A massive asbestos trial against some of the world's largest companies, including ExxonMobil and Honeywell International, began in late September in West Virginia, even as the case is being challenged before the U.S. Supreme Court, according to the Associated Press.

The lawsuit in Kanawha County Circuit Court comprises the cases of 8,000 people who say they were exposed to the deadly agent. But about half of the 259 defendants have appealed to the high court, saying plaintiffs' cases are so dissimilar that consolidating them infringes on their constitutional rights.

Defendants range from manufacturers to groups of employers and building owners, and cases are so numerous the trial was to be split into separate but simultaneous proceedings - one for companies sued over product liability claims and the other for those sued for on-premises exposure to asbestos.

In the last three years, the number of asbestos lawsuits has been increasing, forcing about 50 U.S. corporations into bankruptcy because of related liabilities.

Nationwide, there are some 200,000 pending asbestos claims.

Defense attorneys complain that West Virginia is the venue for the trial because state law allows outsiders to sue companies that operate within the state. Some show no signs of illness. And as many as 5,000 plaintiffs are from out of state, the defense estimates.

Many of the companies being sued did not make asbestos but used it in a range of products, such as car brake linings.

Sources close to the proceedings suggested out-of-court settlements may have whittled the number of defendants down dramatically.