Arsenic: Sources and Health Effects. Chairs: Zheng Baoshan, Chinese Academy of Sciences, China and Robert G. Arnold, University of Arizona, Tucson. The broad scope and interest of the PBC membership and supporting agencies provides a strong base from which to explore all aspects of problems related to human and environmental health.  Environmental arsenic offers an excellent example.  Speakers at the arsenic session covered aspects of arsenic measurement, exposure via inhalation and water ingestion, arsenic toxicokinetics, epidemiological evidence and mechanism of arsenic toxicity, and arsenic treatment including stabilization and disposal of residuals derived from water treatment.  Arsenic is a significant public health concern throughout most of the Pacific Basin, including the poorest countries, where many arsenic removal technologies are economically infeasible.  The PBC has a particular interest in such situations, as reflected by presentations related to arsenic exposure due to poor ventilation and the development of inexpensive methods for measuring toxic levels of arsenic in water.