Marsh said that, generally, markets have given a variety of responses ranging from silence to "amended retroactive endorsements." This week, the broker said some excess liability carriers indicated that they plan to add broadly worded, event-specific exclusions to their 2010-2011 policies that would eliminate coverage from the Deepwater disaster.

Marsh said this is an emerging market trend that raises concerns for clients if they should notify carriers now about a loss event.

The issue is given heightened concern as several carriers indicated they plan to strictly enforce the time limits in the policies, Marsh said.

Examining Marsh's announcement, Diana B. Reitz, editorial director for FC&S Online said in an e-mail, "Everyone knows about this pollution event, but many policyholders cannot yet know with certainty whether their property will be damaged or a product they manufactured will be drawn in to a liability situation. However, insurance policy terms are certain. Timeframes for notice are not unusual and typically are quite clear."

She continued that this reaction "is putting insureds in an untenable situation. Those who fail to give notice, risk claim denials because they did not comply with the black and white terms of the policy. Those who do comply risk voiding coverage for future damages or liability if exclusionary language is attached subsequent to notice. It will be interesting to see what litigation arises if insurers do follow through with this approach and future claims are denied under its banner."