Marcy Borders, who became known as the “dust lady” from a defining picture of her covered in ash and grime on Sept. 11, 2001, died on Monday. She was 42.

Her sister, Dawn Borders, said she died from stomach cancer.

Ms. Borders was an employee of Bank of America in 2001, and was working on the 81st floor of the north tower of the World Trade Center on the day of the terrorist attacks.

She described her experience in a video interview published by the filmmaker Mike McGregor three years ago.

“We had no idea what was going on,” she said of the plane’s impact. “The way the building was shaking, I couldn’t sit there.”