When a company that has been designated a responsible party for environmental cleanup costs files for bankruptcy protection, the ramifications of the filing are not limited to a determination of whether the remediation costs are dischargeable claims. Another important issue is the circumstances under which contribution claims asserted by parties coliable with the debtor will be allowed or disallowed in the bankruptcy case. This question was the subject of rulings handed down early in 2011 by the New York bankruptcy court presiding over the chapter 11 cases of Lyondell Chemical Co.