A new study says mercury emissions from the proposed Carolinas Cement Plant in Castle Hayne would not adversely affect public health. The study by Seattle-based Intertox says a typical resident would encounter less mercury than in one and three-quarter teaspoons of canned tuna a month. Opponents of the plant say pollution, including mercury, would cause harm to people in the area as well as the northeast Cape Fear River. Carolinas Cement paid for the study, but Intertox says the cement company did not receive the results until they were released to the media Monday.