To the Editor.
—In Questions and Answers in the January 22/29, 1992, issue of JAMA, a New Jersey physician asked whether a single Freon exposure at work could have caused subsequently observed hypertension.1 The responders, reasonably, were doubtful of a causative relationship, but did not refer to a published description of an extensive experience with blood pressure surveillance as a nonspecific indicator of workplace intolerance to chemicals, in use from the late 1930s until the early 1950s.Periodic blood pressure surveillance to detect chemical toxic effects was established in 1937 by DuPont in its explosives factories.2,3 Several other explosives manufacturers, including Hercules and American Cyanamid, also used the system for a time. Blood pressure surveillance was applied to workers exposed to lead, hydrogen sulfide, sulfur dioxide, carbon monoxide, a number of solvents, sulfides, aromatic and aliphatic nitro compounds, and chlorinated hydrocarbons (Freon was not mentioned by name).2
Morton WE. Freon and Hypertension. JAMA. 1992;268(12):1540-1541. doi:10.1001/jama.1992.03490120054022