Public health authorities are often confronted with the question of when to issue warnings about potential hazards. In this paper, the epidemiologic records for occupational exposures involving latex gloves and carbonless copy paper (CCP) were compared to illustrate what attributes led to the issuance of a government Alert warning. The history of the use and the reported health effects for workers handling these materials were traced. Epidemiologic studies were compared for case definition and confirmation, strength of association, quality of evidence, and biological plausibility. For latex, an Alert was issued due to the severity of the health effects (allergy, asthma, anaphylaxis and death), the magnitude of the association, and the corroborating experimental evidence. In contrast, for CCP, the severity of health effects generally, skin, eye, and upper respiratory irritation and, rarely, sensitization or systemic reactions did not meet the same level of concern, nor was the strength of the association (generally odds ratios less than 2.0 and extensive potential for recall bias) or experimental evidence strong enough to generate an Alert. In the case of CCP, a hazard review report was issued and widely distributed. In both the Latex Alert and CCP Hazard Review report, recommendations to prevent health problems were provided. The public receives numerous health messages daily from a variety of sources including the news media, academic institutions, nonprofit organizations, and government agencies. It is important that the health messages issued, especially from government agencies, be based on clear science and be appropriate to the potential level and severity of risk.