Regulation is an art as well as a science. Earl Dotter's camera has taught him this.

Dotter's exhibit, a collection of 40 photographs titled "The Quiet Sickness: A Photographic Chronicle of Hazardous Work in America," opened Tuesday at the Department of Labor--timed to coincide with Labor Day on Sept. 6 and Occupational and Environmental Health and Safety Week, sponsored by the American Industrial Hygiene Association, from Aug. 30 to Sept. 3.

The exhibit, open through Sept. 17, includes window washers outside the Empire State Building; a snowplow operator struggling to strap on tire chains during a storm in Tracy, Minn.; lettuce harvesters in Salinas, Calif.; a laborer at the Central Artery tunnel in Boston; and a devastated widow burying her husband after the Scotia mine explosion in Oven Fork, Ky.

Dotter's work, representing 25 years of workplace history, shows in black and white the gritty realities of what it's like to work in the closed space of a mine, the devastation of losing a life from a work-related injury, and the reduced circumstances of families who lose a breadwinner to a dangerous job. Dotter took his camera across the country looking for faces to tell the story of hard work.

"When you put a real individual in the photo, it resonates and gets us away from putting numbers on people's lives and their health and safety," Dotter said as he was hanging his photos Tuesday evening before a reception at the department.

That's the sobering message conveyed by the collection. The brighter picture, Dotter said, is that some of these conditions no longer exist because of improvements brought about by federal standards. Collaborations between the government, unions and industry have removed many hazards that once made hard labor a dangerous way to earn a living.

In mining, fatalities have been cut from 1,695 in 1940 to 80 last year, according to Labor Department statistics. Control of methane in mines, better ventilation, roof supports and control of the dust that causes black-lung disease have been the result of various federal standards.

In the textile industry, brown-lung disease, which results from dust-laden looms that cause unrelenting coughing and sleeplessness, has almost been eradicated. Prior to 1978, there were 40,000 cases annually; in the 1980s, that number was cut to 1,000, as the rate dropped.

Workers no longer climb up on high scaffolds or work on buildings without "fall-arrest systems" to catch them if they drop. Men and women who dig trenches have less fear of being buried by collapsing walls because of rules that mandate how those walls must be shored up. A 1988 grain handling standard cut dust explosions, and deaths, dramatically.

"As eloquently as any testimony offered before Congress, Earl Dotter's photographs make clear the need for such basic but hard-fought health and safety advances as ventilation standards to prevent methane explosions in underground coal mines; fall-protection devices for window washers and other workers on scaffolds; and the cotton-dust standard in the textile industry," Secretary of Labor Alexis M. Herman said in an interview.

Dotter, 56, who at one juncture in his career almost became a fashion photographer, describes himself as a shy person who has derived his own quiet satisfactions from the not-very-lucrative world of being in factories and fields with ordinary workers.

The Labor Department offered its walls for Dotter's work in part because the photos also humanize the subjects of the sometimes contentious debates that have taken place over the years in Washington concerning mine safety, protections for construction workers, workplace ergonomic standards, and safety measures to protect health care, textile and agricultural workers.

Dotter is pleased that he is illustrating progress but he hopes his prints--the collection also is contained in a book of the same name--have the same archival value as photos taken by Lewis Hine that exposed abusive child labor practices at the turn of the last century.

"My job is to document changing work life at the century's turn," said Dotter.

He realizes most of the people portrayed in the exhibit are already distant in time and place from the offices and "clean" jobs that employ a growing number of Americans as technology has changed society. Jobs in some of the industries he photographed have been reduced significantly, displaced by imports, technology and mergers.

Herman's Labor Day address and report, which talk about trends and challenges for work in the 21st century, point out that want ads today seek Webmasters, computer system operators, desktop publishers and other technology wizards.

"Dotter's work depicts where we have come from. But there is still room for improvement. We are not where we need to be," said James Thornton, president of the American Industrial Hygiene Association, whose members are hired by employers to combat some of the workplace hazards that Dotter captured on film.

Dotter, a fellow at the Harvard School of Public Health, is not done setting up his tripod. He turns his focus next to workers in the commercial fishing industry in New England, whom he believes hold the most dangerous jobs in America today.

"It still is a world of work out there--all of us are impacted by those who work for a living," he said.

At least that's how Dotter's camera sees it for the last Labor Day of this century.