Risk Assessment as a Decision-Making Tool for Treatment of Emissions at a New Aluminum Smelter in Iceland: 1. Background and Introduction

ABSTRACT

Protection of human health and ecosystems is gaining importance in corporate decision- making regarding industrial development. During the design phase for an aluminum smelter in East Iceland, it became necessary to determine whether a wet scrubber system should be installed to reduce sulfur dioxide emissions. Predictive risk assessment was used to determine whether there would be a consequential difference in the level of risk to human and ecological receptors from constituents in air emissions from the aluminum smelter, either with or without wet scrubbers. Benchmark exposure concentrations were established for avian, mammalian, and plant receptors and were compared to air modeling predictions to develop risk estimates. Benchmark concentrations were derived using plant uptake models for fluoride and polycyclic aromatic hydrocarbons (PAHs), and food-web modeling for birds and mammals. Exposure models were developed for all receptors, and population-level effects were modeled for plant, bird, and mammal receptors. Results indicated that exposures under both scenarios are lower than risk thresholds, and overall risk was lower for a smelter without wet scrubbers. Thus, although mass loading of sulfur dioxide (and other constituents) would be reduced using wet scrubbers, the corresponding risk to ecological receptors would actually be higher because of higher exposure-point concentrations in air.

Key Words:

• risk assessment
• aluminum smelter
• air emissions
• Iceland

ACKNOWLEDGMENTS

The authors thank Melanie Edwards for technical assistance in statistical analyses, as well as Chris Shirley and Rick Nelson for technical editing, and Jason Pope for improving the graphical presentation of the data. Joe Scire and Irene Lee provided air and deposition modeling estimates used throughout the risk assessment. The authors also thank the anonymous reviewers whose comments and feedback significantly improved this article.

The authors received funding for this risk assessment from Alcoa. The opinions expressed are the independent scientific views of the authors.

Notes

^a BaP is assumed to be 1 percent of PAHs.

^b No difference between growing season and annual average;

^c Same parameters for dry scrubber only case and dry and wet scrubbers case;

^d Based on 1.8% sulfur coke;

^e Based on 3% sulfur coke;

^f Dry and Wet Scrubbers case only.