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Federal Register / Vol. 86, No. 148 / Thursday, August 5, 2021 / Rules and Regulations
immune impairment or delayed e.g., cancer. Although it is true that some bears may be directly affected by spilled oil initially, the long-term impact could be much greater. Long-term effects could be substantial through complex environmental interactions compromising the health of exposed animals. For example, PAHs can impact the food web by concentrating in filterfeeding organisms, thus affecting fish that feed on those organisms, and the predators of those fish, such as the ringed seals that polar bears prey upon.
How these complex interactions would affect polar bears is not well understood, but sublethal, chronic effects of an oil spill may affect the polar bear population due to reduced fitness of surviving animals.
Polar bears are biological sinks for some pollutants, such as polychlorinated biphenyls or organochlorine pesticides, because polar bears are an apex predator of the Arctic ecosystem and are also opportunistic scavengers of other marine mammals.
Additionally, their diet is composed mostly of high-fat sealskin and blubber Norstrom et al. 1988. The highest concentrations of persistent organic pollutants in Arctic marine mammals have been found in seal-eating walruses and polar bears near Svalbard Norstrom et al. 1988, Andersen et al. 2001, Muir et al. 1999. As such, polar bears would be susceptible to the effects of bioaccumulation of contaminants, which could affect their reproduction, survival, and immune systems.
In addition, subadult polar bears are more vulnerable than adults to environmental effects Taylor et al.
1987. Therefore, subadults would be most prone to the lethal and sublethal effects of an oil spill due to their proclivity for scavenging thus increasing their exposure to oiled marine mammals and their inexperience in hunting. Due to the greater maternal investment a weaned subadult represents, reduced survival rates of subadult polar bears have a greater impact on population growth rate and sustainable harvest than reduced litter production rates Taylor et al. 1987.
Evaluation of the potential impacts of spilled Industry waste products and oil suggest that individual bears could be adversely impacted by exposure to these substances Oritsland et al. 1981. The major concern regarding a large oil spill is the impact such a spill would have on the rates of recruitment and survival of the SBS polar bear stock. Polar bear deaths from an oil spill could be caused by direct exposure to the oil. However, indirect effects, such as a reduction of
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prey or scavenging contaminated carcasses, could also cause health effects, death, or otherwise affect rates of recruitment and survival. Depending on the type and amount of oil or wastes involved and the timing and location of a spill, impacts could be acute, chronic, temporary, or lethal. For the rates of polar bear reproduction, recruitment, or survival to be impacted, a large-volume oil spill would have to take place. The following section analyzes the likelihood and potential effects of such a large-volume oil spill.
Risk Assessment of Potential Effects Upon Polar Bears From a Large Oil Spill in the Beaufort Sea In this section, we qualitatively assess the likelihood that polar bear populations on the North Slope may be affected by large oil spills. We considered: 1 The probability of a large oil spill occurring in the Beaufort Sea;
2 the probability of that oil spill impacting coastal polar bear habitat; 3
the probability of polar bears being in the area and coming into contact with that large oil spill; and 4 the number of polar bears that could potentially be impacted by the spill. Although most of the information in this evaluation is qualitative, the probability of all factors occurring sequentially in a manner that impacts polar bears in the Beaufort Sea is low. Since walruses are not often found in the Beaufort Sea, and there is little information available regarding the potential effects of an oil spill upon walruses, this analysis emphasizes polar bears.
The analysis was based on polar bear distribution and habitat use using four sources of information that, when combined, allowed the Service to make conclusions on the risk of oil spills to polar bears. This information included:
1 The description of existing offshore oil and gas production facilities previously discussed in the Description of Activities section; 2 polar bear distribution information previously discussed in the Biological Information section; 3 BOEM Oil-Spill Risk Analysis OSRA for the OCS Li and Smith 2020, including polar bear environmental resource areas ERAs and land segments LSs; and 4 the most recent polar bear risk assessment from the previous ITRs.
Development of offshore production facilities with supporting pipelines increases the potential for large offshore spills. The probability of a large oil spill from offshore oil and gas facilities and the risk to polar bears is a scenario that has been considered in previous regulations 71 FR 43926, August 2, 2006; 76 FR 47010, August 3, 2011; 81

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FR 52275, August 5, 2016. Although there is a slowly growing body of scientific literature e.g., Amstrup et al.
2006, Wilson et al. 2017, the background information available regarding the effects of large oil spills on polar bears in the marine arctic environment is still limited, and thus the impact of a large oil spill is uncertain. As far as is known, polar bears have not been affected by oil spilled as a result of North Slope Industry activities.
The oil-spill scenarios for this analysis include the potential impacts of a large oil spill i.e., 1,000 bbl or more from one of the offshore Industry facilities: Northstar, Spy Island, Oooguruk, Endicott, or the future Liberty. Estimating a large oil-spill occurrence is accomplished by examining a variety of factors and associated uncertainty, including location, number, and size of a large oil spill and the wind, ice, and current conditions at the time of a spill.
BOEM Oil Spill Risk Analysis Because the BOEM OSRA provides the most current and rigorous treatment of potential oil spills in the Beaufort Sea Planning Area, our analysis of potential oil spill impacts applied the results of BOEMs OSRA Li and Smith 2020 to help analyze potential impacts of a large oil spill originating in the Beaufort Sea ITR region to polar bears. The OSRA
quantitatively assesses how and where large offshore spills will likely move by modeling effects of the physical environment, including wind, sea-ice, and currents, on spilled oil. Smith et al.
1982, Amstrup et al. 2006a.
A previous OSRA estimated that the mean number of large spills is less than one over the 20-year life of past, present, and reasonably foreseeable developments in the Beaufort Sea Planning Area Johnson et al. 2002. In addition, large spills are more likely to occur during development and production than during exploration in the Arctic MMS 2008. Our oil spill assessment during a 5-year regulatory period is predicated on the same assumptions.
Trajectory Estimates of Large Offshore Oil Spills Although it is reasonable to conclude that the chance of one or more large spills occurring during the period of these regulations on the Alaskan OCS
from production activities is low, for analysis purposes, we assume that a large spill does occur in order to evaluate potential impacts to polar bears. The BOEM OSRA modeled the trajectories of 3,240 oil spills from 581

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