Scientists have a new tool to measure the pollution in Boston Harbor. Researchers at the Massachusetts Institute of Technology in Cambridge, Mass., have developed a portable, fiber optic spectrofluorometer that detects harmful organic compounds. In particular, the device detects polycyclic aromatic hydrocarbons. When a laser beam excites these compounds, they fluoresce. The more fluorescence detected, the more pollution in the water. The MIT spectrofluorometer is more sensitive than conventional spectrometers because it separates the signals of organic materials from signals of polycyclic aromatic hydrocarbons.