In the study, the Environmental Protection Agency evaluated two of the four laboratory tests currently available to measure the effectiveness of surface washing agents: the inclined trough test and the swirling coupon test. The agency used two standard reference oils (Prudhoe Bay and bunker C), two test surfaces (stainless steel and porcelain tile), and three cleaning agents (Corexit 9580, Corexit 7664, and Citrikleen XPC) to evaluate the precision, cost, and ease of operations of the two tests. The study concluded that the overall performance of the two tests is similar but that costs for the inclined trough test are lower. Overall, there is concern as to whether any of the four existing tests are appropriate measures of surface washing agent effectiveness. Two problems exist: none of the tests measures the amount of oil remaining on the surface after washing, and none of the tests accounts for how easily oil is removed from the water after being washed off the surface. Therefore, more research is needed before a surface washing agent effectiveness test can be adopted as a regulatory tool.