Phase 2 Passive Dustfall Monitoring August 14, 2019 Project No: 19Y0006 EDI ENVIRONMENTAL DYNAMICS INC. 11 Mary River Project Phase 2 Proposal ECCC-FC1 ATTACHMENT 2: HUMAN HEALTH BASED DUSTFALL THRESHOLDS FOR MINE AND PORT SITE Date: October 15, 2019 To: Lou Kamermans, BIM From: Christine Moore, Intrinsik cc : Mike Setterington, EDI; Mike Lepage, RWDI, Richard Cook, KP; Sara Wallace and Dan Jarratt, Stantec Re: Human Health Based Dustfall Thresholds for Mine and Port Site – DRAFT V 3 While dustfall guidelines exist in several jurisdictions (such as Ontario and Alberta), they are generally based on soiling, as opposed to human health considerations. The Government of Nunavut is requesting that Project-specific dustfall guidelines protective of human health be developed for use within the Air Quality and Noise Abatement Management Plan (AQNAMP) to define rates which would be associated with management actions. Project-specific dustfall guidelines developed for consideration of human health within the Project area need to consider the model predictions for dustfall, in addition to the size of affected areas and potential exposure that could occur based on consumption rates for resources harvested within the area. These factors were used to define potential exposure scenarios. An additional consideration when developing dustfall rates protective of human health is the different geochemistry at the mine and port areas based on the existing site-specific geochemistry of the dustfall samples previously collected. As all rock and soil contain naturally occurring metals and metalloids (which will be referred to as metals), the dustfall generated from Project activities also contains metals. Iron is the most common metal in the dustfall, representing 4.43% of total dustfall at the Mine site, and 3.03% at the Port site. This is expected because the ore is rich in iron. Aluminium is the second most common metal in the dustfall (averaging 2.83% at the Mine and 1.58% at the Port). All remaining metals are either present at less than 0.02% (e.g., copper, chromium, barium, nickel), or present at even lower percentages (e.g, antimony, cobalt, lead, silver, thallium). Arsenic was detected in 39 of 216 dustfall samples, with the vast majority of samples being below a level of detection. Mercury and selenium were completely non-detectable in all dustfall samples at the Mine, Port and Tote road stations. Cadmium was also rarely detected in dustfall (7 samples had detectable cadmium levels of 216 samples taken). Human Health Risk Assessment (HHRA) modelling conducted in HC-TIR-03 (Country foods submission, March 2019), and supplementary modelling conducted to determine dust management action trigger levels has indicated that the most sensitive risk drivers are the consumption of berries (as a result of dust deposition onto berries), and consumption of caribou organ meats (due to potential for accumulation of cadmium and/or mercury as a result of lichen consumption by caribou). For berry consumption, arsenic exposure was the most sensitive Chemical of Potential Concern (COPC) at the Milne Port site. At the Mine site, aluminum exposure related to berry consumption was the most sensitive COPC. Page 1 of 7 The HHRA model used conservative (i.e., biased high) cadmium, mercury and arsenic geochemistry ratios for the following reasons: • Cadmium is generally not detectable in the dustfall samples (detected in only 3% of near field dustfall samples from 2015 to 2016). The geochemistry for cadmium applied in the assessment was based on a ratio derived from a single detected sample at the mine site (the rest of the samples from 2015 to 2016 were below the level of detection for cadmium). To be conservative (i.e., concentration biased high), the selected geochemistry ratio of 0.0012% was applied at the Mine (based on a single detected sample), whereas ratios for the Port were lower at 0.0009% (based on an average of all samples). Therefore, since the assumed geochemistry is likely biased high, the predicted risks are also biased high. • Mercury was not detectable in all dustfall samples. The geochemistry ratio at the Mine site was 0.0011%, and at the Port was 0.0021%, based on non-detect values (see TSD-11). The geochemistry ratios are therefore based on a non-detect ratio, and therefore the risk estimates are biased high. • Arsenic geochemistry ratio at the Mine was based on detected samples only (0.00333%), whereas the Port arsenic geochemistry ratio was based on an average of all data (0.018%). Had detected samples been used at the Port, the ratio would have been lower (0.0114%). To identify possible dustfall indicator rates for the AQNAMP to be protective of human health and to derive levels associated with management action trigger levels, the HHRA model was used to run a variety of exposure scenarios based on varying annualized dustfall rates (g/m2/year) selected from the air dispersion modelling isopleths presented in TSD-07. The size of the area affected by dustfall in the isopleth figures was used to tailor the various exposure scenarios [see Figures D-14 (Milne Port) and E- 13 (Mine site) from TSD-07 — attached]. For example, if dust is deposited across a wide area at a given rate, then a higher exposure potential was assumed based on the potential for a greater number of berries to be harvested in a broader area, and for caribou to spend a greater amount of time in a larger area. In contrast, if dustfall of the same concentration occurs in a smaller area, then there is lower exposure potential given the smaller size of the potentially affected area and associated lesser amount of harvest. The following consumption assumptions were either held constant or varied based on the following reasoning: • In all scenarios, the full annualized consumption rate for Arctic hare, ptarmigan and medicinal plants was assumed to occur in the Project areas, regardless of the size of the affected area. • Consumption of berries varied depending on the size of the area potentially affected by dust deposition. Consumption rates were varied in the dust management action trigger level analysis from 100% (i.e., all berry consumption for a year was assumed to come from areas affected by dust), to 50% (half of the annual berry consumption rate was assumed to come from areas affected by dust) to 0%. Note that berries are not prevalent in the area in general (EDI 2015). • Consumption of caribou was held constant (i.e., all caribou meat and organ meat consumption were assumed to come from the Project area experiencing dustfall). However, the time that a Page 2 of 7 caribou spent in the area influenced by dustfall varied from 1% of their annual cycle to up to 33% of their annual cycle. In HC-03, caribou were assumed to be not affected by the Project because the majority of caribou are found distant to the Project area, and the time spent in the Project area has been quantified as less than one day, based on existing collar analysis (EDI; M. Setterington, personal communication). As discussed in HC-TIR-03, collar data for caribou illustrates very low interaction with the PDA (including a 100 m buffer beyond the PDA, which approximates the maximum extent of measurable dustfall). Of the three collared caribou that were found within 100 m of the PDA between 2008 – 2010, the number of hours in a given year ranged from 0:51 hours to 4:05 hours, with a total percentage of time in the PDA/Year ranging from 0.009% to 0.0047% (based on 8,760 hours in a year). Based on this, and the large home range of caribou, the potential for the project to influence either caribou meat or organ meats is extremely low. Regardless, caribou were included in the baseline Country Foods assessment and it was assumed that influence from the Project on meat concentrations was limited. In order to identify management action trigger levels for the dustfall rates in this dust exposure analysis, it was assumed that caribou could move into the area for periods of time, thus accounting for potential exposures which may be incurred from dustfall via consumption of lichen, and to enable the risk-based dustfall rate to reflect this potential. Based on these considerations, a matrix was used to create low, moderate and high exposure scenarios for annual dustfall rates. In each of these scenarios, the Incremental Lifetime Cancer Risk (ILCR) for arsenic exposures remains at levels at or below 1: 100,000, and therefore risks are considered negligible. For other important COPCs, such as cadmium and mercury, Hazard Quotients (HQ) for the Project scenario remain below 0.2, and are therefore considered to be negligible, or are considered acceptable based on the conservative assumptions used (e.g., mercury is non-detect in the ore, but was assumed to be present). Table 1 presents the various scenarios for each of the selected dustfall management action trigger levels. Note that due the arsenic geochemistry ratios at the Milne Port project area being higher than those at the mine (based on the site-specific geochemistry data from the dustfall samples), dust management action trigger levels are more conservative at the Milne Port area than the mine area. The arsenic geochemistry ratio at the Mine (based on detected samples only) was 0.0033%, whereas the ratio applied at the Port (based on all samples, including non-detect samples) was 0.018%. Based on the model results, the dustfall predictions from the Phase 2 Project do not raise concerns about berry or caribou consumption given that; 1) there are few berry sources within the PDA, and 2) caribou are unlikely to be “tied” to foraging in the project area and the exposures used in this model are likely gross overestimates of potential uptake – and even so are unlikely to create a health risk.