An analysis of 1985 pollution data found Ohio, Indiana, Texas and California were the largest emitters of three pollutants linked to the formation of acid rain, the Environmental Protection Agency reports.
In a study touted as the most comprehensive and accurate assessment of manmade acid rain "precursor" emissions to date, the EPA also said that nationwide at least 70 percent of all sulfur dioxide emissions - a key chemical of concern - come from coal-fired electric power plants.The analysis, released last week, included emissions data for nitrogen oxide and volatile organic compounds as well as sulfur dioxide. Those three pollutants are considered major contributors to acid rain, which scientists say has damaged forests, streams and lakes in the Northeast and Canada.
Scientists say sulfur dioxide and nitrogen oxide react with other chemicals in clouds to form sulfuric acid and nitric acid. Volatile organic compounds contribute to both those processes and also figure prominently in the creation of ozone, a primary component of urban smog.
The report was compiled as part of 10-year National Acid Precipitation Assessment Program, which began in 1980. The 1985 "emissions data inventory" is intended to serve as a benchmark by which scientists can measure future air pollution trends.
The report estimated average annual emissions from a wide variety of sources, including electric power plants, factories, smelters, trash incinerators, sewage treatment plants, toxic waste dumps, home furnaces, bakeries, motor vehicles, planes, trains, forest fires and evaporation losses from gasoline as well as organic solvents used in a large number of industrial processes.
The analysis focused on industrial facilities emitting more than 1,000 tons per day of pollution because they account for 97 percent of all sulfur dioxide emissions, 90 percent of all nitrogen oxide emissions and 61 percent of all volatile organic compound emissions. Altogether, the report included estimates of emissions from 3,300 different industrial processes.
The emission estimates were derived from actual pollution measurements from state environmental agencies in all 48 mainland states and the District of Columbia. EPA officials said the estimates were subject to unprecedented double-checking procedures to ensure their validity.
As a result, the report "represents the most complete and accurate inventory of acid rain precursors to date," wrote officials with the EPA's Air and Energy Engineering Laboratory of Triangle Park, N.C., which prepared the study.
Among other conclusions, the report said industrial activity nationwide in 1985 emitted a total of 23 million tons of sulfur dioxide, 20.6 million tons of nitrogen oxide and 22.3 million tons of volatile organic compounds.
A state-by-state breakdown showed that:
-Ohio was the largest emitter of sulfur dioxide, releasing 2.5 million tons. It was followed by Indiana, 1.8 million tons, Texas, 1.47 million tons, Pennsylvania, 1.42 million tons, and Illinois, 1.39 million tons.
-Texas was the biggest emitter of nitrogen oxide, at 2.4 million tons, followed by California, 1.2 million tons, and Ohio, 1 million tons.
-Texas was the greatest source of volatile organic compounds, at 2.3 million tons, followed by California, 2.1 million tons, and Ohio, 1 million tons.
In regard to specific pollutants, the study said power plants emitted 16.2 million tons of sulfur dioxide in 1985 - 70 percent of the total.
It also found that power plants released 56 percent of that sulfur dioxide through smokestacks exceeding 480 feet in height, meaning the pollution was likely to travel great distances before falling back to earth. Scientists believe the use of tall stacks may explain why the Northeast and Canada bear the brunt of sulfur dioxide emissions released in the Midwest.
The study said motor vehicles are the biggest single source of both nitrogen oxide and volatile organic compounds.
For nitrogen oxide, motor vehicles contributed 43 percent of total emissions and power plants 30 percent. For volatile organic compounds, motor vehicles represented 33 percent of total emissions and evaporation of organic solvents account for 21 percent.
In Ohio and Indiana, coal-powered electric generating plants were by far the largest source of sulfur dioxide and also contributed roughly half of each state's output of nitrogen oxide, the study found.
In Texas, coal-fired power plants accounted for about one-third of the state's sulfur dioxide pollution and petroleum and chemical manufacturing also contributed about a third.
Not surprisingly, motor vehicles were the major source of nitrogen oxide and volatile organic compound emissions in California.