The steep slide in BP's share price is bad news for UK pension funds - the vast majority of which will hold a stake in the company.
Defined benefit pension schemes are typically thought to have around 1.5% of their assets invested directly in BP, accounting for around 6% of all the money they hold in UK equities.
But some funds may hold considerably more, for example a pension scheme that tries to replicate the performance of the FTSE 100 would have around 6% of its total assets invested in the company.
BP's share price has now fallen by around a third since the Deepwater Horizon rig exploded and sank on April 20, killing 11 workers.
It is difficult to put a figure on exactly how much this will have wiped off the value of pension schemes, but it is thought to be hundreds of millions of pounds, if not billions of pounds, once the impact on defined contribution schemes and personal pensions is also factored in.
Laith Khalaf, pensions analyst at Hargreaves Lansdown, said: "The poor performance of a big stock like BP can have a disproportionate impact on funds.
"There have also been other falls in the stock market as well. If the market had been doing well in recent months, it might not have been such a big issue."
David Paterson, head of corporate governance at the National Association of Pension Funds, said around 1.5% of a typical defined benefit pension scheme's assets would be held in BP shares.
But he said: "The vast majority of pension schemes will have diversified portfolios, so the impact of either good news or bad news is quite diluted when you adjust it for the size of the holding."
Another concern for pension schemes is whether BP's generous dividend will come under threat as a result of the oil spill.
Last year BP paid out £10 billion in dividends, accounting for £1 out of every £7 paid out in dividends by FTSE 100 companies.
The high yield has made the stock particularly popular with pension funds, as it means investors benefit from a strong annual income, as well as any long-term growth in the share price.
The group has not announced any plans to reduce its dividend, but there are fears that the growing cost of the disaster, which had reached 990 million US dollars (£682.3 million) by yesterday, excluding the impact on BP's share price, will force it to cut the pay-out.