Protocol for the Derivation of Environmental and Human ... - CCME

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Part C, Section 2 • inadequacies of the critical study. An additional uncertainty factor between one and five may be incorporated where there is sufficient information to indicate a potential for interaction with other chemical substances commonly present in the environment. If the chemical substance is essential or beneficial for human health, the dietary requirement is also taken into consideration in deriving the TDI. Numerical values of the uncertainty factor range from 10 to 10,000. Uncertainty factors greater than 10,000 are not applied since the limitations of such a database preclude the development of a reliable TDI. Where there are limitations in the protocol of the critical study a "tentative TDI" may be established. The TDI can be defined as: TDI = NO(A)EL OR LO(A)EL Uncertainty Factors Uncertainty factors are assigned by Health Canada based on professional judgement. Health Canada has accepted the responsibility for determining the Tolerable Daily Intake (TDI) for each contaminant addressed by the NCSRP. 78
Section 3 Exposure to Contaminants 3.1 Exposure to Mixtures of Chemicals No chemical substance exists alone in the environment; however, toxicological studies are usually carried out using single chemicals or simple mixtures. Hence, chemical interactions (additivity, antagonism, synergism, transformation, potentiation) are factors that may alter the risk posed by an individual chemical. In some cases, chemicals with similar structures will exhibit the same toxic effect but with different potency. For example, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) generally occurs in a mixture with other congeners of the polychlorinated dibenzodioxin (PCDD) family. The overall toxicity of a PCDD mixture will be greater than just the toxicity of the 2,3,7,8-TCDD it contains. However, the toxicity will be much less than if all the PCDDs are considered to have the same toxicity as 2,3,7,8-TCDD. In this case, PCDD mixtures are assessed as toxic equivalents (TEQs) with 2,3,7,8-TCDD being the most toxic congener. Other congeners are ascribed a toxic equivalent relative to TCDD. This approach is being investigated for some other chemicals such as Polychlorinated Biphenyls (PCBs) and Polycyclic Aromatic Hydro-carbons (PAHs), but at this time, combined toxicological assessments of more heterogeneous mixtures are not possible, and a chemical-by-chemical approach is recommended. 3.2 Determining Estimated Daily Intake Canadians are exposed to background contamination in the air, food, and water. This background exposure is quantified by the Estimated Daily Intake (EDI) for a particular contaminant. The EDI estimates the typical total concurrent background exposure from all known or suspected sources (air, water, food, soil, consumer products) via all known or suspected routes (inhalation, ingestion, dermal contact), often termed a multi-media exposure assessment (Appendix G), for the average Canadian {Figure 17 (a)}. However, it does not include exposures which may occur from a contaminated or remediated site {see Figure 17 (b)}. This background exposure is with us at all times. Consequently, risks posed by a contaminated site must be determined in addition to this background exposure. In general, mean concentrations in various environmental media used in estimating exposure are those reported to Health Canada by the authors of relevant accounts. Contaminant databases for environmental media may include non-detectable values, particularly for organic chemicals. Calculating a mean concentration requires that numeric values be substituted for non-detectable values. Traditional bounding approaches to this problem, have either been to substitute by zero or to substitute by the detection limit, respectively under- or over-estimating the true value (Haas and Scheff, 1990; Slymen et al., 1994). A simple intermediate assumption is that non-detectable values can be estimated by half the detection limit, although this may lead to an overestimate of exposure. Where appropriate, information on concentrations of NCSRP environmental contaminants in specific locales may also be used to estimate background exposure of some high exposure subgroups in the general population. 79
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A Protocol for the Derivation of En
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Readers' Comments The Canadian Coun
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Overview In response to growing pub
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mechanisms for migration of soil co
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procédures d'élaboration des reco
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• être absorbés par les plantes
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PART B Section 1 Derivation of Envi
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Section 2 Investigation of Contamin
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PART D Section 1 Derivation of the
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List of Figures 1 National Framewor
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Acknowledgements The CCME Subcommit
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Document Organization This document
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Bioaccumulation: The process by whi
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Denitrification: The gaseous loss o
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GGG Guidelines: Generic numerical l
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Mutagenicity: The ability of a chem
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xxxiv human exposure. Risk estimati
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Soil: Normally defined as the uncon
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VVV Volatilization: The chemical pr
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Section 1 The National Contaminated
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Part A, Section 1 6
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Part A, Section 1 1.2.2.2 Remediati
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Part A, Section 1 of, and establish
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Part A, Section 2 Section 2 Nationa
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Part A, Section 2 2.2 Limitations o
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Part A, Section 2 17
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Part A, Section 2 Industrial: where
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• the sensitivity of the test con
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Part A, Section 3 23
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Section 2 Level of Ecological Prote
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Part B, Section 2 2.3 Endpoint Defi
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Part B, Section 2 There is consiste
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Part B, Section 4 Section 4 Potenti
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Part B, Section 4 Figure 4 Simplifi
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Figure 5 Key Receptors and Exposure
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Part B, Section 5 grazing herbivore
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Part B, Section 5 5.2.2 Maintenance
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Page 84 and 85: Section 6 Uncertainty in Guidelines
Page 86 and 87: Section 7 Guidelines Derivation Pro
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Page 90 and 91: Part B, Section 7 a soil quality gu
Page 92 and 93: Where: NPER = no to Potential Effec
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Page 96 and 97: Part B, Section 7 data, the Median
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Page 100 and 101: Where: ERL = Effects Range Low, ECL
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Page 105 and 106: Part B, Section 7 Where the ECL lie
Page 107 and 108: Part B, Section 7 4. Fewer than thr
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Page 112 and 113: Part B, Section 7 Therefore, BCF =
Page 114 and 115: Part B, Section 7 ingestion (SQG I
Page 117 and 118: Section 8 Derivation of the Final E
Page 119 and 120: Part C, Section 1 65
Page 121 and 122: Part C, Section 1 various sites acr
Page 123 and 124: Part C, Section 1 Geographical unce
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Page 129 and 130: Part C, Section 2 Environmental con
Page 131: Part C, Section 2 extent, the steep
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Page 139 and 140: Part C, Section 4 within limits, th
Page 141 and 142: Part C, Section 4 Figure 19 Concept
Page 143 and 144: Part C, Section 4 4.2 Absorption of
Page 145 and 146: Part C, Section 4 In the case of no
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Page 150 and 151: Part C, Section 4 Commercial Land U
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Page 155 and 156: Part C, Section 5 these data are av
Page 157 and 158: Part C, Section 5 GEOCHEM (Mattigod
Page 159 and 160: Part C, Section 5 • K oc (sorptio
Page 161 and 162: Part C, Section 5 5.3.3 Evaluation
Page 163 and 164: Part C, Section 5 parameters, and s
Page 165 and 166: Section 6 Derivation of the Final H
Page 167 and 168: Part D, Section 1 101
Page 169 and 170: does not apply to the commercial or
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Page 174 and 175: References Aldenberg, T., and W. Sl
Page 176 and 177: References -dwelling Organisms", Ab
Page 178 and 179: References 112
Page 180 and 181: References Hill, E.F., and D.J. Hof
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References Paustenbach, D.J., (1989
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References Summers, J.K., H.T. Wils
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Appendix A Appendix A Nutrient and
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Appendix A Figure A.1 Simplified Te
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Appendix A 4.1 Agricultural and Res
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Appendix A References Bååth, E.,
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The Subcommittee considers that exp
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Appendix B P l P r BW = percent pro
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Appendix B Substituting equation 5
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Appendix B Where no MRL exists, the
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Appendix B Then, the remainder (T R
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Appendix B For carcinogens, total i
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Appendix C Rearranging [2] and subs
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Appendix C References Chiou, C.T.,
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Appendix D uncontaminated organic m
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Appendix D R = recharge, m/yr A = a
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Appendix D 2.3.3 Hydraulic Gradient
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Appendix D 2.3.5 Site Length The le
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Appendix D Table D.2 Lower Quantile
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Figure D.2 Conceptual Model of Dilu
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Appendix D Figure D.3 Recharge Esti
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Appendix D 159
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Smith, A.E., P.B. Ryan, and J.S. Ev
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Appendix E C K L V is the climate f
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Appendix E contaminant concentratio
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Appendix F Appendix F Multi-media E
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Appendix F example, fish BCFs are t
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Appendix G 2.2 Contaminant Vapour T
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Appendix G Table G.1 Equations Used
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Appendix G at the outset that, rath
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Appendix G 4.4 Application of the R
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Average outdoor summer temperature
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Appendix G References Alberta Envir
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