CHARLESTON, W.Va. -- Nov. 20, 1968. 5:30 a.m. An explosion rips through Farmington No. 9 Mine in West Virginia. It leaves 78 miners dead, a grim but familiar death toll that reverberates through America's mining communities. There is sorrow and outrage. But there is also action. Congress passes the Federal Coal Mine Health and Safety Act of 1969, a law that will forever transform occupational safety and health in the United States.

Far to the west, in the silver mines of Idaho, a fire engulfs the Sunshine Mine on May 2, 1972. Ninety-one workers die from smoke inhalation and carbon monoxide poisoning. These metal/nonmetal miners are not protected by the 1969 law.

In 1976, two violent blasts shatter the Scotia Mine in Kentucky within days of each other, killing 26 -- including 11 mine inspectors and rescue workers who had arrived to investigate the first explosion. It becomes clear to lawmakers and the public that stronger laws to protect all miners are needed, leading to the passage of the Federal Mine Safety and Health Act of 1977. The law transfers the Interior Department's Mining Enforcement and Safety Administration to the U.S. Department of Labor, which seven years earlier established the Occupational Safety and Health Administration. This action created today's Mine Safety and Health Administration.

On March 9, MSHA commemorated its 35th anniversary. In 1977, there were 273 mining fatalities in the United States. Last year, we brought that number down to 35. Simply stated, this is a law that saves lives.

While all miners gained new protections as a result of the 1977 law, the greatest impact was felt in the metal and nonmetal mining industry. The additional protections for these miners include stringent enforcement of safety and health regulations and mandated inspections, four times per year at underground mines and twice per year at surface mines.

The law also includes provisions that protect miners against loss of pay for the time a miner's representative spends accompanying a federal inspector during an inspection and provides compensation during periods when a mine is idled because of a withdrawal order (which temporarily ceases production) issued by MSHA.

It enhances anti-discrimination provisions and, for the first time, provides miners an opportunity for temporary reinstatement to their jobs while pursuing complaints.

For the first time, it requires mine operators to provide training for new miners and newly hired experienced miners, and annual safety retraining of miners during normal working hours and at normal compensation rates.

It creates effective enforcement tools that allow MSHA to issue citations and orders for "unwarrantable failures" by the mine operator and to address chronic violators -- mine operators who establish a "pattern of violations" of mandatory safety or health standards.

It contains new rulemaking procedures that permits MSHA to promulgate emergency temporary standards when warranted.

And it places increased emphasis on protecting the health of miners to assure they do not suffer material impairment due to exposure to toxic substances and harmful physical agents in mine atmospheres.

Today, more than ever before, miners are vigorously exercising their rights by speaking out about unsafe conditions at their mines. MSHA, in turn, has increased its efforts to enhance miner protection from discrimination, particularly by filing complaints on their behalf, including requests for temporary reinstatement. In 2012 -- through MSHA's investigations -- 46 temporary reinstatement requests were filed, the most in the agency's history.

Enhanced enforcement initiatives, such as the monthly impact inspections of problem mines and pattern of violation notifications, are making a positive difference. Mine operators are getting the message, and their compliance continues to improve.

Like many others who worked in the mines before the 1977 Act, I know the dramatic changes that this law spurred in the mining industry.

The anniversary of MSHA coincides with another significant milestone -- the U.S. Department of Labor turned 100 years old this week. Just as the Labor Department has worked to promote and advance the interests of workers, families, job seekers and retirees for the past 100 years, MSHA strives to protect the welfare of our nation's miners, preventing death, disease and injury so that they can return home to their families after every shift.

Main is U.S. Assistant Secretary of Labor for Mine Safety and Health.