The Environmental Health Laboratory Branch (EHLB) is responsible for analyzing environmental and biological samples for the presence and quantities of toxic substances. These include lead, air pollutants, pesticides, asbestos, and biological contaminants such as molds. EHLB serves as a reference laboratory for public health agencies and as a referee laboratory for chemical testing. It has a multidisciplinary staff of ~30 experts in chemistry, microbiology, ventilation engineering, epidemiology, and statistics. It conducts a wide variety of laboratory analyses and studies, including environmental and clinical analytical services, and it provides leadership in the development of laboratory methods.