The New York state legislature approved a bill yesterday that aims to reduce air pollution drifting into New York from coal-burning power plants in Midwestern and Southern states. Under a federal program, utilities that reduce their emissions of sulfur dioxide below federal limits can sell credits to other companies giving them the right to exceed the limits, but the new legislation would fine New York utilities that sell their pollution credits to utilities in 14 Midwestern and Southern states that are blamed in part for acid rain problems in New York. Some New York utility companies immediately threatened to file suit over the bill.