The systematic attempt to anticipate future environmental problems has usually been associated with the assessment of new or emerging technologies. In recent years, however, it has become clear that environmental problems may suddenly come to light, stemming from aging or obsolescent technological systems, or from industrial practices that have already been discounted or superceded by improved methods. This retrospective mini-assessment of nineteenth century technology has identified industrial and urban technologies of the pre-World War I era which may be the sources of present-day environmental problems or threats to public health and safety. Four case studies were given particular attention in the assessment: (1) arsenic, which was used widely in a number of industries during the last century; (2) coal, which is being reintroduced as a major energy source; (3) iron and steel, the major heavy industries of the nineteenth century; (4) old dams, which potentially contain hazardous materials in the trapped sediments.