Got asbestos in your attic? Many homes do and, in a class action lawsuit tentative settlement, W.R. Grace & Co. has agreed to establish a $140 million fund to compensate homeowners who have been unknowingly exposed to the potentially deadly substance.

The settlement involves Zonolite, asbestos-based insulation that was sold as a "do-it-yourself" product over a 60-year period. During that time, Zonolite was installed in thousands and thousands of American homes, potentially putting the installer and the residents at risk.

One estimate has put the number of homes containing Zonolite at 35 million.

W.R. Grace had prepared a warning label for Zonolite in the 1970s, cautioning that it could cause including asbestosis, lung cancer and malignant mesothelioma. Those who are exposed to asbestos, even on just one occasion, incur a greater risk of developing one of the diseases. But the warning label was never released. The company stopped selling Zonolite in 1984.

The settlement provides that those who used the product can be paid 55 percent of the amount of damages that they claimed in the suit. However, no one filing a claim will be eligible to receive more than $4,125.

Asbestos is a naturally-occuring but highly toxic substance. It was widely used as building insulation and as a fire retardant for decades researchers established the dangers associated with its use.

Facing a staggering number of claims, W.R. Grace filed for bankruptcy protection in 2001 over hundreds of thousands of asbestos-related claims. In April 2008, the company announced a settlement that could be worth $3 billion, which would likely place an end to thousands of lawsuits by those affected with asbestos exposure.

In addition to the Zonolite settlement, Grace has agreed to pay $250 million to clean up contamination in Libby, Montana, former site of an asbestos mine that supplied most of the asbestos used in Zonolite. Residents there have experienced an epidemic of lung disease.

Criminal charges are pending against some current and former Grace executives allegedly involved in the Libby operation.

A Delaware bankruptcy court must give final approval to the settlement.

About abestos

Asbestos has been used in a wide variety of building materials, including insulation products, siding, cements, flooring, and roofing. Once installed, it is generally regarded as safe unless it is damaged or disturbed, which can release asbestos fibers into the air. Inhaling the microscopic fibers can cause several types of cancer and lung disease.

The Environmental Working Group reports that an estimated 10,000 Americans pass away each year from an asbestos-related cancer. Those most at risk include plumbers, joiners, electricians, construction workers, and other maintenance workers.

Mesothelioma, a deadly cancer that attacks the lining of the lungs, heart, or abdomen, is almost exclusively caused by asbestos exposure. But because of an exceptionally long latency period, symptoms may not appear for 20 years or more, delaying diagnosis and severely reducing the chance of survival.