, Canada

Regulations and guidelines for contaminated site remediation in Canada are currently based on the total concentration of the target substance in a particular substrate (soil, sediments or water). Contaminants in soil, however, maybe be tightly bound and thus there is a growing trend to consider bioavailability – the fraction of a substance that is absorbed by the organism – in determining suitable risk based endpoints for site remediation in Canada. Bioavailability is usually measured by using in vivo methodologies, which tend to be expensive and time consuming; bioaccessibility measurements using simulated gastrointestinal conditions to estimate the soluble fraction of a substance are increasing in desirability for incorporation into risk assessment. Bioaccessibility measurements can be carried out with a simple extraction procedure and hence are more accessible, less expensive and quicker than in vivo studies to estimate bioavailability. For these measurements to be meaningful, however, it is important to compare bioaccessibility to in vivo bioavailability results and determine their accuracy. This talk will focus on the development of bioaccessibility methods for arsenic and nickel, validation of the results using soils that have been subjected to in vivo testing, as well as the effect of more realistic exposure scenarios on risk assessment outcomes. It will also provide insight into the acceptance of the bioaccessibility results by Canadian regulators. It will conclude with a description of activities of Bioaccessibility Research Canada (BARC) – a newly formed network of parties interested in furthering the development and implementation of bioaccessibility in Canada.

The Assessment and Remediation of Contaminated Sites in Canada’s Arctic

Ken Reimer, Ken Reimer, Environmental Sciences Group, Royal Military College of Canada, Kingston, Ontario, K7K 7B4, Canada, Tel: 613-541-6000 ext. 6161, Fax: 613-541-6596, Email: reimer-r@rmc.ca
Daniela Loock, Environmental Sciences Group, Royal Military College of Canada, Kingston, Ontario, K7K 7B4, Canada

Procedures for the investigation and remediation of contaminated sites in temperate parts of North America are well developed, but similar activities in cold, remote locations with short work seasons such as the Arctic present unique challenges. It is essential, for example, to obtain a complete understanding of contamination issues during the site assessment so that the specifications for the remediation phase can be complete and not give rise to costly and difficult ‘extras’ during the actual cleanup. The cost of reaching the site with chartered aircraft, as well as the expense of supporting the team, requires the optimal use of field analytical and data management methods. The unique ecosystem, with a more linear food chain, rather than food web, requires a careful assessment of ecological risk. Similarly, the reliance of Inuit on country foods (caribou, seals etc) poses special concerns with respect to human health. The Environmental Sciences Group (ESG) is the Scientific Advisor for Canada’s largest environmental remediation project – the Distant Early Warning (DEW) Line project – and has conducted site assessments at over 100 Arctic sites. As well, they have worked extensively with Inuit in better understanding the risks posed by contaminants in the north and in communicating these risks effectively. This talk will provide an appreciation of the special concerns of working in the Arctic and will describe some of the tools that have been developed for both site assessment and remediation.