On Capitol Hill, the former head of the Environmental Protection Agency, Christine Todd Whitman, will testify today about how the EPA handled air quality issues at Ground Zero following the Sept. 11 attacks. In the days after the twin towers collapsed, Whitman assured New York City residents the air was safe to breathe. Over the weekend, Whitman claimed that former New York Mayor Rudolph Giuliani blocked her efforts to force workers at the World Trade Center to wear respirators.