If you visit a Web site called "Midwest hazecam," you will see blurry skylines of six Midwestern cities, a mixture of blues and greens dulled by ground-level ozone and soot pollution from cars and power plants. The videos are updated every 15 minutes, but they never look very clear. The air is always dirty.

The pictures of Cincinnati are the least blurry of the bunch. There are still days when low-hanging smog clings to the hillsides of the Ohio River, but for a combination of reasons, air quality is considerably better in Cincinnati than it was 20 years ago or even 10 years ago. In 1988, there were 34 days when the air was so dirty it compromised the health of anyone who dared go outside. Since then, there haven't been more than eight such days a year, and in 2000 and 2004, there were none.

Technically, Cincinnati still is not quite up to federal standards. The U.S. Environmental Protection Agency uses six "criteria pollutants" as indicators of air quality, and while Cincinnati now meets acceptable levels on four of them, it's above the prescribed limits on the other two--ozone and particulates. Still, Ohio environmental officials felt confident enough this summer to announce an end to auto emissions testing in Cincinnati and in Dayton, where progress also has been recorded. The tests will end on December 31, when the state's contract with EnviroTest Systems--the company that runs Ohio's E-Check emissions-control program--is set to expire.

Ohio EPA officials are willing to credit E-Check with keeping 100,000 tons of pollutants out of the skies in 14 counties over the past 10 years. But they argue that tailpipe tests have outlived their usefulness as a form of pollution control. "Cars are manufactured cleaner today, emissions equipment lasts longer and there are cleaner fuels available," says Heidi Griesmer, of the Ohio EPA. "These advancements cause the program to be less effective." Griesmer and others insist that simply having a "check engine" light for emissions problems in late-model cars does most of what testing programs were set up to accomplish.

Other states and metropolitan areas have been making similar arguments. In the past six years, four states have ended tailpipe testing entirely, and seven others have scaled it back or modified the process. Minnesota eliminated its eight-year-old testing program in 1999, and Florida stopped in 2000. The city of Louisville ended its program in 2003, asserting that emissions reduction put in place by local businesses had eliminated the need for vehicle testing.

The fact is, tailpipe emissions testing is unpopular with the public and with elected officials everywhere in the country. Critics cite expense, inconvenience and fraud as problems endemic to any testing system. Minnesota's legislature acted after hearing numerous complaints about delays at test garages and the exorbitant cost of fixing carburetors and mufflers that failed to pass. Connecticut had to shut down its testing program for six months last year after employees from several garages around the state were arrested for performing "ghost tests," a fraudulent practice in which results for failing cars are replaced with those from clean ones. This summer, when Ohio's legislature debated whether to ease up on tailpipe tests in Cincinnati, one speaker called the program there "as popular as a flat tire."

The federal government has the legal authority to require virtually any form of air pollution remedy it wishes in any area that fails to meet even one of the six criteria. That includes most of the country. Thirty-six states currently have cities and/or counties in non- attainment for one or more categories. All those states are required to provide an action plan and air improvement timetable for federal approval, and EPA can demand tailpipe testing where it considers that necessary. Thirty-two states are still conducting the tests.

In the past several years, however, EPA has grown increasingly flexible on the tailpipe issue. It approved Louisville's decision, and allowed eight counties in the Detroit area to discontinue testing last year as long as the counties agreed to use other strategies to meet tougher clean-air standards three years ahead of schedule. Similar judgments have been made for parts of Arkansas, Indiana, Maryland, North Carolina, Pennsylvania and Virginia.

"The tests were an essential part of air quality protections for many states--and still are," says John Millett, an EPA spokesman. "But with clean cars coming on line, we are able to reduce emissions to keep up with growth. If a state can make a persuasive case, EPA will consider it."


Some states have acted without EPA approval. Five years ago, when Florida Governor Jeb Bush ended tailpipe testing unilaterally, on the grounds that it was an unnecessary and expensive burden to motorists, there were concerns that the federal government would cut off millions of dollars in highway funds. But Florida imposed stricter rules on power plants and other industrial polluters, and has managed to get all its major metropolitan areas out of non-attainment status.

Still, unilateral cessation of a tailpipe program remains politically risky. Indiana, which eliminated testing programs in two counties this year without federal approval, stands to lose a substantial amount of highway money unless it can come to an agreement with EPA.

Ohio is walking a fine line with the federal agency--EPA is allowing it to quit testing in Cincinnati and Dayton, but insists on continuing in Cleveland and Akron, where ozone levels remain among the highest in the nation. Even in those dirtier parts of the state, however, testing is being cut back substantially--the legislature approved a plan this summer that will exempt an additional 370,000 cars from tailpipe tests in Northeast Ohio, mostly cars that are between two and four years old.

As part of the deal to end testing altogether in Cincinnati and Dayton, Ohio agreed to other measures aimed at achieving the same results over a larger area. The state says that by April 2006, it will implement a comprehensive plan to replace emissions reductions lost through the discontinuation of E-Check. Among the measures being considered are ones that would include mandating of cleaner fuels, lower-evaporating solvents and more efficient spray guns for auto body shops. But Ohio has also hinted that it might take legal action against EPA if it is not granted some of the flexibility in Cleveland and Akron that it received in Cincinnati and Dayton.

Other states are trying different sorts of experiments. California's South Coast Air Quality Management District, which covers most of the Los Angeles region, recently announced a plan to use a remote-testing system to measure air pollution from 1 million vehicles as they enter freeways and navigate roads in Los Angeles, Orange, San Bernardino and Riverside counties.

Under this technology, an emissions analyzer identifies and quantifies tailpipe pollutants using infrared and ultraviolet spectroscopy. The tests are conducted by vans parked along the side of highways and at entrance ramps. A camera photographs the license plate of every vehicle tested. The sensors are supposed to be able to test 3,000 passing vehicles per hour. Colorado is running a pilot project of the same system, and two clean readings in 10 months allow a motorist to pay a $25 testing fee and get a renewed emissions inspection sticker in the mail.

So far, however, EPA will allow remote sensors only to complement tailpipe-testing programs, rather than to replace them. It says the technology is still prone to false readings caused by wind currents, the proximity of vehicles, the temperature of the engine and the presence of water and snow on the roadway. And it continues to insist that for much of the country, the conventional tailpipe test remains the most important pollution-control technique.

"We've reduced air pollution quite a lot over the last 30 years," EPA's John Millett says. "But different areas are going to vary widely--a heavy-industry area will probably have a larger portion of pollution coming from that sector, and that might make mobile sources look insignificant. But you can turn that around in a place like California where mobile sources are the dominant sources of pollution. It's hard to break down. It is all about the state planning process and coming up with the right approach."