Glencore's debt is the most expensive to insure in an index of credit-default swaps on 125 investment-grade companies in Europe, according to data provider S&P Capital IQ. The contracts, which are also the worst performing in the benchmark this year, surged more than fivefold since January to 772 basis points. Anglo American, the next riskiest, rose 380% to 763 basis points. S&P's negative outlook means there's a risk it will review the credit rating if the macro environment is poor, according to Redmond. The company was given a negative outlook in September. Lower commodity prices affect key credit metrics that S&P and Moody's Investors Service use when assigning ratings, such as net debt to Ebitda. If commodity prices fall another 5%, Glencore needs to bring total debt reduction closer to $15 billion to preserve the rating, which is two levels above junk, according to Macquarie.