Black lung disease, long a killer of coal miners, is on the rise again after retreating in the 30 years since Congress passed tougher mine safety laws, health and safety experts said on Friday.

The renewed appearance of the disease emerged from an investigation of the worst U.S. coal mining disaster in four decades. It comes at a time when coal prices have risen sharply and some mine operators have been accused of cutting corners on safety in favor of profits.

Of the 29 miners killed in the blast at the Upper Big Branch mine in West Virginia on April 5 last year, almost 75 percent of them showed signs of black lung disease, according to an independent report released on Thursday.

“That sample ... is a terrifying number, an astonishing number, particularly given the age of some of these individuals,” said Davitt McAteer, who headed the investigation, ordered by West Virginia’s then-governor Joe Manchin.

The report blamed mine owner Massey Energy for safety failings, adding “the operator’s commitment to production comes at the cost of safety.” It cited inadequate ventilation systems and rock dusting standards.

In its response to the report, Massey did not address the black lung issue, but stressed “our goal is to find answers and technologies that ultimately make mining safer.”

Coal dust is one of the main causes of lung diseases such as coal workers pneumoconiosis (CWP), emphysema, silicosis, and bronchitis - known collectively as black lung. It can lead to lung impairment, permanent disability, and death, but like all occupational diseases, can be prevented.

An estimated 1,500 former coal miners die each year from it, according to the United Mine Workers union (UMW). There are about 130,000 coal miners in the United States today, down from a high of 760,000 in 1927, according to the Labor Department.

Data from the National Institute for Occupational Safety and Health (NIOSH) show the incidence of black lung cases declined following the 1977 Coal Mine Safety and Health Act through the early 1990s, but this decline stopped in the 1995-99 period, and the incidence has risen since then.

Among active coal miners with more than 30 years of underground mining, the prevalence of CWP declined from 35 percent in the early 1970s to about 7 percent in the late 1990s. However, it increased to nearly 10 percent in the mid-2000’s, the NIOSH figures show.

From 1995 to 2004, more than three-fourths of all CWP deaths were in the coal-mining states of Pennsylvania, West Virginia, Virginia, and Kentucky. Pennsylvania alone accounted for nearly half of all CWP deaths, the institute said.

“It is still killing miners and there are hot spots such as southern West Virginia and eastern Kentucky, where Massey has operations,” said UMW spokesman Phil Smith.

Although masks and breathing apparatus are available in most mines, Smith said many miners do not wear them. “They do not fit well with facial hair and many miners have beards,” he said. Also they can impair communications underground.

The federal Mine Safety and Health Administration (MSHA) says that while there is no cure for black Lung, there are potentially life-saving measures that MSHA requires to reduce exposure to respirable coal dust.

“Even though these measures have been required for many years, new cases of black lung continue to occur among the nation’s coal miners, even in younger miners,” MSHA said.

According to the McAteer report on the Upper Big Branch disaster, black lung was found in 17 of 24 autopsies carried out. It was not just long-time miners who had the disease, but some were as young as 25, and five had less than 10 years experience working in coal mines.

“The prevalence of coal workers’ pneumoconiosis among the deceased Upper Big Branch miners is both surprising and troubling,” the report said in one of its findings.

It recommended that by 2012, the industry, along with state and federal regulators, adopt rules to reduce the permissible exposure limit for coal mine dust.

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By Steve James

NEW YORK