Effective management of environmental hazards requires knowledge of both physical environmental systems and the psychosocial processes affecting responses to environmental conditions. This journal issue focuses on understanding individual and social group responses to environmental hazards. This article suggests that hazard managers and others are often perplexed by the diversity of people's conclusions about environmental hazards because they adopt an objectivist perspective, which views risk only as a physical characteristic. The constructivists perspective adopted by the social sciences holds that risk assessment reflects human judgments, which are influenced by various psychological and social factors reviewed herein. We conclude that the effective management of may environmental hazards depends on reconciliation of the objectivist and constructivist perspectives. This can be accomplished by recognizing that risk communication, the exchange of information and opinions about hazards, should integrate technical information about hazards with the interests and values of affected parties including the public, in order to develop common solutions to environmental problems.