Amid heated controversy over the Bush administration’s plans to weaken air pollution regulations, two environmental organizations and a large New Jersey utility are releasing today a new study ranking the worst polluters in the power industry. The study, “Benchmarking Air Emissions of the 100 Largest Electric Generation Owners in the U.S. — 2000,” tracked company emissions records for four of the sector’s most toxic compounds: sulfur dioxide and nitrogen oxide (which contribute to acid rain and haze), mercury (which is toxic to humans), and carbon dioxide (which contributes to global warming). It concluded that a handful of companies account for at least half of all those emissions. The three largest U.S. electricity companies (American Electric Power, the Southern Company, and the Tennessee Valley Authority) together produce 17 to 24 percent of the industry’s total emissions — and the last two have heavily lobbied the Bush administration for looser clean air standards.