He said the agency assumes the letter was sent to the State Department, which could explain how that agency's mail system became contaminated and a worker there contracted inhalation anthrax.

The company strongly denies these workers contracted their health problems through factors related to their work.

Today, the radioactive isotopes are long gone, but the diseases those workers contracted are not.

In the first decade of the 20th century, a large number of Japanese immigrants came as workers contracted to companies doing business in the country which needed skilled labor.

The studies suggested that some workers who had been exposed to synthetic mineral fibers for 30 years or more had contracted lung cancer.

Six postal workers have apparently contracted anthrax, including one from the Camden area who was added to the list today.

Potential candidates found the length of service required, at least a year, unappealing; only a few thousand workers ever contracted with the company.

"I really don't know anything about the vaccine," said Denise L. Manley, 49, a machine clerk at the Brentwood office, where two workers contracted anthrax and died.

Legally, it would have been very difficult to prove whether a worker had contracted skin cancer from the workplace, the back garden or the beach.

The next surprise was that postal workers could contract anthrax from spores in mail.